diff --git a/src/analyzer/atsp/cache.cpp b/src/analyzer/atsp/cache.cpp
index 07ecd37803..dbc4d1132c 100644
--- a/src/analyzer/atsp/cache.cpp
+++ b/src/analyzer/atsp/cache.cpp
@@ -21,10 +21,6 @@
 
 #include "atsp.h"
 
-using namespace Yuni;
-
-#define SEP Yuni::Core::IO::Separator
-
 namespace Antares
 {
 void ATSP::cacheCreate()
diff --git a/src/libs/antares/memory/memory.cpp b/src/libs/antares/memory/memory.cpp
index 3819cc8036..5d368137bc 100644
--- a/src/libs/antares/memory/memory.cpp
+++ b/src/libs/antares/memory/memory.cpp
@@ -47,8 +47,6 @@
 
 using namespace Yuni;
 
-#define SEP Yuni::IO::Separator
-
 namespace Antares
 {
 /*extern*/
diff --git a/src/libs/antares/paths/include/antares/paths/list.h b/src/libs/antares/paths/include/antares/paths/list.h
index 135a18ff95..4aa03124f7 100644
--- a/src/libs/antares/paths/include/antares/paths/list.h
+++ b/src/libs/antares/paths/include/antares/paths/list.h
@@ -178,17 +178,6 @@ class PathList
         return item.empty();
     }
 
-    template<class StringT>
-    size_t sizeOnDisk(const StringT& sourceFolder) const
-    {
-        if (item.empty())
-        {
-            return 0;
-        }
-        pTmp = sourceFolder;
-        return (!pTmp) ? 0 : internalSizeOnDisk();
-    }
-
     size_t totalSizeInBytes() const;
 
     template<class StringT>
diff --git a/src/libs/antares/paths/list.cpp b/src/libs/antares/paths/list.cpp
index 5369e24513..ad5efa1a33 100644
--- a/src/libs/antares/paths/list.cpp
+++ b/src/libs/antares/paths/list.cpp
@@ -41,23 +41,6 @@ void PathList::clear()
     item.clear();
 }
 
-size_t PathList::internalSizeOnDisk() const
-{
-    size_t size = 0;
-    Clob buffer;
-
-    const ItemList::const_iterator end = item.end();
-    for (ItemList::const_iterator i = item.begin(); i != end; ++i)
-    {
-        if (!(i->second.options & pathListOptFolder))
-        {
-            buffer.clear() << pTmp << SEP << i->first;
-            size += (size_t)IO::File::Size(pTmp);
-        }
-    }
-    return size;
-}
-
 size_t PathList::totalSizeInBytes() const
 {
     size_t size = 0;
@@ -70,6 +53,7 @@ size_t PathList::totalSizeInBytes() const
     return size;
 }
 
+// TODO VP: remove with tools
 uint PathList::internalDeleteAllEmptyFolders()
 {
     if (!pTmp || item.empty())
diff --git a/src/libs/antares/series/series.cpp b/src/libs/antares/series/series.cpp
index 4c0cca690e..2f0dcd9111 100644
--- a/src/libs/antares/series/series.cpp
+++ b/src/libs/antares/series/series.cpp
@@ -31,10 +31,6 @@
 
 #include <antares/antares/constants.h>
 
-using namespace Yuni;
-
-#define SEP IO::Separator
-
 namespace Antares::Data
 {
 void TimeSeriesNumbers::registerSeries(const TimeSeries* s, std::string label)
@@ -135,8 +131,8 @@ int TimeSeries::saveToFolder(const std::string& areaID,
                              const std::string& folder,
                              const std::string& prefix) const
 {
-    Clob buffer;
-    buffer.clear() << folder << SEP << prefix << areaID << ".txt";
+    Yuni::Clob buffer;
+    buffer.clear() << folder << Yuni::IO::Separator << prefix << areaID << ".txt";
     return timeSeries.saveToCSVFile(buffer, 0);
 }
 
diff --git a/src/libs/antares/study/area/links.cpp b/src/libs/antares/study/area/links.cpp
index 97668638e0..767808693a 100644
--- a/src/libs/antares/study/area/links.cpp
+++ b/src/libs/antares/study/area/links.cpp
@@ -38,11 +38,6 @@ namespace fs = std::filesystem;
 
 #define SEP (IO::Separator)
 
-namespace
-{
-const YString DIRECTORY_NAME_FOR_TRANSMISSION_CAPACITIES = "ntc";
-}
-
 namespace Antares
 {
 namespace Data
@@ -78,15 +73,14 @@ AreaLink::~AreaLink()
 {
 }
 
-bool AreaLink::linkLoadTimeSeries_for_version_below_810(const AnyString& folder)
+bool AreaLink::linkLoadTimeSeries_for_version_below_810(const fs::path& folder)
 {
-    String buffer;
-    buffer.clear() << folder << SEP << with->id << ".txt";
+    fs::path path = folder / static_cast<std::string>(with->id + ".txt");
 
     // Load link's data
     Matrix<> tmpMatrix;
     const uint matrixWidth = 8;
-    if (!tmpMatrix.loadFromCSVFile(buffer,
+    if (!tmpMatrix.loadFromCSVFile(path.string(),
                                    matrixWidth,
                                    HOURS_PER_YEAR,
                                    Matrix<>::optFixedSize | Matrix<>::optImmediate))
@@ -110,26 +104,28 @@ bool AreaLink::linkLoadTimeSeries_for_version_below_810(const AnyString& folder)
     return true;
 }
 
-bool AreaLink::linkLoadTimeSeries_for_version_820_and_later(const AnyString& folder)
+bool AreaLink::linkLoadTimeSeries_for_version_820_and_later(const fs::path& folder)
 {
-    String capacitiesFolder;
-    capacitiesFolder << folder << SEP << "capacities";
-
-    String filename;
     bool success = true;
 
     // Read link's parameters times series
-    filename.clear() << folder << SEP << with->id << "_parameters.txt";
-    success = parameters.loadFromCSVFile(filename, fhlMax, HOURS_PER_YEAR, Matrix<>::optFixedSize)
+    std::string paramId = with->id + "_parameters.txt";
+    fs::path path = folder / paramId;
+    success = parameters.loadFromCSVFile(path.string(),
+                                         fhlMax,
+                                         HOURS_PER_YEAR,
+                                         Matrix<>::optFixedSize)
               && success;
 
+    fs::path capacitiesFolder = folder / "capacities";
+
     // Read link's direct capacities time series
-    filename.clear() << capacitiesFolder << SEP << with->id << "_direct.txt";
-    success = directCapacities.loadFromFile(filename.c_str(), false) && success;
+    path = capacitiesFolder / static_cast<std::string>(with->id + "_direct.txt");
+    success = directCapacities.loadFromFile(path, false) && success;
 
     // Read link's indirect capacities time series
-    filename.clear() << capacitiesFolder << SEP << with->id << "_indirect.txt";
-    success = indirectCapacities.loadFromFile(filename.c_str(), false) && success;
+    path = capacitiesFolder / static_cast<std::string>(with->id + "_indirect.txt");
+    success = indirectCapacities.loadFromFile(path, false) && success;
 
     return success;
 }
@@ -173,7 +169,7 @@ void AreaLink::overrideTransmissionCapacityAccordingToGlobalParameter(
     }
 }
 
-bool AreaLink::loadTimeSeries(const StudyVersion& version, const AnyString& folder)
+bool AreaLink::loadTimeSeries(const StudyVersion& version, const fs::path& folder)
 {
     if (version < StudyVersion(8, 2))
     {
@@ -187,14 +183,12 @@ bool AreaLink::loadTimeSeries(const StudyVersion& version, const AnyString& fold
 
 void AreaLink::storeTimeseriesNumbers(Solver::IResultWriter& writer) const
 {
-    Clob path;
-    std::string buffer;
-
-    path << "ts-numbers" << SEP << DIRECTORY_NAME_FOR_TRANSMISSION_CAPACITIES << SEP << from->id
-         << SEP << with->id << ".txt";
+    std::string filename = with->id + ".txt";
+    fs::path path = fs::path("ts-numbers") / "ntc" / from->id.to<std::string>() / filename;
 
+    std::string buffer;
     timeseriesNumbers.saveToBuffer(buffer);
-    writer.addEntryFromBuffer(path.c_str(), buffer);
+    writer.addEntryFromBuffer(path, buffer);
 }
 
 void AreaLink::detach()
@@ -527,7 +521,7 @@ bool AreaLinksLoadFromFolder(Study& study, AreaList* areaList, Area* area, const
         link.comments.clear();
         link.displayComments = true;
 
-        ret = link.loadTimeSeries(study.header.version, folder.string()) && ret;
+        ret = link.loadTimeSeries(study.header.version, folder) && ret;
 
         // Checks on loaded link's data
         if (study.usedByTheSolver)
diff --git a/src/libs/antares/study/area/list.cpp b/src/libs/antares/study/area/list.cpp
index 0f95023f33..1439e36198 100644
--- a/src/libs/antares/study/area/list.cpp
+++ b/src/libs/antares/study/area/list.cpp
@@ -44,7 +44,7 @@ namespace Antares::Data
 {
 namespace // anonymous
 {
-static bool AreaListLoadThermalDataFromFile(AreaList& list, const Clob& filename)
+static bool AreaListLoadThermalDataFromFile(AreaList& list, const fs::path& filename)
 {
     // Reset to 0
     list.each(
@@ -776,38 +776,39 @@ bool AreaList::saveToFolder(const AnyString& folder) const
     return ret;
 }
 
-template<class StringT>
-static void readAdqPatchMode(Study& study, Area& area, StringT& buffer)
+static void readAdqPatchMode(Study& study, Area& area)
 {
-    if (study.header.version >= StudyVersion(8, 3))
+    if (study.header.version < StudyVersion(8, 3))
+    {
+        return;
+    }
+
+    fs::path adqPath = study.folderInput / "areas" / area.id.to<std::string>()
+                       / "adequacy_patch.ini";
+    IniFile ini;
+    if (ini.open(adqPath))
     {
-        buffer.clear() << study.folderInput << SEP << "areas" << SEP << area.id << SEP
-                       << "adequacy_patch.ini";
-        IniFile ini;
-        if (ini.open(buffer))
+        auto* section = ini.find("adequacy-patch");
+        for (auto* p = section->firstProperty; p; p = p->next)
         {
-            auto* section = ini.find("adequacy-patch");
-            for (auto* p = section->firstProperty; p; p = p->next)
+            CString<30, false> tmp;
+            tmp = p->key;
+            tmp.toLower();
+            if (tmp == "adequacy-patch-mode")
             {
-                CString<30, false> tmp;
-                tmp = p->key;
-                tmp.toLower();
-                if (tmp == "adequacy-patch-mode")
-                {
-                    auto value = (p->value).toLower();
+                auto value = (p->value).toLower();
 
-                    if (value == "virtual")
-                    {
-                        area.adequacyPatchMode = Data::AdequacyPatch::virtualArea;
-                    }
-                    else if (value == "inside")
-                    {
-                        area.adequacyPatchMode = Data::AdequacyPatch::physicalAreaInsideAdqPatch;
-                    }
-                    else
-                    {
-                        area.adequacyPatchMode = Data::AdequacyPatch::physicalAreaOutsideAdqPatch;
-                    }
+                if (value == "virtual")
+                {
+                    area.adequacyPatchMode = Data::AdequacyPatch::virtualArea;
+                }
+                else if (value == "inside")
+                {
+                    area.adequacyPatchMode = Data::AdequacyPatch::physicalAreaInsideAdqPatch;
+                }
+                else
+                {
+                    area.adequacyPatchMode = Data::AdequacyPatch::physicalAreaOutsideAdqPatch;
                 }
             }
         }
@@ -899,7 +900,7 @@ static bool AreaListLoadFromFolderSingleArea(Study& study,
         {
             // if changes are required, please update reloadXCastData()
             fs::path loadPath = study.folderInput / "load" / "prepro" / area.id.to<std::string>();
-            ret = area.load.prepro->loadFromFolder(loadPath.string()) && ret;
+            ret = area.load.prepro->loadFromFolder(loadPath) && ret;
         }
         if (!options.loadOnlyNeeded || !area.load.prepro) // Series
         {
@@ -916,7 +917,7 @@ static bool AreaListLoadFromFolderSingleArea(Study& study,
         {
             // if changes are required, please update reloadXCastData()
             fs::path solarPath = study.folderInput / "solar" / "prepro" / area.id.to<std::string>();
-            ret = area.solar.prepro->loadFromFolder(solarPath.string()) && ret;
+            ret = area.solar.prepro->loadFromFolder(solarPath) && ret;
         }
         if (!options.loadOnlyNeeded || !area.solar.prepro) // Series
         {
@@ -940,7 +941,7 @@ static bool AreaListLoadFromFolderSingleArea(Study& study,
         {
             // if changes are required, please update reloadXCastData()
             fs::path hydroPrepro = pathHydro / "prepro";
-            ret = area.hydro.prepro->loadFromFolder(study, area.id, hydroPrepro.string()) && ret;
+            ret = area.hydro.prepro->loadFromFolder(study, area.id, hydroPrepro) && ret;
             ret = area.hydro.prepro->validate(area.id) && ret;
         }
 
@@ -972,7 +973,7 @@ static bool AreaListLoadFromFolderSingleArea(Study& study,
         {
             // if changes are required, please update reloadXCastData()
             fs::path windPath = study.folderInput / "wind" / "prepro" / area.id.to<std::string>();
-            ret = area.wind.prepro->loadFromFolder(windPath.string()) && ret;
+            ret = area.wind.prepro->loadFromFolder(windPath) && ret;
         }
         if (!options.loadOnlyNeeded || !area.wind.prepro) // Series
         {
@@ -1016,7 +1017,7 @@ static bool AreaListLoadFromFolderSingleArea(Study& study,
     }
 
     // Adequacy patch
-    readAdqPatchMode(study, area, buffer);
+    readAdqPatchMode(study, area);
 
