ML20148P852

Forwards IE Info Notice 80-44, Actuation of ECCS in Recirculation Mode While in Hot Shutdown. No Response Required

ML20148P852
Person / Time
Site:	Rancho Seco
Issue date:	12/16/1980
From:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
To:	Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT
References
NUDOCS 8101150827
Download: ML20148P852 (1)

Text

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UNITED STATES

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• NUCLEAR REGULATORY COMMISSION

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[ $UtTE 202, WALNUT CREEK PLAZA WALNUT CREEK, CAlle ORN! A 9450G December 16, 1980 Docket No. 50-312 Sacramento Municipal Utility District P. O. Box 15830 Sacramento, California 95813 Attention: fir. John J. Mattimoe Assistant General Manager Gentlemen:

The enclosed Informacion flotice provides early notification of an event that may have safety sign Tmnce. Accaroingly, you should review the Information flotice for possible applicability to your facility.

fio specific action or response is requesteo at this time; however, contingent upon the results of further staff evaluation, a Bulletin or a Circular recomnending or requesting specific licensee actions may be issued. If you have any question regarding this matter, please contact me.

Sincerely,

((.2m6 6 A~3d . d. , .

4 R. H. Engelken Dirtetor

Enclosures:

1. IE Information flotice ilo. 80-44

2. Recently. Issued IE Infarration flotices cc w/ enclosures:

R. J. Rodriguez, SMUD '

L. G. Schwieger, Sf'UD THIS DOCUMENT CONTAINS POOR QUAUTY PAGES l

810115082V  :

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t SSINS No.: 6835 Accession No.:

8012160001 IN 80-44 .

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UNITED STATES n

NUCLEAR REGULATORY COMMISSION W D b 0FFICE OF INSPECTI0tl AND ENFORCEtiENT

'!ASHINGTON,

.- D.C. 20555 *6 #J ~

December 15, 1980 IE IrlFORMATION NOTICE NO. 80-44: ACTUATION OF i;rS IN THE RECIRCULATION MODE WHILE IF HOT SHUTDOWN PURPO3E:

The intent of this Information Notice is to alert PWR licensees and holders of construction permits of a potentially generic problem involving inadvertent actuation of the emergency core coolina system (ECCS) in the " Recirculation Mode".

Such an event occurred at the Davis-Besse Nuclear Power Station (Docket No. 50-346) on Decemoer 5, 1980. The plant was in a hot shutdown mode of opera-tion at the time of the event and was undergoing certain maintenance a tivities as described below.

DISCUSSION:

Just prior to the inadvertent actuation of the ECCS, the licensee was attempt-ing to isolate alectrical shorts and/or grounds in the Safety Features Actua-tion System (SFAS). Towaros this end, A-C power had been removed from Channel 3 of the SFAS. Upon reenergizing Channel 3 it was n( ted that an indicating lamp was out; therefore, an attennt was made to replace the failed lamp with a spare unit. While renoving a lamp f rom a . spare output slot in a. Channel 3 chassis, an arc was drawn between the lamp and the module chassis. This arcing was apparent-ly due to a combination of shorts or grounds in the SFAS, which coupled with the " common" connection between Channel 1 and 3 resulted in the loss of a power supply in Channel 1. Since all the bistable trips in Channel 3 had not been completely reset, and since a power supply to Channel 1 was lost, SFAS Levels 1, 2, 3 and 5 were actuated by the two-out-of four actuation logic. Since SFAS Level 5 indicates that the Borated Water Storage Tank (BWST) is at a low level, the ECCS was placed in a recirculation mode (i.e., the ECCS suction was aligned to the emergency contairaent sump.)

In order to place the ECCS system in the recirculation mode, the supply valves leading to the Decay Heat Removal (DHR) pumps from the BWST start closing af ter those in the ECCS line and from the containment emergency sump fully open.

Thus, during this valve transition period, a flow path existed to the reactor coolant system (RCS) via the BWST and the ECCS pumping system (i.e. , the DHR pumps); however, since the RCS pressure was higher than that of the pumping system (2100 vs.1600 psig) no BWST water was pumped into the RCS. Ra ther, during the valve transition time of about 1-1/2 minutes, approximately 15,000 gallons of borated water was drained from the BWST to the containment emergency sump.

