ML20147A329
| ML20147A329 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 08/13/1981 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1980-013-00 | |
| Download: ML20147A329 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
169042 Date:
August 13, 1981
Title:
Degraded High Pressure Injection System During a Loss of Offsite Power at Arkansas Nuclear Unit 1 The failure sequence was:
- i.
With the reactor at full power with atmospheric dump valves isolated due to vibration and failure to close problems, tornado activity resulted in the sequential loss of four of five offsite power lines.
Protective relaying disconnected the remaining offsite power line from the bus tie autotransformer.
(Offsite power was available through manual connection from the 161 kV transmission system).
- 2.
Because of a prior tornado warning, diesel generator No.
1 had been started before the LOOP.
Diesel generator No.
2 started and both provided power to safety-related loads.
- 3.
Both emergency feedwater pumps provided water for steam generator cooling.
- 4.
High-pressure injection was manually initiated to recover system pressure following the trip.
HPI loop B isolation valve CV-1227 failed to open on HPI initiation.
The valve failed to open because of a stuck manual engaging lever.
- 5.
Because of continued UPI flow, pressurizer level increased to above maximum level indication.
The pressurizer PORV and its associated block valve were opened and cycled to ensure the pressurizer was not solid and to reduce RCS pressure.
- 6.
The process and trend computers were unavailable during the event because of incorrectly positioned power switches.
- 7.
On the same day, but prior to the LOOP, maintenance and testing had been completed on EFW pump steam admission valve CV-2667.
The valve did not fully close during testing.
Steam admission valves also did not fully close during recovery from the LOOP.
Also on the same day, quarterly tests of the HPI loop isolation valves had been performed and the valves declared operable.
Forty-two minutes prior to the LOOP, turbine-driven EFW pump P7A had been returned to service following pump gland seal repacking.
Corrective action:
Offsite power was restored via startup transformer ST-2.
The stuck manual engaging lever for HPI valve CV-1227 was freed.
Procedures were revised to require stroking of such valves from the control room after manual operation.
Design purpose of failed system or component:
Offsite power provides the preferred source of power to safety re-lated loads when the unit generator is not available.
The HPI system provides water to the RCS for core cooling during off-normal situations.
Loss of Diesel Emergency HPI manually HPI loop B PORV/PORV offsite generators feedwater initiated due isolation isolation power supply power provided to reduction valve CV-valve to safety-to steam in RCS pressure 2771 fails manually related generators and pressurizer to open due operated loads level to stuck for RCS manual engag-pressure ing lever control Potential Severe Core Damage No No No No No (HPI auto initiation may have occurred)
No No No No Yes No Yes NSIC 169042 - Actual Occurrence for Degraded HPI System During Loop at Arkansas Unit 1
Loss of Turbine Emer-Auxiliary PORV PORV or High Long Offsite Generator gency Feedwater and Demanded PORV Isola-Pressure Term Power Runs Back Power Secondary tion Valve Injection Core and Assumes Heat Removal Closure Cooling House Loads Potential Severe Core Damage Sequence No.
No 1
No 2
No 3
4 Yes Yes 5
No 6
No 7
Yes 8
9 Yes No 10 Yes 11 No 12 Yes 13 NSIC 169042 -
Sequence of Interest for Degraded HPI System During LOOP at Arkansas Unit 1
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:
169042 LER NO.:
80-013 Rev.
1 DATE OF LER:
August 13, 1981 DATE OF EVENT:
April 7, 1980 SYSTEM INVOLVED:
Offsite power, high-pressure injection COMPONENT INVOLVED:
Transmission lines, valve CAUSE:
Tornado damage to transmission lines, failure of valve to open due to stuck manual engaging lever SEQUENCE OF INTEREST:
LOOP ACTUAL OCCURRENCE:
LOOP and failure of HPI valve to open REACTOR NAME:
Arkansas Nuclear Unit 1 DOCKET NUMBER:
50-313 REACTOR TYPE:
PWR DESIGN ELECTRICAL RATING:
850 MWe REACTOR AGE:
5.7 years VENDOR:
Babcock & Wilcox ARCHITECT-ENGINEERS:
Bechtel OPERATORS:
Arkansas Power and Light LOCATION:
6 miles NW of Russellville, Arkansas DURATION:
N/A PLANT OPERATING CONDITION:
100% power TYPE OF FAILURE:
Made inoperable; failed to open DISCOVERY METHOD:
operational event COMMENT: