diff --git a/process/core/init.py b/process/core/init.py
index 3cd0c357d..1844350a1 100644
--- a/process/core/init.py
+++ b/process/core/init.py
@@ -58,7 +58,6 @@
 )
 from process.data_structure.tfcoil_variables import init_tfcoil_variables
 from process.data_structure.times_variables import init_times_variables
-from process.data_structure.vacuum_variables import init_vacuum_variables
 from process.models.stellarator.initialization import st_init
 from process.models.superconductors import (
     SuperconductorMaterial,
@@ -71,7 +70,7 @@
     from process.core.model import DataStructure
 
 
-def init_process(data_structure: DataStructure):
+def init_process(data: DataStructure):
     """Routine that calls the initialisation routines
 
     This routine calls the main initialisation routines that set
@@ -85,7 +84,7 @@ def init_process(data_structure: DataStructure):
     process_output.OutputFileManager.open_files()
 
     # Input any desired new initial values
-    inputs = parse_input_file(data_structure)
+    inputs = parse_input_file(data)
 
     # Set active constraints
     set_active_constraints()
@@ -97,7 +96,7 @@ def init_process(data_structure: DataStructure):
     st_init()
 
     # Check input data for errors/ambiguities
-    check_process(inputs)
+    check_process(inputs, data)
 
     run_summary()
 
@@ -291,7 +290,6 @@ def init_all_module_vars():
     init_primary_pumping_variables()
     init_pfcoil_variables()
     init_structure_variables()
-    init_vacuum_variables()
     init_pf_power_variables()
     init_build_variables()
     init_constraint_variables()
@@ -304,7 +302,7 @@ def init_all_module_vars():
     init_neoclassics_variables()
 
 
-def check_process(inputs):  # noqa: ARG001
+def check_process(inputs, data):  # noqa: ARG001
     """Routine to reset specific variables if certain options are
     being used
 
