05000458/LER-1990-022

LER 90-022-00:on 900518,HPCS Sys Declared Inoperable & 14-day Shutdown Limiting Condition for Operation Entered Due to Inoperative Suppression Pool Level Transmitter.Caused by Personnel Error.Reactor Operators trained.W/900618 Ltr

ML20055C827
Person / Time
Site:	River Bend
Issue date:	06/18/1990
From:	Odell W GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-022, LER-90-22, RBG-33085, NUDOCS 9006250206
Download: ML20055C827 (5)

LER-2090-022,

Event date:
Report date:
4582090022R00 - NRC Website

text

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GULF STA TES UTILITIES COMPANY R!vlR Pf ND $1 A14tN P0$1 Df FKl(13f 220 ET F RANDSO..LL L OJ'biAM U776 Akla CDDE MM f 36 6!%4 44f- lLf 61 June 18, 1990 .

FJo 33085 File 16s. G9.5, G9.25.1.3 U.S. Nuclear Regulatory Ccrmission Document Control Desk Washington, D.C. 20555 Gentlemen:

River Bend Station - Unit 1  ;

Docket No. 50-458 Please find enclosed Licensee Event Report No.90-022 for River Bend Station - Unit 1. This report is being subnitted pursuant to 10CFR50.73.

Sincerely, W. H. Odell Manager-Oversight River Bend Nuclear Group cc: U.S. Nuclear Regulatory Cmmission 611 Ryan Plaza Drive, Suite 1000 i

Arlington, TX 76011 NRC Resident Inspector P.O. Box 1051 St. Francisville, IA 70775 l INFO Records Center 1100 Circle 75 Parkway Atlanta, GA 30339-3064

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. ACILtYv hawl of Docati sevangen iai ,agg <y RIVER BEND STATION oIsIololo14 15 18 1 loFl 014 Pailure to Declare the High Pressure Core Spray Diesel Generator Inoperable as Recuired by Technical Specification 3.5.1 tyth1 Datt lll Lf R tsuMet el i41 htPM1 Daft (7s OTHE R 9 ACitif ell thv0Lvl0 441 WONTH Ca. Vlam vtan lig 66 at4sj MONTn Dat glat s atsuti sn avtl DXatt huwDth;li 01sl0lo10; ; ;

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On 05/18/90 with the unit at 100 percent power (Operational Condition 1), the HPCS system was declared inoperable and a 14 day shutdown limiting condition for operation (LCO) was entered due to an inoperative suppression pool level transmitter. However, Technical Specification (TS) 3.5.1, action c.1 also requires declaring the HPCS diesel generator inoperable and this requirement was overlooked.

This report is submitted pursuant to 10CFR50. 73 (a) (2 t (1) (b) as operation prohibited by the Technical Specifications. The root cause of this event was the failure to recognize the requirement to declare the HPCS diesel generator inoperable. Corrective actions included training of all licensed Reactor Operators (ROs) and Senior Reactor Operators (SROs)on this incident with a review of Technical Specification requirements. Furthermore, the Plant Manager has issued a memorandum emphasizing the importance of meeting all regulatory requirements.

During this event, the HPCS system would still have been available to fulfill its safety function and all redundant backup systems were fully operable. Therefore, this event did not adversely affect the health and safety of the public, t ac.,' "' =

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01 0 012 0F 01 4 verv . . =ac w an..nm REPORTED CONDITION At 0300 on 05/18/90 with the unit at 100 percent power (Operational Condition 1), a high pressure core spray (HPCS) suppression pool level transmitter (*LT*) (1E22*N055G) was discovered inoperable during a channel check surveillance. The allowable tolerance that the instrument was required to meet, when compared to another channel monitoring the same parameter was not within design limits.

Subsequent to this discovery the HPCS system (*BG*) was declared inoperable and a 14 day shutdown LCO was entered. However, Technical Specification (TS) 3.5.1, action c.1 also requires declaring the HPCS diesel generator (*DG*) inoperable (when the HPCS system is declared inoperable) and this requirement was overlooked. All other TS-related systems, structures, and couponents having the potential to impact this event were operable at the time of discovery. No manual or automatic safety system responses occurred as a result of the failed level channel. This report is submitted pursuant to 10CFR50. 7 3 (a) (2) (1) (b) as operation prohibited by the Technical Specifications. The root cause of this event was the failure to recognize the requirement to declare the HPCS diesel generat6r inoperable.

