From a5c52b76520825f994babc34a6856f35fb0e29af Mon Sep 17 00:00:00 2001
From: Codex Agent <codex@example.com>
Date: Sun, 23 Nov 2025 00:39:50 +0100
Subject: [PATCH] Ramp pressure/flow down over spool time when pumps stop

---
 src/reactor_sim/reactor.py | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/src/reactor_sim/reactor.py b/src/reactor_sim/reactor.py
index b5ba99f..0f2980d 100644
--- a/src/reactor_sim/reactor.py
+++ b/src/reactor_sim/reactor.py
@@ -275,11 +275,17 @@ class Reactor:
                 state.primary_loop.pressure, 0.5, dt, self.primary_pump.spool_time
             )
         else:
-            state.primary_loop.mass_flow_rate = 0.0
-            state.primary_loop.pressure = max(0.1, saturation_pressure(state.primary_loop.temperature_out))
+            state.primary_loop.mass_flow_rate = self._ramp_value(
+                state.primary_loop.mass_flow_rate, 0.0, dt, self.primary_pump.spool_time
+            )
+            state.primary_loop.pressure = self._ramp_value(
+                state.primary_loop.pressure, max(0.1, saturation_pressure(state.primary_loop.temperature_out)), dt, self.primary_pump.spool_time
+            )
             for pump_state in state.primary_pumps:
                 pump_state.active = False
-                pump_state.flow_rate = 0.0
+                pump_state.flow_rate = self._ramp_value(
+                    pump_state.flow_rate, 0.0, dt, self.primary_pump.spool_time
+                )
                 pump_state.pressure = state.primary_loop.pressure
                 pump_state.status = "STOPPING" if pump_state.flow_rate > 1.0 else "OFF"
         if self.secondary_pump_active:
@@ -319,11 +325,17 @@ class Reactor:
                 state.secondary_loop.pressure, 0.5, dt, self.secondary_pump.spool_time
             )
         else:
-            state.secondary_loop.mass_flow_rate = 0.0
-            state.secondary_loop.pressure = max(0.1, saturation_pressure(state.secondary_loop.temperature_out))
+            state.secondary_loop.mass_flow_rate = self._ramp_value(
+                state.secondary_loop.mass_flow_rate, 0.0, dt, self.secondary_pump.spool_time
+            )
+            state.secondary_loop.pressure = self._ramp_value(
+                state.secondary_loop.pressure, max(0.1, saturation_pressure(state.secondary_loop.temperature_out)), dt, self.secondary_pump.spool_time
+            )
             for pump_state in state.secondary_pumps:
                 pump_state.active = False
-                pump_state.flow_rate = 0.0
+                pump_state.flow_rate = self._ramp_value(
+                    pump_state.flow_rate, 0.0, dt, self.secondary_pump.spool_time
+                )
                 pump_state.pressure = state.secondary_loop.pressure
                 pump_state.status = "STOPPING" if pump_state.flow_rate > 1.0 else "OFF"