ML20040C844
| ML20040C844 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde, Humboldt Bay, 05000000 |
| Issue date: | 01/25/1982 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| Shared Package | |
| ML20040C837 | List: |
| References | |
| NUDOCS 8201290301 | |
| Download: ML20040C844 (1) | |
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Janeery 25, 1982 Docket Nos. 50-528, 50-529, 50-530 Arizona Public Service Company P. O. Box 21666 Phoenix, Arizona 85036 Attention: Mr. E. E. Van Brunt, Jr.
Vice President, Nuclear Projects Gentlemen:
The enclosed information notice provides early notification of an event that may have safety significance.
It is expected that recipients will review the information notice for possible applicability to their facilities.
If you have any questions regarding this matter, please contact this office.
Sincerely, 0@nsiiignea0 R. H. Engeen R. H. Engelken Regional Administrator
Enclosure:
IE Information Notice No. 82-01 cc w/ enclosure:
F. W. Hartley, APS G. C. Andognini, APS or,,cr y RV/ dot
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NRC f ORM 318 t10,8Oh NRCM O240 0FFICIAL RECOFiD COPY
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SSINS No.: 6835 Accession No.:
8107230043 IN 82-01 UNITED STATES NUCLEAR REGULATORY CCNMISSION OFFICE OF INSPECTION AND ENFORCEMFNT WASHINGTON, D.C.
20555 January 22, 1982 IE INFORMATION NOTICE NO. 82-01: AUXILIARY FEEDWATER PUMP LOCK 0UT RESULTING FROM WESTINGHOUSE W-2 SWITCH CIRCUIT MODIFICATION Description of Circumstances:
On September 14, 1981, Commonwealth Edison's Zion Unit 2 was conducting a normal plant cooldown to begin a refueling outage. The reactor coolant system was operating at 350 psig and 250F.
Both residual heat removal (RHR) systems.were operating to remove decay heat and control reactor coolant system temperature.
Steam generator water levels dropped below the 10% low level auxiliary feedwater (AFW) pump auto-start setpoint, and the motor-driven AFW pumps activated as designed. The operator placed the control switches in the pull-to-lock-out position to stop the AFW pumps.
Later, to control the rate of plant cooldown, the operator tried to increase the cooldown rate.by feeding water to the steam generators. The AFW pumps would not restart on command. The power supply circuit breaker for one of the pumps was momentarily racked out to the disconnect position and then racked back in for service. As a. result of this procedure, the AFW pump restarted. No further problems were encountered during the plant cooldown operation.
Investigation into the problem revealed that the'l.icensee's modification to the Westinghouse W-2 control switch used with the AFW pumps differed from that recommended in'IE Bulletin 80-20 (IEB).
IEB 80-20, entitled " Failures of Westinghouse Type W-2 Spring Return to Neutral Control Switches,"' recommended using only the existing green status light to provide early detection of an open circuit caused by a neutral position (auto-start). contact failure of the control switch. However, in this application, the' licensee's modification included both the red and green status lights. This resulted in a sneak circuit path which prevented AFW pump restart under certain circumstances.
Following an auto-start of the AFW pump and the subsequent securing of that pump by placing the control switch in the pull-to-lock-out position, the licensee found that a live continuous circuit existed ~between the red light and the anti-pump coil. This sneak current path prevented deenergization of the anti-pump coil (circuit reset) that is necessary for pump restart.
The licensee reports that, following the initial circuit modification, the sneak path was noted to cause the red indicating light to glow only dimly when the control switch was placed in the pull-to-lock-out or trip positions (see Figures 1 through 3 and Table 1). However, the sneak path was'not fully analyzed at that time, and no detailed function testing of the modified circuit was performed. Note that when the red light.'is used to indicate " pump on." as in this. application, the light should not go on when the control switch has been.placed in either the pull-to-lock-out or trip positions.
IN 82-01 January 22, 1982 Page 2 of 2 Circuit modifications may have been made at various plants in response to information in IEB 80-20. These modifications, where different from IEB 80-20 recommendations, may have caused sneak paths with various degrees of impact that may-not have been detected by previous engineering analysis or post-installation testing.
This information notice is provided as an early notification of a potentially significant matter.
It is expected that recipients will review the information for applicability to their facilities. No specific action or response is required at.this time.
If you have any questions regarding this matter, please contact the Regional Administrator of the appropriate NRC Regional Office.-
Attachments:
1.
Figures 1, 2 and 3 2.
Recently issued IE Information Notices t
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IN 82-01 January 22, 1982 RECENTLY ISSUED IE INFORMATION NOTICES Information Date of Notice No.
Subject Issue Issued to 81-37 Unnecessary Radiation 12/15/81 All power reactor Exposure to the Public and facilities holding Workers during Events byproduct material Involving Thickness and licenses Level Measuring Devices 81-36 Replacement Diaphragms for 12/3/81-All power reactor Robertshaw Valve (Model facilities with an No. VC-210)
OL or CP 81-35 Check Valve Failures 12/2/81 All power reactor facilities with an OL or CP 81-34 Accidental Actuction of 11/16/81 All power reactor Prompt Public Notification facilities with an System OL or CP 81-33 Locking Devices Inadequately 11/9/81 All power reactor Installed on Main Steam facilities with an Isolation Valves OL or CP 81-32 Transfer and/or Disposal of 10/23/81 All medical licensees Spent Generators 81-31 Failure of Safety Injection 10/8/81 All power reactor Valves to Operate Against facilities with an Differential Pressure OL or CP 81-30 Velan Swing Check Valves 9/28/81 All power reactor facilities with an OL or CP 81-29 Equipment Qualification 9/23/81 All power reactor Testing Experience facilities with an OL or CP 81-28 Failure of Rockwell-Edward 9/3/81 All power reactor Main Steam Isolation Valves facilities with an OL or CP OL = Operating License CP = Construction Permit c
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