@@ -380,7 +378,7 @@ def check_process(inputs):  # noqa: ARG001
             : data_structure.numerics.neqns + data_structure.numerics.nineqns
         ]
         == 63
-    ).any() and data_structure.vacuum_variables.i_vacuum_pumping != "simple":
+    ).any() and data.vacuum.i_vacuum_pumping != "simple":
         raise ProcessValidationError(
             "Constraint 63 is requested without the correct vacuum model (simple)"
         )
diff --git a/process/core/input.py b/process/core/input.py
index 797be7c0b..848458da5 100644
--- a/process/core/input.py
+++ b/process/core/input.py
@@ -958,7 +958,7 @@ def __post_init__(self):
         data_structure.physics_variables, float, range=(0.0, 10.0)
     ),
     "pres_vv_chamber_dwell_start": InputVariable(
-        data_structure.vacuum_variables, float, range=(1e-06, 10000.0)
+        "vacuum", float, range=(1e-06, 10000.0)
     ),
     "temp_blkt_coolant_in": InputVariable(
         data_structure.fwbs_variables, float, range=(200.0, 600.0)
@@ -1090,12 +1090,8 @@ def __post_init__(self):
     "f_z_cs_tf_internal": InputVariable(
         data_structure.pfcoil_variables, float, range=(0.0, 2.0)
     ),
-    "outgasfactor": InputVariable(
-        data_structure.vacuum_variables, float, range=(1e-06, 1000.0)
-    ),
-    "outgasindex": InputVariable(
-        data_structure.vacuum_variables, float, range=(1e-06, 1000.0)
-    ),
+    "outgasfactor": InputVariable("vacuum", float, range=(1e-06, 1000.0)),
+    "outgasindex": InputVariable("vacuum", float, range=(1e-06, 1000.0)),
     "temp_blkt_coolant_out": InputVariable(
         data_structure.fwbs_variables, float, range=(450.0, 900.0)
     ),
@@ -1107,9 +1103,7 @@ def __post_init__(self):
     ),
     "paris_coefficient": InputVariable("cs_fatigue", float, range=(1e-20, 10.0)),
     "paris_power_law": InputVariable("cs_fatigue", float, range=(1.0, 10.0)),
-    "pres_vv_chamber_base": InputVariable(
-        data_structure.vacuum_variables, float, range=(1e-08, 0.001)
-    ),
+    "pres_vv_chamber_base": InputVariable("vacuum", float, range=(1e-08, 0.001)),
     "p_plasma_separatrix_min_mw": InputVariable(
         data_structure.constraint_variables, float, range=(0.1, 1000.0)
     ),
@@ -1167,9 +1161,7 @@ def __post_init__(self):
     "p_fusion_total_max_mw": InputVariable(
         data_structure.constraint_variables, float, range=(1.0, 10000.0)
     ),
-    "pres_div_chamber_burn": InputVariable(
-        data_structure.vacuum_variables, float, range=(0.0, 10.0)
-    ),
+    "pres_div_chamber_burn": InputVariable("vacuum", float, range=(0.0, 10.0)),
     "pres_fw_coolant": InputVariable(
         data_structure.fwbs_variables, float, range=(100000.0, 100000000.0)
     ),
@@ -1191,17 +1183,11 @@ def __post_init__(self):
         data_structure.times_variables, float, range=(0.0, 1.0)
     ),
     "f_a_vac_pump_port_plasma_surface": InputVariable(
-        data_structure.vacuum_variables, float, range=(1e-06, 1.0)
-    ),
-    "f_volflow_vac_pumps_impedance": InputVariable(
-        data_structure.vacuum_variables, float, range=(1e-06, 1.0)
-    ),
-    "volflow_vac_pumps_max": InputVariable(
-        data_structure.vacuum_variables, float, range=(1e-06, 1000.0)
-    ),
-    "molflow_vac_pumps": InputVariable(
-        data_structure.vacuum_variables, float, range=(0.0, 1e30)
+        "vacuum", float, range=(1e-06, 1.0)
     ),
+    "f_volflow_vac_pumps_impedance": InputVariable("vacuum", float, range=(1e-06, 1.0)),
+    "volflow_vac_pumps_max": InputVariable("vacuum", float, range=(1e-06, 1000.0)),
+    "molflow_vac_pumps": InputVariable("vacuum", float, range=(0.0, 1e30)),
     "pflux_plant_floor_electric": InputVariable(
         data_structure.heat_transport_variables, float, range=(0.0, 1000.0)
     ),
@@ -1223,9 +1209,7 @@ def __post_init__(self):
     "radius_fw_channel": InputVariable(
         data_structure.fwbs_variables, float, range=(0.001, 0.5)
     ),
-    "outgrat_fw": InputVariable(
-        data_structure.vacuum_variables, float, range=(1e-10, 1e-06)
-    ),
+    "outgrat_fw": InputVariable("vacuum", float, range=(1e-10, 1e-06)),
     "rbrt": InputVariable(data_structure.buildings_variables, float, range=(0.0, 10.0)),
     "rbvfac": InputVariable(data_structure.buildings_variables, float, range=(0.9, 3.0)),
     "rbwt": InputVariable(data_structure.buildings_variables, float, range=(0.0, 10.0)),
@@ -1552,9 +1536,7 @@ def __post_init__(self):
     "temp_tf_cryo": InputVariable(
         data_structure.tfcoil_variables, float, range=(0.01, 293.0)
     ),
-    "temp_vv_chamber_gas_burn_end": InputVariable(
-        data_structure.vacuum_variables, float, range=(1.0, 1000.0)
-    ),
+    "temp_vv_chamber_gas_burn_end": InputVariable("vacuum", float, range=(1.0, 1000.0)),
     "i_t_current_ramp_up": InputVariable(
         data_structure.times_variables, int, choices=[0, 1]
     ),
@@ -1786,9 +1768,7 @@ def __post_init__(self):
         data_structure.rebco_variables, float, range=(1.0e6, 1.0e10)
     ),
     "cost_model": InputVariable(data_structure.cost_variables, int, choices=[0, 1, 2]),
-    "i_vac_pump_dwell": InputVariable(
-        data_structure.vacuum_variables, int, choices=[0, 1, 2]
-    ),
+    "i_vac_pump_dwell": InputVariable("vacuum", int, choices=[0, 1, 2]),
     "i_fw_blkt_vv_shape": InputVariable(
         data_structure.fwbs_variables, int, range=(1, 2)
     ),
@@ -1993,9 +1973,7 @@ def __post_init__(self):
     "npdiv": InputVariable(data_structure.fwbs_variables, int, range=(0, 4)),
     "nphcdin": InputVariable(data_structure.fwbs_variables, int, range=(0, 4)),
     "nphcdout": InputVariable(data_structure.fwbs_variables, int, range=(0, 4)),
-    "i_vacuum_pump_type": InputVariable(
-        data_structure.vacuum_variables, int, choices=[0, 1]
-    ),
+    "i_vacuum_pump_type": InputVariable("vacuum", int, choices=[0, 1]),
     "num_rh_systems": InputVariable(data_structure.cost_variables, int, range=(1, 10)),
     "output_costs": InputVariable(data_structure.cost_variables, int, choices=[0, 1]),
     "i_p_coolant_pumping": InputVariable(
@@ -2027,9 +2005,7 @@ def __post_init__(self):
     "i_fw_coolant_type": InputVariable(
         data_structure.fwbs_variables, str, choices=["helium", "water"]
     ),
-    "i_vacuum_pumping": InputVariable(
-        data_structure.vacuum_variables, str, choices=["old", "simple"]
-    ),
+    "i_vacuum_pumping": InputVariable("vacuum", str, choices=["old", "simple"]),
     "dcond": InputVariable(data_structure.tfcoil_variables, float, array=True),
     "c_pf_coil_turn_peak_input": InputVariable(
         data_structure.pfcoil_variables, float, array=True
diff --git a/process/core/model.py b/process/core/model.py
index d586f80ac..bad11bc26 100644
--- a/process/core/model.py
+++ b/process/core/model.py
@@ -3,6 +3,7 @@
 
 from process.data_structure.cost_2015_variables import Cost2015Data
 from process.data_structure.cs_fatigue_variables import CSFatigueData
+from process.data_structure.vacuum_variables import VacuumData
 from process.data_structure.water_usage_variables import WaterUseData
 
 initialise_later = object()
@@ -13,6 +14,7 @@ class DataStructure:
     water_use: WaterUseData = initialise_later
     costs_2015: Cost2015Data = initialise_later
     cs_fatigue: CSFatigueData = initialise_later
+    vacuum: VacuumData = initialise_later
 
     def __post_init__(self):
         for f in fields(self):
@@ -27,7 +29,7 @@ class Model(abc.ABC):
     def run(self) -> None:
         """Run the model.
 
-        The run method is resposible for 'running' the model, ensuring it updates the data
+        The run method is responsible for 'running' the model, ensuring it updates the data
         structure with variables that subsequent models will require.
         """
 
diff --git a/process/core/solver/constraints.py b/process/core/solver/constraints.py
index a814e8dad..d383fd4ee 100644
--- a/process/core/solver/constraints.py
+++ b/process/core/solver/constraints.py
@@ -1345,14 +1345,14 @@ def constraint_equation_62(constraint_registration, _data):
 
