ML20044A378

LER 90-023-00:on 900523,discovered That Annulus Ventilation Radiation monitor,1RMS*RE11A Inoperable.Caused by Failure of Radiation Monitor Sample Pump & Failure of Switch to Actuate.Flow Switches replaced.W/900622 Ltr

ML20044A378
Person / Time
Site:	River Bend
Issue date:	06/22/1990
From:	England L, Odell W GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-023, LER-90-23, RBG-33103, NUDOCS 9006280420
Download: ML20044A378 (4)

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. GULF STATES ' UTILITIES - COMPAPJY Ar,tFs BIND STATION POST OFFK:t Box 270 ST FR ANC!$V4).I' LOV@ANA 70775 ARE A CODE SIM $35 6094 ' 346 8651 June 22,1990 RBG- 33103 File Nos. G9.5, G9.25.1.3 i

U.S. Nuclear Regulatory Ocunission i Doctm3nt Control Desk  ;

Washington, D.C.

20555 Gentionen ,

River Bend Station - Unit 1  !

Docket No. 50-4SP  !

Please find enclosed Licensee Event Report No.90-023 for i River Bend Station - Unit 1. This report is being subntitted pursuant to 10CFR50.73.

Sincerely, ,

. i 1 W. .

.'OdellL L Manager-Oversight River Bend Nuclear Group  !

cc: U.S. Nuclear Regulatory Ccmnission I

,, 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 NRC Resident Inspector y P.O. Box 1051 L St. Francisville, LA 70775 INPO Records Center 1100 Circle 75 Parkway Atlanta, GA 30339-3064 i q

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-At approximately 0730 on 05/23/90, with the plant at 100 percent power (Operational. condition 1), the Auxiliary Building Operator discovered that the annulus ventilation radiation monitor, 1RMS*REllA was inoperative. The operator reported this discovery to control room personnel who observed that the control room indication of 1RMS*REllA erroneously indicated that it was operable. Following this discovery, the operating logs were reviewed and it was determined that the annulus mixing and standby gas treatment (SGTS) systems had not been initiated within the time period (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />) required by Technical Specification (TS) 3.3.2, table 3.3.2.1-1.2.d, action 29. Therefore, this report is submitted pursuant to 10CFR50. 73 (a) (2) (1) (b) as operation prohibited by the Technical Specifications.

The root cause of tinis event was the failure of the radiation monitor sample pump and the failure of the sample pump flow switch to actuate.

The failure of the flow switch denied the control room operators the indication needed to confirm the operability status of the sample pump.

During the period of time that 1RMS*REllA was out of service, a reditndant radiation monitor was available. Therefore, this event did ,

not adversely affect the health and safety of the public.

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0l @ 4 -- 0 l0 0 l2 0F 0l3 ren ,- . .e % m m REPORTED CONDITION At approximately 0730 on 05/23/90 with the plant at 100 percent power (Operational Condition 1), the Auxiliary Building Operator discovered that the annulus ventilation radiation monitor (*RA*) 1RMS*RE11A was inoperative. The Operator reported this discovery to control room personne1'who observed that control room indication of 1RMS*REllA erroneously indicated that it was operable. This was due to the failure of the sample pump flow switch (*FIS*) to actuate. The erroneous. indication was corrected when an operator tapped the sample pump flow switch. Following the discovery of the erroneous control room indication, the operating logs were reviewed. This review showed that 1RMS*RE11A was last operable on 05/20/90. Log entries for 05/21/90 and 05/22/90 indicated that the instrument was inoperable, according to local indication. Technical Specification 3.3.2, table 3.3.2.1-1.3.d, action 29 requires that the annulus mixing and standby gas. treatment (SGTS) (*BH*) systems be started within one hour of the failure of 1RMS*REllA. Therefore, this report is submitted pursuant to 10CFR50. 73 (a) (2) (1) (b) as operation prohibited by the Technical Specifications.

INVESTIGATION The investigation revealed three conditions which contributed to the failure to implement the TS actions. First, the flow switch failed to actuate, resulting in the erroneous reading in the control room.

Second, two Operators, one on each of two separate days, 05/21/90 and 05/22/90, did not notify the Unit Operator or Control Operating Foreman (COF) upon detection of the-off-normal readings. Third, the off-normal readings which were recorded and circled in red on the logs by the Operators, were not noticed by the COPS who reviewed the logs.

Note that review by the COP usually occurs late in the shift, approximately 8 to 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> after the equipment is checked.

Therefore, it is not likely that review by the COFs would have prevented this event. However, if either COF had identified the inoperable equipment, the duration of the non-compliance with the TS could have been shortened.

The root cause of this event was the failure of the radiation monitor sample pump and the failure of the sample pump flow switch to actuate.

The failure of the flow switch denied the control room operators the indication needed to confirm the operability status of the sample ,

pump. '

A similar event involving different radiation monitors was reported in

LER 85-015. In this case the sample pumps for both of the control room ventilation local intake radiation monitors (*RA*) (1 RMS

• RE13 A& B) tripped due to an electrical transient. Technical Specification table 3/4.3.7.1-1.1.a requires the initiation of the control room ventilation system (*VI*) in its emergency mode within one hour of the g,acaw =a .u a oro nee +eus46

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0l 0 0l 3 oF 0l3 sea a- , . < ,,a uc w amwo nn loss of the minimum number of channels required for operability of the radiation monitors. In this event both sample pumps remained off for about 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br />.

The subject event of this LER bears a superficial similarity to two additional LERs,88-013 and 88-028. In both events, the operator did not recognize the requirement to initiate the annulus- mixing and standby gas treatment (SGTS) (*BH*) systems as required by TS 3.3.2. ..

This LER, while addressing the same TS requirement has a different '

root cause. In this case, the Unit Operator never had an opportunity to enter the action statement because he was not aware of the inoperable status of the radiation monitor.

! CORRECTIVE ACTION The sample pump flow switch for 1RMS*RE11A has been found stuck in the past. A modification (Modification Request (MR) 88-0293) was initiated to address this problem by replacing the flow switches on all Technical Specification-related process monitors with a different type of switch. This modification is currently scheduled for implementation in June, 1991.

The_ Operation Section Procedure, OSP-012, " Daily Log Report", has been revised to identify important plant equipment with an asterisk. _If an out of specification or off-normal _ reading is noted, the Operator is

! required to immediately contact the COF. ,

S AFETY ' ASSESSMENT During the period of time that 1RMS*REllA was out of service, a-redundant radiation monitor was available. Therefore, this event did l not adversely affect the health and safety of the public.

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

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