     // Nodal Optimization
     fs::path nodalPath = study.folderInput / "areas" / area.id.to<std::string>()
@@ -1160,21 +1161,18 @@ bool AreaList::loadFromFolder(const StudyLoadOptions& options)
     // Thermal data, specific to areas
     {
         logs.info() << "Loading thermal clusters...";
-        buffer.clear() << pStudy.folderInput << SEP << "thermal" << SEP << "areas.ini";
-        ret = AreaListLoadThermalDataFromFile(*this, buffer) && ret;
+        fs::path thermalPath = pStudy.folderInput / "thermal";
+        fs::path areaIniPath = thermalPath / "areas.ini";
+        ret = AreaListLoadThermalDataFromFile(*this, areaIniPath) && ret;
 
-        // The cluster list must be loaded before the method
-        // ensureDataIsInitialized is called
+        // The cluster list must be loaded before the method ensureDataIsInitialized is called
         // in order to allocate data with all thermal clusters.
-        CString<30, false> thermalPlant;
-        thermalPlant << SEP << "thermal" << SEP << "clusters" << SEP;
-
         auto end = areas.end();
         for (auto i = areas.begin(); i != end; ++i)
         {
             Area& area = *(i->second);
-            buffer.clear() << pStudy.folderInput << thermalPlant << area.id;
-            ret = area.thermal.list.loadFromFolder(pStudy, buffer.c_str(), &area) && ret;
+            fs::path areaPath = thermalPath / "clusters" / area.id.to<std::string>();
+            ret = area.thermal.list.loadFromFolder(pStudy, areaPath, &area) && ret;
             ret = area.thermal.list.validateClusters(pStudy.parameters) && ret;
         }
     }
@@ -1203,18 +1201,16 @@ bool AreaList::loadFromFolder(const StudyLoadOptions& options)
     // Renewable data, specific to areas
     if (studyVersion >= StudyVersion(8, 1))
     {
-        // The cluster list must be loaded before the method
-        // ensureDataIsInitialized is called
+        // The cluster list must be loaded before the method ensureDataIsInitialized is called
         // in order to allocate data with all renewable clusters.
-        CString<30, false> renewablePlant;
-        renewablePlant << SEP << "renewables" << SEP << "clusters" << SEP;
+        fs::path renewClusterPath = pStudy.folderInput / "renewables" / "clusters";
 
         auto end = areas.end();
         for (auto i = areas.begin(); i != end; ++i)
         {
             Area& area = *(i->second);
-            buffer.clear() << pStudy.folderInput << renewablePlant << area.id;
-            ret = area.renewable.list.loadFromFolder(buffer.c_str(), &area) && ret;
+            fs::path areaPath = renewClusterPath / area.id.to<std::string>();
+            ret = area.renewable.list.loadFromFolder(areaPath, &area) && ret;
             ret = area.renewable.list.validateClusters() && ret;
         }
     }
diff --git a/src/libs/antares/study/area/store-timeseries-numbers.cpp b/src/libs/antares/study/area/store-timeseries-numbers.cpp
index 9619206239..daa3a250c8 100644
--- a/src/libs/antares/study/area/store-timeseries-numbers.cpp
+++ b/src/libs/antares/study/area/store-timeseries-numbers.cpp
@@ -25,24 +25,22 @@
 #include <antares/study/study.h>
 #include <antares/writer/i_writer.h>
 
-using namespace Yuni;
-
-#define SEP IO::Separator
+namespace fs = std::filesystem;
 
 namespace Antares::Data
 {
 static void storeTSnumbers(Solver::IResultWriter& writer,
                            const TimeSeriesNumbers& timeseriesNumbers,
-                           const String& id,
-                           const String& directory)
+                           const std::string& id,
+                           const fs::path& directory)
 {
-    Clob path;
-    path << "ts-numbers" << SEP << directory << SEP << id << ".txt";
+    std::string fullId = id + ".txt";
+    fs::path path = "ts-numbers" / directory / fullId;
 
     std::string buffer;
     timeseriesNumbers.saveToBuffer(buffer);
 
-    writer.addEntryFromBuffer(path.c_str(), buffer);
+    writer.addEntryFromBuffer(path, buffer);
 }
 
 void storeTimeseriesNumbersForLoad(Solver::IResultWriter& writer, const Area& area)
diff --git a/src/libs/antares/study/binding_constraint/BindingConstraint.cpp b/src/libs/antares/study/binding_constraint/BindingConstraint.cpp
index abdce0befb..ef94fed123 100644
--- a/src/libs/antares/study/binding_constraint/BindingConstraint.cpp
+++ b/src/libs/antares/study/binding_constraint/BindingConstraint.cpp
@@ -34,8 +34,6 @@
 
 using namespace Antares;
 
-#define SEP IO::Separator
-
 #ifdef _MSC_VER
 #define SNPRINTF sprintf_s
 #else
diff --git a/src/libs/antares/study/binding_constraint/BindingConstraintsRepository.cpp b/src/libs/antares/study/binding_constraint/BindingConstraintsRepository.cpp
index e68c97d15c..991a79a0f1 100644
--- a/src/libs/antares/study/binding_constraint/BindingConstraintsRepository.cpp
+++ b/src/libs/antares/study/binding_constraint/BindingConstraintsRepository.cpp
@@ -177,7 +177,7 @@ bool BindingConstraintsRepository::rename(BindingConstraint* bc, const AnyString
 
 bool BindingConstraintsRepository::loadFromFolder(Study& study,
                                                   const StudyLoadOptions& options,
-                                                  const AnyString& folder)
+                                                  const std::filesystem::path& folder)
 {
     // Log entries
     logs.info(); // space for beauty
@@ -203,7 +203,7 @@ bool BindingConstraintsRepository::loadFromFolder(Study& study,
     EnvForLoading env(study.areas, study.header.version);
     env.folder = folder;
 
-    env.iniFilename << env.folder << Yuni::IO::Separator << "bindingconstraints.ini";
+    env.iniFilename = folder / "bindingconstraints.ini";
     IniFile ini;
     if (!ini.open(env.iniFilename))
     {
diff --git a/src/libs/antares/study/include/antares/study/area/links.h b/src/libs/antares/study/include/antares/study/area/links.h
index fd4b8e69d8..ef17bc5e40 100644
--- a/src/libs/antares/study/include/antares/study/area/links.h
+++ b/src/libs/antares/study/include/antares/study/area/links.h
@@ -69,7 +69,7 @@ class AreaLink final: public Yuni::NonCopyable<AreaLink>
     ~AreaLink();
     //@}
 
-    bool loadTimeSeries(const StudyVersion& version, const AnyString& folder);
+    bool loadTimeSeries(const StudyVersion& version, const std::filesystem::path& folder);
 
     void storeTimeseriesNumbers(Solver::IResultWriter& writer) const;
 
@@ -121,8 +121,8 @@ class AreaLink final: public Yuni::NonCopyable<AreaLink>
     void overrideTransmissionCapacityAccordingToGlobalParameter(GlobalTransmissionCapacities tc);
 
 private:
-    bool linkLoadTimeSeries_for_version_below_810(const AnyString& folder);
-    bool linkLoadTimeSeries_for_version_820_and_later(const AnyString& folder);
+    bool linkLoadTimeSeries_for_version_below_810(const std::filesystem::path& folder);
+    bool linkLoadTimeSeries_for_version_820_and_later(const std::filesystem::path& folder);
     NamePair getNamePair() const;
 
 public:
diff --git a/src/libs/antares/study/include/antares/study/binding_constraint/BindingConstraintsRepository.h b/src/libs/antares/study/include/antares/study/binding_constraint/BindingConstraintsRepository.h
index 25809de754..67fd346a1b 100644
--- a/src/libs/antares/study/include/antares/study/binding_constraint/BindingConstraintsRepository.h
+++ b/src/libs/antares/study/include/antares/study/binding_constraint/BindingConstraintsRepository.h
@@ -112,7 +112,7 @@ class BindingConstraintsRepository final: public Yuni::NonCopyable<BindingConstr
     */
     [[nodiscard]] bool loadFromFolder(Data::Study& s,
                                       const Data::StudyLoadOptions& options,
-                                      const AnyString& folder);
+                                      const std::filesystem::path& folder);
 
     /*!
     ** \brief Save all binding constraints into a folder
diff --git a/src/libs/antares/study/include/antares/study/binding_constraint/EnvForLoading.h b/src/libs/antares/study/include/antares/study/binding_constraint/EnvForLoading.h
index 9220f0c1f3..2a69ed2693 100644
--- a/src/libs/antares/study/include/antares/study/binding_constraint/EnvForLoading.h
+++ b/src/libs/antares/study/include/antares/study/binding_constraint/EnvForLoading.h
@@ -42,7 +42,7 @@ class EnvForLoading final
     }
 
     //! INI file
-    Yuni::Clob iniFilename;
+    std::filesystem::path iniFilename;
     //! Current section
     IniFile::Section* section;
 
diff --git a/src/libs/antares/study/include/antares/study/layerdata.h b/src/libs/antares/study/include/antares/study/layerdata.h
index f552dd00e7..9aae946150 100644
--- a/src/libs/antares/study/include/antares/study/layerdata.h
+++ b/src/libs/antares/study/include/antares/study/layerdata.h
@@ -21,6 +21,7 @@
 #ifndef __ANTARES_LIBS_STUDY_LAYERDATA_H__
 #define __ANTARES_LIBS_STUDY_LAYERDATA_H__
 
+#include <filesystem>
 #include <map>
 #include <string>
 
@@ -51,7 +52,7 @@ class LayerData
 
 protected:
     bool saveLayers(const AnyString& filename);
-    void loadLayers(const AnyString& filename);
+    void loadLayers(const std::filesystem::path& filename);
 };
 
 } // namespace Antares::Data
diff --git a/src/libs/antares/study/include/antares/study/output.h b/src/libs/antares/study/include/antares/study/output.h
index 38846330bd..ffebc06d90 100644
--- a/src/libs/antares/study/include/antares/study/output.h
+++ b/src/libs/antares/study/include/antares/study/output.h
@@ -34,6 +34,8 @@ namespace Antares
 {
 namespace Data
 {
+
+// TODO VP: remove with GUI
 class Output final
 {
 public:
diff --git a/src/libs/antares/study/include/antares/study/parameters.h b/src/libs/antares/study/include/antares/study/parameters.h
index 1b2ce027d9..540cf5fc67 100644
--- a/src/libs/antares/study/include/antares/study/parameters.h
+++ b/src/libs/antares/study/include/antares/study/parameters.h
@@ -75,7 +75,7 @@ class Parameters final
     ** \param version Current study version
     ** \return True if the settings have been loaded, false if at least one error has occured
     */
-    bool loadFromFile(const AnyString& filename, const StudyVersion& version);
+    bool loadFromFile(const std::filesystem::path& filename, const StudyVersion& version);
 
     /*!
     ** \brief Prepare all settings for a simulation
diff --git a/src/libs/antares/study/include/antares/study/parts/hydro/container.h b/src/libs/antares/study/include/antares/study/parts/hydro/container.h
index 1da5ab6023..91b668ba6a 100644
--- a/src/libs/antares/study/include/antares/study/parts/hydro/container.h
+++ b/src/libs/antares/study/include/antares/study/parts/hydro/container.h
@@ -114,7 +114,7 @@ class PartHydro
     ** \param folder The targer folder
     ** \return A non-zero value if the operation succeeded, 0 otherwise
     */
-    static bool LoadFromFolder(Study& study, const AnyString& folder);
+    static bool LoadFromFolder(Study& study, const std::filesystem::path& folder);
 
     /*!
     ** \brief Check and validate the loaded datas
@@ -157,7 +157,7 @@ class PartHydro
     /*!
     ** \brief Load daily max energy
     */
-    bool LoadDailyMaxEnergy(const AnyString& folder, const AnyString& areaid);
+    bool LoadDailyMaxEnergy(const std::filesystem::path& folder, const std::string& areaid);
 
     bool CheckDailyMaxEnergy(const AnyString& areaName);
 
diff --git a/src/libs/antares/study/include/antares/study/parts/hydro/prepro.h b/src/libs/antares/study/include/antares/study/parts/hydro/prepro.h
index b35798f862..d85e803686 100644
--- a/src/libs/antares/study/include/antares/study/parts/hydro/prepro.h
+++ b/src/libs/antares/study/include/antares/study/parts/hydro/prepro.h
@@ -95,7 +95,7 @@ class PreproHydro
     ** \param folder The source folder (ex: `input/hydro/prepro`)
     ** \return A non-zero value if the operation succeeded, 0 otherwise
     */
-    bool loadFromFolder(Study& s, const AreaName& areaID, const std::string& folder);
+    bool loadFromFolder(Study& s, const std::string& areaID, const std::filesystem::path& folder);
 
     bool validate(const std::string& areaID);
     /*!
diff --git a/src/libs/antares/study/include/antares/study/parts/hydro/series.h b/src/libs/antares/study/include/antares/study/parts/hydro/series.h
index 343e49e266..e8fae00e36 100644
--- a/src/libs/antares/study/include/antares/study/parts/hydro/series.h
+++ b/src/libs/antares/study/include/antares/study/parts/hydro/series.h
@@ -76,7 +76,7 @@ class DataSeriesHydro
                           StudyVersion version);
 
     // Loading hydro max generation and mqx pumping TS's
-    bool LoadMaxPower(const AreaName& areaID, const std::filesystem::path& folder);
+    bool LoadMaxPower(const std::string& areaID, const std::filesystem::path& folder);
 
     void buildHourlyMaxPowerFromDailyTS(const Matrix<double>::ColumnType& DailyMaxGenPower,
                                         const Matrix<double>::ColumnType& DailyMaxPumpPower);
diff --git a/src/libs/antares/study/include/antares/study/parts/load/prepro.h b/src/libs/antares/study/include/antares/study/parts/load/prepro.h
index bbe3c7a008..9f3f037e4e 100644
--- a/src/libs/antares/study/include/antares/study/parts/load/prepro.h
+++ b/src/libs/antares/study/include/antares/study/parts/load/prepro.h
@@ -52,7 +52,7 @@ class Prepro
     /*!
     ** \brief Load data from a folder
     */
-    bool loadFromFolder(const AnyString& folder);
+    bool loadFromFolder(const std::filesystem::path& folder);
 
