Add delayed kinetics and steam-drum balance

tests/test_thermal.py

@@ -0,0 +1,37 @@
+import pytest
+
+from reactor_sim import constants
+from reactor_sim.state import CoolantLoopState
+from reactor_sim.thermal import ThermalSolver, saturation_temperature
+
+
+def _secondary_loop(temp_in: float = 350.0, pressure: float = 0.5, flow: float = 200.0) -> CoolantLoopState:
+    nominal_mass = constants.SECONDARY_LOOP_VOLUME_M3 * constants.COOLANT_DENSITY
+    return CoolantLoopState(
+        temperature_in=temp_in,
+        temperature_out=temp_in,
+        pressure=pressure,
+        mass_flow_rate=flow,
+        steam_quality=0.0,
+        inventory_kg=nominal_mass,
+        level=constants.SECONDARY_INVENTORY_TARGET,
+    )
+
+
+def test_secondary_heats_to_saturation_before_boiling():
+    solver = ThermalSolver()
+    loop = _secondary_loop(temp_in=330.0, flow=180.0, pressure=0.5)
+    sat_temp = saturation_temperature(loop.pressure)
+    solver.step_secondary(loop, transferred_mw=50.0, dt=1.0)
+    assert loop.steam_quality == pytest.approx(0.0)
+    assert loop.temperature_out < sat_temp
+
+
+def test_secondary_generates_steam_when_energy_exceeds_sensible_heat():
+    solver = ThermalSolver()
+    loop = _secondary_loop(temp_in=330.0, flow=180.0, pressure=0.5)
+    sat_temp = saturation_temperature(loop.pressure)
+    solver.step_secondary(loop, transferred_mw=120.0, dt=1.0)
+    assert loop.temperature_out == pytest.approx(sat_temp, rel=0.02)
+    assert loop.steam_quality > 0.0
+    assert loop.steam_quality < 1.0