ukaea · timothy-nunn · Apr 24, 2025 · Apr 30, 2025 · Apr 30, 2025 · Jun 12, 2025
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -95,7 +95,6 @@ LIST(APPEND PROCESS_SRCS
     structure_variables.f90
     output.f90
     init_module.f90
-    error_handling.f90
     global_variables.f90
     constraint_variables.f90
     vacuum_variables.f90

diff --git a/documentation/proc-pages/usage/troubleshooting.md b/documentation/proc-pages/usage/troubleshooting.md
@@ -8,27 +8,9 @@ it often requires a great deal of painstaking adjustment of the input file to ov
 ## Error handling
 
 In general, errors detected during a run are handled in a consistent manner, with the code 
-producing useful diagnostic messages to help the user understand what has happened.
-
-There are three levels of errors and warnings that may occur:
-
-* **Level 1** -- An *informational* message is produced under certain conditions, for example if 
-  the code modified the user's input choice for some reason.
-* **Level 2** -- A *warning* message is produced if a non-fatal situation has occurred that may 
-  result in an output case that is inaccurate or unreliable in some way.
-* **Level 3** -- An *error* message will occur is a severe of fatal error has occurred and the program cannot continue.
-
-These messages are printed on the screen during the course of a run, and those still active at the 
-final (feasible or unfeasible) solution point are also written to the end of the output file 
-(messages encountered during the iteration process are not copied to the output file, as the 
-convergence to a valid solution might resolve some of the warnings produced earlier in the 
-solution process).
-
-The `error_status` variable returns the highest security level that has been encountered (or zero 
-if no abnormal conditions have been found); of a severe error (level 3) is flagged at any point the 
-program is terminated immediately. The final message number encountered during a run is returned via 
-output variable `error_id` . In addition, with certain messages, a number of diagnostic values may 
-also be given; these can be used to provide extra diagnostic information if the source code is available
+producing useful diagnostic messages to help the user understand what has happened. In the case of an
+unrecoverable error, PROCESS will fail with a Python exception. If the error is recoverable, a warning
+will be logged that is written to the terminal and output file at the end of the run.
 
 ### General problems
 

diff --git a/process/blanket_library.py b/process/blanket_library.py
@@ -15,16 +15,13 @@
     build_variables,
     constants,
     divertor_variables,
-    error_handling,
     fwbs_variables,
     heat_transport_variables,
     physics_variables,
     primary_pumping_variables,
 )
-from process.fortran import (
-    error_handling as eh,
-)
 from process.utilities.f2py_string_patch import f2py_compatible_to_string
+from process.warning_handler import WarningManager
 
 # Acronyms for this module:
 # BB          Breeding Blanket
@@ -647,7 +644,9 @@ def thermo_hydraulic_model_pressure_drop_calculations(self, output: bool):
                 if (blanket_library.bllengi < (fwbs_variables.b_bz_liq * 3)) or (
                     blanket_library.bllengo < (fwbs_variables.b_bz_liq * 3)
                 ):
-                    eh.report_error(278)
+                    WarningManager.create_warning(
+                        "Your blanket modules are too small for the Liquid Metal pipes"
+                    )
 
             # Unless there is no IB blanket...
             else:
@@ -661,7 +660,9 @@ def thermo_hydraulic_model_pressure_drop_calculations(self, output: bool):
                 ) / fwbs_variables.nopipes
                 # Poloidal
                 if blanket_library.bllengo < (fwbs_variables.b_bz_liq * 3):
-                    eh.report_error(278)
+                    WarningManager.create_warning(
+                        "Your blanket modules are too small for the Liquid Metal pipes"
+                    )
 
         # Calculate total flow lengths, used for pressure drop calculation
         # Blanket primary coolant flow
@@ -1345,7 +1346,9 @@ def liquid_breeder_properties(self, output: bool = False):
             (t_ranges[:, 0] > mid_temp_liq).any()
             or (t_ranges[:, 1] < mid_temp_liq).any()
         ):
-            error_handling.report_error(280)
+            WarningManager.create_warning(
+                "Outside temperature limit for one or more liquid metal breeder properties"
+            )
 
             if output:
                 po.ocmmnt(

diff --git a/process/build.py b/process/build.py
@@ -12,13 +12,13 @
F438
@
     constants,
     current_drive_variables,
     divertor_variables,
-    error_handling,
     fwbs_variables,
     numerics,
     pfcoil_variables,
     physics_variables,
     tfcoil_variables,
 )
+from process.warning_handler import WarningManager
 
 logger = logging.getLogger(__name__)
 
