ML19276H020

Forwards LER 79-018/03L-0

ML19276H020
Person / Time
Site:	Cooper
Issue date:	08/03/1979
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19276H021	List: ML19276H020 ML19276H022
References
CNSS790365, NUDOCS 7908310357
Download: ML19276H020 (2)

Text

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P COOPER NUCLEAR STATION

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Nebraska Public Power District " " iA"E0"~RA'20's*25" " 1

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CNSS790365 ,

August 3, 1979 Mr. K. V. Seyfrit U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region IV

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611 Ryan Plaza Suits 1000 Arlington, Texas 76011

Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.1 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on July 6, 1979. A licensee event report form is also enclosed.

Report No.: 50-298-79-18 Report Date: August 3, 1979 Occurrence Date: Tuly 6,1979 Facility: oooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

Operation with an engineered safety feature instrument setting less conservative than those established in Table 3.2. A of the Technical Specifications.

Conditions Prior to Occurrence:

The reactor was operating at a steady state power level of sp-proximately 95~ of rated thermal power.

Description of Occurrence:

While performing routine Surveillance Test Procedure 6.2.1.7, the level indicating switch NBI-LIS-58A auxiliary switch number one setpoint was found set at a level lower than allowed by Technical Specifications.

Designation of Apparent Cause of Occurrence:

Examination of NBI-LIS-58A revealed a small amount or sediment consisting of dust and moisture. This allowed the subject aux-iliary switch assembly to become slightly sluggish resulting in an ,

out of tolerance setpoint.

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August 3,1979

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Analysis of Occurrence: , .

NBI-LIS-57A and 58A are Yarway Model 4418C levcl indicators and are installed as redundant level indicat:1.na switches with two sets of

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, auxiliary switches each, designated one and two respectively.

3 Auxiliary switch number one initiates a MSIV closure at a reactor a vessel level of >-37 inches. Auxiliary switch number two initiates

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' a ATWS reactor recirculation pump trip at a reactor vessel level of

>-37 inches.

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/ \ The subject level indicator was indicating properly and auxiliary g /, switch nurser two would have initiated a ATWS reactor recirculation

( pump tripNif the reactor vessel water level had decreased to the

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setpoint. Redundant NBI-LIS-57A was also operable and would have

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initiated the '4SIV closure associated with auxiliary switch number one if the re&ctor vessel water level had decreased to the setpoint.

The equipment history:for i'3I-LIS-58A revealed that a similar

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problem had previou Q occurred and, auxiliary switch number two had been replaced. In . addition, the case containing the two auxiliary switches had been sealed to prerent intrusion of dust and moisture.

It is believed that the sediment found in this occurrence is a latent affect -Irom the previous identified problem in that the casing was not thoroughly cleaned' prior ir sealing. This occur-

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rence presented no adverse consequences from the standpoint of i public health end safety.

(( Ccrrective Actic't:

The interior cf the switch was thoroughly cleaned and proper op-

?. ration of the suxiliary switches was verified. Both LIS casings

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were inspected to insure they were tightly sealed to prevent mois- '

i , ture intrusion of the auxiliary switch. Surveillance Test Proce-

'k dure 6.2.1.7 was performed this da*.e and NBI-LIS-58A auxiliary

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i. switch one and two were verified op.rable at the specified set-point. Additionally, a new mechanical can actuated solid state

switch module is available from Yarway and this modification is currently under eve 1.uation for future installation. This occur-

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rence has been discussed with all personnel involved.

' Sincerely, ') f) 7, / ]gg u

L. C. Lessor Station Superintendent

, Co-per Nuclear Station LCL:cg s Attach. s

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