Add pressurizer and coolant inventory controls

src/reactor_sim/constants.py

@@ -35,6 +35,21 @@ SECONDARY_OUTLET_TARGET_K = 520.0
 PRIMARY_NOMINAL_PRESSURE = 7.0  # MPa typical RBMK channel header pressure
 SECONDARY_NOMINAL_PRESSURE = 7.0  # MPa steam drum/steam line pressure surrogate
 STEAM_GENERATOR_UA_MW_PER_K = 25.0  # overall UA for steam generator (MW/K)
+# Loop volume / inventory assumptions
+PRIMARY_LOOP_VOLUME_M3 = 350.0
+SECONDARY_LOOP_VOLUME_M3 = 320.0
+PRIMARY_PRESSURIZER_SETPOINT_MPA = 7.0
+PRIMARY_PRESSURIZER_DEADBAND_MPA = 0.15
+PRIMARY_PRESSURIZER_HEAT_RATE_MPA_PER_S = 0.08
+PRIMARY_PRESSURIZER_SPRAY_RATE_MPA_PER_S = 0.12
+PRIMARY_PRESSURIZER_LEVEL_DRAW_PER_S = 0.002
+PRIMARY_PRESSURIZER_LEVEL_FILL_PER_S = 0.001
+LOOP_INVENTORY_CORRECTION_RATE = 0.08  # fraction of nominal mass restored per second toward target
+PRIMARY_INVENTORY_TARGET = 0.95
+SECONDARY_INVENTORY_TARGET = 0.9
+SECONDARY_STEAM_LOSS_FRACTION = 0.02  # fraction of steam mass that leaves the loop each second
+NPSH_REQUIRED_MPA = 0.25
+LOW_LEVEL_FLOW_FLOOR = 0.05
 # Threshold inventories (event counts) for flagging common poisons in diagnostics.
 KEY_POISON_THRESHOLDS = {
     "Xe": 1e20,  # xenon