05000331/LER-1987-001, :on 870114,RWCU Sys Isolated on Signal from F Temp Differential Switch.Caused by Steam Leak in Root Isolation Valve.Corrective Maint Action Request Generated to Repack Root Valve & Investigate Leak
| ML20210U957 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 02/13/1987 |
| From: | Mineck D, Bernard Thomas IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| DAEC-87-0092, DAEC-87-92, LER-87-001, LER-87-1, NUDOCS 8702180645 | |
| Download: ML20210U957 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2) |
| 3311987001R00 - NRC Website | |
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NAME TELEPHONE NUM0ER AREA CODE Bradford N. Thomas. Technical Support Enoineer 31119 81 S il l -17131019 COMPLETE ONE LINE FOR EACM COMPONENT FAILURE DESCRISED IN THt$ REPORT 8131 RTAgE
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On January 14,1987 at 2009 hours0.0233 days <br />0.558 hours <br />0.00332 weeks <br />7.644245e-4 months <br /> the Reactor Water Cleanup (RWCU) System isolated on a signal from the "F" temperature differential switch. This temperature differential switch receives inputs from temperature sensing elements which monitor temperatures in the RWCU heat exchanger room. The switch was found reading slightly below the isolation set point of 14 degrees fahrenheit. The system responded as designed with the closure of the RWCU outboard isolation valve, and closure of the RWCU feedwater return isolation valve'. Operations personnel were dispatched to inspect the RWCU heat exchanger room. They reported a slight steam leak coming from the root isolation valve on the pressure indicator for the regenerative heat exchanger. At this time the inboard isolation valve was closed by operators from the control room. The root valve was back seated, and the packing was tightened. At 2328 hours0.0269 days <br />0.647 hours <br />0.00385 weeks <br />8.85804e-4 months <br /> the RWCU system was returned to service. This event is being reported in accordance with 10CFR50.73(a)(2)(iv) as an event or condition that resulted in manual or automatic actuation of an Engineered Safety Feature.
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"=.'t C'.O Duane Arnold Energy Center o is t o lo lo i 31311 81 7 01011 010 012 oF 0l3 TEXT IJF mese mem a reenwet am em 4AC passe 3 gs (173 On January 14,1987 at 2009 hours0.0233 days <br />0.558 hours <br />0.00332 weeks <br />7.644245e-4 months <br /> with the reactor operating at 84% of rated thermal power and in coastdown toward the Cycle 8/9 refuel outage the Reactor Water Cleanup (RWCU) system isolated on a signal from the "F" temperature differential switch (EIIS Component Identifier CE-TDS-2743F). The system responded as designed with the closure of the RWCU outboard isolation valve (CE-M0-2701), and closure of the RWCU feedwater return isolation valve (CE-MO-2740). Another differential temperature switch monitoring temperatures in the same general area indicated there was indeed possible system leakage taking place. Operations personnel were dispatched to inspect the RWCU heat exchanger room. They reported a steam leak coming from the root valve (manuf actured by the Velan Valve Corporation) on the pressure indicator (CE-PI-2714) for the regenerative heat exchanger (CE-HX-214A). The root valve packing was determined to be leaking. At this time operators closed the inboard RWCU isolation valve (CE-M0-2700). The root valve was then back seated, and the packing was tightened.
The RWCU steam leak detection logic consists of six temperature differential switches. These switches receive inputs from twelve temperature sensing elements which monitor temperatures in close proximity to inlet and outlet ventilation flow paths in the areas containing RWCU equipment. Any of these differential switches reaching their designed'setpoint results in automatic isolation of the RWCU system from the reactor.
In addition to the temperature differential switches the RWCU leak detection system also uses area room high ambient air temperature sensing elements, and high differential flow indicators in the RWCU piping. Throughout this event the only instrumentation to reach its designed system isolation setpoint was CE-TDS-2743F.
The RWCU system was returned to service at 2328 hours0.0269 days <br />0.647 hours <br />0.00385 weeks <br />8.85804e-4 months <br /> following successful root valve back seating and packing adjustment. The root cause of the packing leak is unknown at this time. A Corrective Maintenance Action Request (CMAR) has been generated to repack the root valve and further investigate the packing leak the next time the RWCU system is removed from service for planned maintenance. The results of this work will be reported in a revision to this report. A review of past plant documentation reveals this particular root valve was discovered slightly leaking during routine plant walkdowns twice since 1985.
In both instances the root valve was back seated packing tightened, and during the next planned RWCU system shutdown the valve was repacked.
In neither instance was the steam leak great enough to cause RWCU isolation.
A review of LERs (1984 to present) on RWCU isolations due to actual system leakage indicates one other similar occurrence. LER 86-004 (Reactor Water Cleanup System Isolation Due to Ventilation High Differential Temperature) reported a leaking drain valve from the RWCU system regenerative heat exchanger (CE-HX-214A) which ra'ised the differential temperature across the room and caused a differential temperature switch system isolation setpoint to be reached. The drain valve was tightened and the system was returned to service.
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. - -,.c w am.,,nn Throughout this particular isolation all safety related equipment responded as designed. The RWCU system is used to reduce impurities from the reactor water, reduce secondary sources of beta and gamma radiation by the removal of corrosive impurities, and to drain excess reactor water during certain operational modes. The only safety related function associated with the RWCU system is the primary containment isolation function. The RWCU system is not needed to safely shut the plant down, nor is it needed do keep the plant safely shutdown. Therefore, this event had no effect on the safe operation of the plant. This event is being reported in accordance with 10 CFR 50.73(a)(2)(IV) as "any event or condition that resulted in manual or automatic actuation of any engineering safety feature (ESF)".
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s-Iowa Electric Light and hwer Company L
February 13, 1987 DAEC-87-0092 U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C.
20555 Subject: Duane Arnold Energy Center Docket No. 50-331 Op. License DPR-49 ~
Licensee Event Report No.87-001 l
Gentlemen:
l In accordance with 10 CFR 50.73 please find attached a copy of the -
l subject Licensee Event Report.
- - Very truly yours,
) { f.9 0 7 Daniel
. Mineck 8
P1 ant Superintendent - Nuclear DLM/BNT/pl Attachment - LER 87-001 l
cc: Mr. James G. Keppler Regional Administrator Region III U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 NRC Resident Inspector - DAEC l
File A-118a f
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Duane ArnoM Enerny Center e P.O. Bos 33i e Cedar llapide, Iowa 32406 e 319/8314611