ML20149K479
| ML20149K479 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1981-076-00 | |
| Download: ML20149K479 (4) | |
Text
Accession Number: 171939
- October 28, 1981 Inadvertent Steam Dump Valve Opening and Safety Injection at North Anna 2 failure sequence was:
With the reactor at 100% power, a turbine trip and reactor trip oc-curred as a result of a failure in an electrohydraulic control line to No. 4 governor valve.
Three and one-half hours later, with the reactor at 2% power, it was observed that the steam dumps were in the T mode in lieu of the steam pressure mode of operation.
The operator switched to the steam pressure mode of operation and shifted the steam dump controller to auto. All eight steam dumps opened.
The operator immediately shifted to manual on the controller and to the Ta position on the steam dump selector switch.
Either lhis action or the low-low T avg interlock closed the dump valves but not before safety injection was initiated.
All safety injection equipment operated as required, except the pressurizer liquid space inside isolation valve failed to close.
The specific cause for the high controller output was not determined, and an investigation of equipment failure and human error revealed no discrepancies.
rective action:
The event was reviewed for equipment failure and human error and no e could be determined.
gn purpose of failed system or component:
The steam dump valves provide for steam generator pressure control owing plant trip by venting steam to the condenser.
tot in Tavg mode mode and shifted all 8 atmos- switches to initiated either the Core in lieu of steam the steam dump pheric dump manual on operator's Damage pressure mode controller to valves controller actions or to (reactor at 2% auto (cause not and to Tavg iow-low Tavg power) determined) on steam interlock dump selec-tor switch No No - safety injection provides core protect'on No No - safety injection available for core protection if required No No No 9 - Actual Occurrence for Inadvertent Steam Dump Valve Opening and Safety Injection at North Anna 2
No 2 Yes 3 No 4 No S No 6 Yes 7 Yes 8 No 9 No 10 Yes 11 No 12 Yes 13 Yes 14 No 15 Yes 16 Yes 17 Yes 18 Yes 19 939 - Sequence of Interest for Inadvertent Steam Dump Valve Opening and Safety Injection at North Anna 2
ACCESSION NUMBER: 171939 NO.: 81-076 OF LER: October 28, 1981 OF EVENT: October 3, 1981 EM INVOLVED: Steam dump to condenser ONENT INVOLVED: Dump valves E: Inadvertent opening ENCE OF INTEREST: Main steam line break AL OCCURRENCE: Eight opened dump valves TOR NAME: North Anna 2 ET NUMBER: 50-339 TOR TYPE: PWR GN ELECTRICAL RATING: 907 MWe (net)
TOR AGE: 1.3 years OR: Westinghouse ITECT-ENGINEERS: Stone and Webster ATORS: Virginia Electric & Power Co.
TION: 40 miles NW of Richmond, Virginia ATION: N/A T OPERATING CONDITION: 2% power following a trip OF FAILURE: Inadequate performance OVERY METHOD: Operational event ENT: