ML20168A551
| ML20168A551 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1979-010-00 | |
| Download: ML20168A551 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
152183 Date:
August 13, 1979
Title:
Pressurizer Power Operated Relief Valve Opens at Connecticut Yankee The failure sequence was:
- 1. With the reactor at 100% power, a bistable in a pressurizer pressure controller failed and resulted in the opening of pressurizer power operated relief valve V-570 and its isolation valve MOV-569 and consequent RCS blowdown.
Corrective action:
- 1. The operator overrode the pressure controller signal and closed the PORT isolation valve.
- 2. The failed bistable was repaired.
Design purpose of failed system or component:
The pressure controller provides a control signal to one of two pressurizer power operated relief valves, opening the valve when the pressurizer pressure reaches a preset point.
Unavailability of system per WASH 1400:
- not addressed Unavailability of component per WASH 1400:
- bistable (instrumentation -
low power application):
1 x 10-6/hr.
Unavailabilities are in units of per demand D-1.
Failure rates are in units of per hour HR'*.
I Reactor at 100% Power Pressurizer Power Operated Relief Valve v-570 and
-Its Isolation Valve MOV-569 Open Due to Pressure Controller Bistable Failure Operator Overrides Controller Signal and Closes PORV Isolation Valve Potential Severe Core Damage No No -
small LOCA, High Head Safety Injection Available for Core Protection No NSIC 152183 -
Actual Occurrence for Pressurizer Power Operated Relief Valve Opens at Connecticut Yankee
Small Reactor Auxiliary JHigh Low Pressure LOCA Trip Feedwater and Pressure Recirculation Secondary jInjection and LPR/HPI Heat Removal tross-Connect Potential Severe Core Damage Sequence No.
2 3
4 5
6 7
NSIC 152183 -
Sequence of Interest for Opens at Connecticut Yankee Failure requires the operator to fail Pressurizer Power Operated Relief Valve to close the PORV isolation valve.
CATEGORIZATLON OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:
152183 DATE OF LER:
September 7, 1979 DATE OF EVENT:
August 13, 1979 SYSTEM INVOLVED:
pressure relief COMPONENT INVOLVED:
power operated relief valve and its isolation valve CAUSE:
failed pressure controller bistable SEQUENCE OF INTEREST:
small LOCA ACTUAL OCCURRENCE:
open power operated relief valve and isolation valve REACTOR NAME:
Connecticut Yankee DOCKET NUMBER:
50-213 REACTOR TYPE:
PWR DESIGN ELECTRICAL RATING:
575 NWe REACTOR AGE:
12.1 yr VENDOR : Westinghouse ARCHITECT-ENGINEERS:
Stone & Webster OPERATORS:
Connecticut Yankee Atomic Power Co.
LOCATION:
13 miles east of Meriden, Conn.
DURATION:
N/A PLANT OPERATING CONDITION:
100% power SAFETY FEATURE TYPE OF FAILURE:
(a) inadequate performance; (b) failed to start; (c) made inoperable;Q0failed open DISCOVERY METHOD:
operator observation COMMENT:
According to the plant's FSAR, the PORV isolation valve is not controlled by the pressure controller, only manually.