ML20127M166
| ML20127M166 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 06/24/1985 |
| From: | Tucker H DUKE POWER CO. |
| To: | Adensam E, Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| GL-83-28, NUDOCS 8507010126 | |
| Download: ML20127M166 (6) | |
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D DUKE POWER GOMPANY P.O. Box 03180 C11ARLOTTE, N.C. 28242 HALH. TUCKER Tetzenoxz vns,emasoant (704) 373-4531 June 24, 1985
.m:me,-os Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Attention:
Ms. E. G. Adensam, Chief Licensing Branch No. 4
Subject:
Catawba Nuclear Station' Docket Nos. 50-413 and 50-414
Dear Mr. Denton:
Please find attached our responses to NRC requests for information dated June 4, 1985 concerning Generic Letter 83-28.
These responses address Items 4.2.1 and 4.2.2 which have to do with reactor trip system reliability and trending aspects of the preventative maintenance program for reactor
. trip breakers.
This submittal parallels portions of our letter of May 24, 1985, in which these items were addressed for McGuire Nuclear Station. Our responses are essentially the same for both stations.
This letter supercedes my letter of June 21, 1985 which did not contain the attachments. Please disregard the previous submittal.
Very truly yours, hb.
jg Hal B. Tucker RWO: sib Attachments cc:
Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission Region II
- 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 NRC Resident Inspector Catawba Nuclear Station 4
g Dr. K. Jabbour, Project Manager
' E [.7 Division of Licensing Office of Nuclear Regu1Latory Commission Li I
Washington, D. C.
20555 8507010126 850624 PDR ADOCK 05000413 P
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s Mr7 Hardld1R.'Denten Dirretor
. June.24, 1985 Page Two ec:- Palmetto-Alliance 2135 Devine Street
_ Columbia, South Carolina 29205 Mr. Jesse L. Riley Carolina Environmental Study Group 854 Henley Place Charlotte, North Carolina 28207' Robert Guild, Esq.
P.'O. Box 12097.
Charleston, South Carolina 29412
CATAWBA NUCLEAR STATION, UNITS 1 AND 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION GL 83-28, ITEMS 4.2.1 AND 4.2.2 NRC Letter of June 4, 1985 I.
Item 4'.2.1 - Periodic Maintenance Program fo'r Reactor Trip Breakers.
~I.1 Criteria for Evaluating Compliance with Item 4.2.1 The Catawba Nuclear Station Units 1 and 2 Reactor Trip Systems utilize Westinghouse DS-146 circuit breakers. The primary criteria for an acceptable maintenance program for the DS-416 Reactor Trip Breaker (RTB) are contained in Westinghouse Maintenance Manual
.for the DS Reactor Trip Circuit Breaker,-Revision 0, Octorber 1984.
The NRC staff,. Equipment Qualification Branch, has reviewed this document and endorsed the maintena'nce program described in it.
More specifically, the criteria used to evaluate compliance include.those items in this document that relate to the safety function of the breaker, supplemented by those measures that must be taken to accumu-late data for trending.
I.2 : Issues Relating to Item 4.2.1 The applicant response states'that the preventive maintenance is performed on the Catawba Reactor Trip Breakers in accordance with the current manufacturer's recommendations as described in the technical manual. This maintenance is currently performed once per 6 months.
~This frequency is under review and changes may be proposed later.
The maintenance procedure is not included as a part of the submittal.
The Catawba Nuclear Station Units 1.and 2 periodic maintenance program for the reactor trip breakers should include, on a six-month basis (or'when 500 breaker operations have been counted, whichever comes first):
1.
General inspection to include checking of breaker's cleanliness, all bolts and nuts, pole bases, arc chutes, insulating link, wiring and auxiliary switches; 2.
The retaining rings inspection, including those on the under-voltage trip attachment (UVTA) and shunt trip attachment (STA);
3.
Arcing and main contacts inspection as specified by the Westinghouse Maintenance Manual;
-4.
UVTA check as specified by the Westinghouse Maintenance Manual, including replacement of UVTA if dropout voltage is greater than 60%
or:less than 30% of rated UVTA coil voltage; 5.
STA check as specified by the Westinghouse Maintenance Manual;
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6.
Lubrication as specified by the_ Westinghouse Maintenance Manual; 7.
Functional' check of_the breaker's operation prior to returning it to service.
The Catawba' Nuclear Station Units:1 and 2 Periodic Maintenance Program for the reactor trip breakers should include, on a refueling interval basis (or when 500 breaker operations have been counted, whichever comes first):
1.
Pre-cleaning insulation resistance measurement and recording; 2.
RTB_ dusting and cleaning; 3.
