Add generator power model and meltdown handling

src/reactor_sim/constants.py

@@ -8,7 +8,8 @@ NEUTRON_LIFETIME = 0.1  # seconds, prompt neutron lifetime surrogate
 FUEL_ENERGY_DENSITY = 200.0 * MEGAWATT  # J/kg released as heat
 COOLANT_HEAT_CAPACITY = 4_200.0  # J/(kg*K) for water/steam
 COOLANT_DENSITY = 700.0  # kg/m^3 averaged between phases
-MAX_CORE_TEMPERATURE = 1_800.0  # K
+CORE_MELTDOWN_TEMPERATURE = 2_873.0  # K (approx 2600C) threshold for irreversible meltdown
+MAX_CORE_TEMPERATURE = CORE_MELTDOWN_TEMPERATURE  # Allow simulation to approach meltdown temperature
 MAX_PRESSURE = 15.0  # MPa typical PWR primary loop limit
 CONTROL_ROD_SPEED = 0.03  # fraction insertion per second
 CONTROL_ROD_WORTH = 0.042  # delta rho contribution when fully withdrawn
@@ -20,6 +21,10 @@ MEV_TO_J = 1.602_176_634e-13
 ELECTRON_FISSION_CROSS_SECTION = 5e-16  # cm^2, tuned for simulation scale
 PUMP_SPOOL_TIME = 5.0  # seconds to reach commanded flow
 TURBINE_SPOOL_TIME = 12.0  # seconds to reach steady output
+GENERATOR_SPOOL_TIME = 10.0  # seconds to reach full output
+# Auxiliary power assumptions
+PUMP_POWER_MW = 12.0  # MW draw per pump unit
+BASE_AUX_LOAD_MW = 5.0  # control, instrumentation, misc.
 # Threshold inventories (event counts) for flagging common poisons in diagnostics.
 KEY_POISON_THRESHOLDS = {
     "Xe": 1e20,  # xenon