 
 @ConstraintManager.register_constraint(63, "", "<=")
-def constraint_equation_63(constraint_registration, _data):
+def constraint_equation_63(constraint_registration, data):
     """Upper limit on n_iter_vacuum_pumps (i_vacuum_pumping = simple)
 
     tfno: number of TF coils (default = 50 for stellarators)
     n_iter_vacuum_pumps: number of high vacuum pumps (real number), each with the throughput
     """
     return leq(
-        data_structure.vacuum_variables.n_iter_vacuum_pumps,
+        data.vacuum.n_iter_vacuum_pumps,
         data_structure.tfcoil_variables.n_tf_coils,
         constraint_registration,
     )
diff --git a/process/data_structure/vacuum_variables.py b/process/data_structure/vacuum_variables.py
index c938b7b56..adf982428 100644
--- a/process/data_structure/vacuum_variables.py
+++ b/process/data_structure/vacuum_variables.py
@@ -1,127 +1,89 @@
-i_vacuum_pumping: str = None
-"""switch for vacuum pumping model:
+from dataclasses import dataclass
 
- - ='old' for old detailed ETR model
- - ='simple' for simple steady-state model with comparison to ITER cryopumps
-  !#TODO: old and simple not suitable names.
-"""
-
-n_iter_vacuum_pumps: float = None
-"""number of high vacuum pumps (real number), each with the throughput of one
-ITER cryopump (50 Pa m3 s-1), all operating at the same time (`i_vacuum_pumping='simple'`)
-"""
-
-i_vacuum_pump_type: int = None
-"""switch for vacuum pump type:
-
-   - =0 - for turbomolecular pump (magnetic bearing) with speed of 2.0 m3/s
-     (1.95 for N2, 1.8 for He, 1.8 for DT)
-   - =1 - for compound cryopump with nominal speed of 10.0 m3/s
-     (9.0 for N2, 5.0 for He and 25.0 for DT)
-"""
-
-n_vv_vacuum_ducts: int = None
-"""number of ducts (torus to pumps)"""
-
-dlscal: float = None
-"""vacuum system duct length scaling"""
-
-pres_vv_chamber_base: float = None
-"""base pressure during dwell before gas pre-fill(Pa)"""
-
-pres_div_chamber_burn: float = None
-"""divertor chamber pressure during burn (Pa)"""
-
-molflow_vac_pumps: float = None
-"""Pump throughput (molecules/s) (default is ITER value)"""
-
-outgrat_fw: float = None
-"""plasma chamber wall outgassing rate (Pa-m/s)"""
-
-temp_vv_chamber_gas_burn_end: float = None
-"""neutral gas temperature in chamber (K)"""
-
-m_vv_vacuum_duct_shield: float = None
-"""mass of vacuum duct shield (kg)"""
-
-dia_vv_vacuum_ducts: float = None
-"""diameter of duct passage (m)"""
-
-n_vac_pumps_high: int = None
-"""number of high vacuum pumps"""
-
-i_vac_pump_dwell: int = None
-"""switch for dwell pumping options:
-
-   - =0 pumping only during t_plant_pulse_dwell
-   - =1 pumping only during t_plant_pulse_coil_precharge
-   - =2 pumping during t_plant_pulse_dwell + t_plant_pulse_coil_precharge
-
-   The following are used in the Battes, Day and Rohde pump-down model
-   See "Basic considerations on the pump-down time in the dwell phase of a pulsed fusion DEMO"
-   http://dx.doi.org/10.1016/j.fusengdes.2015.07.011)(i_vacuum_pumping=simple')
-"""
-
-f_a_vac_pump_port_plasma_surface: float = None
-"""area of one pumping port as a fraction of plasma surface area"""
-
-volflow_vac_pumps_max: float = None
-"""maximum pumping speed per unit area for deuterium & tritium, molecular flow"""
-
-f_volflow_vac_pumps_impedance: float = None
-"""effective pumping speed reduction factor due to duct impedance"""
-
-pres_vv_chamber_dwell_start: float = None
-"""initial neutral pressure at the beginning of the dwell phase (Pa)"""
-
-outgasindex: float = None
-"""outgassing decay index"""
-
-outgasfactor: float = None
-"""outgassing prefactor kw: outgassing rate at 1 s per unit area (Pa m s-1)"""
-
-
-def init_vacuum_variables():
-    """Initialise Vacuum variables"""
-    global \
-        i_vacuum_pumping, \
-        n_iter_vacuum_pumps, \
-        i_vacuum_pump_type, \
-        n_vv_vacuum_ducts, \
-        dlscal, \
-        pres_vv_chamber_base, \
-        pres_div_chamber_burn, \
-        molflow_vac_pumps, \
-        outgrat_fw, \
-        temp_vv_chamber_gas_burn_end, \
-        m_vv_vacuum_duct_shield, \
-        dia_vv_vacuum_ducts, \
-        n_vac_pumps_high, \
-        i_vac_pump_dwell, \
-        f_a_vac_pump_port_plasma_surface, \
-        volflow_vac_pumps_max, \
-        f_volflow_vac_pumps_impedance, \
-        pres_vv_chamber_dwell_start, \
-        outgasindex, \
-        outgasfactor
-
-    i_vacuum_pumping = "old"
-    n_iter_vacuum_pumps = 0.0
-    i_vacuum_pump_type = 1
-    n_vv_vacuum_ducts = 0
-    dlscal = 0.0
-    pres_vv_chamber_base = 5.0e-4
-    pres_div_chamber_burn = 0.36
-    molflow_vac_pumps = 1.2155e22
-    outgrat_fw = 1.3e-8
-    temp_vv_chamber_gas_burn_end = 300.0
-    m_vv_vacuum_duct_shield = 0.0
-    dia_vv_vacuum_ducts = 0.0
-    n_vac_pumps_high = 0
-    i_vac_pump_dwell = 0
-    f_a_vac_pump_port_plasma_surface = 0.0203
-    volflow_vac_pumps_max = 27.3
-    f_volflow_vac_pumps_impedance = 0.167
-    pres_vv_chamber_dwell_start = 1.0
-    outgasindex = 1.0
-    outgasfactor = 0.0235
+
+@dataclass
+class VacuumData:
+    i_vacuum_pumping: str = "old"
+    """switch for vacuum pumping model:
+
+    - ='old' for old detailed ETR model
+    - ='simple' for simple steady-state model with comparison to ITER cryopumps
+      !#TODO: old and simple not suitable names.
+    """
+
+    n_iter_vacuum_pumps: float = 0.0
+    """number of high vacuum pumps (real number), each with the throughput of one
+    ITER cryopump (50 Pa m3 s-1), all operating at the same time (`i_vacuum_pumping='simple'`)
+    """
+
+    i_vacuum_pump_type: int = 1
+    """switch for vacuum pump type:
+
+      - =0 - for turbomolecular pump (magnetic bearing) with speed of 2.0 m3/s
+        (1.95 for N2, 1.8 for He, 1.8 for DT)
+      - =1 - for compound cryopump with nominal speed of 10.0 m3/s
+        (9.0 for N2, 5.0 for He and 25.0 for DT)
+    """
+
+    n_vv_vacuum_ducts: int = 0
+    """number of ducts (torus to pumps)"""
+
+    dlscal: float = 0.0
+    """vacuum system duct length scaling"""
+
+    pres_vv_chamber_base: float = 5.0e-4
+    """base pressure during dwell before gas pre-fill(Pa)"""
+
+    pres_div_chamber_burn: float = 0.36
+    """divertor chamber pressure during burn (Pa)"""
+
+    molflow_vac_pumps: float = 1.2155e22
+    """Pump throughput (molecules/s) (default is ITER value)"""
+
+    outgrat_fw: float = 1.3e-8
+    """plasma chamber wall outgassing rate (Pa-m/s)"""
+
+    temp_vv_chamber_gas_burn_end: float = 300.0
+    """neutral gas temperature in chamber (K)"""
+
+    m_vv_vacuum_duct_shield: float = 0.0
+    """mass of vacuum duct shield (kg)"""
+
+    dia_vv_vacuum_ducts: float = 0.0
+    """diameter of duct passage (m)"""
+
+    n_vac_pumps_high: int = 0
+    """number of high vacuum pumps"""
+
+    i_vac_pump_dwell: int = 0
+    """switch for dwell pumping options:
+
+      - =0 pumping only during t_plant_pulse_dwell
+      - =1 pumping only during t_plant_pulse_coil_precharge
+      - =2 pumping during t_plant_pulse_dwell + t_plant_pulse_coil_precharge
+
+      The following are used in the Battes, Day and Rohde pump-down model
+      See "Basic considerations on the pump-down time in the dwell phase of a pulsed fusion DEMO"
+      http://dx.doi.org/10.1016/j.fusengdes.2015.07.011)(i_vacuum_pumping=simple')
+    """
+
+    f_a_vac_pump_port_plasma_surface: float = 0.0203
+    """area of one pumping port as a fraction of plasma surface area"""
+
+    volflow_vac_pumps_max: float = 27.3
+    """maximum pumping speed per unit area for deuterium & tritium, molecular flow"""
+
+    f_volflow_vac_pumps_impedance: float = 0.167
+    """effective pumping speed reduction factor due to duct impedance"""
+
+    pres_vv_chamber_dwell_start: float = 1.0
+    """initial neutral pressure at the beginning of the dwell phase (Pa)"""
+
+    outgasindex: float = 1.0
+    """outgassing decay index"""
+
+    outgasfactor: float = 0.0235
+    """outgassing prefactor kw: outgassing rate at 1 s per unit area (Pa m s-1)"""
+
+
+CREATE_DICTS_FROM_DATACLASS = VacuumData
diff --git a/process/main.py b/process/main.py
index cd2d57cc7..21599bf6a 100644
--- a/process/main.py
+++ b/process/main.py
@@ -707,6 +707,11 @@ def models(self) -> tuple[Model, ...]:
             self.cs_fatigue,
             self.cs_coil,
             self.pfcoil,
+            self.vacuum,
+            self.vacuum_vessel,
+            self._costs_1990,
+            self.availability,
+            self.ife,
         )
 
