ML20062C382
| ML20062C382 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 10/24/1990 |
| From: | Blosser J UNION ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 90-02, 90-2, ULNRC-2312, NUDOCS 9010310191 | |
| Download: ML20062C382 (5) | |
Text
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" un,og Etecruic L ad j
CMaway nant October 24, 1990
. S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555 ULNRC 2312 Gentlemen:
1 DOCKET NUMBER 50 483 CALLAWAY PLANT UNIT 1 FACILITY OPERATING LICENSE NPP 30 SPECIAL' REPORT 90-02
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INVALID DIESEL GENERATOR FAILURE DUE TO IMPROPER OUTPUT-BREAKER PLUNGER CLEARANCE This Special Report is being sub'mitted pursuant to Technical i
Specification (T/S) 4.8.1.1.3 and 6.9.2 concerning the invalid failure of Diesel Generator (D/G)
'B' due to a D/G output breaker plunger bolt being out of adjustment.
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J'. D. Blosser
' Manager, Callaway Plant TPS/MKD/dj r
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Distribution attached j
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.i 's O 9010310191 901024 PDR ADOCK 05000483 PDC i
Maky Actitess P.O Box 62Q Ftkn MO 652SI.
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-o cc distribution for ULNRC-2312 Mr. A. Bert Davis Mr.; Anthony T. Cody (2' copies)
Regional Administrator U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission OWFN-- Mail Stop E1321 Region III Washington,'D.C.
20555 799 Roosevelt Road-Glen Ellyn, IL 60137 j
American Nuclear Insurers Mr. O. Maynard c/o Dottie Sherman, Library Wolf Creek Nuclear Operating Corp.
The Exchango Suite 245 P. O. Box 411-
. 1 270 Farmington Avenue
_Burlington, KS 66839 i
Farmington, CT 06032 Manager, Electric Department Mr. Merlin Williams Missouri Public Service Commission Supt._of Regulatory _ Quality &
P. O. Box 360 Administrative Services Jefferson City, MO 65102 Wolf Creek Nuclear Operating Corp.
P. 0. Box 411~
3 Burlington, 105 66839
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Records Center Mr. R. L. Hague i
Institute of Nuclear Power Operations Chief, Project Section 3A Suite 1500 U.S. Nuclear Regulatory Commission j
1100 circle 75 Parkway Region III Atlanta, CA 30339 799 Roosevelt Road
-Glen Ellyn, IL 60137 NRC Resident Inspector
. l D. F. Schnell (400)
C. L. Randolph R. P.-Wendling (470)
J. V. Laux
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A. C. 'Passwater/D. E. Shafer/D. J. Walker (490)-
C. A. Hughes j
Z170.0005 (QA Record)
- i Z40SR (Z170.0009 Commercial Record)
M. S, Evans l
M. E. Taylor j
H. Wuertenbaecher, Jr. (100)
S. L. Auston (490)(NSRB)
S. J. Bellers/D. R. Oelrichs J. G. Beck E210.0001 Z40ULNRC A160.0761 N. Date (Sandra Auston)(490)'
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SPECIAL REPORT 90 02 INVAL1D DIESEL GENERATOR FAILURE DUE TO IMPROPER OUTPUT BREAKER PLUNGER GLEARA11CE Surveillance procedure ISP SA 2413B, Diesel Generator and Sequencer Testing i
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, Gold Shutdown, on 9/23/90. During performance of the
"'B' Train Blackout without SIS" portion of ISP.SA-2413B, the
'B' emergency diesel generator (D/G) was intentionally secured without' loading to at least 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.related bus (NB02) energized by
'B' D/G. The D/G could have been i
manually loaded and a valid test consleted.
The operators intentionally secured the b/G after troubleshooting of the load sequencer.
Since the successful D/G start was terminated intentionally without loading to at least 50% of continuous rating, it is not considered a valid test or failure. This position is consistent with Regulatory Guide 1,108,G,2.c(4).
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),
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- No loads sequenced onto the D/G.
- The
'B' Essential Service Water (ESW) pump was manually loaded onto the D/G.
- 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 send a start signal to the load sequencer.
- The D/G was secured and the plunger bolt was adjusted. The test was repeated successfully.
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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 1
stationary auxiliary switch test position link (test link) was installed prior to the "SI" test. The test link was removed prior to the " Blackout without SIS",
The root cause of this failure has been determined to be improper movement of the test link during'breeker 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 the 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 3
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.
Because the root cause has now been determined to be use of the test link, the following corrective actions are being taken:
1.
The gap betwcon the plunger and the operating rod will be verified 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 l
performed.
3.
An evaluation will he performed to determine 10 CFR Part 21 reportability, i
4.
The bent clips will be replaced at the first available opportunity following receipt of parts, i
Surveillance tests are currently performed at least once per 31 days for j
D/G
'B'. This is in conformance with T/S table 4.8-1 which requires a test interval of not more than 31 days if the number of failures in-the last 20 valid tests is one or zero, or if the number of failures in the last 100 valid tests is four or less, y
The starting history of D/G
'B' as of the date of this report is summarized as follows:
Number of Number of Number of Failures During Failures During i
Valid Tests Valid Tests Invalid Tests 92 1#.
4
- LER 89-001-01 i
- Special Reports 85 05, 89 01, 89 08
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- Attachment Special Report 90-02 l
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Plunger I
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Spring 1
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PLUNGER INTERLOCK l
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