Add chemistry-driven fouling and HX/condenser penalties

tests/test_simulation.py

@@ -268,6 +268,28 @@ def test_auto_control_resets_shutdown_and_moves_rods():
     assert reactor.control.rod_fraction < 0.95
 
 
+def test_chemistry_builds_fouling_and_backpressure():
+    reactor = Reactor.default()
+    state = reactor.initial_state()
+    # Push impurities high to accelerate fouling dynamics.
+    state.dissolved_oxygen_ppm = 200.0
+    state.sodium_ppm = 100.0
+    state.secondary_loop.mass_flow_rate = 20_000.0
+    state.secondary_loop.steam_quality = 0.3
+    state.secondary_loop.temperature_out = 600.0
+    state.secondary_loop.temperature_in = 560.0
+    base_hx = state.hx_fouling
+    base_foul = state.turbines[0].fouling_penalty if state.turbines else 0.0
+    base_pressure = state.turbines[0].condenser_pressure if state.turbines else constants.CONDENSER_BASE_PRESSURE_MPA
+
+    reactor._update_chemistry(state, dt=20.0)
+
+    assert state.hx_fouling > base_hx
+    if state.turbines:
+        assert state.turbines[0].fouling_penalty > base_foul
+        assert state.turbines[0].condenser_pressure >= base_pressure
+
+
 def test_full_power_reaches_steam_and_turbine_output():
     """Integration: ramp to full power with staged rod control and verify sustained steam/electric output."""
     reactor = Reactor.default()