INVESTIGATION At the time of discovery of the failed instrument channel check the SS initiated efforts to determine which of the two instruments was .

providing the faulty indication. He ascertained the 'G' transmitter to be inoperable first by utilizing other independent indications of suppression pool level and comparing with those of the suspect channels. This comparison caused suspicion that the lower reading level instrument had failed. Field investigation followed revealing a degraded air supply to the level transmitter bubbler system. The air regulator supply lines were found full of water and partially plugged with debris. With a restricted air supply to the bubbler system a lower indicated level would result, causing the entire channel to be in a non-conservative state. The safety related function of this circuit would not have actuated within the required tolerance of the instrument setpoint.

The HPCS suppression pool level transmitters (*LT*) are designed to provide an automatic transfer for the HPCS system (*BG*) to draw suction from the suppression pool and isolate the suction path from the condensate storage tank (CST) (*TK*) whenever a high suppression pool icvel condition exists. This would be expected to occur during a loss of coolant accident in which a HPCS initiation signal would be present. In the accident analysis no credit is taken for the CST

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Following the determination that the level transmitter was inoperable, the COF consulted the TS and proceeded to initiate an LCO to align the HPCS system (*BG*) to the suppression pool. This would maintain the system in an operable condition. No further action pending restoration of the level transmitter (*LT*) would have been necessary.

The SS however, was concerned over the contamination and radiation I levels present in the pool water and was hesitant to realign the l system. Weeping safety relief valves (*RV*) together with a small fuel cladding leak have elevated plant background and suppression pool radiation levels. The SS determined a better course would be to I declare the HPCS system (*BG*) inoperable and maintain its alignment to the CST (*TK*). The COP then initiated a new LCO declaring the 1 HPCS system (*BG* ) inoperable. In effecting this LCO the requirement i to declare the HPCS diesel generator (*DG*) inoperable was overlooked and this was the root cause of the event.

A review of previously submitted LERs has identified four events which are similar. LER 85-025 describes an event in which reactor water conductivity recorders (*CR*) were taken out of service. Technical Specifications require conductivity measurements to be taken every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> when the plant is in cold shutdown with the recorders inoperative. This requirement was overlooked by plant personnel.

Corrective actions included improving the shift turnover procedure to put more emphasis on chemistry status, and revising the LCO tracking system. LER 88-013 desc ribed a failure to initiate the annulus mixing and standbv gas treatment (SGTS) (*BH*) systems due to a misinterpretation of TS 3.3.2. Action 29 of this TS requires that annulus mixing and at least one train of the SGTS be initiated within one hour when an annulus exhaust radiation monitor (*IL*) is rendered inoperable. Additional training was provided to plant personnel on the interpretation of Technical Specifications. LER 88-028 described an event identical to LER 88-013. In this case, corrective actions included review of LERs88-028 and 88-013 for the responsible party and enhancing the station test procedures to clarify the requirements for annulus mixing and SGTS operation when the annulus exhaust radiation monitors are taken out of service. LER 90-021 described another failure to implement actions required by TS 3.3.2. In this case, a division of the reactor water cleanup system (RWCU) differential flow instrumentation (*FT*) was in an inoperable condition for a period of time greater than allowable due to a misinterpretation of the minimum number of channels required for operability.

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01 0 01 4 0F 014 on.. . e an.v nn CORRECTIVE ACTION The root cause of this event was operator error on the part of the COP and SS. They have been counseled on the importance of thorough review and follow-up of all TS-related actions. Training on this event has been provided for all licensed ROs and SR0s with a review of Technical Specification requirements. In addition, the Plant Manager has issued a memorandum emphasizing the importance of fully meeting all regulatory requirements.

SAFETY ASSESSMENT During this event, the HPCS system (*BC*) would still have been available to fulfill its safety function and all redundant backup systems were fully operable. The requirement to declare the !!PCS diesel generator (*DG*) inoperable is in cot.:ideration of reduced loading on the engine should it be required to carry less loads. With the HPCS pump (*P*) not available as a load the engine temperatures in the exhaust manifold would be sufficiently high to create the potential for a fire. The !!PCS pump (*P*) in this instance was available as a bus load and all automatic start circuits remained fully functional throughout the event. Therefore, this event did not adversely affect the health and safety of the public.

NOTE: Energy Industry Identification System Codes are identified in the text as (*XX*).

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