@@ -100,9 +100,9 @@ def portsz(self):
             current_drive_variables.rtanmax = f * np.cos(eps) - 0.5e0 * c
 
         else:  # coil separation is too narrow for beam...
-            error_handling.fdiags[0] = g
-            error_handling.fdiags[1] = c
-            error_handling.report_error(63)
+            WarningManager.create_warning(
+                "Max beam tangency radius set =0 temporarily; change beamwd", g=g, c=c
+            )
 
             current_drive_variables.rtanmax = 0.0e0
 
@@ -1757,9 +1757,11 @@ def calculate_radial_build(self, output: bool) -> None:
 
                 # Notify user that build_variables.r_cp_top has been set to 1.01*build_variables.r_tf_inboard_out (lvl 2 error)
                 if build_variables.r_cp_top < 1.01e0 * build_variables.r_tf_inboard_out:
-                    error_handling.fdiags[0] = build_variables.r_cp_top
-                    error_handling.fdiags[1] = build_variables.r_tf_inboard_out
-                    error_handling.report_error(268)
+                    WarningManager.create_warning(
+                        "TF CP top radius (r_cp_top) replaced by 1.01*r_tf_inboard_out -> potential top rbuild issue",
+                        r_cp_top=build_variables.r_cp_top,
+                        r_tf_inboard_out=build_variables.r_tf_inboard_out,
+                    )
 
                     # build_variables.r_cp_top correction
                     build_variables.r_cp_top = build_variables.r_tf_inboard_out * 1.01e0
@@ -1773,9 +1775,11 @@ def calculate_radial_build(self, output: bool) -> None:
             elif build_variables.i_r_cp_top == 1:
                 # Notify user that build_variables.r_cp_top has been set to 1.01*build_variables.r_tf_inboard_out (lvl 2 error)
                 if build_variables.r_cp_top < 1.01e0 * build_variables.r_tf_inboard_out:
-                    error_handling.fdiags[0] = build_variables.r_cp_top
-                    error_handling.fdiags[1] = build_variables.r_tf_inboard_out
-                    error_handling.report_error(268)
+                    WarningManager.create_warning(
+                        "TF CP top radius (r_cp_top) replaced by 1.01*r_tf_inboard_out -> potential top rbuild issue",
+                        r_cp_top=build_variables.r_cp_top,
+                        r_tf_inboard_out=build_variables.r_tf_inboard_out,
+                    )
 
                     # build_variables.r_cp_top correction
                     build_variables.r_cp_top = build_variables.r_tf_inboard_out * 1.01e0
@@ -1809,8 +1813,10 @@ def calculate_radial_build(self, output: bool) -> None:
             )
             + tfcoil_variables.drtop
         ):
-            error_handling.fdiags[0] = build_variables.r_cp_top
-            error_handling.report_error(256)
+            WarningManager.create_warning(
+                "Top CP radius larger that its value determined with plasma shape",
+                r_cp_top=build_variables.r_cp_top,
+            )
         if build_variables.i_tf_inside_cs == 1:
             #  Radial position of vacuum vessel [m]
             build_variables.r_vv_inboard_out = (
@@ -2064,24 +2070,34 @@ def calculate_radial_build(self, output: bool) -> None:
                 )
                 po.ocmmnt(self.outfile, " its range of applicability.)")
                 po.oblnkl(self.outfile)
-                error_handling.report_error(62)
+                WarningManager.create_warning(
+                    "Ripple result may be inaccurate, as the fit has been extrapolated"
+                )
 
