ML20168A433
| ML20168A433 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1979-005 | |
| Download: ML20168A433 (4) | |
Text
PRECURSOR DESCRIPTION ANDý DATA NSIC Accession Number:
148764 Date:
January 18, 1979
Title:
Steam Dump Valves Fail to Close Following Load Rejection at Beaver Valley 1 The failure sequence was:
- 1. With the reactor at 92%4 power, the lB heater drain pump tripped due to low heater drain tank level.
- 2. During the subsequent load rejection, the condenser steam dump valves opened as required, but failed to 'close because the valve operators were exposed to cold temperatures due to improperly positioned air dampers in the turbine building.
- 3. Low steam line pressure resulted in a reactor trip and safety injection.
Corrective action:
The air dampers were properly positioned.
Design purpose of failed system or component:
The condenser steam dump valves direct steam flow from the steam generators directly to the main condenser in the event of a loss of load or turbine trip, permitting reactor runback in lieu of trip.
Unavailability of system per WASH 1400:
- not addressed in WASH-1400.
Unavailability of component per WASH 1400: *motor-operated valve, failure to operate:
1 x 10 '/D.
Unavailabilities are in units of per demand D_.
Failure rates are in units of per hour HR-1
Reactor at lB Heater Drain Condenser Steam Ccndenser Steam Reactor Safety 92% Power Pump Trips Due Dump Valves Dump. Valves Fail Trip Injection to Low Heater Open for Unit Open Due to Drain Tank Level Load Rejection Excessively Low Operator Tempera-tuares Due to Mis-position Ventila-tion Danpers Potential Severe Core Damage No
.Potential NSIC 148764 -
Actual Sequence for Steam Dump Valves Fail to Close Following Load Rejection at Beaver Valley
Steam Reactor Steam Auxiliary High PORV Opened PORV or Long Line Trip Generator Feedwater and Pressure Due to Con-PORV Isola-Term Break Isolation Secondary Injection tinued HPI tion Valve Core Heat Removal Closure Cooling Potential Se Severe No Core Damage
-No
-No
-Yes
-No Pos sib le (with worst case stuck rod)
-No
-Yes
-Yes
-Yes
-Yes quence 2
3 4
5 6
7 8
9 10 NSIC 148764 -
Sequence of Interest for Steam Dump Valves Fail to Close Following Load Rejection at Beaver Valley 1 small
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:
148764 DATE OF LER:
April 18, 1979 DATE OF EVENT:
January 18, 1979 SYSTEM INVOLVED:
Main steam COM4PONENT INVOLVED:
Condenser steam dump valves CAUSE: Valves failed to close due to exposure to abnormally low temperatures resulting from improper damper position, human error SEQUENCE OF INTEREST:
Steam line break ACTUAL OCCURRENCE:
Stuck open steam dump valves REACTOR NAME:
Beaver Valley 1 DOCKET NUMBER:
50-334 REACTOR TYPE: PWR DESIGN ELECTRICAL RATING:
852 N~e REACTOR AGE:
2.7 yr VENDOR:
Westinghouse ARCHITECT-ENGINEERS:
Stone & Webster OPERATORS:
Duquesne Light Co.
LOCATION:
5 miles east of East Liverpool, Ohio DURATION:
N/A PLANT OPERATING CONDITION:
92%/ power SAFETY FEATURE TYPE OF FAILURE:
(a) inadequate performance; (b) failed to start; (c) made inoperable; (9
failed to close DISCOVERY METHOD:
Operator observation, SI initiation COMMENT:
The LER does not specify how many of these valves stuck open. However, the FSAR (section 10.3) states that all the steam dump valves open on a step load decrease and the failure of 9 remaining open is equivalent to a steam line break.