ML13304A341
| ML13304A341 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/24/1988 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML13304A340 | List: |
| References | |
| GL-83-28, IEIN-85-058, IEIN-85-58, NUDOCS 8807110510 | |
| Download: ML13304A341 (4) | |
Text
SAFETY EVALUATION REPORT DOCKET NOS. 50-361 AND 50-362 SAN ONOFRE NUCLEAR GENERATING STATION, UNITS 2,3 GENERIC LETTER 83-28, ITEM 4.2 (PARTS 1 AND 2)
REACTOR TRIP BREAKER RELIABILITY INTRODUCTION AND
SUMMARY
Generic Letter 83-28 was issued by the NRC on July 8, 1983, indicating actions to be taken by licensees based on the generic implications of the Salem ATWS events.
Item 4.2 (Parts 1 and 2) states a staff position which requires licensees and applicants to submit a description of their program for periodic maintenance and trending of parameters of their reactor trip breakers. Southern California Edison Company, the licensee for San Onofre 2 and 3, responded by letters dated November 29, 1983; March 25, 1986; and November 25, 1987.
Our review of these responses finds them to be acceptable.
EVALUATION Staff's evaluation criteria are based on NRC Inspection and Enforcement (IE)
Information Notice No. 85-58, and on General Electric Service Advice 175-9.3S and 175-9.20, and General Electric "Maintenance Instruction GE-50299El, Power Circuit Breakers, Types AK-2/2A-15, AK-2/3/2A/3A-25, AKU-2/3/2A/3A-25."
Those items for periodic surveillance and maintenance that should be included in the licensee's program are as follows:
- 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.
87110510 880624 fl PDR ADOCK 05000361 P
-2
- 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.
- 5.
Verification of proper trip latch engagement, as specified in GE Service Advice 175-9.3S, Item #S2.
- 6.
Verification of undervoltage pick-up setting, as specified in GE Service Advice 175-9.3S, Item #S3, and of dropout voltage.
- 7.
Verification that the trip torque required on the trip shaft is less than 1.5 pound-inches, as specified in GE 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 GE Service Advice 175-9.3S, Item #S5.
- 9.
Verification of proper trip response time, as specified in GE Service Advice 175-9.3S, Item #S6.
- 10.
Verification of shunt trip attachment (STA) operation.
- 11.
Examination and cleaning of breaker enclosure.
- 12.
Functional test of the breaker prior to returning it to service.
-3 The licensee states that periodic maintenance is performed on at least a 6-month basis.
All the elements detailed above are included with the exception of post maintenance verification of the trip shaft torque required. The licensee con siders response time testing to be superior to trip torque testing as a pre dictive parameter of breaker degradation, and trip torque testing as merely add ing to component wear. Staff agrees that breaker response time testing is more conclusive, and finds licensee's justification for not performing post-maintenance trip torque testing to be acceptable.
In addition to the above verifications, the staff considers the following measure ments applicable for trending:
- 1. Undervoltage trip attachment dropout voltage.
- 2. Trip torque required.
- 3. Breaker response time for undervoltage trip.
- 4. Breaker insulation resistance.
The licensee has committed to a program for breaker response time trending. They do not consider the other parameters of value in assessing breaker degradation.
The other parameters are recorded however, during routine maintenance. We find this to be acceptable.
Inspection and enforcement (IE) Information Notice 85-58 cautions that the armature of the undervoltage trip attachment of the breaker should be down in the energized position when measuring the roller rivet armature clearance. The licensee should confirm that their procedures specify such measurement.
-4 CONCLUSION The staff has reviewed Southern California Edison's responses to Generic Letter 83-28, Item 4.2, Parts 1 and 2 for the San Onofre plant, Units 2 and 3. We find the responses acceptable upon confirmation that the procedures specify that the armature of the undervoltage trip attachment be down in the energized position when measuring the roller rivet armature clearance.