ML20168A431
| ML20168A431 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1974-013-00 | |
| Download: ML20168A431 (5) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number: 97779 Date: December 3, 1974
Title:
Reactor Coolant Pump Underpower/Overpower Monitoring Relays Fail to Function at Arkansas Nuclear 1 The failure sequence was:
- 1. With the reactor at 20% power, RCPs A and D were shutdown for two pump testing.
The RFS saw neither pump trip.
- 2. RCPs A and D were restarted and RC~s B and C were tripped.
The RPS saw neither pump trip.
- 4. Concurrent with a trip of the C RCP, the D pump monitor relay also tripped (D pump still running), resulting in a reactor trip.
(See attached page)
Corrective action:
The relays were correctly readjusted for the pump power monitor application.
Design purpose of failed system or component:
The pump power monitors provide pump operating status indication to the RPS.
The RPS is designed to trip the reactor if more than one pump is lost during four pump operation or If any pump is lost during less than four loop operation.
Unavailability of system per WASH 1400:
Not considered.
Unavailability of component per WASH 1400:
Relay, failure to de-energize:
not specified.
Unavailabilities are in units of per demand D-1.
Failure rates are in units of per hour H1C1.
The failure sequence was:
(continued)
- 5. Investigation revealed that the relays had been adjusted two days before in accordance with the relay manufacturers instructions.
However, in this application, the relays had to be adjusted to operate at a specific pre-determined power level.
Concurrent With Trip of C RCP, D RCP Monitor Inadvertantly Tripped, Resulting in a Reactor Trip Potential Severe Core Damage No NSIC 97779 -
Actual Occurrence for Reactor Coolant Pump Underpower/Overpower Monitoring Relays Fall to Function at Arkansas 1
Reactor at Reactor Coolant RPS Senses other RPS Trips Power With Pump Fails Pump Failure Provide Protection Three RCPs During Operation to Run and Prior to Core Operating Trips Damage Potential Severe Core Damage
.Yes NSIC 97779 -
Sequence of Interest for Reactor Coolant Pump Undervoltage/Overpower Monitoring Relays Fail to Function at Arkansas Nuclear I
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NS27' ACCESSION NUMBER:
97779 DATE OF LER:
December 3, 1974 DATE OF EVENT:
November 24, 1974 SYSTEM INVOLVED: Reactor Protection System COMPONENT INVOLVED: Pump Power Monitor Relays CAUSE:
Relays incorrectly adjusted SEQUENCE OF INTEREST:
Reactor coolant pump trip during three loop operation ACTUAL OCCURRENCE:
Failure of RPS to see trips during testing REACTOR NAME:
Arkansas Nuclear 1 DOCKET NUMBER:
50-313 REACTOR TYPE:
PWR DESIGN ELECTRICAL RATING:
850 MWe REACTOR AGE:
.30 yr VENDOR:
B&W ARCHITECT-ENGINEERS:
Bechtel OPERATORS: Arkansas Power & Light Co.
LOCATION: 6 lniles'NW'.of Russelville, Ark.
DURATION:
48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> PLANT OPERATING CONDITION: 20% power SAFETY FEATURE TYPE OF FAILURE:
(a Inadequate performance; (b) failed to start; 0 made inoperable; (d)
DISCOVERY METHOD: During testing COMIMENT: