ML20168A734
| ML20168A734 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1973-005 | |
| Download: ML20168A734 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
89205 Date:
November 30, 1973
Title:
Failure of Reactor Coolant Pump Shaft at Surry 1 The failure sequence was:
- 1. With the reactor at 95% power, operations personnel noted reactor coolant flow fluctuations varying between 96-100% and a 12 mil (peak-peak) vibration of reactor coolant pump (RCP) A.
- 2. A controlled shutdown was initiated.
- 3. At 42% power the reactor tripped coincident with a sudden loss of flow in loop A, which resulted from the failure of the RCP A shaft between the thermal barrier and the lower radial bearing.
Corrective action:
- 1. The pump was disassembled and the shaft removed for examination. Westinghouse and Battelle concluded the failure was caused by fatigue at an improperly machined groove on the shaft.
- 2. A more recently manufactured shaft was installed in the pump.
Design purpose of failed system or component:
The reactor coolant pumps provide forced reactor coolant flow through the core and steam generators.
Unavailability of system per WASH 1400:*
N.A.
Unavailability of component per WASH 1400:
- pump, failure to run: 3 x 104 /hr.
linavailabilities are i-, units of per demand D-1.
Failure rates rE-e in units of per hour HR-.
Reactor at 95%
Controled reactor RCP A shaft failure Reactor Loop "1A" flowe vratindC shudw itaed rslots of loop e
Ari flwsoo tdoand plowevriatindC shudw lntatd rsuls in l
uden trp A locoltdoand and RCP vibra-Iinitiate tion occur I____
Potential Severe Core Damage
-(not a reasonable occurrence) reactor power low to permit to be idled sufficiently one loop reactor power sufficiently low to permit one loop to be idled. (not a reasonable occurrence)
-(not a reasonable occurrence)
NSIC 89205 -
Actual Occurrence for Failure af a Reactor Coolant Pump Shaft at Surry 1
Reactor at full power and RCP A shaft failure results in locked rotor condition Reactor PORV/safety Auxiliary feedwater trip valve closed and secondary heat removal High pressure injection Long term Potential core Severe cooling Core Damage No Yes No Yes i
Yes Yes NSIC 89205 -
Sequence of Interest for. Wai.lure of a Reactor Cool~ant Pump. Shaft at -Surry 1
- Surry pump failure at full power instead of at 42% power and with perhaps a more abrupt stopping of the pump impeller.
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:
89205 DATE OF LER:
February 24, 1974 DATE OF EVENT:
November 30, 1973 SYSTEM INVOLVED:
Reactor Coolant System COMPONENT INVOL\\ -D:
Reactor Coolant Pump CAUSE:
Failed shaft SEQUENCE OF INTEREST:
Locked RCP Rotor at Full Power ACTUAL OCCURRENCE:
Failed RCP Shaft at 42% Power REACTOR NAME:
Surry 1 DOCKET NUMBER:
50-280 REACTOR TYPE:
PWR DESIGN ELECTRICAL RATING:
822 MWe REACTOR AGE:
1.4 yr VENDOR:
Westinghouse ARCHITECT-ENGINEERS:
Stone & Webster OPERATORS:
Virginia Electric and Power Co.
LOCATION:
17 mi Northwest of Newport News, Va.
DURATION:
N/A PLANT OPERATING CONDITION:
42% power SAFETY FEATURE TYPE OF FAILURE:
(a) inadequate performance; (b) failed to start; Onade inoperable; (d)____________
DISCOVERY METHOD:
operator observation COMMENT:
A reactor coolant isolation valve shaft also failed during the shutdow~n f or this incident.