PWR Operator Manual ·
Open the simulator
10 — Glossary
Document: PWR-GL-01
Revision: 24
Terms used in the PWR manuals and on the simulator board. Acronym first, then plain meaning.
Plant MODES
Convention: write Mode N, Name (example: Mode 1, At Power).
| MODE | Full form | Short definition |
|---|
| 1 | Mode 1, At Power | Critical, thermal power > 5 %, RCS hot |
| 2 | Mode 2, Startup | Critical, power ≤ 5 %, RCS hot |
| 3 | Mode 3, Hot Standby | Subcritical, RCS hot (NOP T/P) |
| 4 | Mode 4, Hot Shutdown | Subcritical, intermediate RCS temperature |
| 5 | Mode 5, Cold Shutdown | Subcritical, RCS cold |
| 6 | Mode 6, Refueling | Cold, vessel head not fully tensioned (out of scope here) |
Mode 5, Cold Shutdown → Mode 1, At Power and Mode 1, At Power → Mode 5, Cold Shutdown master procedures: 05_MODE_TRANSITIONS.md (PWR-T20, PWR-T21). Both run end to end on integrated physics — Mode 5 was restored 2026-08-31 when the water-property floor moved below its boundary (09 §11.0).
Not plant MODES: turbine load modes Follow / Manual / Disconnected.
A
| Term | Definition |
|---|
| AC / DC | Alternating-current / direct-current electrical power. |
| AFW | Auxiliary Feedwater — backup water supply to the Steam Generators when main feed is lost. |
| ATWS | Anticipated Transient Without Scram — event where the reactor should trip but rods fail to insert fully. |
| AUTO / MAN | Automatic / manual control of a plant channel. AUTO reads instruments and issues commands to hold a setpoint; MAN leaves control to the operator. |
B–C
| Term | Definition |
|---|
| Borate / Dilute | Raise / lower dissolved boron concentration via CVCS (adds / removes negative reactivity) — done by setting the BORON CONTROL target ppm (batch dose), not a live meter seek. |
| CHEM SAMPLE / chemistry sample | RCS grab sample analyzed by the lab; the result (posted after a real 30-minute lab turnaround) is the authoritative boron ppm — there is no online boron meter on the board. |
| BOP | Balance of Plant — turbine, condenser, feedwater, and related secondary systems. |
| CVCS | Chemical & Volume Control System — charging, letdown, boron adjust, inventory make-up. |
| Critical / Criticality | Steady chain reaction: reactivity ≈ 0; power neither grows nor dies away on its own. |
| Cold Shutdown | RCS cool and depressurized, RHR carrying the heat sink — Mode 5, Cold Shutdown. [sim]: a Free Play initial condition, and the full path to and from power runs on integrated physics (PWR-T20 / PWR-T21). |
D
| Term | Definition |
|---|
| Decay heat | Heat from radioactive decay after fission stops (~7 % of rated after a power run, then falling). |
| RHR | Residual Heat Removal — the low-pressure system that removes leftover decay heat after shutdown. |
| DNB | Departure from Nucleate Boiling — heat-transfer crisis; fuel temperature rises sharply. |
| Doppler | Negative reactivity feedback from hotter fuel absorbing more neutrons (prompt stabilizer). |
| DPM | Decades Per Minute — unit of Startup Rate (one decade = factor of ten in power). |
E–F
| Term | Definition |
|---|
| ECCS | Emergency Core Cooling System — here, merged HPI/LPI plus passive accumulators. |
| ESF | Engineered Safety Features — systems such as HPI and AFW with AUTO/MAN arms. |
| Follow (load mode) | Turbine electrical load automatically tracks reactor power. |
H
| Term | Definition |
|---|
| Heat sink | Where core heat goes — primarily the Steam Generators (secondary water/steam). |
| Hot Full Power (HFP) | ~100 % power, ~100 MWe, equilibrium — full-power Mode 1, At Power. |
| Hot Standby | Subcritical, hot, at operating temperature and pressure — Mode 3, Hot Standby. |
| Hot Shutdown | Subcritical with RCS not yet cold — commercial Mode 4, Hot Shutdown. [sim]: the trainer derives it from power, reactivity and Tavg, so it is what the board declares while transiting between Mode 3 and Mode 5, and what the hot_shutdown preset loads. A post-trip board still at operating temperature is Mode 3, Hot Standby by temperature class. |
| Cold Shutdown | Subcritical and cold — Mode 5, Cold Shutdown. [sim] — see the Cold Shutdown entry under C. |
| HPI / LPI | High- / Low-Pressure Injection — merged emergency injection with a two-segment pump curve. |