     /*!
     ** \brief Save data to a folder
diff --git a/src/libs/antares/study/include/antares/study/parts/renewable/cluster_list.h b/src/libs/antares/study/include/antares/study/parts/renewable/cluster_list.h
index 275d495020..d596384cc4 100644
--- a/src/libs/antares/study/include/antares/study/parts/renewable/cluster_list.h
+++ b/src/libs/antares/study/include/antares/study/parts/renewable/cluster_list.h
@@ -22,6 +22,8 @@
 #ifndef __ANTARES_LIBS_STUDY_PARTS_RENEWABLE_CLUSTER_LIST_H__
 #define __ANTARES_LIBS_STUDY_PARTS_RENEWABLE_CLUSTER_LIST_H__
 
+#include <filesystem>
+
 #include "../../fwd.h"
 #include "../common/cluster_list.h"
 #include "cluster.h"
@@ -38,7 +40,7 @@ class RenewableClusterList: public ClusterList<RenewableCluster>
     std::string typeID() const override;
     uint64_t memoryUsage() const override;
 
-    bool loadFromFolder(const AnyString& folder, Area* area);
+    bool loadFromFolder(const std::filesystem::path& folder, Area* area);
     bool validateClusters() const;
 
     bool saveToFolder(const AnyString& folder) const override;
diff --git a/src/libs/antares/study/include/antares/study/parts/solar/prepro.h b/src/libs/antares/study/include/antares/study/parts/solar/prepro.h
index 4365c0c6cf..e6f15d1d42 100644
--- a/src/libs/antares/study/include/antares/study/parts/solar/prepro.h
+++ b/src/libs/antares/study/include/antares/study/parts/solar/prepro.h
@@ -52,7 +52,7 @@ class Prepro
     /*!
     ** \brief Solar data from a folder
     */
-    bool loadFromFolder(const AnyString& folder);
+    bool loadFromFolder(const std::filesystem::path& folder);
 
     /*!
     ** \brief Save data to a folder
diff --git a/src/libs/antares/study/include/antares/study/parts/wind/prepro.h b/src/libs/antares/study/include/antares/study/parts/wind/prepro.h
index 1d0ed8722e..c62669d0a6 100644
--- a/src/libs/antares/study/include/antares/study/parts/wind/prepro.h
+++ b/src/libs/antares/study/include/antares/study/parts/wind/prepro.h
@@ -49,7 +49,7 @@ class Prepro
     /*!
     ** \brief Load data from a folder
     */
-    bool loadFromFolder(const AnyString& folder);
+    bool loadFromFolder(const std::filesystem::path& folder);
 
     /*!
     ** \brief Save data to a folder
diff --git a/src/libs/antares/study/include/antares/study/simulation.h b/src/libs/antares/study/include/antares/study/simulation.h
index b3ca6addd8..2a34d9c343 100644
--- a/src/libs/antares/study/include/antares/study/simulation.h
+++ b/src/libs/antares/study/include/antares/study/simulation.h
@@ -34,6 +34,8 @@ namespace Data
 /*!
 ** \brief Set of settings for a simulation
 */
+
+// TODO VP: remove with GUI
 class SimulationComments final
 {
 public:
diff --git a/src/libs/antares/study/include/antares/study/study.h b/src/libs/antares/study/include/antares/study/study.h
index 9b348a28f5..6ed7ce9b5c 100644
--- a/src/libs/antares/study/include/antares/study/study.h
+++ b/src/libs/antares/study/include/antares/study/study.h
@@ -467,6 +467,7 @@ class Study: public Yuni::NonCopyable<Study>, public LayerData
     //! \name Simulation
     //@{
     //! The current Simulation
+    // TODO VP: remove with GUI
     SimulationComments simulationComments;
 
     int64_t pStartTime;
diff --git a/src/libs/antares/study/include/antares/study/xcast/xcast.h b/src/libs/antares/study/include/antares/study/xcast/xcast.h
index cc7e281763..a8b5eebe7a 100644
--- a/src/libs/antares/study/include/antares/study/xcast/xcast.h
+++ b/src/libs/antares/study/include/antares/study/xcast/xcast.h
@@ -140,7 +140,7 @@ class XCast final: private Yuni::NonCopyable<XCast>
     /*!
     ** \brief Load data from a folder
     */
-    bool loadFromFolder(const AnyString& folder);
+    bool loadFromFolder(const std::filesystem::path& folder);
 
     /*!
     ** \brief Save data to a folder
diff --git a/src/libs/antares/study/layerdata.cpp b/src/libs/antares/study/layerdata.cpp
index 781a807037..cd8606dbaf 100644
--- a/src/libs/antares/study/layerdata.cpp
+++ b/src/libs/antares/study/layerdata.cpp
@@ -33,7 +33,7 @@ using namespace Yuni;
 
 namespace Antares::Data
 {
-void LayerData::loadLayers(const AnyString& filename)
+void LayerData::loadLayers(const std::filesystem::path& filename)
 {
     IniFile ini;
     if (std::ifstream(filename.c_str()).good() && ini.open(filename)) // check if file exists
diff --git a/src/libs/antares/study/load.cpp b/src/libs/antares/study/load.cpp
index c6b61a6e61..3a756333f3 100644
--- a/src/libs/antares/study/load.cpp
+++ b/src/libs/antares/study/load.cpp
@@ -26,16 +26,9 @@
 #include "antares/study/ui-runtimeinfos.h"
 #include "antares/study/version.h"
 
-using namespace Yuni;
-using Antares::Constants::nbHoursInAWeek;
-
 namespace fs = std::filesystem;
 
-#define SEP IO::Separator
-
-namespace Antares
-{
-namespace Data
+namespace Antares::Data
 {
 bool Study::internalLoadHeader(const fs::path& path)
 {
@@ -82,8 +75,8 @@ bool Study::internalLoadIni(const fs::path& path, const StudyLoadOptions& option
         }
     }
     // Load the general data
-    buffer.clear() << folderSettings << SEP << "generaldata.ini";
-    bool errorWhileLoading = !parameters.loadFromFile(buffer, header.version);
+    fs::path generalDataPath = folderSettings / "generaldata.ini";
+    bool errorWhileLoading = !parameters.loadFromFile(generalDataPath, header.version);
 
     parameters.validateOptions(options);
 
@@ -98,8 +91,8 @@ bool Study::internalLoadIni(const fs::path& path, const StudyLoadOptions& option
     }
 
     // Load the layer data
-    buffer.clear() << path << SEP << "layers" << SEP << "layers.ini";
-    loadLayers(buffer);
+    fs::path layersPath = path / "layers" / "layers.ini";
+    loadLayers(layersPath);
 
     return true;
 }
@@ -238,40 +231,32 @@ bool Study::internalLoadCorrelationMatrices(const StudyLoadOptions& options)
     if (!options.loadOnlyNeeded || timeSeriesLoad & parameters.timeSeriesToRefresh
         || timeSeriesLoad & parameters.timeSeriesToGenerate)
     {
-        buffer.clear() << folderInput << SEP << "load" << SEP << "prepro" << SEP
-                       << "correlation.ini";
-        preproLoadCorrelation.loadFromFile(*this, buffer);
+        fs::path loadPath = folderInput / "load" / "prepro" / "correlation.ini";
+        preproLoadCorrelation.loadFromFile(*this, loadPath.string());
     }
 
     // Solar
     if (!options.loadOnlyNeeded || timeSeriesSolar & parameters.timeSeriesToRefresh
         || timeSeriesSolar & parameters.timeSeriesToGenerate)
     {
-        buffer.clear() << folderInput << SEP << "solar" << SEP << "prepro" << SEP
-                       << "correlation.ini";
-        preproSolarCorrelation.loadFromFile(*this, buffer);
+        fs::path solarPath = folderInput / "solar" / "prepro" / "correlation.ini";
+        preproSolarCorrelation.loadFromFile(*this, solarPath.string());
     }
 
     // Wind
+    if (!options.loadOnlyNeeded || timeSeriesWind & parameters.timeSeriesToRefresh
+        || timeSeriesWind & parameters.timeSeriesToGenerate)
     {
-        if (!options.loadOnlyNeeded || timeSeriesWind & parameters.timeSeriesToRefresh
-            || timeSeriesWind & parameters.timeSeriesToGenerate)
-        {
-            buffer.clear() << folderInput << SEP << "wind" << SEP << "prepro" << SEP
-                           << "correlation.ini";
-            preproWindCorrelation.loadFromFile(*this, buffer);
-        }
+        fs::path windPath = folderInput / "wind" / "prepro" / "correlation.ini";
+        preproWindCorrelation.loadFromFile(*this, windPath.string());
     }
 
     // Hydro
+    if (!options.loadOnlyNeeded || (timeSeriesHydro & parameters.timeSeriesToRefresh)
+        || (timeSeriesHydro & parameters.timeSeriesToGenerate))
     {
-        if (!options.loadOnlyNeeded || (timeSeriesHydro & parameters.timeSeriesToRefresh)
-            || (timeSeriesHydro & parameters.timeSeriesToGenerate))
-        {
-            buffer.clear() << folderInput << SEP << "hydro" << SEP << "prepro" << SEP
-                           << "correlation.ini";
-            preproHydroCorrelation.loadFromFile(*this, buffer);
-        }
+        fs::path hydroPath = folderInput / "hydro" / "prepro" / "correlation.ini";
+        preproHydroCorrelation.loadFromFile(*this, hydroPath.string());
     }
     return true;
 }
@@ -280,8 +265,8 @@ bool Study::internalLoadBindingConstraints(const StudyLoadOptions& options)
 {
     // All checks are performed in 'loadFromFolder'
     // (actually internalLoadFromFolder)
-    buffer.clear() << folderInput << SEP << "bindingconstraints";
-    bool r = bindingConstraints.loadFromFolder(*this, options, buffer);
+    fs::path constraintPath = folderInput / "bindingconstraints";
+    bool r = bindingConstraints.loadFromFolder(*this, options, constraintPath);
     if (r)
     {
         r &= bindingConstraintsGroups.buildFrom(bindingConstraints);
@@ -291,16 +276,15 @@ bool Study::internalLoadBindingConstraints(const StudyLoadOptions& options)
 
 bool Study::internalLoadSets()
 {
-    const fs::path path = fs::path(folderInput.c_str()) / "areas" / "sets.ini";
     // Set of areas
     logs.info();
     logs.info() << "Loading sets of areas...";
 
     // filename
-    buffer.clear() << folderInput << SEP << "areas" << SEP << "sets.ini";
+    const fs::path setPath = folderInput / "areas" / "sets.ini";
 
     // Load the rules
-    if (setsOfAreas.loadFromFile(path))
+    if (setsOfAreas.loadFromFile(setPath))
     {
         // Apply the rules
         SetHandlerAreas handler(areas);
@@ -321,6 +305,7 @@ void Study::reloadCorrelation()
     internalLoadCorrelationMatrices(options);
 }
 
+// TODO remove with GUI
 bool Study::reloadXCastData()
 {
     // if changes are required, please update AreaListLoadFromFolderSingleArea()
@@ -333,17 +318,16 @@ bool Study::reloadXCastData()
           assert(area.wind.prepro);
 
           // Load
-          buffer.clear() << folderInput << SEP << "load" << SEP << "prepro" << SEP << area.id;
-          ret = area.load.prepro->loadFromFolder(buffer) && ret;
+          fs::path loadPath = folderInput / "load" / "prepro" / area.id.to<std::string>();
+          ret = area.load.prepro->loadFromFolder(loadPath.string()) && ret;
           // Solar
-          buffer.clear() << folderInput << SEP << "solar" << SEP << "prepro" << SEP << area.id;
-          ret = area.solar.prepro->loadFromFolder(buffer) && ret;
+          fs::path solarPath = folderInput / "solar" / "prepro" / area.id.to<std::string>();
+          ret = area.solar.prepro->loadFromFolder(solarPath.string()) && ret;
           // Wind
-          buffer.clear() << folderInput << SEP << "wind" << SEP << "prepro" << SEP << area.id;
-          ret = area.wind.prepro->loadFromFolder(buffer) && ret;
+          fs::path windPath = folderInput / "wind" / "prepro" / area.id.to<std::string>();
+          ret = area.wind.prepro->loadFromFolder(windPath.string()) && ret;
       });
     return ret;
 }
 
-} // namespace Data
-} // namespace Antares
+} // namespace Antares::Data
diff --git a/src/libs/antares/study/output.cpp b/src/libs/antares/study/output.cpp
index 0409f2bb6e..c28a1c95a2 100644
--- a/src/libs/antares/study/output.cpp
+++ b/src/libs/antares/study/output.cpp
@@ -35,6 +35,8 @@ namespace Antares::Data
 {
 namespace // anonymous
 {
+
+// TODO VP: remove with GUI
 class OutputFolderIterator: public IO::Directory::IIterator<true>
 {
 public:
@@ -189,6 +191,7 @@ bool Output::loadFromFolder(const AnyString& folder)
     return true;
 }
 
+// TODO VP: remove with GUI
 void Output::RetrieveListFromStudy(List& out, const Study& study)
 {
     out.clear();
diff --git a/src/libs/antares/study/parameters.cpp b/src/libs/antares/study/parameters.cpp
index 72be2dd7b4..9db123b5d8 100644
--- a/src/libs/antares/study/parameters.cpp
+++ b/src/libs/antares/study/parameters.cpp
@@ -1980,7 +1980,7 @@ void Parameters::saveToINI(IniFile& ini) const
     }
 }
 