     def setup_data_structure(self):
diff --git a/process/models/availability.py b/process/models/availability.py
index e695ac75c..a34cbba1d 100644
--- a/process/models/availability.py
+++ b/process/models/availability.py
@@ -15,7 +15,6 @@
 from process.data_structure import physics_variables as pv
 from process.data_structure import tfcoil_variables as tfv
 from process.data_structure import times_variables as tv
-from process.data_structure import vacuum_variables as vacv
 from process.models.tfcoil.base import TFConductorModel
 
 logger = logging.getLogger(__name__)
@@ -375,7 +374,9 @@ def avail_2(self, output: bool):
         # Vacuum systems
 
         # Number of redundant pumps
-        cv.redun_vac = math.floor(vacv.n_vac_pumps_high * cv.redun_vacp / 100.0 + 0.5e0)
+        cv.redun_vac = math.floor(
+            self.data.vacuum.n_vac_pumps_high * cv.redun_vacp / 100.0 + 0.5e0
+        )
 
         u_unplanned_vacuum = self.calc_u_unplanned_vacuum(output)
 
@@ -1018,7 +1019,7 @@ def calc_u_unplanned_vacuum(self, output: bool) -> float:
         cryo_main_time = 1.0e0 / 6.0e0
 
         # Total pumps = pumps + redundant pumps
-        total_pumps = vacv.n_vac_pumps_high + cv.redun_vac
+        total_pumps = self.data.vacuum.n_vac_pumps_high + cv.redun_vac
 
         # Cryopump failure rate per machine operational period
         # From "Selected component failure rate values from fusion
@@ -1059,7 +1060,7 @@ def calc_u_unplanned_vacuum(self, output: bool) -> float:
                 self.outfile,
                 "Number of pumps (excluding redundant pumps)",
                 "(n_vac_pumps_high)",
-                vacv.n_vac_pumps_high,
+                self.data.vacuum.n_vac_pumps_high,
                 "OP ",
             )
             po.ovarin(
@@ -1184,7 +1185,9 @@ def avail_st(self, output: bool):
         # Vacuum systems
 
         # Number of redundant pumps
-        cv.redun_vac = math.floor(vacv.n_vac_pumps_high * cv.redun_vacp / 100.0 + 0.5e0)
+        cv.redun_vac = math.floor(
+            self.data.vacuum.n_vac_pumps_high * cv.redun_vacp / 100.0 + 0.5e0
+        )
 
         u_unplanned_vacuum = self.calc_u_unplanned_vacuum(output)
 
diff --git a/process/models/costs/costs.py b/process/models/costs/costs.py
index 981bd40e8..533c9a3f7 100644
--- a/process/models/costs/costs.py
+++ b/process/models/costs/costs.py
@@ -5,6 +5,7 @@
 from process.core import constants
 from process.core import process_output as po
 from process.core.exceptions import ProcessValueError
+from process.core.model import Model
 from process.data_structure import (
     build_variables,
     buildings_variables,
@@ -22,14 +23,13 @@
     structure_variables,
     tfcoil_variables,
     times_variables,
-    vacuum_variables,
 )
 from process.models.tfcoil.base import TFConductorModel
 
 logger = logging.getLogger(__name__)
 
 
-class Costs:
+class Costs(Model):
     def __init__(self):
         self.outfile = constants.NOUT
 
@@ -1990,13 +1990,13 @@ def acc224(self):
         This routine evaluates the Account 224 (vacuum system) costs.
         The costs are scaled from TETRA reactor code runs.
         """
-        if vacuum_variables.i_vacuum_pump_type == 1:
+        if self.data.vacuum.i_vacuum_pump_type == 1:
             cost_variables.c2241 = (
-                1.0e-6 * vacuum_variables.n_vac_pumps_high * cost_variables.UCCPMP
+                1.0e-6 * self.data.vacuum.n_vac_pumps_high * cost_variables.UCCPMP
             )
         else:
             cost_variables.c2241 = (
-                1.0e-6 * vacuum_variables.n_vac_pumps_high * cost_variables.uctpmp
+                1.0e-6 * self.data.vacuum.n_vac_pumps_high * cost_variables.UCTPMP
             )
 
         cost_variables.c2241 = cost_variables.fkind * cost_variables.c2241
@@ -2004,7 +2004,7 @@ def acc224(self):
         #  Account 224.2 : Backing pumps
 
         cost_variables.c2242 = (
-            1.0e-6 * vacuum_variables.n_vv_vacuum_ducts * cost_variables.UCBPMP
+            1.0e-6 * self.data.vacuum.n_vv_vacuum_ducts * cost_variables.UCBPMP
         )
         cost_variables.c2242 = cost_variables.fkind * cost_variables.c2242
 
@@ -2012,8 +2012,8 @@ def acc224(self):
 
         cost_variables.c2243 = (
             1.0e-6
-            * vacuum_variables.n_vv_vacuum_ducts
-            * vacuum_variables.dlscal
+            * self.data.vacuum.n_vv_vacuum_ducts
+            * self.data.vacuum.dlscal
             * cost_variables.UCDUCT
         )
         cost_variables.c2243 = cost_variables.fkind * cost_variables.c2243
@@ -2023,8 +2023,8 @@ def acc224(self):
         cost_variables.c2244 = (
             1.0e-6
             * 2.0e0
-            * vacuum_variables.n_vv_vacuum_ducts
-            * (vacuum_variables.dia_vv_vacuum_ducts * 1.2e0) ** 1.4e0
+            * self.data.vacuum.n_vv_vacuum_ducts
+            * (self.data.vacuum.dia_vv_vacuum_ducts * 1.2e0) ** 1.4e0
             * cost_variables.UCVALV
         )
         cost_variables.c2244 = cost_variables.fkind * cost_variables.c2244
@@ -2033,8 +2033,8 @@ def acc224(self):
 
         cost_variables.c2245 = (
             1.0e-6
-            * vacuum_variables.n_vv_vacuum_ducts
-            * vacuum_variables.m_vv_vacuum_duct_shield
+            * self.data.vacuum.n_vv_vacuum_ducts
+            * self.data.vacuum.m_vv_vacuum_duct_shield
             * cost_variables.UCVDSH
         )
         cost_variables.c2245 = cost_variables.fkind * cost_variables.c2245
diff --git a/process/models/ife.py b/process/models/ife.py
index e0f32b984..c9384406a 100644
--- a/process/models/ife.py
+++ b/process/models/ife.py
@@ -19,7 +19,6 @@
     ife_variables,
     physics_variables,
     structure_variables,
-    vacuum_variables,
 )
 
 MATERIALS = [
@@ -2432,11 +2431,11 @@ def ifevac(self):
         <P>The calculated values are hard-wired; they are based loosely
         on those for a tokamak of 6m major radius. F/MI/PJK/LOGBOOK12, p.87
         """
-        vacuum_variables.dlscal = 2.0
-        vacuum_variables.n_vv_vacuum_ducts = 16
-        vacuum_variables.m_vv_vacuum_duct_shield = 0.0
-        vacuum_variables.dia_vv_vacuum_ducts = 0.3
-        vacuum_variables.n_vac_pumps_high = 32
+        self.data.vacuum.dlscal = 2.0
+        self.data.vacuum.n_vv_vacuum_ducts = 16
+        self.data.vacuum.m_vv_vacuum_duct_shield = 0.0
+        self.data.vacuum.dia_vv_vacuum_ducts = 0.3
+        self.data.vacuum.n_vac_pumps_high = 32
 
 
 def _material_string_generator(chmatv, fwmatv, v1matv, blmatv, v2matv, shmatv, v3matv):
diff --git a/process/models/vacuum.py b/process/models/vacuum.py
index cafb85e9e..f03c4c828 100644
--- a/process/models/vacuum.py
+++ b/process/models/vacuum.py
@@ -14,7 +14,6 @@
     physics_variables,
     tfcoil_variables,
     times_variables,
-    vacuum_variables,
 )
 from process.models.blankets.blanket_library import dshellvol, eshellvol
 from process.models.build import FwBlktVVShape
@@ -60,17 +59,17 @@ def run(self, output: bool = False):
             * constants.UMASS
         )
 