| HR1 | Simulator hard rule: protection and alarms read instruments, never true state. |
I–L
| Term | Definition |
|---|
| Instrument / Indication | What the operator sees — lagged, noisy, possibly failed — not necessarily truth. |
| IR | Intermediate Range — compensated ion chamber (amperes) from SR handoff up to ~10 % power. |
| LOCA | Loss-Of-Coolant Accident — primary coolant escaping the RCS. |
| LOFW | Loss Of Feedwater — main feed to the SGs lost. |
| Load rejection | Sudden loss of electrical load / turbine trip; steam demand collapses. |
M–O
| Term | Definition |
|---|
| MSIV | Main Steam Isolation Valve — isolates Steam Generators from the turbine. |
| MTC | Moderator Temperature Coefficient — in a PWR, negative: hotter water → less reactivity. |
| MWe / MWt | Megawatts electric (grid) / megawatts thermal (reactor heat). |
| Natural circulation | Flow driven by density difference after pumps stop — weaker than forced RCP flow. |
| NOP | Normal Operating Pressure/Temperature (hot operating conditions). |
P
| Term | Definition |
|---|
| P-6 | Permissive: intermediate range on scale (≥ 1e-10 A). Allows the source-range trip to be blocked, which also switches the detector off (Trip Blocks panel, SR HIGH FLUX); resets below 5e-11 A, clearing the block. See 09 §2.0. |
| P-10 | Nuclear at-power permissive (8 % on this plant, the same crossing as P-7) — allows blocking the intermediate-range and power-range low-setpoint trips, and revokes a standing block below itself. |
| pcm | Percent millirho — unit of reactivity (1 pcm = 10⁻⁵ Δk/k). |
| POAH | Point of Adding Heat — power level where fission heat exceeds system losses. |
| PORV | Power-Operated Relief Valve — controllable RCS pressure relief on the pressurizer. |
| PORV block valve | Isolation valve upstream of the PORV; closes the relief line if the PORV sticks open. |
| PR | Power Range — main power % neutron channels at power. |
| Primary / RCS | Reactor Coolant System — high-pressure water loop through the core. |
| PWR | Pressurized Water Reactor. |
| PZR | Pressurizer — steam/water vessel that sets primary pressure. |
R
| Term | Definition |
|---|
| RCP | Reactor Coolant Pump — forced circulation in the primary loop. |
| Reactivity (ρ) | Tendency of the chain reaction to grow (+) or shrink (−); critical ≈ 0. |
| Reactor period | Time for power to change by a factor of e (~2.72); long period = slow change. |
| RPS | Reactor Protection System — automatic SCRAM logic. |
| Rod bank (control) | Operable control rods for reactivity control. |
| Rod bank (shutdown) | Scram rods, normally fully withdrawn; drive in on SCRAM. |
S
| Term | Definition |
|---|
| SBLOCA | Small-Break LOCA — e.g. stuck-open PORV. |
| SBO | Station Blackout — loss of all AC power (as modeled). |
| SCRAM | Rapid full insertion of control rods — emergency/automatic shutdown. |
| Secondary | Steam side: SG secondary, turbine, condenser, feedwater. |
| Setpoint (SP) | Value an automatic controller holds; often captured from the current reading when AUTO engages. |
| SG | Steam Generator — heat exchanger boiling secondary water using primary heat. |
| SGTR | Steam Generator Tube Rupture — primary-to-secondary leak. |
| Shrink and swell | Indicated SG level moves “wrong way” briefly on fast power/load changes. |
| SR | Source Range — startup neutron counter (counts per second). |
| Subcooling margin | How far primary coolant is below boiling temperature at current pressure — TMI truth-teller. |
| SUR | Startup Rate — how fast power is changing, in decades per minute (DPM). |
T–X
| Term | Definition |
|---|
| Tavg | Average primary coolant temperature. |
| Thot / Tcold | Hot-leg / cold-leg temperatures. |
| TMI | Three Mile Island (1979 accident). |
| True state | Actual physics values in the model — hidden from normal operator view. |
| Void / void fraction | Steam bubbles in the coolant; reduce heat transfer; affect inventory presentation. |
| Xenon (Xe-135) | Strong neutron-absorbing fission product; builds after power drops; decays over hours. |
01_GENERAL_DESCRIPTION.md 09_SETPOINTS_LIMITS.md - In-product Manual → Glossary section
These manuals are licensed
CC BY 4.0
— see Legal. Training documents for an educational
simulator, not licensing-basis documents for a real plant.