-bool Parameters::loadFromFile(const AnyString& filename, const StudyVersion& version)
+bool Parameters::loadFromFile(const std::filesystem::path& filename, const StudyVersion& version)
 {
     // Loading the INI file
     IniFile ini;
diff --git a/src/libs/antares/study/parts/common/cluster_list.cpp b/src/libs/antares/study/parts/common/cluster_list.cpp
index b8e16c5081..0feee3a77f 100644
--- a/src/libs/antares/study/parts/common/cluster_list.cpp
+++ b/src/libs/antares/study/parts/common/cluster_list.cpp
@@ -28,7 +28,7 @@
 #include <antares/utils/utils.h>
 #include "antares/study/study.h"
 
-using namespace Yuni;
+namespace fs = std::filesystem;
 
 namespace Antares::Data
 {
@@ -88,21 +88,20 @@ void ClusterList<ClusterT>::resizeAllTimeseriesNumbers(uint n) const
     }
 }
 
-#define SEP IO::Separator
-
 template<class ClusterT>
 void ClusterList<ClusterT>::storeTimeseriesNumbers(Solver::IResultWriter& writer) const
 {
-    Clob path;
     std::string ts_content;
+    fs::path basePath = fs::path("ts-numbers") / typeID();
 
     for (auto& cluster: each_enabled())
     {
-        path.clear() << "ts-numbers" << SEP << typeID() << SEP << cluster->parentArea->id << SEP
-                     << cluster->id() << ".txt";
+        fs::path path = fs::path(cluster->parentArea->id.c_str())
+                        / std::string(cluster->id() + ".txt");
+
         ts_content.clear(); // We must clear ts_content here, since saveToBuffer does not do it.
         cluster->series.timeseriesNumbers.saveToBuffer(ts_content);
-        writer.addEntryFromBuffer(path.c_str(), ts_content);
+        writer.addEntryFromBuffer(path, ts_content);
     }
 }
 
diff --git a/src/libs/antares/study/parts/hydro/container.cpp b/src/libs/antares/study/parts/hydro/container.cpp
index 336595b95b..6ee131b4f3 100644
--- a/src/libs/antares/study/parts/hydro/container.cpp
+++ b/src/libs/antares/study/parts/hydro/container.cpp
@@ -25,10 +25,9 @@
 #include "antares/study/parts/hydro/hydromaxtimeseriesreader.h"
 #include "antares/study/study.h"
 
-using namespace Antares;
-using namespace Yuni;
+namespace fs = std::filesystem;
 
-#define SEP IO::Separator
+#define SEP Yuni::IO::Separator
 
 namespace Antares::Data
 {
@@ -102,7 +101,7 @@ void PartHydro::reset()
 template<class T>
 static bool loadProperties(Study& study,
                            IniFile::Property* property,
-                           const std::string& filename,
+                           const fs::path& filename,
                            T PartHydro::*ptr)
 {
     if (!property)
@@ -132,14 +131,13 @@ static bool loadProperties(Study& study,
     return ret;
 }
 
-bool PartHydro::LoadFromFolder(Study& study, const AnyString& folder)
+bool PartHydro::LoadFromFolder(Study& study, const fs::path& folder)
 {
-    auto& buffer = study.bufferLoadingTS;
     bool ret = true;
 
     // Initialize all alpha values to 0
     study.areas.each(
-      [&ret, &buffer, &study, &folder](Data::Area& area)
+      [&ret, &study, &folder](Data::Area& area)
       {
           area.hydro.interDailyBreakdown = 1.;
           area.hydro.intraDailyModulation = 24.;
@@ -174,7 +172,7 @@ bool PartHydro::LoadFromFolder(Study& study, const AnyString& folder)
                       enabledModeIsChanged = true;
                   }
 
-                  ret = area.hydro.LoadDailyMaxEnergy(folder, area.id) && ret;
+                  ret = area.hydro.LoadDailyMaxEnergy(folder.string(), area.id) && ret;
 
                   if (enabledModeIsChanged)
                   {
@@ -183,7 +181,7 @@ bool PartHydro::LoadFromFolder(Study& study, const AnyString& folder)
               }
               else
               {
-                  ret = area.hydro.LoadDailyMaxEnergy(folder, area.id) && ret;
+                  ret = area.hydro.LoadDailyMaxEnergy(folder.string(), area.id) && ret;
 
                   // Check is moved here, because in case of old study
                   // dailyNbHoursAtGenPmax and dailyNbHoursAtPumpPmax are not yet initialized.
@@ -192,36 +190,38 @@ bool PartHydro::LoadFromFolder(Study& study, const AnyString& folder)
               }
           }
 
-          buffer.clear() << folder << SEP << "common" << SEP << "capacity" << SEP
-                         << "creditmodulations_" << area.id << '.' << study.inputExtension;
-          ret = area.hydro.creditModulation.loadFromCSVFile(buffer,
+          fs::path capacityPath = folder / "common" / "capacity";
+
+          std::string creditId = "creditmodulations_" + area.id + ".txt";
+          fs::path creditPath = capacityPath / creditId;
+          ret = area.hydro.creditModulation.loadFromCSVFile(creditPath.string(),
                                                             101,
                                                             2,
                                                             Matrix<>::optFixedSize,
                                                             &study.dataBuffer)
                 && ret;
 
-          buffer.clear() << folder << SEP << "common" << SEP << "capacity" << SEP << "reservoir_"
-                         << area.id << '.' << study.inputExtension;
-          ret = area.hydro.reservoirLevel.loadFromCSVFile(buffer,
+          std::string reservoirId = "reservoir_" + area.id + ".txt";
+          fs::path reservoirPath = capacityPath / reservoirId;
+          ret = area.hydro.reservoirLevel.loadFromCSVFile(reservoirPath.string(),
                                                           3,
                                                           DAYS_PER_YEAR,
                                                           Matrix<>::optFixedSize,
                                                           &study.dataBuffer)
                 && ret;
 
-          buffer.clear() << folder << SEP << "common" << SEP << "capacity" << SEP << "waterValues_"
-                         << area.id << '.' << study.inputExtension;
-          ret = area.hydro.waterValues.loadFromCSVFile(buffer,
+          std::string waterValueId = "waterValues_" + area.id + ".txt";
+          fs::path waterValuePath = capacityPath / waterValueId;
+          ret = area.hydro.waterValues.loadFromCSVFile(waterValuePath.string(),
                                                        101,
                                                        DAYS_PER_YEAR,
                                                        Matrix<>::optFixedSize,
                                                        &study.dataBuffer)
                 && ret;
 
-          buffer.clear() << folder << SEP << "common" << SEP << "capacity" << SEP
-                         << "inflowPattern_" << area.id << '.' << study.inputExtension;
-          ret = area.hydro.inflowPattern.loadFromCSVFile(buffer,
+          std::string inflowId = "inflowPattern_" + area.id + ".txt";
+          fs::path inflowPath = capacityPath / inflowId;
+          ret = area.hydro.inflowPattern.loadFromCSVFile(inflowPath.string(),
                                                          1,
                                                          DAYS_PER_YEAR,
                                                          Matrix<>::optFixedSize,
@@ -230,103 +230,96 @@ bool PartHydro::LoadFromFolder(Study& study, const AnyString& folder)
       });
 
     IniFile ini;
-    if (not ini.open(buffer.clear() << folder << SEP << "hydro.ini"))
+    auto path = folder / "hydro.ini";
+    if (not ini.open(path))
     {
         return false;
     }
 
     if (IniFile::Section* section = ini.find("inter-daily-breakdown"))
     {
-        ret = loadProperties(study, section->firstProperty, buffer, &PartHydro::interDailyBreakdown)
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::interDailyBreakdown)
               && ret;
     }
 
     if (IniFile::Section* section = ini.find("intra-daily-modulation"))
     {
-        ret = loadProperties(study,
-                             section->firstProperty,
-                             buffer,
-                             &PartHydro::intraDailyModulation)
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::intraDailyModulation)
               && ret;
     }
 
     if (IniFile::Section* section = ini.find("reservoir"))
     {
-        ret = loadProperties(study, section->firstProperty, buffer, &PartHydro::reservoirManagement)
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::reservoirManagement)
               && ret;
     }
 
     if (IniFile::Section* section = ini.find("reservoir capacity"))
     {
-        ret = loadProperties(study, section->firstProperty, buffer, &PartHydro::reservoirCapacity)
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::reservoirCapacity)
               && ret;
     }
 
     if (IniFile::Section* section = ini.find("follow load"))
     {
-        ret = loadProperties(study,
-                             section->firstProperty,
-                             buffer,
-                             &PartHydro::followLoadModulations)
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::followLoadModulations)
               && ret;
     }
 
     if (IniFile::Section* section = ini.find("use water"))
     {
-        ret = loadProperties(study, section->firstProperty, buffer, &PartHydro::useWaterValue)
-              && ret;
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::useWaterValue) && ret;
     }
 
     if (IniFile::Section* section = ini.find("hard bounds"))
     {
         ret = loadProperties(study,
                              section->firstProperty,
-                             buffer,
+                             path,
                              &PartHydro::hardBoundsOnRuleCurves)
               && ret;
     }
 
     if (IniFile::Section* section = ini.find("use heuristic"))
     {
-        ret = loadProperties(study, section->firstProperty, buffer, &PartHydro::useHeuristicTarget)
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::useHeuristicTarget)
               && ret;
     }
 
     if (IniFile::Section* section = ini.find("power to level"))
     {
-        ret = loadProperties(study, section->firstProperty, buffer, &PartHydro::powerToLevel)
-              && ret;
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::powerToLevel) && ret;
     }
 
     if (IniFile::Section* section = ini.find("initialize reservoir date"))
     {
         ret = loadProperties(study,
                              section->firstProperty,
-                             buffer,
+                             path,
                              &PartHydro::initializeReservoirLevelDate)
               && ret;
     }
 
     if (IniFile::Section* section = ini.find("use leeway"))
     {
-        ret = loadProperties(study, section->firstProperty, buffer, &PartHydro::useLeeway) && ret;
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::useLeeway) && ret;
     }
 
     if (IniFile::Section* section = ini.find("leeway low"))
     {
-        ret = loadProperties(study, section->firstProperty, buffer, &PartHydro::leewayLowerBound)
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::leewayLowerBound)
               && ret;
     }
 
     if (IniFile::Section* section = ini.find("leeway up"))
     {
-        ret = loadProperties(study, section->firstProperty, buffer, &PartHydro::leewayUpperBound)
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::leewayUpperBound)
               && ret;
     }
 
     if (IniFile::Section* section = ini.find("pumping efficiency"))
     {
-        ret = loadProperties(study, section->firstProperty, buffer, &PartHydro::pumpingEfficiency)
+        ret = loadProperties(study, section->firstProperty, path, &PartHydro::pumpingEfficiency)
               && ret;
     }
 
@@ -480,7 +473,7 @@ bool PartHydro::SaveToFolder(const AreaList& areas, const AnyString& folder)
         return false;
     }
 
-    String buffer;
+    Yuni::String buffer;
     buffer.clear() << folder << SEP << "common" << SEP << "capacity";
 
     struct AllSections
@@ -704,26 +697,21 @@ void PartHydro::copyFrom(const PartHydro& rhs)
     }
 }
 
-bool PartHydro::LoadDailyMaxEnergy(const AnyString& folder, const AnyString& areaid)
+bool PartHydro::LoadDailyMaxEnergy(const fs::path& folder, const std::string& areaid)
 {
-    YString filePath;
     Matrix<>::BufferType fileContent;
     bool ret = true;
 
-    filePath.clear() << folder << SEP << "common" << SEP << "capacity" << SEP
-                     << "maxDailyGenEnergy_" << areaid << ".txt";
-
-    ret = dailyNbHoursAtGenPmax.loadFromCSVFile(filePath,
+    fs::path genPath = folder / "common" / "capacity" / ("maxDailyGenEnergy_" + areaid + ".txt");
+    ret = dailyNbHoursAtGenPmax.loadFromCSVFile(genPath.string(),
                                                 1,
                                                 DAYS_PER_YEAR,
                                                 Matrix<>::optFixedSize,
                                                 &fileContent)
           && ret;
 
-    filePath.clear() << folder << SEP << "common" << SEP << "capacity" << SEP
-                     << "maxDailyPumpEnergy_" << areaid << ".txt";
-
-    ret = dailyNbHoursAtPumpPmax.loadFromCSVFile(filePath,
+    fs::path pumpPath = folder / "common" / "capacity" / ("maxDailyPumpEnergy_" + areaid + ".txt");
+    ret = dailyNbHoursAtPumpPmax.loadFromCSVFile(pumpPath.string(),
                                                  1,
                                                  DAYS_PER_YEAR,
                                                  Matrix<>::optFixedSize,
diff --git a/src/libs/antares/study/parts/hydro/prepro.cpp b/src/libs/antares/study/parts/hydro/prepro.cpp
index 13711759f4..945b65cf23 100644
--- a/src/libs/antares/study/parts/hydro/prepro.cpp
+++ b/src/libs/antares/study/parts/hydro/prepro.cpp
@@ -32,6 +32,8 @@
 using namespace Antares;
 using namespace Yuni;
 
+namespace fs = std::filesystem;
+
 #define SEP IO::Separator
 
 namespace Antares
@@ -46,7 +48,7 @@ static bool PreproHydroSaveSettings(PreproHydro* h, const char* filename)
     return ini.save(filename);
 }
 
-static bool PreproHydroLoadSettings(PreproHydro* h, const std::string& filename)
+static bool PreproHydroLoadSettings(PreproHydro* h, const fs::path& filename)
 {
     IniFile ini;
     IniFile::Section* s;
@@ -145,7 +147,7 @@ bool PreproHydro::saveToFolder(const AreaName& areaID, const char* folder)
     return false;
 }
 
