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Add enthalpy-based secondary boil-off and turbine mapping

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Codex Agent
2025-11-25 17:47:37 +01:00
parent 4162ecf712
commit 0f54540526
7 changed files with 113 additions and 38 deletions
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8
TODO.md
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@@ -8,7 +8,7 @@
- [ ] Flesh out condenser behavior: vacuum pump limits, cooling water temperature coupling, and dynamic back-pressure with fouling.
- [ ] Dashboard polish: compact turbine/generator rows, color critical warnings (SCRAM/heat-sink), and reduce repeated log noise.
- [ ] Incremental realism plan:
- Add stored enthalpy for primary/secondary loops and a steam-drum mass/energy balance (sensible + latent) while keeping existing pump logic and tests passing.
- Adjust HX/pressure handling to use stored energy (saturation clamp and pressure rise) and validate steam formation with both pumps at ~3 GW.
- Update turbine power mapping to consume steam enthalpy/quality and align protection trips with real steam presence.
- Add integration test: cold start → gens/pumps 2/2 → ramp to ~3 GW → confirm steam quality threshold → enable all turbines and require electrical output.
- Add stored enthalpy for primary/secondary loops and a steam-drum mass/energy balance (sensible + latent) while keeping existing pump logic and tests passing. Target representative PWR conditions: primary 15–16 MPa, 290–320 °C inlet/320–330 °C outlet, secondary saturation ~6–7 MPa with boil at ~490–510 K.
- Adjust HX/pressure handling to use stored energy (saturation clamp and pressure rise) and validate steam formation with both pumps at ~3 GW. Use realistic tube-side material assumptions (Inconel 690/SS cladding) and clamp steam quality to phase-equilibrium enthalpy.
- Update turbine power mapping to consume steam enthalpy/quality and align protection trips with real steam presence; drive inlet steam around 6–7 MPa, quality/enthalpy-based flow to ~550–600 MW(e) per machine class if steam is available.
- Add integration test: cold start → gens/pumps 2/2 → ramp to ~3 GW → confirm steam quality threshold at the secondary drum → enable all turbines and require electrical output. Include a step that tolerates one secondary pump off for a period to prove redundancy still yields steam.

