Physics behind the simulator
The plant — SLX-100
The SLX-100 (Single-Loop eXperimental) is a compact PWR of about 100 MWe: one RCS loop (core, RCP, U-tube SG, pressurizer), BOP, CVCS, ECCS, RHR, and RPS/ESF. Cold shutdown through full power is one continuous plant.
Model in short: six-group point kinetics · lumped heat and mass balances · load coupled through the secondary · protection on instrument channels · degraded regimes open · no spatial core.
Core power and reactivity
- Point kinetics, six delayed-neutron groups — one average power, no flux shape. Period and startup rate drive the nuclear instruments.
- Reactivity terms: rods (S-curve bank worth), Doppler (fuel temperature), moderator from coolant density (not a fixed MTC), boron, xenon, and core excess.
- I–Xe chain with burnout — whole-core only, no spatial oscillation.
- Decay heat with power-history dependence (two-term exponential production).
Heat, pressure, and inventory
- Lumped nodes (fuel, cladding hot node, coolant, secondary) with first-order heat transfer — not a TH systems code.
- Pressurizer thermodynamics (heaters, spray, PORV / safeties); solid and empty ends are reachable.
- Inventory from CVCS, ECCS, accumulators, leaks, and relief. Subcooling tracked; primary can void; RCP cavitation from suction margin.
- Degraded regimes stay open — uncovered SG tubes cut heat transfer; voided primary and solid pressurizer are allowed states, not clamped out.
Secondary and electrical
- SG mass-energy balance couples steam, feed, dumps, and isolation to primary heat removal.
- Turbine / condenser / generator: load is a steam demand on the primary; loss of turbine or heat sink leaves energy in the plant.
Instruments and protection
Board quantities are lagged instrument channels (optional stuck/drift). Trips, interlocks, safeguards, and automatic controllers take those channel values — not true state. A failed transmitter misleads both the operator and the automation.
What is left out on purpose
- No spatial neutronics or xenon tilt.
- One loop, lumped nodes — no multi-loop or subchannel TH.
- No containment / LOCA licensing stack (core-damage paths for training progression only).
- Not a digital twin of a named unit.
Coefficients, step order, and declared departures: simulation-physics chapter in the in-sim manual, or the engine sources on GitHub (AGPL).