-bool PreproHydro::loadFromFolder(Study& s, const AreaName& areaID, const std::string& folder)
+bool PreproHydro::loadFromFolder(Study& s, const std::string& areaID, const fs::path& folder)
 {
     enum
     {
@@ -153,15 +155,17 @@ bool PreproHydro::loadFromFolder(Study& s, const AreaName& areaID, const std::st
     };
 
     constexpr int maxNbOfLineToLoad = 12;
-
     data.resize(hydroPreproMax, 12, true);
-    String& buffer = s.bufferLoadingTS;
 
-    buffer.clear() << folder << SEP << areaID << SEP << "prepro.ini";
-    bool ret = PreproHydroLoadSettings(this, buffer);
+    fs::path preproPath = folder / areaID / "prepro.ini";
+    bool ret = PreproHydroLoadSettings(this, preproPath);
 
-    buffer.clear() << folder << SEP << areaID << SEP << "energy.txt";
-    ret = data.loadFromCSVFile(buffer, hydroPreproMax, maxNbOfLineToLoad, mtrxOption, &s.dataBuffer)
+    fs::path energyPath = folder / areaID / "energy.txt";
+    ret = data.loadFromCSVFile(energyPath.string(),
+                               hydroPreproMax,
+                               maxNbOfLineToLoad,
+                               mtrxOption,
+                               &s.dataBuffer)
           && ret;
 
     return ret;
diff --git a/src/libs/antares/study/parts/hydro/series.cpp b/src/libs/antares/study/parts/hydro/series.cpp
index 52a087b975..818fef9dc2 100644
--- a/src/libs/antares/study/parts/hydro/series.cpp
+++ b/src/libs/antares/study/parts/hydro/series.cpp
@@ -40,15 +40,14 @@ namespace Antares::Data
 {
 
 static bool loadTSfromFile(Matrix<double>& ts,
-                           const AreaName& areaID,
+                           const std::string& areaID,
                            const fs::path& folder,
                            const std::string& filename,
                            unsigned int height)
 {
-    YString filePath;
+    fs::path filePath = folder / areaID / filename;
     Matrix<>::BufferType fileContent;
-    filePath.clear() << folder << SEP << areaID << SEP << filename;
-    return ts.loadFromCSVFile(filePath, 1, height, &fileContent);
+    return ts.loadFromCSVFile(filePath.string(), 1, height, &fileContent);
 }
 
 static void ConvertDailyTSintoHourlyTS(const Matrix<double>::ColumnType& dailyColumn,
@@ -157,18 +156,23 @@ bool DataSeriesHydro::loadGenerationTS(const AreaName& areaID,
     return ret;
 }
 
-bool DataSeriesHydro::LoadMaxPower(const AreaName& areaID, const fs::path& folder)
+bool DataSeriesHydro::LoadMaxPower(const std::string& areaID, const fs::path& folder)
 {
     bool ret = true;
-    YString filepath;
     Matrix<>::BufferType fileContent;
 
-    filepath.clear() << folder << SEP << areaID << SEP << "maxHourlyGenPower.txt";
-    ret = maxHourlyGenPower.timeSeries.loadFromCSVFile(filepath, 1, HOURS_PER_YEAR, &fileContent)
+    fs::path filePath = folder / areaID / "maxHourlyGenPower.txt";
+    ret = maxHourlyGenPower.timeSeries.loadFromCSVFile(filePath.string(),
+                                                       1,
+                                                       HOURS_PER_YEAR,
+                                                       &fileContent)
           && ret;
 
-    filepath.clear() << folder << SEP << areaID << SEP << "maxHourlyPumpPower.txt";
-    ret = maxHourlyPumpPower.timeSeries.loadFromCSVFile(filepath, 1, HOURS_PER_YEAR, &fileContent)
+    filePath = folder / areaID / "maxHourlyPumpPower.txt";
+    ret = maxHourlyPumpPower.timeSeries.loadFromCSVFile(filePath.string(),
+                                                        1,
+                                                        HOURS_PER_YEAR,
+                                                        &fileContent)
           && ret;
 
     return ret;
diff --git a/src/libs/antares/study/parts/load/prepro.cpp b/src/libs/antares/study/parts/load/prepro.cpp
index 68ae63a322..b5a5342c82 100644
--- a/src/libs/antares/study/parts/load/prepro.cpp
+++ b/src/libs/antares/study/parts/load/prepro.cpp
@@ -38,7 +38,7 @@ Prepro::~Prepro()
 {
 }
 
-bool Prepro::loadFromFolder(const AnyString& folder)
+bool Prepro::loadFromFolder(const std::filesystem::path& folder)
 {
     return xcast.loadFromFolder(folder);
 }
diff --git a/src/libs/antares/study/parts/renewable/cluster.cpp b/src/libs/antares/study/parts/renewable/cluster.cpp
index 749ed53a57..0d87c28776 100644
--- a/src/libs/antares/study/parts/renewable/cluster.cpp
+++ b/src/libs/antares/study/parts/renewable/cluster.cpp
@@ -38,8 +38,6 @@
 using namespace Yuni;
 using namespace Antares;
 
-#define SEP IO::Separator
-
 namespace Antares::Data
 {
 Data::RenewableCluster::RenewableCluster(Area* parent):
diff --git a/src/libs/antares/study/parts/renewable/cluster_list.cpp b/src/libs/antares/study/parts/renewable/cluster_list.cpp
index aa1c915a75..5c8429d046 100644
--- a/src/libs/antares/study/parts/renewable/cluster_list.cpp
+++ b/src/libs/antares/study/parts/renewable/cluster_list.cpp
@@ -28,6 +28,8 @@
 
 using namespace Yuni;
 
+namespace fs = std::filesystem;
+
 namespace Antares::Data
 {
 
@@ -143,7 +145,7 @@ static bool ClusterLoadFromProperty(RenewableCluster& cluster, const IniFile::Pr
     return false;
 }
 
-static bool ClusterLoadFromSection(const AnyString& filename,
+static bool clusterLoadFromSection(const fs::path& filename,
                                    RenewableCluster& cluster,
                                    const IniFile::Section& section)
 {
@@ -176,7 +178,7 @@ static bool ClusterLoadFromSection(const AnyString& filename,
     return true;
 }
 
-bool RenewableClusterList::loadFromFolder(const AnyString& folder, Area* area)
+bool RenewableClusterList::loadFromFolder(const fs::path& folder, Area* area)
 {
     assert(area and "A parent area is required");
 
@@ -184,11 +186,10 @@ bool RenewableClusterList::loadFromFolder(const AnyString& folder, Area* area)
     logs.info() << "Loading renewable configuration for the area " << area->name;
 
     // Open the ini file
-    YString buffer;
-    buffer << folder << SEP << "list.ini";
+    fs::path filename = folder / "list.ini";
 
     IniFile ini;
-    if (ini.open(buffer, false))
+    if (ini.open(filename, false))
     {
         bool ret = true;
 
@@ -204,7 +205,7 @@ bool RenewableClusterList::loadFromFolder(const AnyString& folder, Area* area)
                 auto cluster = std::make_shared<RenewableCluster>(area);
 
                 // Load data of a renewable cluster from a ini file section
-                if (!ClusterLoadFromSection(buffer, *cluster, *section))
+                if (!clusterLoadFromSection(filename, *cluster, *section))
                 {
                     continue;
                 }
diff --git a/src/libs/antares/study/parts/short-term-storage/properties.cpp b/src/libs/antares/study/parts/short-term-storage/properties.cpp
index b4592105fe..28d6afe9a8 100644
--- a/src/libs/antares/study/parts/short-term-storage/properties.cpp
+++ b/src/libs/antares/study/parts/short-term-storage/properties.cpp
@@ -27,8 +27,6 @@
 
 #include <antares/logs/logs.h>
 
-#define SEP Yuni::IO::Separator
-
 namespace Antares::Data::ShortTermStorage
 {
 
diff --git a/src/libs/antares/study/parts/solar/prepro.cpp b/src/libs/antares/study/parts/solar/prepro.cpp
index e11b4e00ea..0e3af8f016 100644
--- a/src/libs/antares/study/parts/solar/prepro.cpp
+++ b/src/libs/antares/study/parts/solar/prepro.cpp
@@ -43,7 +43,7 @@ Prepro::~Prepro()
 {
 }
 
-bool Prepro::loadFromFolder(const AnyString& folder)
+bool Prepro::loadFromFolder(const std::filesystem::path& folder)
 {
     return xcast.loadFromFolder(folder);
 }
diff --git a/src/libs/antares/study/parts/thermal/cluster.cpp b/src/libs/antares/study/parts/thermal/cluster.cpp
index 9198bc1ec6..3070518f05 100644
--- a/src/libs/antares/study/parts/thermal/cluster.cpp
+++ b/src/libs/antares/study/parts/thermal/cluster.cpp
@@ -42,8 +42,6 @@ using namespace Antares;
 
 #define THERMALAGGREGATELIST_INITIAL_CAPACITY 10
 
-#define SEP IO::Separator
-
 namespace Yuni::Extension::CString
 {
 bool Into<Antares::Data::StatisticalLaw>::Perform(AnyString string, TargetType& out)
diff --git a/src/libs/antares/study/parts/wind/prepro.cpp b/src/libs/antares/study/parts/wind/prepro.cpp
index f631a5db81..fd449e61a1 100644
--- a/src/libs/antares/study/parts/wind/prepro.cpp
+++ b/src/libs/antares/study/parts/wind/prepro.cpp
@@ -21,17 +21,9 @@
 
 #include "antares/study/parts/wind/prepro.h"
 
-#include <yuni/yuni.h>
-#include <yuni/io/directory.h>
-
 #include <antares/logs/logs.h>
 #include "antares/study/study.h"
 
-using namespace Yuni;
-using namespace Antares;
-
-#define SEP IO::Separator
-
 namespace Antares::Data::Wind
 {
 Prepro::Prepro():
@@ -43,7 +35,7 @@ Prepro::~Prepro()
 {
 }
 
-bool Prepro::loadFromFolder(const AnyString& folder)
+bool Prepro::loadFromFolder(const std::filesystem::path& folder)
 {
     return xcast.loadFromFolder(folder);
 }
diff --git a/src/libs/antares/study/scenario-builder/sets.cpp b/src/libs/antares/study/scenario-builder/sets.cpp
index 76dbcb9166..78cdffb3d9 100644
--- a/src/libs/antares/study/scenario-builder/sets.cpp
+++ b/src/libs/antares/study/scenario-builder/sets.cpp
@@ -26,8 +26,6 @@
 
 using namespace Yuni;
 
-#define SEP IO::Separator
-
 namespace Antares::Data::ScenarioBuilder
 {
 Sets::Sets():
diff --git a/src/libs/antares/study/study.cpp b/src/libs/antares/study/study.cpp
index 1b5493e750..cd20e14348 100644
--- a/src/libs/antares/study/study.cpp
+++ b/src/libs/antares/study/study.cpp
@@ -655,6 +655,7 @@ Area* Study::areaAdd(const AreaName& name, bool updateMode)
     return area;
 }
 
+// TODO VP: delete with GUI
 bool Study::areaDelete(Area* area)
 {
     if (not area)
@@ -702,6 +703,7 @@ bool Study::areaDelete(Area* area)
     return true;
 }
 
+// TODO VP: delete with GUI
 void Study::areaDelete(Area::Vector& arealist)
 {
     if (arealist.empty())
@@ -764,6 +766,7 @@ void Study::areaDelete(Area::Vector& arealist)
     }
 }
 
+// TODO VP: delete with GUI
 bool Study::linkDelete(AreaLink* lnk)
 {
     // Impossible to find the attached area
@@ -789,6 +792,7 @@ bool Study::linkDelete(AreaLink* lnk)
     return true;
 }
 
+// TODO VP: delete with GUI
 bool Study::areaRename(Area* area, AreaName newName)
 {
     // A name must not be empty
@@ -871,6 +875,7 @@ bool Study::areaRename(Area* area, AreaName newName)
     return ret;
 }
 
+// TODO VP: delete with GUI
 bool Study::clusterRename(Cluster* cluster, ClusterName newName)
 {
     // A name must not be empty
diff --git a/src/libs/antares/study/study.importprepro.cpp b/src/libs/antares/study/study.importprepro.cpp
index 69a0fe058b..3cf520c5eb 100644
--- a/src/libs/antares/study/study.importprepro.cpp
+++ b/src/libs/antares/study/study.importprepro.cpp
@@ -29,6 +29,8 @@ using namespace Yuni;
 
 namespace Antares::Data
 {
+
+// TODO VP: remove with time series TS generation before solver execution
 bool Study::importTimeseriesIntoInput()
 {
     // Special case: some thermal clusters may force TS generation
diff --git a/src/libs/antares/study/xcast/xcast.cpp b/src/libs/antares/study/xcast/xcast.cpp
index 0f2e05956b..d8f055775a 100644
--- a/src/libs/antares/study/xcast/xcast.cpp
+++ b/src/libs/antares/study/xcast/xcast.cpp
@@ -30,6 +30,8 @@
 
 using namespace Yuni;
 
+namespace fs = std::filesystem;
+
 #define SEP IO::Separator
 
 namespace Antares::Data
@@ -181,7 +183,7 @@ void XCast::resetToDefaultValues()
     useTranslation = tsTranslationNone;
 }
 
-bool XCast::loadFromFolder(const AnyString& folder)
+bool XCast::loadFromFolder(const fs::path& folder)
 {
     // reset
     distribution = dtBeta;
@@ -196,13 +198,13 @@ bool XCast::loadFromFolder(const AnyString& folder)
     // Return value
     bool ret = true;
     // Settings
-    buffer.clear() << folder << SEP << "settings.ini";
+    fs::path settingsPath = folder / "settings.ini";
 