21
src/reactor_sim/reactor.py
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@@ -16,7 +16,7 @@ from .fuel import FuelAssembly, decay_heat_fraction
from .generator import DieselGenerator, GeneratorState
from .neutronics import NeutronDynamics
from .state import CoolantLoopState, CoreState, PlantState, PumpState, TurbineState
from .thermal import ThermalSolver, heat_transfer, saturation_pressure, temperature_rise
from .thermal import ThermalSolver, heat_transfer, saturation_pressure, saturation_temperature, temperature_rise
from .turbine import SteamGenerator, Turbine
LOGGER = logging.getLogger(__name__)
@@ -126,6 +126,7 @@ class Reactor:
steam_quality=0.0,
inventory_kg=primary_nominal_mass * constants.PRIMARY_INVENTORY_TARGET,
level=constants.PRIMARY_INVENTORY_TARGET,
energy_j=primary_nominal_mass * constants.PRIMARY_INVENTORY_TARGET * constants.COOLANT_HEAT_CAPACITY * ambient,
)
secondary = CoolantLoopState(
temperature_in=ambient,
@@ -135,6 +136,7 @@ class Reactor:
steam_quality=0.0,
inventory_kg=secondary_nominal_mass * constants.SECONDARY_INVENTORY_TARGET,
level=constants.SECONDARY_INVENTORY_TARGET,
energy_j=secondary_nominal_mass * constants.SECONDARY_INVENTORY_TARGET * constants.COOLANT_HEAT_CAPACITY * ambient,
)
primary_pumps = [
PumpState(active=self.primary_pump_active and self.primary_pump_units[idx], flow_rate=0.0, pressure=0.5)
@@ -434,6 +436,17 @@ class Reactor:
cooling_drop = min(40.0, max(10.0, 0.2 * excess))
state.secondary_loop.temperature_in = max(env, state.secondary_loop.temperature_out - cooling_drop)
# Keep stored energies consistent with updated temperatures/quality.
cp = constants.COOLANT_HEAT_CAPACITY
primary_avg = 0.5 * (state.primary_loop.temperature_in + state.primary_loop.temperature_out)
state.primary_loop.energy_j = max(0.0, state.primary_loop.inventory_kg * cp * primary_avg)
sat_temp_sec = saturation_temperature(max(0.05, state.secondary_loop.pressure))
sec_liquid_energy = state.secondary_loop.inventory_kg * cp * min(state.secondary_loop.temperature_out, sat_temp_sec)
sec_latent = state.secondary_loop.inventory_kg * state.secondary_loop.steam_quality * constants.STEAM_LATENT_HEAT
superheat = max(0.0, state.secondary_loop.temperature_out - sat_temp_sec)
sec_superheat = state.secondary_loop.inventory_kg * cp * superheat if state.secondary_loop.steam_quality >= 1.0 else 0.0
state.secondary_loop.energy_j = max(0.0, sec_liquid_energy + sec_latent + sec_superheat)
state.primary_to_secondary_delta_t = max(0.0, state.primary_loop.temperature_out - state.secondary_loop.temperature_in)
state.heat_exchanger_efficiency = 0.0 if total_power <= 0 else min(1.0, max(0.0, transferred / max(1e-6, total_power)))
@@ -578,7 +591,13 @@ class Reactor:
if loop.mass_flow_rate <= 0.0 or loop.steam_quality <= 0.0:
return
steam_mass = loop.mass_flow_rate * loop.steam_quality * constants.SECONDARY_STEAM_LOSS_FRACTION * dt
if steam_mass <= 0.0:
return
prev_mass = max(1e-6, loop.inventory_kg)
loop.inventory_kg = max(0.0, loop.inventory_kg - steam_mass)
# Scale stored energy with the remaining mass to keep specific enthalpy consistent.
ratio = max(0.0, loop.inventory_kg) / prev_mass
loop.energy_j *= ratio
nominal = self._nominal_inventory(constants.SECONDARY_LOOP_VOLUME_M3)
loop.level = min(1.2, max(0.0, loop.inventory_kg / nominal)) if nominal > 0 else 0.0

18
src/reactor_sim/state.py
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@@ -4,6 +4,8 @@ from __future__ import annotations
from dataclasses import dataclass, field, asdict
from . import constants
from .generator import GeneratorState
@@ -51,6 +53,7 @@ class CoolantLoopState:
steam_quality: float # fraction of vapor
inventory_kg: float = 0.0 # bulk mass of coolant
level: float = 1.0 # fraction full relative to nominal volume
energy_j: float = 0.0 # stored thermal/latent energy for the loop
def average_temperature(self) -> float:
return 0.5 * (self.temperature_in + self.temperature_out)
@@ -135,8 +138,8 @@ class PlantState:
delta_t = data.get("primary_to_secondary_delta_t", 0.0)
return cls(
core=CoreState(**core_blob, fission_product_inventory=inventory, emitted_particles=particles),
primary_loop=CoolantLoopState(**data["primary_loop"]),
secondary_loop=CoolantLoopState(**data["secondary_loop"]),
primary_loop=CoolantLoopState(**_with_energy(data["primary_loop"])),
secondary_loop=CoolantLoopState(**_with_energy(data["secondary_loop"])),
turbines=turbines,
primary_pumps=[PumpState(**p) for p in prim_pumps_blob],
secondary_pumps=[PumpState(**p) for p in sec_pumps_blob],
@@ -146,3 +149,14 @@ class PlantState:
primary_to_secondary_delta_t=delta_t,
time_elapsed=data.get("time_elapsed", 0.0),
)
def _with_energy(loop_blob: dict) -> dict:
"""Backwards compatibility: derive energy if missing."""
if "energy_j" in loop_blob:
return loop_blob
energy = 0.5 * (loop_blob.get("temperature_in", 295.0) + loop_blob.get("temperature_out", 295.0))
energy *= loop_blob.get("inventory_kg", 0.0) * constants.COOLANT_HEAT_CAPACITY
out = dict(loop_blob)
out["energy_j"] = energy
return out

