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Abnormals > AB.ROD-0002 — Dropped Rod

AB.ROD-0002 — Dropped Rod

⚠️ DRAFT

AB.ROD-0002 — Dropped Rod

Purpose

Provides guidance for responding to a dropped control rod, including diagnosis via NIS indications, withdrawal rate restrictions based on time elapsed, and rod recovery authorization requirements.

Key Actions / Information

Exam — 2022 Q19
The Power Range NIS channel nearest a dropped rod will indicate lower compared to other PR channels (local flux depression). Per step 3.36, if less than 4 hours have elapsed since first indication of a dropped rod, no withdrawal rate, power level, or ramp rate restrictions apply during rod recovery.
JPM — 2022 RO-A3
Following dropped rod 2D4 from Control Bank Delta at 100% power: OHAs E-46 (LOWER SECT DEV ABV 50% PWR) and E-38 (UPPER SECT DEV ABV 50% PWR) annunciate. Must reduce power to 74% per TSAS 3.1.3.1.c.3.d. Manual QPTR surveillance (S2.OP-ST.NIS-0002) required — dropped rod causes asymmetric flux in the affected quadrant, resulting in QPTR exceeding 1.02 (TS LCO 3.2.4 NOT met).
Exam — 2020 Q19
Before withdrawing a dropped rod, AB.ROD-0002 directs resetting the group step counter to zero so the step counter matches actual rod position and the rod is withdrawn to the proper height. For Control Bank D Group 1 rods, the P/A converter is also reset to zero (performed locally at the RPI-2 cabinet) to ensure bank overlap is maintained. The group step counter does NOT input into the P/A converter — P/A converter input is from the Group 1 Data Logging card. After P/A converter reset, OHAs E-8 RIL LO and E-16 RIL LO-LO WILL annunciate (expected). OHA E-40 ROD BANK URGENT FAILURE will also annunciate following rod withdrawal due to Power Cabinet Regulation failure with lift coil disconnect switches in OFF.
Scenario — 2019 #3
Two dropped control rods at ~89% power during load reduction (Event 5). Reactor trip demand present but auto trip fails — ATWT. Manual Rx trip handles also fail. Rod speed controller fails at 8 spm in Auto. Crew recognizes and inserts rods in Manual at 48 spm. This event leads directly into EOP-FRSM-1 for ATWS response.
Exam — 2018 Q30
Dropped rod recovery per AB.ROD-0002: with ROD BANK SELECTOR SWITCH in CBA (Control Bank A), the dropped rod will be withdrawn at 48 steps per minute in small increments per reactor Engineering guidance. Trap: 72 SPM is AUTO maximum speed, 64 SPM is Shutdown Bank speed (SBA/SBB/SBC/SBD), 8 SPM is AUTO minimum speed. Control Bank positions (CBA/CBB/CBC/CBD) = 48 SPM.

Connections