Post-cleaning insulation resistance measurement and recording, as specified by the Westinghouse Maintenance Manual; 4.
Inspection of main and secondary disconnecting contacts, bolt tightness, secondary wiring, mechanical parts, cell switches,
' instruments, relays and other panel mounted devices; 5.
UVTA trip force and breaker load check as specified by'the Westing-house Maintenance Manual; 6.
Measurement and recording RTB response time for the undervoltage trip; 7.
Functional test of the breaker prior to returning to service as specified by'the Westinghouse Maintenance Manual.
The maintenance procedure should include a caution to the maintenance personnel against undocumented adjustments or modifications to RTBs.
.The applicant is to confirm that the periodic maintenance program
~ includes these fourteen items at_the specified intervals or commit to their inclusion.
Response
We have discussed this item with Westinghouse and believe that NRC has not' correctly interpreted the periodic maintenance program requirements contained in the manual. The following paragraphs are provided to clarify the requirements of the manual.
These items to be. included on a six-month basis, according to your letter, are currently included in the RTB Program. Operation and Maintenance experience, Westinghouse concurrence, and a clean operating environment for the RTBs has shown that the frequencies as proposed in the Westinghouse Maintenance Manual are. sufficient to adequately assure breaker reliability.
Of the Items 'to be included ~on a refueling interval basis, nos.1-4
. correspond to Group B activities 15 through 19 of the Maintenance Manual and are not considered related to the safety function of the. breaker, and are not
.part of the required maintenance program.
Item no.-5 concerning UVTA trip
. force and breaker load check is included in the Catawba RTB Program.
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Item 6 of this group addresses measurement and recording of the RTB re-sponse time for the U.V. trip on a refueling interval basis or when 500 breaker operations have been counted, whichever comes first. We presently measure and record.the time response for each main RTB on a monthly basis and also measure and record the time response of each breaker before and after six month breaker maintenance. All data is recorded by procedure and can be made available for
~
analysis by recall under our work request system.
Item 7 of this group addresses a funtional test of the breaker prior to returning it to service after breaker maintenance is performed either on a
~ refueling basis or when 500 breaker operations have been counted, whichever comes first. This' activity is currently performed in conjunction with the time response verification and includes a verification of the U.V. trip inde-pendent of the shunt trip and vice-versa.
The addition of a caution step in the maintenance procedure against undocumented adjustments or modifications to the RTBs will be added to the pro-cedure.
The Westinghouse Owner's Group and Westinghouse may consider revising the manual to reflect the clarifications provided herein.
NRC Letter of June 4,1985 II.
Item 4.2.2 - Trending of Reactor Trip Breaker Parameters to Forecast Degradation of Operability.
II.1 Criteria for Evaluating Compliance with Item 4.2.2 Four parameters have. been identified as trendable and are included in the criteria for evaluation. These are (a) under-voltage trip attachment dropout voltage, (b) trip force, (c) breaker response time for undervoltage trip, and (d) breaker insulation resistance.
II.2 Issues Relating to Item 4.2.2 The applicant states that trending of parameters is not j
currently recommended by the manufacturer. The cyclic life testing program (described in the applicant's response) "will provide information to determine the need for trending of parameters."
At the present time the NRC requires recording the four 4
identified parameters to forecast degradation of operability.
The applicant is to commit to inclusion of trip force, breaker response time and dropout voltage for undervoltage trip and breaker insulation resistance as trending parameters. The applicant should also identify the organization which will perform i
trend analysis, how often the analysis will be performed and how the information derived from the analysis will be used to affect periodic maintenance.
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Response
Catawba currently records the data for (a) undervoltage trip attachment dropout voltage,~(b) trip force, and (c) breaker response time for undervoltage trip. This data can be recalled from procedure data sheets which are perma-nently recorded in the station work request system.
Breaker insulation resistance (d) is not being measured at this time. Duke questions the need to measure breaker insulation resistance and the correlation between the bus insulation resistance and breaker reliability / operability.
The recently issued " Maintenance Manual for the DS-416 Reactor Trip Circuit Breaker" by Westinghouse provides the guidance to adequately maintain the RTB's through periodic maintenance procedures, performance tests and checks as.well as performance tolerance measurements to detect a degraded
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condition.
It is Duke's position, supported by a review of Westinghouse test data, that a formal trending program of the RTB parameters (a through d) is not necessary or beneficial to predict degradation of operation. This position is based on operating and maintenance experience at our McGuire facility and the results contained in " Report of the DS-416 Reactor Trip Breaker Undervoltage and Shunt Trip Attachments Life Cycle Tests" soon to be released by the Westinghouse Owners Group.
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