Add spool dynamics for pumps and turbines

src/reactor_sim/constants.py

@@ -17,6 +17,8 @@ ENVIRONMENT_TEMPERATURE = 295.0  # K
 AMU_TO_KG = 1.660_539_066_60e-27
 MEV_TO_J = 1.602_176_634e-13
 ELECTRON_FISSION_CROSS_SECTION = 5e-16  # cm^2, tuned for simulation scale
+PUMP_SPOOL_TIME = 5.0  # seconds to reach commanded flow
+TURBINE_SPOOL_TIME = 12.0  # seconds to reach steady output
 # Threshold inventories (event counts) for flagging common poisons in diagnostics.
 KEY_POISON_THRESHOLDS = {
     "Xe": 1e20,  # xenon