ML19325E590

LER 89-028-00:on 891008,concluded That Operation of Fuel Pool Cooling & Cleanup Sys to Upper Containment Pools Caused Containment Vacuum Breaker Actuations.Caused by Unrecognized Sys Interaction.Operating Instruction revised.W/891103 Ltr

ML19325E590
Person / Time
Site:	Perry
Issue date:	11/03/1989
From:	Dunn G, Kaplan A CLEVELAND ELECTRIC ILLUMINATING CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-028, LER-89-28, PY-CEI-NRR-1089, NUDOCS 8911080064
Download: ML19325E590 (4)

Text

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G 8' THE CLEVELAND ELECTRI P.O. ROX 97 3 PERMY, OHIO 44041 5 TELEPHONE (216) 2694737 FMOW CLEVELAND: 479 1200 3

5 ADDMEsS 10 CENTER ROAD TELtX: 2416s0 ANsWEMBACet: CCIPRYO j i

Al KAplan Serving The Best locatica in the Nation PERRY NUCLEAR POWER PLANT  !

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94WLI684 GNNf' November 3, 1989  !

PY-CE1/NRR-1089 L l U.S. Nuclear Regulatory Commission Document Control Desk j Washington, D. C. 20555  ;

Perry Nuclear Power Plant l Docket No. 50-440 j LER 89-028 Gentlemen Enclosed is Licensee Event Report 89-028 for the Perry Nuclear Power Plant.

Note that per Section 6.2.1.1 4.2 of the USAR: " Vacuum breaker opening for i other than the inadvertent containment spray actuation scenarios presented in this section is considered a non-EST actuation. Conditions which result in .

changes to the containment atmosphere, (such as containment venting and cooling, suppression pool level changes and weather changes), and subsequently ,

result in containment vacuum breaker operation, are considered normal and l expectsd, and are bounded by the limiting inadvertent containment spray situation." However, based upon the unexpected operational impact on the  ;

. Containment Vacuum Relief System, this event is being reported as an unexpected Engineered Safety Feature actuation.

Very truly yours, kA Al Kaplan h  !

k Vice President t Nuclear Group l AKinjc Enclosure LER 89-028 .

cc T. Colburn >

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U.S. NRC Region 111 i g 8911000044 891103 PDR ADOCK0500gO S

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.ast .Ct rating Instruction was revised to provide a caution that FPCC Upper ]

Containment Pools operation with a low surge tank level can cause containment '

vacuue breaker actuation. Additionally, actions were initiated to revise FPCC i

Surge 'iank Low Level Alarm setpoints. As part nf the established l requalitication training program all plant licensed operators will be l l instructei on the lessons learned from this event.

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0l 0 0l2 or 0l3 m, w . cs m.mm i On October 8, 1989 it was concluded that operation of the Fuel Pool Cooling l and Cleanup System (FPCC) [DA) to the Upper Containment Pools (UCP) caused i Containment Vacuum Relief System [BF) vacuum breaker [VACB) actuations that 1 occurred between September 19 and October 8, 1989. Flow from the UCP to the FPCC Surge Tank [TK) was secured for additional testing. Tne plant was in 1 Operational Condition 1 (Power Operation) at approximately 100 percent of l rated thermal power. The Reactor Pressure Vessel [RPV) was at saturated 1 conditions at approximately 1000 psig.

On October 2, 1989 it was noted that containment vacuum breakers cycled ,  !

repeatedly between September 19 and September 30, 1989. Plant Operators I postulated that containment vacuum breaker cycling might be related to )

containment lower air lock [AL) maintenance. An investigation was initiated j to determine if lower containment air lock inner door maintenance, during the 1 September 19 thru 30 time frame, contributed to the containment vacuum breaker cycling problem. The lower containment air lock was tested with helium to check for leakage from the air lock to the annulus. No leakage was detected. l As no correlation was found between the maintenance and vacuum breaker t actuation, the investigation continued to investigate other potential causes.

