PWR Operator Manual · Open the simulator

01 — Plant General Description

Document: PWR-GD-01
Plant: Pressurized Water Reactor (PWR)
Plant: SLS-100 (Single Loop Simulated, 100 MWe) Rating: ≈ 100 MWe / ≈ 300 MWt — a compact single-loop experimental PWR (one reactor coolant pump, one U-tube steam generator, one main steam line). Small and generously margined by design, and reactor trips are reserved for genuine limits. The steam dump is sized at 40 % of rated steam flow, the prototypical Westinghouse capacity: a 50 % loss of load is absorbed with no trip and no relief lift, and a larger rejection is ridden out by the reactor itself running back, with the PORV as the backstop.
Revision: 24

1.0 Purpose

This document describes the Reactor⚛️Dynamics PWR unit: design concept, major systems, operating modes, and deliberate simplifications. Operators should read this before free-play or procedure training.

2.0 Design concept

A Pressurized Water Reactor keeps primary coolant water under high pressure so it does not boil in the core. Heat is transferred through Steam Generators (SG) into a separate secondary loop that produces steam for the turbine-generator.

Why high primary pressure? Subcooling margin (how far the coolant is from boiling) is the plant’s guarantee that the primary stays liquid. Lose pressure or overheat the coolant, and boiling (voids) begins — the lesson behind Three Mile Island.

3.0 Energy path (what the operator is controlling)

FISSION HEAT (core)
    → Primary coolant (hot leg → SG U-tubes → cold leg → RCP → core)
    → Steam Generator (secondary boils; loops never mix)
    → Main steam → Turbine-Generator → Grid (MWe)
    → Condenser → Feed pumps → SG

Pressurizer (PZR) sits on the hot leg: heaters raise pressure, spray lowers it, and the Power-Operated Relief Valve (PORV) with block valve protects / can mislead.

Negative feedbacks (Doppler and Moderator Temperature Coefficient) make the plant self-regulating: hotter fuel and hotter moderator reduce reactivity. Power tends to follow steam demand.

4.0 Major systems

4.1 Reactor core and reactivity control

Simplification: One control group + one shutdown group (no multi-bank overlap sequencing).

4.2 Reactor Coolant System (RCS) / primary

Simplification: Single lumped primary loop (one representative RCP/SG), uniform primary pressure (no leg ΔP model).

4.3 Secondary / Balance of Plant (BOP)

4.4 Protection and safety automation

5.0 Plant MODES (Mode 1, At Power through Mode 6, Refueling)

This trainer uses commercial PWR MODE numbers. In prose, say Mode 1, At Power, Mode 2, Startup, … Mode 6, Refueling.

Modes 3/4/5 are decided by TEMPERATURE alone, not by pressure. A subcritical plant at 392 °F (200 °C) and 500 psi (3.45 MPa) is Mode 3 here even though it is nowhere near normal operating pressure — the boundaries above are the whole definition. 5_percent is a Mode 1 initial condition: it is authored at ~6 % power, deliberately just above the 5 % boundary.

Full commercial paths (see 05_MODE_TRANSITIONS.md) — both run on integrated physics, end to end on the board:

• Mode 5, Cold Shutdown → Mode 1, At Power — procedure PWR-T20, starting from the cold_shutdown initial condition (09 §11.0).
• Mode 1, At Power → Mode 5, Cold Shutdown — procedure PWR-T21, down to a cold, depressurized plant on RHR.

NOTE: the heatup runs on real plant rates — ride the long legs at time acceleration; on the cooldown side the depressurisation rate remains deliberately compressed. See 12 §14.

Sim-only everyday path: Mode 3, Hot Standby ↔ Mode 1, At Power (PWR-T03 / PWR-T04).

Post-trip with the plant still hot is still Mode 3, Hot Standby by temperature class (subcritical, hot), even though crews often say “hot shutdown.”

6.0 Turbine load modes (not plant MODES)

Independent of plant MODE, the generator has three load modes:

Manual is the default you actually get, not Follow. Follow is the engine's own fallback and is what 5_percent starts in; the startup lineup overrides it to Manual at both main at-power initial conditions, and hot_shutdown spawns off line.

Coupled feedwater is a fallback, not the level control. Feed is briefly tied to the load target, but the three-element feed controller (STEAM GEN FEED → AUTO) is engaged by default in Free Play and takes the steam generator level as soon as it acts — measured, the coupling drops out within about three minutes of a full-power start. Treat three-element AUTO as the level backbone (PWR-N12); coupled feed is what remains when it is off.

Rule of thumb: The turbine leads, up and down: set LOAD, then move the rods to hold AVG COOLANT TEMPERATURE on program (Westinghouse Technology Systems Manual 19.0, ADAMS ML11223A342, App. 19-1 step 22: "Increase generator load at the desired rate while maintaining Tavg with manual rod control."). Mismatch floods or drains the SG.

These are never called Mode 1, At Power / Mode 5, Cold Shutdown.

7.0 What the operator never sees by default

Golden rule: Trust subcooling margin and diverse indications more than any single light.

8.0 Deliberate simplifications (honest scope)

Where the model understates reality, training commentary and these manuals say so.

This table is a summary. The full account — what the engine actually computes, every deliberate simplification, and everything that is not modeled at all — is 12_SIM_PHYSICS.md.

9.0 Flagship accident

Three Mile Island Unit 2 (1979) is hosted on this plant. Root teaching theme: an accident of information — a stuck-open PORV with an indicator that read closed, pressurizer level that rose while inventory fell, and operators who throttled High-Pressure Injection (HPI) based on the wrong story.

See 08_ACCIDENT_TMI.md and procedure PWR-X01.

10.0 Related documents

• 02_SIMULATOR_USER_GUIDE.md — using the trainer
• 03_CONTROLS_AND_INDICATIONS.md — board inventory
• 09_SETPOINTS_LIMITS.md — numbers
• 10_GLOSSARY.md — terms

These manuals are licensed CC BY 4.0 — see Legal. Training documents for an educational simulator, not licensing-basis documents for a real plant.