Add pressurizer and coolant inventory controls

tests/test_pressurizer.py

@@ -0,0 +1,35 @@
+from reactor_sim.reactor import Reactor
+from reactor_sim.commands import ReactorCommand
+
+
+def test_pressurizer_raises_pressure_with_level():
+    reactor = Reactor.default()
+    state = reactor.initial_state()
+    state.primary_loop.pressure = 5.0
+    reactor.pressurizer_level = 0.8
+    reactor.primary_pump_active = False
+    reactor.secondary_pump_active = False
+
+    reactor.step(state, dt=1.0, command=ReactorCommand.scram_all())
+
+    assert state.primary_loop.pressure > 5.0
+    assert reactor.pressurizer_level < 0.8
+
+
+def test_low_npsh_limits_primary_flow():
+    reactor = Reactor.default()
+    state = reactor.initial_state()
+    reactor.shutdown = False
+    reactor.control.manual_control = True
+    reactor.control.rod_fraction = 0.0
+    reactor.primary_pump_active = True
+    reactor.primary_pump_units = [True, True]
+    reactor.secondary_pump_active = False
+    state.primary_loop.pressure = 0.05  # near-vacuum to force cavitation
+    state.primary_loop.temperature_in = 400.0
+    state.primary_loop.temperature_out = 600.0
+
+    reactor.step(state, dt=1.0, command=ReactorCommand(generator_units={1: True}))
+
+    assert state.primary_pumps[0].status == "CAV"
+    assert state.primary_loop.mass_flow_rate < 100.0