-        self.i_vacuum_pumping = vacuum_variables.i_vacuum_pumping
+        self.i_vacuum_pumping = self.data.vacuum.i_vacuum_pumping
 
         # i_vacuum_pumping required to be compared to a b string
         # as this is what f2py returns
         if self.i_vacuum_pumping == "old":
             (
                 pumpn,
-                vacuum_variables.n_vv_vacuum_ducts,
-                vacuum_variables.dlscal,
-                vacuum_variables.m_vv_vacuum_duct_shield,
-                vacuum_variables.dia_vv_vacuum_ducts,
+                self.data.vacuum.n_vv_vacuum_ducts,
+                self.data.vacuum.dlscal,
+                self.data.vacuum.m_vv_vacuum_duct_shield,
+                self.data.vacuum.dia_vv_vacuum_ducts,
             ) = self.vacuum(
                 physics_variables.p_fusion_total_mw,
                 physics_variables.rmajor,
@@ -97,12 +96,12 @@ def run(self, output: bool = False):
                 output=output,
             )
             # MDK pumpn is real: convert to integer by rounding.
-            vacuum_variables.n_vac_pumps_high = math.floor(pumpn + 0.5e0)
+            self.data.vacuum.n_vac_pumps_high = math.floor(pumpn + 0.5e0)
         elif self.i_vacuum_pumping == "simple":
-            vacuum_variables.n_iter_vacuum_pumps = self.vacuum_simple(output=output)
+            self.data.vacuum.n_iter_vacuum_pumps = self.vacuum_simple(output=output)
         else:
             logger.error(
-                f"i_vacuum_pumping is invalid: {vacuum_variables.i_vacuum_pumping}"
+                f"i_vacuum_pumping is invalid: {self.data.vacuum.i_vacuum_pumping}"
             )
 
     def vacuum_simple(self, output) -> float:
@@ -124,15 +123,15 @@ def vacuum_simple(self, output) -> float:
         # Issue #304
         n_iter_vacuum_pumps = (
             physics_variables.molflow_plasma_fuelling_required
-            / vacuum_variables.molflow_vac_pumps
+            / self.data.vacuum.molflow_vac_pumps
         )
 
         # Pump-down:
         # Pumping speed per pump m3/s
         pumpspeed = (
-            vacuum_variables.volflow_vac_pumps_max
-            * vacuum_variables.f_a_vac_pump_port_plasma_surface
-            * vacuum_variables.f_volflow_vac_pumps_impedance
+            self.data.vacuum.volflow_vac_pumps_max
+            * self.data.vacuum.f_a_vac_pump_port_plasma_surface
+            * self.data.vacuum.f_volflow_vac_pumps_impedance
             * physics_variables.a_plasma_surface
             / tfcoil_variables.n_tf_coils
         )
@@ -140,10 +139,10 @@ def vacuum_simple(self, output) -> float:
         wallarea = (physics_variables.a_plasma_surface / 1084.0e0) * 2000.0e0
         # Required pumping speed for pump-down
         pumpdownspeed = (
-            vacuum_variables.outgasfactor
+            self.data.vacuum.outgasfactor
             * wallarea
-            / vacuum_variables.pres_vv_chamber_base
-        ) * times_variables.t_plant_pulse_dwell ** (-vacuum_variables.outgasindex)
+            / self.data.vacuum.pres_vv_chamber_base
+        ) * times_variables.t_plant_pulse_dwell ** (-self.data.vacuum.outgasindex)
         # Number of pumps required for pump-down
         npumpdown = pumpdownspeed / pumpspeed
 
@@ -318,7 +317,7 @@ def vacuum(
         # nitrogen, DT, helium, DT again
         sp = (
             [1.95, 1.8, 1.8, 1.8]
-            if vacuum_variables.i_vacuum_pump_type == 0
+            if self.data.vacuum.i_vacuum_pump_type == 0
             else [9.0, 25.0, 5.0, 25.0]
         )
 
@@ -336,8 +335,8 @@ def vacuum(
 
         area = plasma_sarea * (aw + dsol) / aw
 
-        ogas = vacuum_variables.outgrat_fw * area * 10.0e0  # Outgassing rate (Pa-m^3/s)
-        s.append(ogas / vacuum_variables.pres_vv_chamber_base)
+        ogas = self.data.vacuum.outgrat_fw * area * 10.0e0  # Outgassing rate (Pa-m^3/s)
+        s.append(ogas / self.data.vacuum.pres_vv_chamber_base)
 
         #  Pumpdown between burns
         #  s(2) = net pump speed (DT) required for pumpdown between burns (m^3/s)
@@ -345,7 +344,7 @@ def vacuum(
         #  t_plant_pulse_dwell = dwell time between burns (s)
 
         pend = (
-            0.5e0 * nplasma * k * vacuum_variables.temp_vv_chamber_gas_burn_end
+            0.5e0 * nplasma * k * self.data.vacuum.temp_vv_chamber_gas_burn_end
         )  # pressure in plasma chamber after burn (Pa)
         pstart = 0.01e0 * pend  # pressure in chamber before start of burn (Pa)
 
@@ -356,9 +355,9 @@ def vacuum(
         volume = plasma_vol * (aw + dsol) * (aw + dsol) / (aw * aw)
 