                 if build_python_variables.ripflag == 1:
-                    error_handling.fdiags[0] = (
-                        tfcoil_variables.wwp1
-                        * tfcoil_variables.n_tf_coils
-                        / physics_variables.rmajor
+                    WarningManager.create_warning(
+                        "(TF coil ripple calculation) Dimensionless coil width X out of fitted range",
+                        diagnostic=(
+                            tfcoil_variables.wwp1
+                            * tfcoil_variables.n_tf_coils
+                            / physics_variables.rmajor
+                        ),
                     )
-                    error_handling.report_error(141)
+
                 elif build_python_variables.ripflag == 2:
                     # Convert to integer as idiags is integer array
-                    error_handling.idiags[0] = int(tfcoil_variables.n_tf_coils)
-                    error_handling.report_error(142)
+                    WarningManager.create_warning(
+                        "(TF coil ripple calculation) No of TF coils not between 16 and 20 inclusive",
+                        n_tf_coils=tfcoil_variables.n_tf_coils,
+                    )
                 else:
-                    error_handling.fdiags[0] = (
-                        physics_variables.rmajor + physics_variables.rminor
-                    ) / build_variables.r_tf_outboard_mid
-                    error_handling.report_error(143)
+                    WarningManager.create_warning(
+                        "(TF coil ripple calculation) (R+a)/rtot out of fitted range",
+                        diagnostic=(
+                            (physics_variables.rmajor + physics_variables.rminor)
+                            / build_variables.r_tf_outboard_mid
+                        ),
+                    )
 
             po.ovarin(
                 self.outfile,

diff --git a/process/constraints.py b/process/constraints.py
@@ -6,6 +6,7 @@
 
 import process.fortran as fortran
 from process.exceptions import ProcessError, ProcessValueError
+from process.warning_handler import WarningManager
 
 ConstraintSymbolType = Literal["=", ">=", "<="]
 
@@ -1026,7 +1027,9 @@ def constraint_equation_33():
     j_tf_wp: winding pack current density (A/m2)
     """
     if fortran.constraint_variables.fiooic > 0.7:
-        fortran.error_handling.report_error(285)
+        WarningManager.create_warning(
+            "fiooic shouldn't be above 0.7 for engineering reliability"
+        )
 
     cc = (
         fortran.tfcoil_variables.j_tf_wp / fortran.tfcoil_variables.jwdgcrt

diff --git a/process/current_drive.py b/process/current_drive.py
@@ -10,10 +10,8 @@
     heat_transport_variables,
     physics_variables,
 )
-from process.fortran import (
-    error_handling as eh,
-)
 from process.plasma_profiles import PlasmaProfile
+from process.warning_handler import WarningManager
 
 
 class NeutralBeam:
@@ -793,7 +791,6 @@ def legend(self, zlocal, arg):
         Abramowitz and Stegun, equation 8.12.1
         """
         if abs(arg) > (1.0e0 + 1.0e-10):
-            eh.fdiags[0] = arg
             raise ProcessValueError("Invalid argument", arg=arg)
 
         arg2 = min(arg, (1.0e0 - 1.0e-10))
@@ -1073,7 +1070,9 @@ def lhrad(self):
             rat0 = rat1
 
         else:
-            eh.report_error(16)
+            WarningManager.create_warning(
+                "LH penetration radius not found after lapno iterations, using 0.8*rminor"
+            )
             rat0 = 0.8e0
 
         return rat0

diff --git a/process/fw.py b/process/fw.py
@@ -8,13 +8,10 @@
     blanket_library,
     build_variables,
     constants,
-    error_handling,
     fwbs_variables,
 )
-from process.fortran import (
-    error_handling as eh,
-)
 from process.utilities.f2py_string_patch import f2py_compatible_to_string
+from process.warning_handler import WarningManager
 
 
 class Fw:
@@ -151,10 +148,12 @@ def fw_temp(
 
         # Print debug info if temperature too low/high or NaN/Inf
         if np.isnan(temp_k):
-            eh.report_error(223)
+            WarningManager.create_warning("NaN first wall temperature")
         elif (temp_k <= 100) or (temp_k > 1500):
-            eh.fdiags[0] = temp_k
-            eh.report_error(224)
+            WarningManager.create_warning(
+                "First wall temperature (temp_k) out of range : [100-1500] K",
+                temp_k=temp_k,
+            )
 
         # Thermal conductivity of first wall material (W/m.K)
         tkfw = self.fw_thermal_conductivity(temp_k)
@@ -445,17 +444,19 @@ def heat_transfer(
 
