ML20084T902

LER BFRO-50-259/7616:on 760921,rod Worth Minimizer Latched in First Rod of Rod Group 5.Cause Suspected to Be Failure During Software Data Transfer to Minimizer.Rod Movements for 50% of Rods Verified Before Startup

ML20084T902
Person / Time
Site:	Browns Ferry
Issue date:	10/04/1976
From:	Fox H TENNESSEE VALLEY AUTHORITY
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
LER-BFRO-50-259-761, NUDOCS 8306240258
Download: ML20084T902 (3)

Text

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Event Description

• At about 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br /> the rod worth minimizer (RWM) latched in the first rod of group 5 following proper operation during startup and withdrawal of the previous 4 rod groups. Before withdrawing the first group 5 rod, a shutdown was initiated due to other plant prob 1 ems. The shutdown proceeded through rod group still 4 and upon latched selection in group of the first rod in group 3, the RWM was discovered

5. From the time of this discovery, a second operator was used to satisfactorily confirm all required rod moves during shutdown.

The RSCS was operable and enforcing. (BFRO-50-259/7616) e Cause Description s Normal diagnostic checks failed to indicate a reason for the RWM problem.

Failure during software data transfer to the RWM is suspected since three redundant hardware channels are available to establish required rod blocks.

Additional Factors To ensure that the RWM was properly enforcing, rod movements for approximate'ly 50%r of the rods were verified upon startup of,the reactor. .

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. ,e*%r o TENNESSEE VALLEY AUTHORITY o ggp2%.

CHATTANOOGA. TENNESSEE 37401

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October 4, 1976 Mr. Norman C. !foseley, Director U.S. Nuclear Regulatory Commi,ssion Region II 230 Peachtree Street, NW., 8th Floor Atlanta, Georgia 30303 .

Dear Mr. Moseley:

TENNESSEE VALLEY AUTHORITT - BROWNS PERRY NUCLEAR PLANT UNIT 1 -

DOCKET No. 50-259 - FAC OPERATING LICENSE DPR REPORTABLE OCCURRENCE REPORT BFR 50-259 7616 The enclosed report is to provide details concerning the rod worth minimiser (RWM) that latched in the first rod of group 5 following proper operation during startup and withdrawal of the previous 4 rod groups.

This report is sub:itted in accordance with Browns Ferry Technical

. Specifications Section 6. This event occurred on Browns Ferry Nuclear Plant unit 1..

Very truly yours, TENNESSEE VALLEY AUTHORITY r

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ir t of Power Production (

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Enclosure (3) ~

CC (Enclosure):  %*'Q* %gwon -

. C-4 Director (3) \

Office of Management Information and Program. Control 49 i U.S. Nuclear Regulatory Cocasiasion ' '. g ' ..i\'~~

Washington, D. . 20555

_ Director (40)

Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission d  ; Washington, D.C. 20555

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$X)PY SENT REGION ._

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i An Equal Opportunity Employer hhd

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