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o IN 80-44 December 16, 1980 Page 2 of 2 l

The Davis-Besse Nuclear Power Station has experienced several events during the

-past three and one-half years which have either degraded the DHR system or caused a temporary interruption of DHR operation. Of these, the one most closely I paralleling the event described above occurred on April 19, 1980. (See IE Infor-mation Notice 80-20, " Loss of Decay Heat Removal Operability at Davis Besse Unit 1 While in A Refuelino Mode" dated May 8,1980 and IE Bulletin No. 12,

" Decay Heat Removal System Operability" dated May 9,1980. ) During the Decem-ber 5,1980 event, the plant was in a hot shutdown mode with RCS pressure at approximately 2100 psig; therefore, the coerator was able to promptly trip the DHR numos, thereby precluding air entrapment in the system or pump damage.

In contrast, the Anril 19, 1980 event occurred while the plant was in a cuasi refueling mode (i.e., the reactor head was in place but detensioned, RCS water level was below the steam generator's bottom plate, the RCS was vented to the atmosphere by an open manhole at the too of the steam generator, and decay heat was being removed by one DHR system). Since the DHR pump was being used to remove decay heat during the April 19 event, it was lef t running for approxi-mately two minutes after the pump had been aligned to the recirculation mode of operation, and tripped when water was discharged from a temporary tygon line.

Since the DHR system was the only system available for decay heat removal, the {

DHR pumn was. restarted approximately forty minutes later; however, it was i

tripped shortly thereaf ter when it was determined that there was air in the i suction line of the system, in all, the April 19, 1980 event required approx-imately two and one-half hours to vent the DHR syttem and reestablish DHR fl ow. As a consequence of the relatively long recovery time, the temperature limit specified in the Technical Specification for the refueling mode of opera-tion was exceeded during the April 19, 1980 event.

The above events illustrate means whereby the integrity of a major ECCS system can be jeopardized by inadvertently or prematurely aligning the ECCS to the recircula tion mode of operation. The major concern in such cases.is that the 1

DHR pumps could become air bound if their suction lines are aligned to a dry sump. l At best, with the pumps air bound, the pump motor would trip automatically j or could be tripped cianually before any damage occurred, in which case flow could '

be established af ter the system is vented; at worst, the pumps could.be damaged and become inoperable, in which case the active portion of the ECCS would not l be available, if needed at that time.

This Information Notice is provided as an early notification of a possibly signi-ficant matter that is still under review by the NRC staff. Recipients should re-view the information for possible applicability to their facilities. No specific action or resoonse is requested at this time; however, if NRC evaluations so indicate, further licensee actions may be reouested or required.

j If you have any question regarding this matter, please contact the director of the appropriate NRC Regional Office.

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I IN 80-44 I December 16, 1980 RECENTLY ISSUED IE INFORMATION NOTICES Information Date of Notice No. Sub,iect Issue Issued to 80-43 Failures of the Continuous 12/5/80 All power reactor Water Level Monitor for facilities with OL the Scram Discharge Volume or CP at Dresden Unit No. 2 80-42 Effo;t or Padiation on 11/24/80 All power reactor Hydra .i ._ Snubber Fluid facilities with OL or CP 80-41 Failure of Swing Check 11/10/80 All power reactor Valve in the Decay Heat facilities with an OL Removal System at Davis- or CP Desse Unit No. 1 80-40 Excessive Nitronen Suoply 11/10/80 All power reactor Pressure Actuates Safety- facilities with Relief Valve Operation to OL or CP Cause Reactor Depressur-12ation 80-39 Nalfunctions of Solenoid 10/31/80 All light water reactor

'!alves Manufactured By facilities with

!alcor tngineering Corporation OLs or cps 80-33 Cochino in Chargino Pump 10/30/80 All PWR facilities rasing Cladding with an OL or CP 80-37 Containment Cooler Leaks 10/24/80 All power reactor and Reactor Cavity facilities with Flooding at Indian Point OLs or cps Unit 2 80-36 Failure of Steam 10/10/80 All power reactor Generator Support Bol ting facilities with OLs or cps 80-35 1eaking and Dislodged 10/10/80 All categories G and lodine-124 Implant Seeds G1 medical licensees 80-34 Boron Dilution of Reactor 9/26/80 All PWR Coolant During Steam facilities with Generator Decontamination OLs OL = Operatinq Licemes CP = Construction P, qnits-

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