ML20213E721
| ML20213E721 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Salem |
| Issue date: | 01/16/1984 |
| From: | Alexion T Office of Nuclear Reactor Regulation |
| To: | Holahan G Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20213E339 | List: |
| References | |
| FOIA-87-152, RTR-NUREG-0916, RTR-NUREG-1000, RTR-NUREG-916 GL-83-28, IEB-83-01, IEB-83-04, IEB-83-08, IEB-83-1, IEB-83-4, IEB-83-8, IEIN-83-18, NUDOCS 8401260469 | |
| Download: ML20213E721 (3) | |
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JAN 16154 MEMORAN0UM FOR:
Gary M. Holahan, Chief Operating Reactors Assessment Branch FROM:
Thomas W. Alexion Operating Reactors Assessment Branch
SUBJECT:
SALEM SCRAM EVENTS AND RESULTING NRC ACTION A few days ago, you requested that I initiate a 1 to 2 page sumary on the above subject. Attaclied is the current revision of that sumary.
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Thomas W. Alexion Operating Reactors Assessment Branch
Enclosure:
As Stated DISTRIBUTION
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SALEM SCRAM EVENTS AND RESULTING NRC ACTIONS On February 25, 1983, a signal that water in one of the steam generators was too low generated a reactor trip signal to the Salem Unit I reactor during a routine startup following a refueling outage. Both reactor trip breakers remained closed until operators manually tripped the reactor about 30 seconds later. At that time the reactor trip breakers opened and the control rods dropped into the reactor core to bring the reactor to a stable shutdown condition.
Initial licensee investigation disclosed that the reactor trip breakers failed to open because of mechanical binding of the latch mechanism in the undervoltage trip attachment on the circuit breakers. During a subsequent review of this event and a previous reactor scram on February 22, 1983, the licensee determined that a trip demand condition without scram had also existed for about three seconds on February 22, 1983. The reactor trip had resulted from a transient initiated by the loss of electrical power during
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transfer to the auxiliary power transformer. The Unit I reactor was placed in a cold shutdown condition pending completion of a review of these events.
A number of short term actions were taken through Bulletins and an Information Notice issued by the NRC Office of Inspection and Enforcement (IE).
!E Bulletin's 83-01 and 83-04 were issued to require testing of all circuit breakers in reactor trip systems with an undervoltage trip attschment.
IE Information Notice 83-18 described the failures of the reactor trip breakers discovered in the testing required by the IE Bulletins.
In December 1983,. the NRC issued IE Bulletin 83-08 to assure proper operation of circuit breakers with undervoltage trip attachments being used in safety-related applications other than as reactor trip breakers.
A detailed review of the Salem event and the licensee's corrective actions was perfomed prior to authorizing restart of the facility. This review is documented in NUREG-0916 In addition, an NRC Task Force was established to determine the generic implications of the Salem events. This work is documented in NUREG-1000 Volumes 1 and 2 and Generic Letter 83-28. Generic Lotter 83-28 contained intermediate-term actions to be taken by licensees as a result of the Salem events. The actions address issues related to reactor trip system reliability and general nnagement capability. Specifically the issues to be addressed are:
Post-Trip Review Equipment Classification and Vendor Interface Post-Maintenance Testing Reactor Trip System Reliability The staff has received the initial responses to Generic Letter 83-28 and is currently organizing its review. Within each area of concern, we have identified those aspects which are of higher priority and need earlier attention.
The schedules for implementation of these actions are being developed consistent with the goal of integrating new requirements, considering the unique status of each plant and the relative safety importance of the improvements, combined with all other existing plant programs.
With implementation of these issues, we expect significant improvement in the reactor trip system reliability and overall plant management capability.
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4 The staff has been working with industry owner's groups to improve reliability of circuit breakers using undervoltage trip attachments. The review of reported breaker failures indicates most failures can be attributed to the undervoltage trip attachments and their associated linkages. Examples of problems include improper lubrication, excessive wear of moving parts, inadequate adjustment of spring tension, and hardening / contamination of grease in bearings.
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