     IniFile ini;
-    if (ini.open(buffer))
+    if (ini.open(settingsPath))
     {
         ini.each(
-          [this, &buffer](const IniFile::Section& section)
+          [this, &settingsPath](const IniFile::Section& section)
           {
               // For each property
               if (section.name == "general")
@@ -217,7 +219,7 @@ bool XCast::loadFromFolder(const AnyString& folder)
                           distribution = StringToDistribution(p->value);
                           if (distribution == dtNone)
                           {
-                              logs.warning() << buffer
+                              logs.warning() << settingsPath
                                              << ": Invalid probability distribution. The beta "
                                                 "distribution will be used";
                               distribution = dtBeta;
@@ -230,7 +232,7 @@ bool XCast::loadFromFolder(const AnyString& folder)
                           if (capacity < 0.)
                           {
                               logs.warning()
-                                << buffer << ": The capacity can not be a negative value";
+                                << settingsPath << ": The capacity can not be a negative value";
                               capacity = 0.;
                           }
                           continue;
@@ -246,18 +248,18 @@ bool XCast::loadFromFolder(const AnyString& folder)
                           continue;
                       }
 
-                      logs.warning() << buffer << ": Unknown property '" << p->key << "'";
+                      logs.warning() << settingsPath << ": Unknown property '" << p->key << "'";
                   }
               }
               else
               {
-                  logs.warning() << buffer << ": unknown section '" << section.name << "'";
+                  logs.warning() << settingsPath << ": unknown section '" << section.name << "'";
               }
           });
     }
     else
     {
-        logs.error() << "I/O Error: unable to open '" << buffer << "'";
+        logs.error() << "I/O Error: unable to open '" << settingsPath << "'";
         ret = false;
     }
 
@@ -265,22 +267,22 @@ bool XCast::loadFromFolder(const AnyString& folder)
     // fix invalid data
 
     // Coefficients
-    buffer.clear() << folder << SEP << "data.txt";
+    fs::path p = folder / "data.txt";
 
     // Performing normal loading
-    ret = data.loadFromCSVFile(buffer, (uint)dataMax, 12, Matrix<>::optFixedSize, &readBuffer)
+    ret = data.loadFromCSVFile(p.string(), (uint)dataMax, 12, Matrix<>::optFixedSize, &readBuffer)
           && ret;
 
     // K
-    buffer.clear() << folder << SEP << "k.txt";
-    ret = K.loadFromCSVFile(buffer, 12, 24, Matrix<>::optFixedSize, &readBuffer) && ret;
+    p = folder / "k.txt";
+    ret = K.loadFromCSVFile(p.string(), 12, 24, Matrix<>::optFixedSize, &readBuffer) && ret;
 
     uint opts = Matrix<>::optNone;
 
     // Time-series translation
-    buffer.clear() << folder << SEP << "translation.txt";
+    p = folder / "translation.txt";
 
-    ret = translation.loadFromCSVFile(buffer, 1, HOURS_PER_YEAR, opts, &readBuffer) && ret;
+    ret = translation.loadFromCSVFile(p.string(), 1, HOURS_PER_YEAR, opts, &readBuffer) && ret;
     if (!JIT::usedFromGUI)
     {
         if (translation.empty())
@@ -303,8 +305,9 @@ bool XCast::loadFromFolder(const AnyString& folder)
     opts = Matrix<>::optNone;
 
     // Transfer function
-    buffer.clear() << folder << SEP << "conversion.txt";
-    ret = conversion.loadFromCSVFile(buffer, 3, 2, opts, &readBuffer) && ret;
+    p = folder / "conversion.txt";
+
+    ret = conversion.loadFromCSVFile(p.string(), 3, 2, opts, &readBuffer) && ret;
     if (not JIT::enabled)
     {
         if (conversion.width >= 3 && conversion.width <= conversionMaxPoints)
@@ -318,7 +321,7 @@ bool XCast::loadFromFolder(const AnyString& folder)
             {
                 if (conversion[x][0] <= -1.0e+19 || conversion[x][0] >= +1.0e+19)
                 {
-                    logs.error() << "TS-Generator: Conversion: Invalid range: " << buffer;
+                    logs.error() << "TS-Generator: Conversion: Invalid range: " << p;
                 }
             }
             conversion[conversion.width - 1][0]
@@ -327,7 +330,7 @@ bool XCast::loadFromFolder(const AnyString& folder)
         }
         else
         {
-            logs.warning() << "Invalid transfer function: '" << buffer << "'";
+            logs.warning() << "Invalid transfer function: '" << p << "'";
             resetTransferFunction();
             useConversion = false;
         }
diff --git a/src/libs/antares/writer/immediate_file_writer.cpp b/src/libs/antares/writer/immediate_file_writer.cpp
index 3554598de3..40a90ec067 100644
--- a/src/libs/antares/writer/immediate_file_writer.cpp
+++ b/src/libs/antares/writer/immediate_file_writer.cpp
@@ -68,7 +68,7 @@ void ImmediateFileResultWriter::addEntryFromBuffer(const std::string& entryPath,
 }
 
 // Write to file immediately, creating directories if needed
-void ImmediateFileResultWriter::addEntryFromBuffer(const std::string& entryPath,
+void ImmediateFileResultWriter::addEntryFromBuffer(const fs::path& entryPath,
                                                    std::string& entryContent)
 {
     fs::path output;
@@ -121,7 +121,7 @@ void NullResultWriter::addEntryFromBuffer(const std::string&, Yuni::Clob&)
 {
 }
 
-void NullResultWriter::addEntryFromBuffer(const std::string&, std::string&)
+void NullResultWriter::addEntryFromBuffer(const fs::path&, std::string&)
 {
 }
 
diff --git a/src/libs/antares/writer/in_memory_writer.cpp b/src/libs/antares/writer/in_memory_writer.cpp
index 182fee1927..2c5e282fcb 100644
--- a/src/libs/antares/writer/in_memory_writer.cpp
+++ b/src/libs/antares/writer/in_memory_writer.cpp
@@ -75,9 +75,9 @@ void InMemoryWriter::addEntryFromBuffer(const std::string& entryPath, Yuni::Clob
     addToMap(pEntries, entryPath, entryContent, pMapMutex, pDurationCollector);
 }
 
-void InMemoryWriter::addEntryFromBuffer(const std::string& entryPath, std::string& entryContent)
+void InMemoryWriter::addEntryFromBuffer(const fs::path& entryPath, std::string& entryContent)
 {
-    addToMap(pEntries, entryPath, entryContent, pMapMutex, pDurationCollector);
+    addToMap(pEntries, entryPath.string(), entryContent, pMapMutex, pDurationCollector);
 }
 
 void InMemoryWriter::addEntryFromFile(const fs::path& entryPath, const fs::path& filePath)
diff --git a/src/libs/antares/writer/include/antares/writer/i_writer.h b/src/libs/antares/writer/include/antares/writer/i_writer.h
index 40fd3799ee..473ae6daa4 100644
--- a/src/libs/antares/writer/include/antares/writer/i_writer.h
+++ b/src/libs/antares/writer/include/antares/writer/i_writer.h
@@ -35,7 +35,9 @@ class IResultWriter
 public:
     using Ptr = std::shared_ptr<IResultWriter>;
     virtual void addEntryFromBuffer(const std::string& entryPath, Yuni::Clob& entryContent) = 0;
-    virtual void addEntryFromBuffer(const std::string& entryPath, std::string& entryContent) = 0;
+    virtual void addEntryFromBuffer(const std::filesystem::path& entryPath,
+                                    std::string& entryContent)
+      = 0;
     virtual void addEntryFromFile(const std::filesystem::path& entryPath,
                                   const std::filesystem::path& filePath)
       = 0;
@@ -52,7 +54,7 @@ class IResultWriter
 class NullResultWriter: public Solver::IResultWriter
 {
     void addEntryFromBuffer(const std::string&, Yuni::Clob&) override;
-    void addEntryFromBuffer(const std::string&, std::string&) override;
+    void addEntryFromBuffer(const std::filesystem::path&, std::string&) override;
     void addEntryFromFile(const std::filesystem::path&, const std::filesystem::path&) override;
     void flush() override;
     bool needsTheJobQueue() const override;
diff --git a/src/libs/antares/writer/include/antares/writer/in_memory_writer.h b/src/libs/antares/writer/include/antares/writer/in_memory_writer.h
index 9fc465a83f..e5be52be24 100644
--- a/src/libs/antares/writer/include/antares/writer/in_memory_writer.h
+++ b/src/libs/antares/writer/include/antares/writer/in_memory_writer.h
@@ -38,7 +38,8 @@ class InMemoryWriter: public IResultWriter
     explicit InMemoryWriter(Benchmarking::DurationCollector& duration_collector);
     virtual ~InMemoryWriter();
     void addEntryFromBuffer(const std::string& entryPath, Yuni::Clob& entryContent) override;
-    void addEntryFromBuffer(const std::string& entryPath, std::string& entryContent) override;
+    void addEntryFromBuffer(const std::filesystem::path& entryPath,
+                            std::string& entryContent) override;
     void addEntryFromFile(const std::filesystem::path& entryPath,
                           const std::filesystem::path& filePath) override;
     void flush() override;
diff --git a/src/libs/antares/writer/private/immediate_file_writer.h b/src/libs/antares/writer/private/immediate_file_writer.h
index 1711bbfe96..1c340ee066 100644
--- a/src/libs/antares/writer/private/immediate_file_writer.h
+++ b/src/libs/antares/writer/private/immediate_file_writer.h
@@ -36,7 +36,8 @@ class ImmediateFileResultWriter: public IResultWriter
     virtual ~ImmediateFileResultWriter();
     // Write to file immediately, creating directories if needed
     void addEntryFromBuffer(const std::string& entryPath, Yuni::Clob& entryContent) override;
-    void addEntryFromBuffer(const std::string& entryPath, std::string& entryContent) override;
+    void addEntryFromBuffer(const std::filesystem::path& entryPath,
+                            std::string& entryContent) override;
     void addEntryFromFile(const std::filesystem::path& entryPath,
                           const std::filesystem::path& filePath) override;
     void flush() override;
diff --git a/src/libs/antares/writer/private/zip_writer.h b/src/libs/antares/writer/private/zip_writer.h
index f24c353018..948c3aaa04 100644
--- a/src/libs/antares/writer/private/zip_writer.h
+++ b/src/libs/antares/writer/private/zip_writer.h
@@ -82,7 +82,8 @@ class ZipWriter: public IResultWriter
               Benchmarking::DurationCollector& duration_collector);
     virtual ~ZipWriter();
     void addEntryFromBuffer(const std::string& entryPath, Yuni::Clob& entryContent) override;
-    void addEntryFromBuffer(const std::string& entryPath, std::string& entryContent) override;
+    void addEntryFromBuffer(const std::filesystem::path& entryPath,
+                            std::string& entryContent) override;
     void addEntryFromFile(const std::filesystem::path& entryPath,
                           const std::filesystem::path& filePath) override;
     void flush() override;
@@ -109,7 +110,8 @@ class ZipWriter: public IResultWriter
 
 private:
     template<class ContentType>
-    void addEntryFromBufferHelper(const std::string& entryPath, ContentType& entryContent);
+    void addEntryFromBufferHelper(const std::filesystem::path& entryPath,
+                                  ContentType& entryContent);
 };
 } // namespace Antares::Solver
 
diff --git a/src/libs/antares/writer/private/zip_writer.hxx b/src/libs/antares/writer/private/zip_writer.hxx
index a435768b5a..2bc13ff316 100644
--- a/src/libs/antares/writer/private/zip_writer.hxx
+++ b/src/libs/antares/writer/private/zip_writer.hxx
@@ -27,7 +27,8 @@
 namespace Antares::Solver
 {
 template<class ContentType>
-void ZipWriter::addEntryFromBufferHelper(const std::string& entryPath, ContentType& entryContent)
+void ZipWriter::addEntryFromBufferHelper(const std::filesystem::path& entryPath,
+                                         ContentType& entryContent)
 {
     if (pState != ZipState::can_receive_data)
     {
@@ -37,7 +38,7 @@ void ZipWriter::addEntryFromBufferHelper(const std::string& entryPath, ContentTy
     EnsureQueueStartedIfNeeded ensureQueue(this, pQueueService);
     pendingTasks_.add(Concurrency::AddTask(
       *pQueueService,
-      ZipWriteJob<ContentType>(*this, entryPath, entryContent, pDurationCollector),
+      ZipWriteJob<ContentType>(*this, entryPath.string(), entryContent, pDurationCollector),
       Yuni::Job::priorityLow));
 }
 
diff --git a/src/libs/antares/writer/zip_writer.cpp b/src/libs/antares/writer/zip_writer.cpp
index 007524377a..008f7fdd9c 100644
--- a/src/libs/antares/writer/zip_writer.cpp
+++ b/src/libs/antares/writer/zip_writer.cpp
@@ -157,7 +157,7 @@ void ZipWriter::addEntryFromBuffer(const std::string& entryPath, Yuni::Clob& ent
     addEntryFromBufferHelper<Yuni::Clob>(entryPath, entryContent);
 }
 
-void ZipWriter::addEntryFromBuffer(const std::string& entryPath, std::string& entryContent)
+void ZipWriter::addEntryFromBuffer(const fs::path& entryPath, std::string& entryContent)
 {
     addEntryFromBufferHelper<std::string>(entryPath, entryContent);
 }
diff --git a/src/solver/constraints-builder/load.cpp b/src/solver/constraints-builder/load.cpp
index 73beec49c1..36868da082 100644
--- a/src/solver/constraints-builder/load.cpp
+++ b/src/solver/constraints-builder/load.cpp
@@ -18,17 +18,10 @@
  * You should have received a copy of the Mozilla Public Licence 2.0
  * along with Antares_Simulator. If not, see <https://opensource.org/license/mpl-2-0/>.
  */
-#include <yuni/io/file.h>
-
-#include <antares/inifile/inifile.h>
 #include "antares/config/config.h"
 #include "antares/solver/constraints-builder/cbuilder.h"
 #include "antares/study/area/constants.h"
 
-using namespace Yuni;
-
-#define SEP Yuni::IO::Separator
-
 namespace Antares
 {
 bool CBuilder::completeFromStudy()
diff --git a/src/solver/hydro/management/daily.cpp b/src/solver/hydro/management/daily.cpp
index 8bf59df763..ee11407f1f 100644
--- a/src/solver/hydro/management/daily.cpp
+++ b/src/solver/hydro/management/daily.cpp
@@ -141,7 +141,7 @@ struct DebugData
             buffer << '\n';
         }
         auto buffer_str = buffer.str();
-        pWriter.addEntryFromBuffer(path.string(), buffer_str);
+        pWriter.addEntryFromBuffer(path, buffer_str);
     }
 
     void writeDailyDebugData(const Date::Calendar& calendar,
@@ -210,7 +210,7 @@ struct DebugData
             }
         }
         auto buffer_str = buffer.str();
-        pWriter.addEntryFromBuffer(path.string(), buffer_str);
+        pWriter.addEntryFromBuffer(path, buffer_str);
     }
 };
 
diff --git a/src/solver/hydro/management/monthly.cpp b/src/solver/hydro/management/monthly.cpp
index 62658e277d..0b004a11ef 100644
--- a/src/solver/hydro/management/monthly.cpp
+++ b/src/solver/hydro/management/monthly.cpp
@@ -304,7 +304,7 @@ void HydroManagement::prepareMonthlyOptimalGenerations(const double* random_rese
                   buffer << '\n';
               }
               auto content = buffer.str();
-              resultWriter_.addEntryFromBuffer(path.string(), content);
+              resultWriter_.addEntryFromBuffer(path, content);
           }
           indexArea++;
       });
diff --git a/src/solver/main.cpp b/src/solver/main.cpp
index a0f012a9ef..3840446c73 100644
--- a/src/solver/main.cpp
+++ b/src/solver/main.cpp
@@ -28,9 +28,6 @@
 #include "antares/application/application.h"
 
 using namespace Antares;
-using namespace Yuni;
-
-#define SEP Yuni::IO::Separator
 
 namespace
 {
diff --git a/src/solver/simulation/TimeSeriesNumbersWriter.cpp b/src/solver/simulation/TimeSeriesNumbersWriter.cpp
index 09122c32e0..d35dd5fdc5 100644
--- a/src/solver/simulation/TimeSeriesNumbersWriter.cpp
+++ b/src/solver/simulation/TimeSeriesNumbersWriter.cpp
@@ -48,7 +48,7 @@ static void genericStoreTimeseriesNumbers(Solver::IResultWriter& writer,
 
     std::string buffer;
     timeseriesNumbers.saveToBuffer(buffer);
-    writer.addEntryFromBuffer(path.string(), buffer);
+    writer.addEntryFromBuffer(path, buffer);
 }
 
 void BindingConstraintsTimeSeriesNumbersWriter::write(
diff --git a/src/solver/simulation/opt_time_writer.cpp b/src/solver/simulation/opt_time_writer.cpp
index a09f3feaa8..8ea4091a26 100644
--- a/src/solver/simulation/opt_time_writer.cpp
+++ b/src/solver/simulation/opt_time_writer.cpp
@@ -47,5 +47,5 @@ void OptimizationStatisticsWriter::finalize()
     const path filename = path("optimization") / "week-by-week"
                           / ("year_" + std::to_string(pYear) + ".txt");
     std::string s = pBuffer.str();
-    pWriter.addEntryFromBuffer(filename.string(), s);
+    pWriter.addEntryFromBuffer(filename, s);
 }
diff --git a/src/solver/simulation/solver_utils.cpp b/src/solver/simulation/solver_utils.cpp
index 76f5fc0ce3..401aa3db68 100644
--- a/src/solver/simulation/solver_utils.cpp
+++ b/src/solver/simulation/solver_utils.cpp
@@ -22,21 +22,18 @@
 #include "antares/solver/simulation/solver_utils.h"
 
 #include <cmath>
+#include <filesystem>
 #include <iomanip>
 #include <iostream>
 #include <limits>
 #include <sstream>
 
-#include <yuni/io/file.h>
-
-#define SEP Yuni::IO::Separator
+namespace fs = std::filesystem;
 
 static const std::string systemCostFilename = "annualSystemCost.txt";
 static const std::string criterionsCostsFilename = "checkIntegrity.txt";
-static const std::string optimizationTimeFilename = std::string("optimization") + SEP
-                                                    + "solve-durations.txt";
-static const std::string updateTimeFilename = std::string("optimization") + SEP
-                                              + "update-durations.txt";
+static const fs::path optimizationTimeFilename = fs::path("optimization") / "solve-durations.txt";
+static const fs::path updateTimeFilename = fs::path("optimization") / "update-durations.txt";
 
 static std::ostream& toScientific(std::ostream& os)
 {
diff --git a/src/solver/ts-generator/hydro.cpp b/src/solver/ts-generator/hydro.cpp
index dd5af1a25e..966625aa81 100644
--- a/src/solver/ts-generator/hydro.cpp
+++ b/src/solver/ts-generator/hydro.cpp
@@ -30,7 +30,7 @@
 
 using namespace Antares;
 
-#define SEP Yuni::IO::Separator
+namespace fs = std::filesystem;
 
 #define EPSILON ((double)1.0e-9)
 
@@ -281,26 +281,22 @@ bool GenerateHydroTimeSeries(Data::Study& study, uint currentYear, Solver::IResu
         {
             logs.info() << "Archiving the hydro time-series";
             study.areas.each(
-              [&study, &currentYear, &writer, &progression](const Data::Area& area)
+              [&currentYear, &writer, &progression](const Data::Area& area)
               {
                   const int precision = 0;
-                  Yuni::String output;
-                  study.buffer.clear() << "ts-generator" << SEP << "hydro" << SEP << "mc-"
-                                       << currentYear << SEP << area.id;
-
-                  {
-                      std::string buffer;
-                      area.hydro.series->ror.timeSeries.saveToBuffer(buffer, precision);
-                      output.clear() << study.buffer << SEP << "ror.txt";
-                      writer.addEntryFromBuffer(output.c_str(), buffer);
-                  }
-
-                  {
-                      std::string buffer;
-                      area.hydro.series->storage.timeSeries.saveToBuffer(buffer, precision);
-                      output.clear() << study.buffer << SEP << "storage.txt";
-                      writer.addEntryFromBuffer(output.c_str(), buffer);
-                  }
+                  std::string mcYear = "mc-" + currentYear;
+                  fs::path outputFolder = fs::path("ts-generator") / "hydro" / mcYear
+                                          / area.id.to<std::string>();
+
+                  std::string buffer;
+                  area.hydro.series->ror.timeSeries.saveToBuffer(buffer, precision);
+                  fs::path outputFile = outputFolder / "ror.txt";
+                  writer.addEntryFromBuffer(outputFile, buffer);
+
+                  area.hydro.series->storage.timeSeries.saveToBuffer(buffer, precision);
+                  outputFile = outputFolder / "storage.txt";
+                  writer.addEntryFromBuffer(outputFile, buffer);
+
                   ++progression;
               });
         }
diff --git a/src/solver/ts-generator/prepro.cpp b/src/solver/ts-generator/prepro.cpp
index b26faefb50..04cc371b8a 100644
--- a/src/solver/ts-generator/prepro.cpp
+++ b/src/solver/ts-generator/prepro.cpp
@@ -20,18 +20,11 @@
 */
 
 #include <yuni/yuni.h>
-#include <yuni/core/math.h>
-#include <yuni/io/directory.h>
-#include <yuni/io/file.h>
 
 #include <antares/logs/logs.h>
 #include <antares/solver/ts-generator/prepro.h>
 #include "antares/study/study.h"
 
-using namespace Yuni;
-
-#define SEP IO::Separator
-
 namespace Antares::Data
 {
 PreproAvailability::PreproAvailability(const YString& id, unsigned int unitCount):
@@ -50,10 +43,10 @@ void PreproAvailability::copyFrom(const PreproAvailability& rhs)
 
 bool PreproAvailability::saveToFolder(const AnyString& folder) const
 {
-    if (IO::Directory::Create(folder))
+    if (Yuni::IO::Directory::Create(folder))
     {
-        String buffer;
-        buffer.clear() << folder << SEP << "data.txt";
+        Yuni::String buffer;
+        buffer.clear() << folder << Yuni::IO::Separator << "data.txt";
         return data.saveToCSVFile(buffer, /*decimal*/ 6);
     }
     return false;
diff --git a/src/solver/ts-generator/xcast/xcast.cpp b/src/solver/ts-generator/xcast/xcast.cpp
index 3f42862cb5..7af0d35da5 100644
--- a/src/solver/ts-generator/xcast/xcast.cpp
+++ b/src/solver/ts-generator/xcast/xcast.cpp
@@ -25,16 +25,12 @@
 #include <sstream>
 #include <string>
 
-#include <yuni/yuni.h>
-
 #include <antares/antares/fatal-error.h>
 #include <antares/logs/logs.h>
 #include <antares/study/study.h>
 #include "antares/solver/ts-generator/xcast/predicate.hxx"
 
-using namespace Yuni;
-
-#define SEP (IO::Separator)
+namespace fs = std::filesystem;
 
 namespace Antares::TSGenerator::XCast
 {
@@ -71,20 +67,18 @@ void XCast::exportTimeSeriesToTheOutput(Progression::Task& progression, Predicat
         logs.info() << "Exporting " << predicate.timeSeriesName()
                     << " time-series into the output (year:" << year << ')';
 
-        String output;
-        String filename;
-
-        output << "ts-generator" << SEP << predicate.timeSeriesName() << SEP << "mc-" << year;
-        filename.reserve(output.size() + 80);
+        fs::path output = "ts-generator";
+        output /= fs::path(predicate.timeSeriesName()) / std::string("mc-" + year);
 
         study.areas.each(
-          [this, &filename, &progression, &predicate, &output](Data::Area& area)
+          [this, &progression, &predicate, &output](Data::Area& area)
           {
-              filename.clear() << output << SEP << area.id << ".txt";
+              std::string areaId = area.id + "txt";
+              fs::path filename = output / areaId;
               std::string buffer;
               predicate.matrix(area).saveToBuffer(buffer);
 
-              pWriter.addEntryFromBuffer(filename.c_str(), buffer);
+              pWriter.addEntryFromBuffer(filename, buffer);
 
               ++progression;
           });
diff --git a/src/solver/variable/include/antares/solver/variable/container.hxx b/src/solver/variable/include/antares/solver/variable/container.hxx
index 0f9559b3a2..fe62b761f9 100644
--- a/src/solver/variable/include/antares/solver/variable/container.hxx
+++ b/src/solver/variable/include/antares/solver/variable/container.hxx
@@ -23,13 +23,10 @@
 
 #include <memory>
 
-#include <yuni/yuni.h>
 #include <yuni/core/static/types.h>
 
 #include "antares/solver/variable/surveyresults/reportbuilder.hxx"
 
-#define SEP Yuni::IO::Separator
-
 namespace Antares
 {
 namespace Solver
@@ -254,7 +251,8 @@ void List<NextT>::buildSurveyReport(SurveyResults& results,
 
     // The new filename
     results.data.filename.clear();
-    results.data.filename << results.data.output << SEP;
+    results.data.filename << std::filesystem::path(static_cast<std::string>(results.data.output))
+                               / "";
     Category::FileLevelToStream(results.data.filename, fileLevel);
     results.data.filename << '-';
     Category::PrecisionLevelToStream(results.data.filename, precision);
@@ -283,7 +281,8 @@ void List<NextT>::buildAnnualSurveyReport(SurveyResults& results,
 
     // The new filename
     results.data.filename.clear();
-    results.data.filename << results.data.output << SEP;
+    results.data.filename << std::filesystem::path(static_cast<std::string>(results.data.output))
+                               / "";
     Category::FileLevelToStream(results.data.filename, fileLevel);
     results.data.filename << '-';
     Category::PrecisionLevelToStream(results.data.filename, precision);
diff --git a/src/solver/variable/include/antares/solver/variable/surveyresults/reportbuilder.hxx b/src/solver/variable/include/antares/solver/variable/surveyresults/reportbuilder.hxx
index 6354169b96..11a9277dab 100644
--- a/src/solver/variable/include/antares/solver/variable/surveyresults/reportbuilder.hxx
+++ b/src/solver/variable/include/antares/solver/variable/surveyresults/reportbuilder.hxx
@@ -36,8 +36,6 @@
 #include "../info.h"
 #include "../surveyresults.h"
 
-#define SEP Yuni::IO::Separator
-
 namespace Antares
 {
 namespace Solver
@@ -272,8 +270,10 @@ public:
         }
         // THIS FILE IS DEPRECATED !!!
         YString digestFileName;
-        digestFileName << results.data.originalOutput << SEP << "grid" << SEP << "digest.txt";
-        writer.addEntryFromBuffer(digestFileName.c_str(), digestBuffer);
+        std::filesystem::path path = static_cast<std::string>(results.data.originalOutput);
+        path /= "grid";
+        path /= "digest.txt";
+        writer.addEntryFromBuffer(path, digestBuffer);
     }
 
 private:
@@ -320,9 +320,11 @@ private:
             {
                 logs.info() << "Exporting results : " << area.name;
                 // The new output
-                results.data.output.clear();
-                results.data.output << results.data.originalOutput << SEP << "areas" << SEP
-                                    << area.id;
+                std::filesystem::path path = static_cast<std::string>(results.data.originalOutput);
+                path /= "areas";
+                path /= area.id.to<std::string>();
+
+                results.data.output = path.string();
                 SurveyReportBuilderFile<GlobalT, NextT, CDataLevel>::Run(list, results, numSpace);
             }
 
@@ -354,9 +356,11 @@ private:
 
                 logs.info() << "Exporting results : " << area.name << " :: " << cluster->name();
                 // The new output
-                results.data.output.clear();
-                results.data.output << results.data.originalOutput << SEP << "areas" << SEP
-                                    << area.id << SEP << "thermal" << SEP << cluster->id();
+                std::filesystem::path path = static_cast<std::string>(results.data.originalOutput);
+                path /= std::filesystem::path("areas") / area.id.to<std::string>() / "thermal"
+                        / cluster->id();
+
+                results.data.output = path.string();
 
                 SurveyReportBuilderFile<GlobalT, NextT, CDataLevel>::Run(list, results, numSpace);
             }
@@ -405,9 +409,14 @@ private:
                     Antares::logs.info() << "Exporting results : " << area.name << " - "
                                          << results.data.link->with->name;
                     // The new output
-                    results.data.output.clear();
-                    results.data.output << results.data.originalOutput << SEP << "links" << SEP
-                                        << area.id << " - " << results.data.link->with->id;
+                    std::filesystem::path path = static_cast<std::string>(
+                      results.data.originalOutput);
+                    std::string areaId = static_cast<std::string>(area.id) + " - "
+                                         + results.data.link->with->id;
+                    path /= std::filesystem::path("links") / areaId;
+
+                    results.data.output = path.string();
+
                     SurveyReportBuilderFile<GlobalT, NextT, CDataLevel>::Run(list,
                                                                              results,
                                                                              numSpace);
@@ -449,11 +458,13 @@ private:
 
             logs.info() << "Exporting results : " << sets.caption(i);
             // The new output
-            results.data.output.clear();
-            results.data.output << results.data.originalOutput << SEP << "areas" << SEP << "@ "
-                                << sets.nameByIndex(i);
+            std::filesystem::path path = static_cast<std::string>(results.data.originalOutput);
+            std::string setId = "@ " + sets.nameByIndex(i);
+            path /= std::filesystem::path("areas") / setId;
 
+            results.data.output = path.string();
             results.data.setOfAreasIndex = indx++;
+
             SurveyReportBuilderFile<GlobalT, NextT, CDataLevel>::Run(list, results, numSpace);
         }
     }
@@ -469,8 +480,10 @@ private:
         {
             logs.info() << "Exporting results : binding constraints";
             // The new output
-            results.data.output.clear();
-            results.data.output << results.data.originalOutput << SEP << "binding_constraints";
+            std::filesystem::path path = static_cast<std::string>(results.data.originalOutput);
+            path /= "binding_constraints";
+
+            results.data.output = path.string();
             SurveyReportBuilderFile<GlobalT, NextT, CDataLevel>::Run(list, results, numSpace);
         }
     }
@@ -496,7 +509,4 @@ public:
 } // namespace Solver
 } // namespace Antares
 
-// cleanup
-#undef SEP
-
 #endif // __SOLVER_VARIABLE_SURVEYRESULTS_REPORT_BUILDER_HXX__
diff --git a/src/solver/variable/surveyresults/surveyresults.cpp b/src/solver/variable/surveyresults/surveyresults.cpp
index 8df87678e4..6a89d2cb14 100644
--- a/src/solver/variable/surveyresults/surveyresults.cpp
+++ b/src/solver/variable/surveyresults/surveyresults.cpp
@@ -31,11 +31,8 @@
 #include <antares/study/study.h>
 #include <antares/utils/utils.h>
 
-using namespace Yuni;
 using namespace Antares;
 
-#define SEP IO::Separator
-
 namespace Antares::Solver::Variable::Private
 {
 void InternalExportDigestLinksMatrix(const Data::Study& study,
@@ -114,12 +111,12 @@ void InternalExportDigestLinksMatrix(const Data::Study& study,
 }
 
 static void ExportGridInfosAreas(const Data::Study& study,
-                                 const Yuni::String& originalOutput,
+                                 const std::string& originalOutput,
                                  IResultWriter& writer)
 {
-    Clob out;
-    Clob outLinks;
-    Clob outThermal;
+    Yuni::Clob out;
+    Yuni::Clob outLinks;
+    Yuni::Clob outThermal;
 
     out << "id\tname\n";
     outLinks << "upstream\tdownstream\n";
@@ -164,11 +161,12 @@ static void ExportGridInfosAreas(const Data::Study& study,
 
           } // each thermal cluster
       }); // each area
-    auto add = [&writer, &originalOutput](const YString& filename, Clob&& buffer)
+    auto add = [&writer, &originalOutput](const std::string& filename, Yuni::Clob&& buffer)
     {
-        YString path;
-        path << originalOutput << SEP << "grid" << SEP << filename;
-        writer.addEntryFromBuffer(path.c_str(), buffer);
+        std::filesystem::path path = originalOutput;
+        path /= "grid";
+        path /= filename;
+        writer.addEntryFromBuffer(path.string(), buffer);
     };
 
     add("areas.txt", std::move(out));
@@ -176,7 +174,7 @@ static void ExportGridInfosAreas(const Data::Study& study,
     add("thermal.txt", std::move(outThermal));
 }
 
-SurveyResultsData::SurveyResultsData(const Data::Study& s, const String& o):
+SurveyResultsData::SurveyResultsData(const Data::Study& s, const Yuni::String& o):
     columnIndex((uint)-1),
     thermalCluster(nullptr),
     area(nullptr),
@@ -511,7 +509,7 @@ static inline void WriteIndexHeaderToFileDescriptor(int precisionLevel,
     s += '\n';
 }
 
-SurveyResults::SurveyResults(const Data::Study& s, const String& o, IResultWriter& writer):
+SurveyResults::SurveyResults(const Data::Study& s, const Yuni::String& o, IResultWriter& writer):
     data(s, o),
     yearByYearResults(false),
     isCurrentVarNA(nullptr),
diff --git a/src/tests/src/libs/antares/study/short-term-storage-input/short-term-storage-input-output.cpp b/src/tests/src/libs/antares/study/short-term-storage-input/short-term-storage-input-output.cpp
index d7de940912..427eeadb73 100644
--- a/src/tests/src/libs/antares/study/short-term-storage-input/short-term-storage-input-output.cpp
+++ b/src/tests/src/libs/antares/study/short-term-storage-input/short-term-storage-input-output.cpp
@@ -31,17 +31,16 @@
 
 #include "antares/study/parts/short-term-storage/container.h"
 
-#define SEP Yuni::IO::Separator
-
 using namespace std;
 using namespace Antares::Data;
 
+namespace fs = std::filesystem;
+
 namespace
 {
-std::string getFolder()
+fs::path getFolder()
 {
-    std::filesystem::path tmpDir = std::filesystem::temp_directory_path();
-    return tmpDir.string();
+    return fs::temp_directory_path();
 }
 
 void resizeFillVectors(ShortTermStorage::Series& series, double value, unsigned int size)
@@ -57,7 +56,7 @@ void resizeFillVectors(ShortTermStorage::Series& series, double value, unsigned
     series.costLevel.resize(size, value);
 }
 
-void createIndividualFileSeries(const std::string& path, double value, unsigned int size)
+void createIndividualFileSeries(const fs::path& path, double value, unsigned int size)
 {
     std::ofstream outfile(path);
 
@@ -69,7 +68,7 @@ void createIndividualFileSeries(const std::string& path, double value, unsigned
     outfile.close();
 }
 
-void createIndividualFileSeries(const std::string& path, unsigned int size)
+void createIndividualFileSeries(const fs::path& path, unsigned int size)
 {
     std::ofstream outfile;
     outfile.open(path, std::ofstream::out | std::ofstream::trunc);
@@ -85,40 +84,40 @@ void createIndividualFileSeries(const std::string& path, unsigned int size)
 
 void createFileSeries(double value, unsigned int size)
 {
-    std::string folder = getFolder();
+    fs::path folder = getFolder();
 
-    createIndividualFileSeries(folder + SEP + "PMAX-injection.txt", value, size);
-    createIndividualFileSeries(folder + SEP + "PMAX-withdrawal.txt", value, size);
-    createIndividualFileSeries(folder + SEP + "inflows.txt", value, size);
-    createIndividualFileSeries(folder + SEP + "lower-rule-curve.txt", value, size);
-    createIndividualFileSeries(folder + SEP + "upper-rule-curve.txt", value, size);
+    createIndividualFileSeries(folder / "PMAX-injection.txt", value, size);
+    createIndividualFileSeries(folder / "PMAX-withdrawal.txt", value, size);
+    createIndividualFileSeries(folder / "inflows.txt", value, size);
+    createIndividualFileSeries(folder / "lower-rule-curve.txt", value, size);
+    createIndividualFileSeries(folder / "upper-rule-curve.txt", value, size);
 
-    createIndividualFileSeries(folder + SEP + "cost-injection.txt", value, size);
-    createIndividualFileSeries(folder + SEP + "cost-withdrawal.txt", value, size);
-    createIndividualFileSeries(folder + SEP + "cost-level.txt", value, size);
+    createIndividualFileSeries(folder / "cost-injection.txt", value, size);
+    createIndividualFileSeries(folder / "cost-withdrawal.txt", value, size);
+    createIndividualFileSeries(folder / "cost-level.txt", value, size);
 }
 
 void createFileSeries(unsigned int size)
 {
-    std::string folder = getFolder();
+    fs::path folder = getFolder();
 
-    createIndividualFileSeries(folder + SEP + "PMAX-injection.txt", size);
-    createIndividualFileSeries(folder + SEP + "PMAX-withdrawal.txt", size);
-    createIndividualFileSeries(folder + SEP + "inflows.txt", size);
-    createIndividualFileSeries(folder + SEP + "lower-rule-curve.txt", size);
-    createIndividualFileSeries(folder + SEP + "upper-rule-curve.txt", size);
+    createIndividualFileSeries(folder / "PMAX-injection.txt", size);
+    createIndividualFileSeries(folder / "PMAX-withdrawal.txt", size);
+    createIndividualFileSeries(folder / "inflows.txt", size);
+    createIndividualFileSeries(folder / "lower-rule-curve.txt", size);
+    createIndividualFileSeries(folder / "upper-rule-curve.txt", size);
 
-    createIndividualFileSeries(folder + SEP + "cost-injection.txt", size);
-    createIndividualFileSeries(folder + SEP + "cost-withdrawal.txt", size);
-    createIndividualFileSeries(folder + SEP + "cost-level.txt", size);
+    createIndividualFileSeries(folder / "cost-injection.txt", size);
+    createIndividualFileSeries(folder / "cost-withdrawal.txt", size);
+    createIndividualFileSeries(folder / "cost-level.txt", size);
 }
 
 void createIniFile(bool enabled)
 {
-    std::string folder = getFolder();
+    fs::path folder = getFolder();
 
     std::ofstream outfile;
-    outfile.open(folder + SEP + "list.ini", std::ofstream::out | std::ofstream::trunc);
+    outfile.open(folder / "list.ini", std::ofstream::out | std::ofstream::trunc);
 
     outfile << "[area]" << std::endl;
     outfile << "name = area" << std::endl;
@@ -135,10 +134,10 @@ void createIniFile(bool enabled)
 
 void createIniFileWrongValue()
 {
-    std::string folder = getFolder();
+    fs::path folder = getFolder();
 
     std::ofstream outfile;
-    outfile.open(folder + SEP + "list.ini", std::ofstream::out | std::ofstream::trunc);
+    outfile.open(folder / "list.ini", std::ofstream::out | std::ofstream::trunc);
 
     outfile << "[area]" << std::endl;
     outfile << "name = area" << std::endl;
@@ -155,18 +154,17 @@ void createIniFileWrongValue()
 
 void createEmptyIniFile()
 {
-    std::string folder = getFolder();
+    fs::path folder = getFolder();
 
     std::ofstream outfile;
-    outfile.open(folder + SEP + "list.ini", std::ofstream::out | std::ofstream::trunc);
+    outfile.open(folder / "list.ini", std::ofstream::out | std::ofstream::trunc);
 
     outfile.close();
 }
 
 void removeIniFile()
 {
-    std::string folder = getFolder();
-    std::filesystem::remove(folder + SEP + "list.ini");
+    fs::remove(getFolder() / "list.ini");
 }
 } // namespace
 
@@ -183,18 +181,18 @@ struct Fixture
 
     ~Fixture()
     {
-        std::filesystem::remove(folder + SEP + "PMAX-injection.txt");
-        std::filesystem::remove(folder + SEP + "PMAX-withdrawal.txt");
-        std::filesystem::remove(folder + SEP + "inflows.txt");
-        std::filesystem::remove(folder + SEP + "lower-rule-curve.txt");
-        std::filesystem::remove(folder + SEP + "upper-rule-curve.txt");
-
-        std::filesystem::remove(folder + SEP + "cost-injection.txt");
-        std::filesystem::remove(folder + SEP + "cost-withdrawal.txt");
-        std::filesystem::remove(folder + SEP + "cost-level.txt");
+        fs::remove(folder / "PMAX-injection.txt");
+        fs::remove(folder / "PMAX-withdrawal.txt");
+        fs::remove(folder / "inflows.txt");
+        fs::remove(folder / "lower-rule-curve.txt");
+        fs::remove(folder / "upper-rule-curve.txt");
+
+        fs::remove(folder / "cost-injection.txt");
+        fs::remove(folder / "cost-withdrawal.txt");
+        fs::remove(folder / "cost-level.txt");
     }
 
-    std::string folder = getFolder();
+    fs::path folder = getFolder();
 
     ShortTermStorage::Series series;
     ShortTermStorage::Properties properties;
@@ -345,7 +343,7 @@ BOOST_FIXTURE_TEST_CASE(check_file_save, Fixture)
 
     removeIniFile();
 
-    BOOST_CHECK(container.saveToFolder(folder));
+    BOOST_CHECK(container.saveToFolder(folder.string()));
 
     BOOST_CHECK(container.createSTStorageClustersFromIniFile(folder));
 
@@ -356,7 +354,7 @@ BOOST_FIXTURE_TEST_CASE(check_series_save, Fixture)
 {
     resizeFillVectors(series, 0.123456789, 8760);
 
-    BOOST_CHECK(series.saveToFolder(folder));
+    BOOST_CHECK(series.saveToFolder(folder.string()));
     resizeFillVectors(series, 0, 0);
 
     BOOST_CHECK(series.loadFromFolder(folder));