         # Check that Reynolds number is in valid range for the Gnielinski correlation
         if (reynolds <= 3000.0) or (reynolds > 5.0e6):
-            error_handling.fdiags[0] = reynolds
-            error_handling.report_error(225)
+            WarningManager.create_warning(
+                "Reynolds number out of range : [3e3-5000e3]", reynolds=reynolds
+            )
 
         # Check that Prandtl number is in valid range for the Gnielinski correlation
         if (pr < 0.5) or (pr > 2000.0):
-            error_handling.fdiags[0] = pr
-            error_handling.report_error(226)
+            WarningManager.create_warning(
+                "Prandtl number out of range : [0.5-2000]", pr=pr
+            )
 
         # Check that the Darcy friction factor is in valid range for the Gnielinski correlation
         if f <= 0.0:
-            error_handling.report_error(227)
+            WarningManager.create_warning("Negative Darcy friction factor (f)")
 
         return heat_transfer_coefficient
 

diff --git a/process/hcpb.py b/process/hcpb.py
@@ -18,9 +18,7 @@
     primary_pumping_variables,
     tfcoil_variables,
 )
-from process.fortran import (
-    error_handling as eh,
-)
+from process.warning_handler import WarningManager
 
 
 class CCFE_HCPB:
@@ -574,11 +572,13 @@ def nuclear_heating_blanket(self):
         )
 
         if fwbs_variables.p_blkt_nuclear_heat_total_mw < 1:
-            eh.fdiags[0] = fwbs_variables.p_blkt_nuclear_heat_total_mw
-            eh.fdiags[1] = ccfe_hcpb_module.exp_blanket
-            eh.fdiags[2] = physics_variables.p_fusion_total_mw
-            eh.fdiags[3] = mass
-            eh.report_error(274)
+            WarningManager.create_warning(
+                "Blanket heating is <1 MW or NaN. Is something wrong?",
+                p_blkt_nuclear_heat_total_mw=fwbs_variables.p_blkt_nuclear_heat_total_mw,
+                exp_blanket=ccfe_hcpb_module.exp_blanket,
+                fusion_power=physics_variables.p_fusion_total_mw,
+                mass=mass,
+            )
 
     def nuclear_heating_shield(self):
         """Nuclear heating in the shield for CCFE HCPB model

diff --git a/process/init.py b/process/init.py
@@ -52,6 +52,7 @@
 from process.tf_coil import init_tfcoil_variables
 from process.utilities.f2py_string_patch import f2py_compatible_to_string
 from process.vacuum import init_vacuum_variables
+from process.warning_handler import WarningManager
 from process.water_use import init_watuse_variables
 
 
@@ -63,9 +64,6 @@ def init_process():
     the default values for the global variables, reads in data from
     the input file, and checks the run parameters for consistency.
     """
-    # Initialise error handling
-    fortran.error_handling.initialise_error_list()
-
     # Initialise the program variables
     iteration_variables.initialise_iteration_variables()
 
@@ -252,11 +250,11 @@ def init_all_module_vars():
     run. This matters ever since Process is used as a shared library, rather
     than a 'run-once' executable.
     """
+    WarningManager.reinitialise()
     fortran.numerics.init_numerics()
     init_buildings_variables()
     init_cost_variables()
     init_divertor_variables()
-    fortran.error_handling.init_error_handling()
     init_fwbs_variables()
     fortran.global_variables.init_global_variables()
     init_ccfe_hcpb_module()
@@ -293,8 +291,6 @@ def init_all_module_vars():
     init_cost_variables_new()
     init_python_build_variables()
 
-    fortran.init_module.init_fortran_modules()
-
 
 def check_process(inputs):  # noqa: ARG001
     """Routine to reset specific variables if certain options are

diff --git a/process/io/process_config.py b/process/io/process_config.py
@@ -120,10 +120,7 @@ def error_status2readme(self, directory="."):
         if os.path.isfile("MFILE.DAT"):
             m_file = MFile(filename=directory + "/MFILE.DAT")
 
-            error_status = (
-                f"Error status: {m_file.data['error_status'].get_scan(-1)}  "
-                f"Error ID: {m_file.data['error_id'].get_scan(-1)}\n"
-            )
+            error_status = f"Error status: {m_file.data['error_status'].get_scan(-1)}  "
 
             if self.comment != "":
                 with open(directory + "/README.txt", "a") as readme: