Add spool dynamics for pumps and turbines

tests/test_turbine.py

@@ -0,0 +1,33 @@
+import pytest
+
+from reactor_sim.state import CoolantLoopState, TurbineState
+from reactor_sim.turbine import Turbine
+
+
+def test_turbine_spools_toward_target_output():
+    turbine = Turbine()
+    loop = CoolantLoopState(
+        temperature_in=600.0,
+        temperature_out=650.0,
+        pressure=6.0,
+        mass_flow_rate=20_000.0,
+        steam_quality=0.9,
+    )
+    state = TurbineState(
+        steam_enthalpy=0.0,
+        shaft_power_mw=0.0,
+        electrical_output_mw=0.0,
+        condenser_temperature=300.0,
+    )
+    target_electric = min(
+        turbine.rated_output_mw, 300.0 * turbine.mechanical_efficiency * turbine.generator_efficiency
+    )
+
+    dt = 5.0
+    turbine.step(loop, state, steam_power_mw=300.0, dt=dt)
+    assert 0.0 < state.electrical_output_mw < target_electric
+
+    for _ in range(5):
+        turbine.step(loop, state, steam_power_mw=300.0, dt=dt)
+
+    assert state.electrical_output_mw == pytest.approx(target_electric, rel=0.05)