ML20065K135

Revised Special Rept 90-02-01:on 900924,invalid Diesel Generator Failure Occurred Due to Improper Output Breaker Plunger Clearance.Rev Changes Basis for Invalidity of Diesel Generator Failure Per Reg Guide 1.108

ML20065K135
Person / Time
Site:	Callaway
Issue date:	11/05/1990
From:	Blosser J UNION ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-REGGD-01.108 90-02-01, ULNRC-2319, NUDOCS 9011150258
Download: ML20065K135 (6)

Text

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[' November 5, 1990. (U. S. Ndelear Regulatory Commission Document Control Desk

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Washington, D.C. 20555 ULNRC 2319 Gentlemen: - DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 FACILITY OPERATING LICENSE NPF 30 SPECIAL REPORT 90 02-01 ,j INVALID DIESEL CENERATOR FAILURE-DUE TO .j

                                                           . IMPROPER OUTPUT BREAKER PLUNCER CLEARANCE                  ij F,

This.Special-~ Report is'being submitted pursuant to Technical ,,

  ,                               ) Specification;(T/S) 4.8,1.1.3 and 6,9,2 concerning the invalid                         1
                                  ' failure of Diesel-Generator (D/G) 'Bdue to a D/G outpuc breaker                   b
                                 , plunger bolt being out' of: adjustment. This revised report changcs the
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                                  - basis for: invalidity of the.D/G, failure. The ch ege was deeme'd necessary af ter 'further . review' of Regulatory Guide -1.108.                                   l

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                                                                                                 . D,1Blosser U

ll ' Manager, Callaway Plant

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Ta' .: l cc distribution for ULNRC 2319 Mr. A. Bert Davis- Mr. Anthony T. Gody.(2' copies)

                              . Regional Administrator                                                U.S. Nuclear Regulatory Commission     ;

U.S. Nuclear Regulatory Commission OWFN - Mail Stop E1321 l

                             . Region-III. .          _

Washington, D.C. 20555

                              .799 Roosevelt Road Glen Ellyn, IL: 60137 lAmerican Nuclear Insurers                                               Mr. O. Maynard c/o Dottie Sherman, Library                                           Wolf Creek Nuclear Operating Corp.

The! Exchange Suite 245 P. O. Box 411 270 Farmington Avenue Burlington, KS 66839 Farmington, CT- 06032

                              ~ Manager, Electric Department                                          Mr. Merlin Williams            .

j Missouri'Public Service Commission Supt. of Regulatory Quality & P. O. Box 360 Administrative Services Jefferson City, MO 65102 Wolf Creek Nuclear Operating Corp. P. O. Box 411 Burlington, KS 66839

                      , ,       Records Center                                                        Mr. R. L. llague                          l Institute of Nuclear Power Operations                                 Chief, Project Section 3A'          1 Suite'1500.                                                           U.S. Nuclear Regulatory Commission-
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                               -1100 Circle:75 Parkway                                                Region III                                1 Atlanta', GA 30339                                                    799 Roosevelt Road                        !

Glen Ellyn, IL 60137  ; c NRC Resident Inspector lD.1F; Schnell-(400) l

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d . SPECIAL REPORT 90 02, REV 1 INVALID DIESEL GENERATOR FAILURE DUE TO IMPROPER OUTPUT BREAKER PLUNGER CLEARANCE Surveillance procedure ISP-SA.2413B, Diesel Generator and Sequencer Testing Train B , was in progress on 9/24/90 to satisfy various 18 month Technical Specification (T/S) surveillance requirements. The plant had entered Mode 5, Cold Shutdown, on 9/23/90. During performanco of the "'B' Train Blackout without SIS" portion of ISP-SA-2413B, the 'B' cmergency diesel generator (D/G) was intentionally secured without loading to at 1 cast 50% of continuous rating. The D/G was secured to investigate a failure of the load sequencer to properly sequence the required emergency loads onto the 4.16 KV safety-rolated bus (NB02) energized by 'B' D/C. The D/G could have been manually loaded and a valid test completed. The operators intentionally secured the D/G after troubleshooting of the load sequencer. Initially, the basis for the invalidity of the D/G failure was detailed as: Since the successful D/G start was terminated intentionally without loading to at least 50% of continuous ratin5, it is not considered a valid test or failure. This position in consistent with Regulatory Guide l 1.108.C.2.e(4). After further review of Regulatory Guido 1.108, it was determined that credit should not be taken for manual lord'.ag subsequent to the unsuccessful intended, sequential loading attempt. This event was a successful start followed by an unsuccessful automatic, sequential loading attempt, due to a failed component which is not part of the defined diesel generator unit. As such, this was an invalid failure. To further support this position, this failed component is not tested during periodic testing of the D/G units during normal plant operations but is tested only during the 18 month surveillance. This position is consistent with Regulatory Guide 1.108.C.2.c(5) and 1.108.C.2.e(2). The D/G surveillance test interval of T/S Table 4.8-1 is not affected.