63
src/reactor_sim/thermal.py
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@@ -95,6 +95,10 @@ class ThermalSolver:
core.fuel_temperature += heating - cooling
# Keep fuel temperature bounded and never below the coolant outlet temperature.
core.fuel_temperature = min(max(primary.temperature_out, core.fuel_temperature), constants.MAX_CORE_TEMPERATURE)
avg_temp = 0.5 * (primary.temperature_in + primary.temperature_out)
primary.energy_j = max(
0.0, primary.inventory_kg * constants.COOLANT_HEAT_CAPACITY * avg_temp
)
LOGGER.debug(
"Primary loop: flow=%.0f kg/s temp_out=%.1fK core_temp=%.1fK",
primary.mass_flow_rate,
@@ -103,42 +107,47 @@ class ThermalSolver:
)
def step_secondary(self, secondary: CoolantLoopState, transferred_mw: float, dt: float = 1.0) -> None:
"""Update secondary loop using a simple steam-drum mass/energy balance."""
if transferred_mw <= 0.0 or secondary.mass_flow_rate <= 0.0:
secondary.steam_quality = max(0.0, secondary.steam_quality - 0.02 * dt)
secondary.temperature_out = max(
constants.ENVIRONMENT_TEMPERATURE, secondary.temperature_out - 0.5 * dt
)
secondary.pressure = max(
0.1, min(constants.MAX_PRESSURE, saturation_pressure(secondary.temperature_out))
)
return
temp_in = secondary.temperature_in
mass_flow = secondary.mass_flow_rate
"""Update secondary loop using a stored-energy steam-drum balance."""
cp = constants.COOLANT_HEAT_CAPACITY
sat_temp = saturation_temperature(max(0.05, secondary.pressure))
energy_j = max(0.0, transferred_mw) * constants.MEGAWATT * dt
mass = max(1e-6, secondary.inventory_kg)
if secondary.energy_j <= 0.0:
secondary.energy_j = mass * cp * secondary.average_temperature()
# Energy needed to heat incoming feed to saturation.
sensible_j = max(0.0, sat_temp - temp_in) * mass_flow * cp * dt
if energy_j <= sensible_j:
delta_t = temperature_rise(transferred_mw, mass_flow)
secondary.temperature_out = temp_in + delta_t
secondary.steam_quality = 0.0
# Add transferred heat; if no heat, bleed toward ambient.
if transferred_mw > 0.0:
secondary.energy_j += transferred_mw * constants.MEGAWATT * dt
else:
energy_left = energy_j - sensible_j
steam_mass = energy_left / constants.STEAM_LATENT_HEAT
produced_fraction = steam_mass / max(1e-6, mass_flow * dt)
secondary.temperature_out = sat_temp
secondary.steam_quality = min(1.0, max(0.0, produced_fraction))
bleed = 0.01 * (secondary.temperature_out - constants.ENVIRONMENT_TEMPERATURE)
secondary.energy_j = max(
mass * cp * constants.ENVIRONMENT_TEMPERATURE, secondary.energy_j - max(0.0, bleed) * mass * cp * dt
)
sat_temp = saturation_temperature(max(0.05, secondary.pressure))
liquid_energy = mass * cp * sat_temp
available = secondary.energy_j
if available <= liquid_energy:
# Subcooled or saturated liquid.
temp = available / (mass * cp)
secondary.temperature_out = max(temp, constants.ENVIRONMENT_TEMPERATURE)
secondary.steam_quality = max(0.0, secondary.steam_quality - 0.01 * dt)
else:
excess = available - liquid_energy
quality = min(1.0, excess / (mass * constants.STEAM_LATENT_HEAT))
superheat_energy = max(0.0, excess - quality * mass * constants.STEAM_LATENT_HEAT)
superheat_temp = superheat_energy / (mass * cp) if quality >= 1.0 else 0.0
secondary.temperature_out = sat_temp + superheat_temp
secondary.steam_quality = quality
# Re-normalize stored energy to the realized state.
secondary.energy_j = liquid_energy + quality * mass * constants.STEAM_LATENT_HEAT + superheat_energy
secondary.pressure = min(
constants.MAX_PRESSURE, max(secondary.pressure, saturation_pressure(secondary.temperature_out))
)
LOGGER.debug(
"Secondary loop: transferred=%.1fMW temp_out=%.1fK quality=%.2f",
"Secondary loop: transferred=%.1fMW temp_out=%.1fK quality=%.2f energy=%.1eJ",
transferred_mw,
secondary.temperature_out,
secondary.steam_quality,
secondary.energy_j,
)

8
src/reactor_sim/turbine.py
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@@ -6,6 +6,7 @@ from dataclasses import dataclass
import logging
from . import constants
from .thermal import saturation_temperature
from .state import CoolantLoopState, TurbineState
LOGGER = logging.getLogger(__name__)
@@ -50,10 +51,13 @@ class Turbine:
throttle = min(constants.TURBINE_THROTTLE_MAX, max(constants.TURBINE_THROTTLE_MIN, self.throttle))
throttle_eff = 1.0 - constants.TURBINE_THROTTLE_EFFICIENCY_DROP * (constants.TURBINE_THROTTLE_MAX - throttle)
enthalpy = 2_700.0 + loop.steam_quality * 600.0
sat_temp = saturation_temperature(max(0.05, loop.pressure))
superheat = max(0.0, loop.temperature_out - sat_temp)
enthalpy = (constants.STEAM_LATENT_HEAT / 1_000.0) + (superheat * constants.COOLANT_HEAT_CAPACITY / 1_000.0)
mass_flow = effective_mass_flow * 0.6 * throttle
computed_power = (enthalpy * mass_flow / 1_000.0) / 1_000.0
computed_power = (enthalpy * mass_flow) / 1_000.0 # MW from enthalpy flow
available_power = steam_power_mw if steam_power_mw > 0 else computed_power
available_power = min(available_power, computed_power)
backpressure_loss = 1.0 - _backpressure_penalty(loop)
shaft_power_mw = available_power * self.mechanical_efficiency * throttle_eff * backpressure_loss
electrical = shaft_power_mw * self.generator_efficiency

28
tests/test_simulation.py
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@@ -266,3 +266,31 @@ def test_auto_control_resets_shutdown_and_moves_rods():
assert reactor.shutdown is False
assert reactor.control.manual_control is False
assert reactor.control.rod_fraction < 0.95
def test_full_power_reaches_steam_and_turbine_output():
"""Integration: cold start -> pumps/gens on -> ramp to ~3 GW -> steam -> turbines online."""
reactor = Reactor.default()
state = reactor.initial_state()
reactor.step(
state,
dt=1.0,
command=ReactorCommand(
generator_units={1: True, 2: True},
primary_pumps={1: True, 2: True},
secondary_pumps={1: True, 2: True},
rod_manual=False,
),
)
for i in range(600):
cmd = None
if i == 200:
cmd = ReactorCommand(secondary_pumps={2: False})
if i == 300:
cmd = ReactorCommand(secondary_pumps={2: True})
if i == 400:
cmd = ReactorCommand(turbine_on=True, turbine_units={1: True, 2: True, 3: True})
reactor.step(state, dt=1.0, command=cmd)
assert state.secondary_loop.steam_quality > 0.02
assert state.total_electrical_output() > 50.0

5
tests/test_thermal.py
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@@ -30,8 +30,9 @@ def test_secondary_heats_to_saturation_before_boiling():
def test_secondary_generates_steam_when_energy_exceeds_sensible_heat():
solver = ThermalSolver()
loop = _secondary_loop(temp_in=330.0, flow=180.0, pressure=0.5)
loop.inventory_kg *= 0.1 # reduce mass to let boil-up happen quickly
sat_temp = saturation_temperature(loop.pressure)
solver.step_secondary(loop, transferred_mw=120.0, dt=1.0)
assert loop.temperature_out == pytest.approx(sat_temp, rel=0.02)
solver.step_secondary(loop, transferred_mw=120.0, dt=100.0)
assert loop.temperature_out == pytest.approx(sat_temp, rel=0.05)
assert loop.steam_quality > 0.0
assert loop.steam_quality < 1.0