AB.STM-0001 — Excessive Steam Flow
⚠️ DRAFT — Reconstructed from exam materials
Purpose
Provides guidance for responding to excessive/uncontrolled steam flow events, including failed-open atmospheric relief valves (MS10s), steam leaks, and other steam system malfunctions.
Key Actions / Information
Continuous Action Statement (CAS)
Exam — 2020 Q43
AB.STM-0001 CAS directs: (1) Trip the reactor, (2) Initiate Main Steam Line Isolation (MSLI). After MSLI, the CAS asks if the steam leak is isolated. If the leak is NOT isolated (e.g., MS10 failed open — MSLI closes MSIVs but does not affect MS10 valves downstream), then initiate a manual Safety Injection. An MS10 failed open is NOT isolated by MSLI — the MS10 is downstream of the MSIV, so the steam leak continues even after MSLI actuation.
Connections
- Related systems: Main Steam
- Related exam questions: 2020 Q43
- Related exam: 2020 NRC Written Exam, 2023 NRC Operating Exam