ML20147A545
| ML20147A545 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 04/23/1982 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1980-054-00 | |
| Download: ML20147A545 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
174073 Date:
April 23, 1982
Title:
Stuck Open Relief Valve at Duane Arnold The failure sequence was:
- 1. With the reactor at 7% power during a startup, an operator noticed a higher than normal discharge line temperature from a Target Rock Model 67F-6XI0 main steam relief
- valve, which indicated a small steam leakage from the reactor coolant system (RCS).
- 2.
An operator manually cycled the valve at rated pressure to attempt a better valve seating.
- 3.
The valve stuck open and remained open for 7.5 min, resulting in RCS depressurization to <880 psig.
- 4.
The MSIVs closed on low RCS pressure and an automatic reactor scram occurred.
- 5.
The vessel water level fell 7.5 in.
below instrument zero level (150.5 in.
above the active fuel).
- 6.
ECCS initiation was not required and ECCS was not employed in the recovery (water level and pressure were above ECCS actuation set point.
- 7.
One train (group 3 channel A) of the containment isolation actuation logic failed to actuate on low vessel water level as required.
A wiring error made during a design change and not detectable by postinstallation testing or normal surveillance tests was discovered.
One valve in a number of pairs of isolation valves failed to close.
Channel B did actuate and the containment was isolated.
- 8.
The reactor was placed in cold shutdown until repairs were completed.
Corrective action:
The valve was replaced.
The cause of the closure failure could not be determined.
Design purpose of failed system or component:
The relief valve provides over-pressure protection for the RCS during a transient event.
Operator manually cycles MSIVs close Automatic reactor [ Reactor Containment relief valve to seat it; on low steam scram due to MSIV inventory A isolation valve sticks open pressure closure is maintained logic fails Potential Severe Core Damage No No Yes Yes No No Yes Yes NSIC 174073 - Actual Occurrence Tree for Stuck Open Relief Valve at Duane Arnold
Small Reactor Standby High Automatic LPCI Long Potential Sequence Loss of Scram Liquid Pressure Depressuri-or CS Term Severe No.
Coolant Control Cooling zation
Response
Core Core Accident Initiated Provided System Adequate Cooling Damage
_Operates No 1
Yes 2
No 3
Yes 4
Yes 5
Yes 6
No 7
Yes 8
Yes 9
Yes 10 NSIC 174073 -
Sequence of Interest Tree for Stuck Open Relief Valve at Duane Arnold
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:
174073 LER NO:
80-054/01X-i DATE OF LER:
April 23, 1982 DATE OF EVENT:
January 11, 1980 SYSTEM INVOLVED:
Over-pressure protection system COMPONENT INVOLVED:
Main steam relief valve CAUSE:
Unknown SEQUENCE OF INTEREST:
Small break LOCA ACTUAL OCCURRENCE:
Small break LOCA REACTOR NAME:
Duane Arnold DOCKET NUMBER:
50-331 REACTOR TYPE:
BWR DESIGN ELECTRICAL RATING:
538 MWe REACTOR AGE:
5.8 years VENDOR:
General Electric ARCHITECT-ENGINEERS:
Bechtel OPERATORS:
Iowa Light and Power LOCATION:
8 miles NW of Cedar Rapids, Iowa DURATION:
7.5 min PLANT OPERATING CONDITION:
7% full power (starting up)
TYPE OF FAILURE:
Failed to close DISCOVERY METHOD:
Operational event COMMENT:
This event could have occurred at full power.
Note:
LER Rev.
0 for this event was filed as NSIC 161716.