                       'The following is a summary of the events applicable to this incident:

The " Blackout Without SIS" portion of the ISP-SA-2413B began at approximately 1800 on 9/24/90.

                               . Loads shed off bus NB02 as required when the test signal
                                 -(blackout without SIS) was initiated.
                               .  'B' D/G.successfully started and attained the required voltage and frequency.
                               .  'B' D/G output breaker closed and energized the safety related bus (NB02).
                               - No loads sequenced onto the D/G.
                               - The  'B'  Essential Service Water (ESW) pump was manually loaded onto the D/G.

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                                  ; SPECI Ali REPORT 90 02, REV.1-Page-2 ULNRC 2319'
                                              -The D/G output breaker was maintained closed until troubleshooting was completed, in order to ensure that evidence of the root cause was maintained.
                                            - Troubleshooting of the 'B' D/G output breaker identified that
                   .                             the plunger bolt (which actuates the stationary auxiliary switches when the breaker closes) was out of adjustment.

Consequently, the stationary switch did not scad a start signal to the load sequencer.

                                             . The D/C was secured and the plunger bolt was adjusted. The test was repeated successfully.

Verification of proper adjustment of the plunger-bolt for 'B' D/G output

                                   -breaker was last performed on 6/6/90 during'a 6 month preventive

maintenance inspection. The contact did operate during performance of

                                      ." Blackout with SIS" which had been performed earlier on 9/24/90. Then, a stationary auxiliary switch test position link (test link) was installed prior to the "SI" test; The test link was removed prior to the." Blackout c   -without SIS".

The root cause =of this failure.has been determined to be improper movement -

                                     .of theitest link during breaker testing. An evaluation revealed that use of the test, link,;in some cases, caused'the. plunger clip to bend. See attached drawing.- This bending results in an. increase in the gap between the plunger
                                     .and tho' operating rod, preventing the operating rod from moving sufficiently to actuate the switch upon breaker closure. An engineering
                                    ' evaluation verified that the affected breakers are operable in their existing condition provided that'the-plunger interlock gap distance is maintained within vendor specifications.
                                    'This event.is similar to Special Report 86-01, Revision 1, dated 4/15/86.

The corrective action'for the earlier event.was to change the periodicity-

                                    'of the; preventive maintenance inspection from:18 months to 6 months.

1Because the root cause has now been determined to be use of the test' link, the'following. corrective' actions are being taken; <

1. The gap between the' plunger dan' the operating rod will be verified l

following each breaker rack-in on the D/G output breaker and other similar safety-related breakers.

                                     ' 2.: An~ evaluation of the design and use of the test link will be performed'.

3. An evaluation will be performed to determine 10 CFR Part 21 reportability.

                                      -4. The bent clips will be replaced at the first available opportunity following receipt of parts, i

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1 m Surveillance tests are currently performed at least once per 31 d4ys for ' L; D/G 'B'..;This is'in conformance with T/S table 4.8-1 which requires a test interval'of not more than131; days if the number of failures in'the last 20-

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gi # , hF valid tests is :one. or zero,' or-if the number of failures in *.no last 100

               ;ys:                                   1    valid tests is four or less.

LTh'e' starting history of D/G 'B' as of the'date of-this report is n,; - summarized as follows: n n , '~-;; Number of Number of

;                                                                        -Number of        Failures During          Failures During s,                                                        Valid Tests.           Valid Tests-           Invalid Tests 1

92 i# 4

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• Special Reports 85 05, 89,01, 89 08 ,

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