ML20133G312
| ML20133G312 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 10/10/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20133G301 | List: |
| References | |
| GL-83-28, NUDOCS 8510150339 | |
| Download: ML20133G312 (3) | |
Text
o, UNITED STATES j
NUCLEAR REGULATORY COMMISSION D
j WASHINGTON, D. C. 20555
\\*.***/
SAFETY EVALUATION BY THE OFFICE OF NUCL$AR REACTOR REGt'LATION YANKEE NUCLEAR POWER STATION DOCKET NO. 50-29 REACTOR TRIP SYSTEM RELIABILITY ITEMS 4.2.1 AND 4.2.2 0F GENERIC LETTER 83-28
1.0 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 ained at assuring that a comprehensive program of preventive maintenance and surveillance testing is implemented for the reactor trip breakers (PTBs) in pressurized water reactors.
In particular, Iten 4.2 of the letter reoufred 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 recomended by the equipment supplier.
GL, Item 4.2.2 Trending of parameters affecting operation and measured during testing to forecast degradation of operation.
Yankee Atomic Electric Company, the licensee for Yankee Nuclear Power Station, submitted responses to the Generic Letter on November 5,1983, January 3, 1984 February 21, 1985, March 19, 1985 and September 10, 1985.
This report presents an evaluation cf the adequacy of those responses and of the licensee's preventive maintenance and surveillance programs for RTBs.
2.0 EVALUATION CRITERIA 2.1 Periodic Maintenance Program The primary source for periodic maintenance program criteria is Westinohouse Maintenance Program for DB-50 Reactor Trip Switchgear, Rev. O.
This document is the breaker manufacturer's recomended maintenance program for the DB-50 breaker and provides specific direction with regard to schedule, inspection and testing, cleening, lubrication, corrective maintenance and record keeping.
The document was reviewed to identify those items that contribute to bre?lrer trip reliability consistent with the generic letter. Those itens identified for maintenance at six month intervals that should he. included in the licensee's RTB maintenance program are:
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1.
Verification of trip bar freedon 2.
Verification of operating mechanism alignnent and freedom 3.
Retaining ring verification 4.
Verification of nut and bolt tightness 5.~
Verification of pole bases physical condition 6.
Verification of arcing and main contacts physical condition 7.
Verification of insulating link's physical condition 8.
Verification of wiring insulation and termination physical condition 9.
Verification of arc chute physical condition 10.
Verification of breaker cleanliness 11.
Undervoltage Trip Attachment (UVTA) dropout voltage test and lubrication 12.
Shunt Trip Attachment (STA) operation verification 13.
Verification of operation of auxiliary switches 14 Inspection of positioning lever condition 15.
Functional test of the breaker prior to returnino it to service.
The licensee's P.TP periodic maintenance should also include, on a refueling interval basis:
16.
Verification of cell interlock operation 17.
Examination and cleanino of breaker enclosure 18.
Measurement of trip force required 19.
Functional test of the breaker prior to returning it to service 20.
Preaker response time for undervoltage trip.
All of the items listed above are recommended by the manufacturer except Item 20.
This ' item is the breater trip response time measurement which is implied by the
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2.2 Trending of Paraneters Generic Letter Item 4.2.2 specifies that the licensee's preventative nafntenance and surveillance program is to include trending of paraneters affectino operation and neasured during testing to forecast degradation of operation. The parameters measured during the maintenance progran described above which are applicable for trending are undervoltage trip attachment-dropout voltace, trip force, 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 denradation 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.
3.0 EVALUATION 3.1 Item 4.2.1 Because. Yankee uses DB-25 breekers rather than DB-50s for RTBs, the licensee's
, preventative maintenance program differs in some details, e.g., clearances and number of retaining rings, frcm that specified in the referenced Westinghouse progran. The licensee states that his preventative maintenance program for PTB's contains all the elements detailed in Section 2.1 of this SE except these related to the UVTA; the RTBs at Yankee do not use UVTAs. The staff finds the licensee maintenance program to be acceptable.
The licensee perfoms those itens of maintenance recommended for six nonth
'intervels at refueling intervals. The licensee justified his variation frer the recorrended six month interval for the majority of the items in Section ?.1 of this SE on the basis that the Yankee reactor trip systen was not designed to pemit on-line testing, and so does not have bypass breakers.
Iten 4.5.2 of Generic Letter 83-28 requires the licensee to provide on-line testing capability or to provide,iustification for its continued omission. The staff is currently reviewing the licensee response to item 4.5.2.
Preliminary review by the staff has indicated that Yankee will not be reovired to provide on-line testing of RTBs. The maintenance interval is acceptable provided that no more than 200 RTB actuations are expected to occur between refuelings. Not exceeding 200 RTB actuatiors is based on operability experience determined by Westinghouse.
In the September 10, 1985 letter, the licensee indicated that exceeding ?00 RTB actuations between refueling intervals was highly unlikely, based on past operating history. On these bases, the rairtenance interval cf once per refueling cycle is acceptable, pending final staff ecceptance of the licensee's design which currently does not allow on-line testing.
3.2 Item 4.2.2 The licensee has comitted to performance of trend analysis of trip force and insulation resistance. Because the RTBs at Yankee do not use UVTAs, dropout voltage and response time for undervoltage trip are neither measurable nor trendable. The licensee has identified the organization which will perfom trend analysis, ber often it will be perforned and how the infomation 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.
4.0 CONCLUSION
S Based on a review of the licensee responses as discussed in the preceding paragraphr, the staff finds the licensee positions on Items 4.2.1 and 4.2.2 of Generic Letter 83-28 to be acceptable.
5.0 ACKNOWLEDGMENT Principal contributors:
N. Romney J. Clifford Dated: October 10, 1985
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