On October 6, 1989 at 0414 a containment vacuum breaker opened for approximately 5 minutes. The lower containment airlock was checked and the inner door was verified shut and sealed. At 0700 another containment vacuum breaker alarmed as if open, but no indicating light came on indicating the vacuum breaker was open. Action was initiated to correct the "open indication" problem. At 0945 an Investigation Team was formed to determine the cause of containment vacuum breaker cycling. Between October 6 and Occober 8, 1989, containment vacuum breakers cycled approximately 49 times.

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While performing a plant tour on October 8, the Shift Supervisor noticed an i

unusual sound coming from the return line from the UCP to the FPCC Surge Tank.

l At 0957 the flow from the UCP to the FPCC Surge Tank was isolated.

l Containinent pressure increased and the containment vacuum breakers stopped l cycling.

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On October 9, 1989 FPCC flow to the UCP was restored at the request of the Investigation Team. A smoke tester was used to verify that air was being drawn into the UCP Skimmers [SKR). It was also determined that air '

entrainment in the FPCC UCP Return Line was dependent upon Surge Tank level.

When Surge Tank level was decreased beyond a specific value, air entrainment I started. Further testing from October 9 thru October 12 determined l quantitative relationships between FPCC Flow to UCP, FPCC Surge Tank Level, I

and air entrainment in the FPCC UCP Return Line.

The root cause of the containment vacuum breaker actuations was a previously unrecognized system interaction. FPCC System Operating Instruction (S01-G41(FPCC)) allowed too wide of an operational band for flow to the UCP and too wide of an operational band for Surge Tank Level. This allowed FPCC

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0 l0 0l3 - or 0l3 l ru, u-. m nc m mn enm to be operated in a manner which caused air to be entrained in the FPCC UCP  !

Return Line. Removal of this air irom containment caused a decreasing pressure which caused containment vacuum breaker actuation.

The Containment Vacuum Relief System is designed to. prevent any pressure differential acting inward on the Containment Vessel from exceeding the design value of 0.8 paid in the event of an inadvertent Containment Spray Initiation.

This is described in Section 6.2.1.1.4.2 of the USAR. " Vacuum breaker opening for other than the inadvertent containment spray actuation scenarios presented j in this section is considered a non-ESF actuation. Conditions which result in changes to the containment atmosphere, (such as containment venting and i cooling, suppression pool level changes and weather changes), and subsequently result in containment vacuum breaker operation, are considered normal and expected, and are bounded by the limiting inadvertent containment spray situations." However, based upon the operational impact on the Containment Vacuum Relief System, this event is being reported as an unexpected Engineered  :

Safety Feature actuation.

During this event the vacuum breakers opened as designed and their safety function was not impaired. There were also two additional redundant vacuum -

breakers available. The FPCC System is designed to remove decay heat >

generated by spent fuel stored in the spent fuel storage pool. In addition, this system maintains the purity, clarity, and level of water in the UCP and the fuel storage pools in the Fuel Handling Building. In the event of a Loss of Coolant Accident, FPCC would have been isolated from containment and air entrainment would have stopped.  ;

Although containment atmosphere was being moved to the Intermediate Building by this event, the air was monitored by the Intermediate Building Exhaust ,

Radiation Monitor before being released to atmospaere through the Unit 1 plant vent. No abnormal effluent release rates were present during this event.

Both FPCC and the Containment Vacuum Relief System were operated in accordance with their designs and all operator actions taken were in accordance with approved procedures. Consequently, this event had no safety significance. No previous similar events were identified.

In order to prevent recurrence, S01-C41 (FPCC) was revised to restrict Surge Tank level and flow to dCP to prevent entraining air in the return line. The Containment Vacuum Relief System Operating Instruction was revised to state that FPCC UCP operation with a low Surge Tank level can cause containment vacuum breaker actuation. Also actions were initiated to raise FPCC Surge Tank Low Level Alarm Instrumentation setpoints to enhance maintaining FPCC Surge Tank level within its restricted operational band. As part of the established requalification training program all plant licensed operators will be instructed on the lessons learned from this event.

Energy Industry Identification System Codes are identified in the text as

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