ML16152A477
| ML16152A477 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/06/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML16152A475 | List: |
| References | |
| GL-83-28, NUDOCS 8509180167 | |
| Download: ML16152A477 (4) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION GENERIC LETTER 83-28, ITEMS 4.2.1 AND 4.2.2 REACTOR TRIP SYSTEM RELIABILITY DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNITS 1, 2 AND 3 DOCKETS NOS. 50-269, 50-270 AND 50-287
- 1. INTRODUCTION On July 8, 1983, the Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 83-28. This letter addressed intermediate-term actions to be taken by licensees and applicants aimed at assuring that a comprehensive program of preventive maintenance and surveillance testing is implemented for the reactor trip breakers (RTBs) in pressurized water reactors. In particular, Item 4.2 of the letter required the licensees and applicants to submit a description of their preventive maintenance and surveillance program to ensure reliable reactor trip breaker operation.
The description of the submitted program was to include the following:
GL, Item 4.2.1 A planned program of periodic maintenance, including lubrication, housekeeping, and other items recommended by the equipment supplier.
GL, Item 4.2.2 Trending of parameters affecting operation and measured during testing to forecast degradation of operation.
Duke Power Company, the licensee for Oconee, submitted responses to the Generic Letter on November 4, 1983, and March 29, 1985. This report presents an evaluation of the adequacy of those responses and of the licensee's preventive maintenance and surveillance programs for RTBs.
8509180167 850906 PDR ADOCK 05000269 P
PDR 1
- 2. EVALUATION CRITERIA 2.1 Periodic Maintenance Program The primary criteria for an acceptable periodic maintenance program are contained in Maintenance Instruction GEI-50299EI*, Power Circuit Breakers, Types AK-2/2A-15, AK-2/3/2A/3A-25, AKU-2/3/2A/3A-25," and Service Advice 175-9.3S and 175-9.20, by General Electric. The NRC Staff, Equipment Qualification Branch, has reviewed these items and endorsed the maintenance program they describe. The criteria include those items in the General Electric instructions and advisories that relate to the safety function of the breaker, supplemented by those measurements which must be taken to accumulate data for trending. Those items identified for maintenance at six month intervals that should be included in the licensee's RTB maintenance program are:
- 1. Verification of breaker cleanliness and insulation structure; all foreign materials, such as paint, dust, or oil, should be removed to prevent electrical breakdown between points of different potential;
- 2. Verification of breaker physical condition, including wiring insulation and termination, all retaining rings, pole bases, arc quencher, stationary and movable contacts, and tightness of nuts and bolts;
- 3. Verification of proper manual operation of the breaker, including checks for excessive friction, trip bar freedom, latch engagement, operating mechanism alignment and freedom, and undervoltage trip (UVT) device armature freedom;
- 4. Verification of the optimum freedom of the armature as specified in General Electric Service Advice 175-9.3S, Item #S1;
- 5. Verification of proper trip latch engagement as specified in Service Advice 175-9.3S, Item #S2.
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- 6. Verification of undervoltage pick-up setting, as specified in Service Advice 175-9.3S, Item #S3, and dropout voltage;
- 7. Verification that the trip torque required on the trip shaft is less than 1.5 pound-inches, as specified in Service Advice 175-9.3S, Item #S4; "Before" and "After" maintenance torque values should be recorded;
- 8. Verification of positive tripping by checking the adjustment between the UVT device and trip paddle as specified in Service Advice 175-9.3S, Item #SS;
- 9. Verification of proper trip response time as specified in Service Advice 175-9.3S, Item #S6;
- 10.
Shunt Trip Attachment (STA) operation verification;
- 11.
Examination and cleaning of breaker enclosure;
- 12.
Functional test of the breaker prior to returning it to service.
2.2 Trending of Parameters Generic Letter Item 4.2.2 specifies that the licensee's preventative maintenance and surveillance program is to include trending of parameters affecting operation and measured during testing to forecast degradation of operation. The parameters measured during the maintenance program described above which are applicable for trending are undervoltage trip attachment dropout voltage, trip torque, and breaker response time for undervoltage trip. The staff position is that the above three parameters in addition to the breaker insulation resistance are acceptable and recommended trending parameters to forecast breaker operation degradation or failure. If subsequent experience indicates that any.of these parameters is not useful as a tool to anticipate failures or degradation, the licensee may, with justification and NRC approval, elect to remove that parameter from those to be tracked.
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- 3. EVALUATION 3.1 Evaluation of the Licensee Position on Item 4.2.1 The licensee states that his preventative maintenance procedures for RTB's are being revised and, by July 31, 1985, will contain all the elements detailed in Section 2.1 of thi s SER. The licensee states that they will perform maintenance at six-month intervals. Subsequent to establishment of an adequate data base, the licensee will evaluate the performance of preventative maintenance at twelve month intervals. The staff finds the licensee position on Item 4.2.1 to be acceptable.
3.2 Evaluation of the Licensee's Position on Item 4.2.2 The licensee has committed to measurement of trip torque, breaker response time and undervoltage trip pickup and dropout voltage; the licensee has elected not to monitor insulation resistance, contending that it is not a performance-related parameter. The staff recommends that all of the parameters identified in Section 2.1 of this SER be monitored, but, as the three parameters which the licensee does measure are demonstrably performance-related, the staff finds the licensee position acceptable.
The licensee is a participant in the B&W Owners Group Relability Monitoring program, which is attempting to identify the most effective parameters to forecast breaker degradation or failure. The licensee is providing these data to the B&W Owners Group Availability Group, which will perform trend analysis. The licensee has identified how often data will be collected and how the information derived from the analysis will be used to affect periodic maintenance. The staff finds the licensee position on Item 4.2.2 to be acceptable.
- 4. CONCLUSIONS Based on a review of the licensee responses, the staff finds the licensee position on Item 4.2.1 and 4.2.2 of Generic Letter 83-28 to be acceptable.
Dated:
Principal Contributor: N. Romney 4