ML20133P901
| ML20133P901 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 08/07/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20133P884 | List: |
| References | |
| GL-83-28, NUDOCS 8508140523 | |
| Download: ML20133P901 (3) | |
Text
.-
/
'o UNITED STATES
~,,
NUCLEAR REGULATORY COMMISSION c.
I PASHINGTON, D C. 2o555
~s.,...../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION MAINE YANKEE ATOMIC POWER COMPANY MAINE YANKEE ATOMIC POWER STATION DOCKET NO. 50-309 REACTOR TRIP 5YSTEM RELIABILITY ITEMS 4.2.1 AND 4.2.2 0F GENERIC LtiltR 83-28 1.
INTRODUCTICN 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 mainte'iance and surveillance testing is implemented for the reactor trip breakers (RTBs) in pressur' zed water reactors.
In particular, Item 4.2 of the letter required the licensees and }
applicants to suomit 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.
Maine Yankee Atomic Power Company, the licensee for Maine Yankee, submitted responses to the Generic Letter on November 10, 1933, and January 25, 1985. This report presents an evaluation of the adequacy of those responses and of the licensee's preventive maintenance and surveillance programs for RTBs.
8508140523 850807 1
PDR ADOCK 05000309 P
4 2.
EVALUATION CRITERIA 2.1 Periodic Maintenance Program The primary criteria for an acceptable periodic maintenance program are
- contained in Maintenance Instruction GEI-50299E1*, 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 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 i~ ~ ~
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 optiraum freedom of the armature as specified in General Electric Service Advice 175-9.35, Item #51; 5.
Verification of proper trip latch engagement as specified in Service Advice 175-9.35, Item #S2.
2
6.
Verification of undervoltage pick-up setting, as specified in Service Advice 175-9.35, 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 175-9.35, 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 175-9.35, Item #S5; 9.
Verification of proper trip response time as specified in Service Advice 175-9.35, 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 83-28 Item 4.2.2 hpecifies that the licensee's preventative maintenance and survefilance 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.
l 3
L
W' 3.
EVALUATION 3.1 Evaluation of the Licensee Posi: ion on Item 4.2.1 The licensee states :5a: his preventative maintenance program for RTB's contains all :ne elements detailed in Se:: ion 2.1 of this SE.
Tha licensee's preventative maintenance is presently performed oath quarterly and during refueling. The staff fin:s :ne licensee position on Item 4.2.1 to be acceptacle.
.3.2 Evaluation of the Licensee's position on Item 4.2.2 The licensee measures trip :oroue, creaker response time, undervoltage trip oickuo and dro::out vol. age and insulation resistan:e. While the i
licensee cerforms trenc analysis ::n only breaker opening times, ne is a carti:icant in the Combu:: ton Engineering (CE) Okners 3rou:: Availability Data Program, wnich is attem:::ing :o icentify :ne most effe::ive parameters to forecast breaker cegra:ation or failure.
The licensee nas identified-tne organi:ation wnich will ::erform trend analysis, now of ten 1 will be 6
[
cerformed anc how the inf::rmation ::erived from :ne analysis will De used to effe:t periodi:: maintenance. The staff finds ne licensee cosi; ion on (tem 4.2.2 to be a::e;;a::le.
While not stri::ly a cart of tne parametric trending program at Maine Yankee, the licensee has found a precursor to at least one type of undervoltage coil failure. Cbservation of undervoltage coil ::urrent ::uring a: uation shows, in the event cf in:inient coil failure, a :nara::eristi:
signature; when :na carticular waveform is observed during maintenance, the licensee replaces tne coil.
4.
CONCLUSIONS Based on a review of the licensee responses, the staff finds the l
licensee positions on Items 4.2.1 and 4.2.2 of Generic Letter 83-23 to be acceptable.
I Date:
August 7, 1985 Principal Contributor:
i N. Romney.
R. Haroidsen, INEL l
4 l l
.,----_,.,,-,-v
-, -