         #  dwell pumping options
-        if (vacuum_variables.i_vac_pump_dwell == 1) or (t_plant_pulse_dwell == 0):
+        if (self.data.vacuum.i_vac_pump_dwell == 1) or (t_plant_pulse_dwell == 0):
             tpump = times_variables.t_plant_pulse_coil_precharge
-        elif vacuum_variables.i_vac_pump_dwell == 2:
+        elif self.data.vacuum.i_vac_pump_dwell == 2:
             tpump = t_plant_pulse_dwell + times_variables.t_plant_pulse_coil_precharge
         else:
             tpump = t_plant_pulse_dwell
@@ -375,12 +374,12 @@ def vacuum(
         fhe = source / (frate * 4.985e5)
         s.extend(
             (
-                (source / vacuum_variables.pres_div_chamber_burn / fhe),
+                (source / self.data.vacuum.pres_div_chamber_burn / fhe),
                 #  Removal of dt on steady state basis
                 #  s(4) = net speed (D-T) required to remove dt at fuelling rate (m^3/s)
                 (
                     (frate * 4.985e5 - source)
-                    / (vacuum_variables.pres_div_chamber_burn * (1.0e0 - fhe))
+                    / (self.data.vacuum.pres_div_chamber_burn * (1.0e0 - fhe))
                 ),
             ),
         )
@@ -514,7 +513,7 @@ def vacuum(
         #  If cryopumps are used then an additional pump is required
         #  for continuous operation with regeneration.
 
-        if vacuum_variables.i_vacuum_pump_type == 1:
+        if self.data.vacuum.i_vacuum_pump_type == 1:
             pumpn *= 2.0e0
 
         #  Information for costing routine
@@ -541,7 +540,7 @@ def vacuum(
                 self.outfile,
                 "First wall outgassing rate (Pa m/s)",
                 "(outgrat_fw)",
-                vacuum_variables.outgrat_fw,
+                self.data.vacuum.outgrat_fw,
             )
             process_output.ovarre(
                 self.outfile, "Total outgassing load (Pa m3/s)", "(ogas)", ogas, "OP "
@@ -550,7 +549,7 @@ def vacuum(
                 self.outfile,
                 "Base pressure required (Pa)",
                 "(pres_vv_chamber_base)",
-                vacuum_variables.pres_vv_chamber_base,
+                self.data.vacuum.pres_vv_chamber_base,
             )
             process_output.ovarre(
                 self.outfile, "Required N2 pump speed (m3/s)", "(s(1))", s[0], "OP "
@@ -577,7 +576,7 @@ def vacuum(
                 self.outfile,
                 "Allowable pumping time switch",
                 "(i_vac_pump_dwell)",
-                vacuum_variables.i_vac_pump_dwell,
+                self.data.vacuum.i_vac_pump_dwell,
             )
             process_output.ovarre(
                 self.outfile,
@@ -613,7 +612,7 @@ def vacuum(
                 self.outfile,
                 "Divertor chamber gas pressure (Pa)",
                 "(pres_div_chamber_burn)",
-                vacuum_variables.pres_div_chamber_burn,
+                self.data.vacuum.pres_div_chamber_burn,
             )
             process_output.ovarre(
                 self.outfile,
@@ -660,7 +659,7 @@ def vacuum(
                 process_output.oblnkl(self.outfile)
 
             i_fw_blkt_shared_coolant = (
-                "cryo " if vacuum_variables.i_vacuum_pump_type == 1 else "turbo"
+                "cryo " if self.data.vacuum.i_vacuum_pump_type == 1 else "turbo"
             )
 
             process_output.oblnkl(self.outfile)
diff --git a/tests/unit/test_availability.py b/tests/unit/test_availability.py
index a992e670a..c2ee4e386 100644
--- a/tests/unit/test_availability.py
+++ b/tests/unit/test_availability.py
@@ -12,17 +12,16 @@
 from process.data_structure import physics_variables as pv
 from process.data_structure import tfcoil_variables as tfv
 from process.data_structure import times_variables as tv
-from process.models.availability import Availability
 
 
 @pytest.fixture
-def availability():
+def availability(process_models):
     """Provides Availability object for testing.
 
     :return availability: initialised Availability object
     :type availability: process.availability.Availability
     """
-    return Availability()
+    return process_models.availability
 
 
 @pytest.mark.parametrize(
diff --git a/tests/unit/test_costs_1990.py b/tests/unit/test_costs_1990.py
index 4e8abb1b5..911ebd76e 100644
--- a/tests/unit/test_costs_1990.py
+++ b/tests/unit/test_costs_1990.py
@@ -23,19 +23,17 @@
     structure_variables,
     tfcoil_variables,
     times_variables,
-    vacuum_variables,
 )
-from process.models.costs.costs import Costs
 
 
 @pytest.fixture
-def costs():
-    """Provides Pulse object for testing.
+def costs(process_models):
+    """Provides Costs object for testing.
 
-    :returns: initialised Pulse object
-    :rtype: process.pulse.Pulse
+    :returns: initialised Costs object
+    :rtype: process.costs.Costs
     """
-    return Costs()
+    return process_models._costs_1990
 
 
 def acc2261_param(**kwargs):
@@ -3226,26 +3224,40 @@ def test_acc224(acc224param, monkeypatch, costs):
 
     monkeypatch.setattr(cost_variables, "fkind", acc224param.fkind)
 
-    monkeypatch.setattr(vacuum_variables, "dlscal", acc224param.dlscal)
+    monkeypatch.setattr(
+        costs.data.vacuum,
+        "dlscal",
+        acc224param.dlscal,
+    )
 
     monkeypatch.setattr(
-        vacuum_variables, "m_vv_vacuum_duct_shield", acc224param.m_vv_vacuum_duct_shield
+        costs.data.vacuum,
+        "m_vv_vacuum_duct_shield",
+        acc224param.m_vv_vacuum_duct_shield,
     )
 
     monkeypatch.setattr(
-        vacuum_variables, "n_vac_pumps_high", acc224param.n_vac_pumps_high
+        costs.data.vacuum,
+        "n_vac_pumps_high",
+        acc224param.n_vac_pumps_high,
     )
 
     monkeypatch.setattr(
-        vacuum_variables, "dia_vv_vacuum_ducts", acc224param.dia_vv_vacuum_ducts
+        costs.data.vacuum,
+        "dia_vv_vacuum_ducts",
+        acc224param.dia_vv_vacuum_ducts,
     )
 
     monkeypatch.setattr(
-        vacuum_variables, "i_vacuum_pump_type", acc224param.i_vacuum_pump_type
+        costs.data.vacuum,
+        "i_vacuum_pump_type",
+        acc224param.i_vacuum_pump_type,
     )
 
     monkeypatch.setattr(
-        vacuum_variables, "n_vv_vacuum_ducts", acc224param.n_vv_vacuum_ducts
+        costs.data.vacuum,
+        "n_vv_vacuum_ducts",
+        acc224param.n_vv_vacuum_ducts,
     )
 
     monkeypatch.setattr(cost_variables, "c22", acc224param.c22)
diff --git a/tests/unit/test_vacuum.py b/tests/unit/test_vacuum.py
index aea71c4ed..6ba9cc46f 100644
--- a/tests/unit/test_vacuum.py
+++ b/tests/unit/test_vacuum.py
@@ -5,28 +5,26 @@
 from process.data_structure import physics_variables as pv
 from process.data_structure import tfcoil_variables as tfv
 from process.data_structure import times_variables as tv
-from process.data_structure import vacuum_variables as vacv
-from process.models.vacuum import Vacuum, VacuumVessel
 
 
 @pytest.fixture
-def vacuum():
-    """Provides Vacuum object for testing.
+def vacuum(process_models):
+    """Fixture to get the Vacuum instance from process_models.
 
     :return vacuum: initialised Vacuum object
     :type vacuum: process.vacuum.Vacuum
     """
-    return Vacuum()
+    return process_models.vacuum
 
 
 @pytest.fixture
-def vacuum_vessel():
-    """Provides Vacuum object for testing.
+def vacuum_vessel(process_models):
+    """Fixture to get the VacuumVessel instance from process_models.
 
-    :return vacuum: initialised Vacuum object
-    :type vacuum: process.vacuum.Vacuum
+    :return vacuum: initialised VacuumVessel object
+    :type vacuum: process.vacuum.VacuumVessel
     """
-    return VacuumVessel()
+    return process_models.vacuum_vessel
 
 
 class TestVacuum:
@@ -47,13 +45,15 @@ def test_simple_model(self, monkeypatch, vacuum):
         monkeypatch.setattr(pv, "a_plasma_surface", 1500.3146527709359)
         monkeypatch.setattr(tfv, "n_tf_coils", 18)
         monkeypatch.setattr(tv, "t_plant_pulse_dwell", 500)
-        monkeypatch.setattr(vacv, "outgasfactor", 0.0235)
-        monkeypatch.setattr(vacv, "outgasindex", 1)
-        monkeypatch.setattr(vacv, "pres_vv_chamber_base", 0.0005)
-        monkeypatch.setattr(vacv, "f_a_vac_pump_port_plasma_surface", 0.0203)
-        monkeypatch.setattr(vacv, "f_volflow_vac_pumps_impedance", 0.4)
-        monkeypatch.setattr(vacv, "volflow_vac_pumps_max", 27.3)
-        monkeypatch.setattr(vacv, "molflow_vac_pumps", 1.2155e22)
+        monkeypatch.setattr(vacuum.data.vacuum, "outgasfactor", 0.0235)
+        monkeypatch.setattr(vacuum.data.vacuum, "outgasindex", 1)
+        monkeypatch.setattr(vacuum.data.vacuum, "pres_vv_chamber_base", 0.0005)
+        monkeypatch.setattr(
+            vacuum.data.vacuum, "f_a_vac_pump_port_plasma_surface", 0.0203
+        )
+        monkeypatch.setattr(vacuum.data.vacuum, "f_volflow_vac_pumps_impedance", 0.4)
+        monkeypatch.setattr(vacuum.data.vacuum, "volflow_vac_pumps_max", 27.3)
+        monkeypatch.setattr(vacuum.data.vacuum, "molflow_vac_pumps", 1.2155e22)
 
         n_iter_vacuum_pumps = vacuum.vacuum_simple(output=False)
 
@@ -67,12 +67,16 @@ def test_old_model(self, monkeypatch, vacuum):
         monkeypatch.setattr(pv, "p_fusion_total_mw", 2115.3899563651776)
         monkeypatch.setattr(pv, "temp_plasma_electron_vol_avg_kev", 15.872999999999999)
         monkeypatch.setattr(tv, "t_plant_pulse_coil_precharge", 30)
-        monkeypatch.setattr(vacv, "i_vac_pump_dwell", 0)
-        monkeypatch.setattr(vacv, "i_vacuum_pump_type", 1)
-        monkeypatch.setattr(vacv, "pres_vv_chamber_base", 0.00050000000000000001)
-        monkeypatch.setattr(vacv, "pres_div_chamber_burn", 0.35999999999999999)
-        monkeypatch.setattr(vacv, "outgrat_fw", 1.3000000000000001e-08)
-        monkeypatch.setattr(vacv, "temp_vv_chamber_gas_burn_end", 300)
+        monkeypatch.setattr(vacuum.data.vacuum, "i_vac_pump_dwell", 0)
+        monkeypatch.setattr(vacuum.data.vacuum, "i_vacuum_pump_type", 1)
+        monkeypatch.setattr(
+            vacuum.data.vacuum, "pres_vv_chamber_base", 0.00050000000000000001
+        )
+        monkeypatch.setattr(
+            vacuum.data.vacuum, "pres_div_chamber_burn", 0.35999999999999999
+        )
+        monkeypatch.setattr(vacuum.data.vacuum, "outgrat_fw", 1.3000000000000001e-08)
+        monkeypatch.setattr(vacuum.data.vacuum, "temp_vv_chamber_gas_burn_end", 300)
 
         ndiv = 1
         pfusmw = 2115.3899563651776