ML20085E698

Final Deficiency Rept Re Violation of Electrical Divisional Separations Criteria in RHR Sys.Initially Reported on 760615.Memo Issued Requesting Reevaluation of Existing Controls on Drawing Verification & Mods.Wires Disconnected

ML20085E698
Person / Time
Site:	Browns Ferry
Issue date:	07/23/1976
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8308160335
Download: ML20085E698 (3)

Text

...- Jilo+ 830 Pow:r Building e IEFILE COPY ENNESSEE VALLEY AUTH Y CHATTANOOGA. TENNcSSCE 374o1

%s.3# M 23 W6 Mr. Norman C. Moseley, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region II - Suite 818 230 Peachtree Street, NW.

Atlanta, Georgia 30303

Dear Mr. Moseley:

BROWNS FERRY NUCLEAR PLANT UNIT 3 - REPORTABLE DEFICIENCY - VIOLATION OF ESS SEPARATIONS CRITEPIA IN THE RHR SYSTEMS Initial report of the subject reportable deficiency was made to G. R. Klingler, NRC-IE, Region II, on June 15, 1976. In compliance with paragraph 50.55(e) of 10 CFR Part 50, we are enclosing a final report of the deficiency.

As discussed with Mr. Klingler on July 22, 1976, we regret that this report is being submitted past the established due date. We will attempt to prohibit submitting late reports in the future.

Very truly yours,

(. x- (J) ices,

',( "J. E. Gilleland i Assistant Manager of Power /

Enclosure CC (Enclosure):

Dr. E. Volgenau, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555 f'

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PDR ADOCK0308160335 S 05000296 760723 PDR

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An Equal Opportanity Employer

- 9 ENCLOSUP2 9 ERO. INS FERRY UUCLEAR PIRIT UNITS 1-3 VIOLATION OF ESS SEPARATIONS CRITERIA IH RHR SYSTEM DDR 234 FINAL REPORT Or.' Jun e 15, 1976, an initial report was made by telephone to NRC-0IE Region II Inspector, Gerald R. Elingler, by W. K. Anders, T. W. Barkalow, L. W. Blevins, and D. J. Cash in accordance with 10CFR50 55(c). This is the final report on this deficiency and covers all three units.

Description of Deficiency ,

While conducting a review of drawings, an engineer discovered that the -

electrical divisional separations criteria had been violated in the RHR system logic. In all three units, a cable designated and routed for the Division II RHR logic control power connected into the Division I RHR logic control power. The BHR logic control power is used to energize and dcenergize the relay and RHR control circuits. In addition, in unit 3 a cable designated and routed for the Division I RHR logic control pouer also connected into the Division II RHR logic control power. This double error in unit 3 led to separate divisional cables terminating in close proximity in a set of limit switches for a valve without adequate barriers or distance to separate them.

Cause of Deficiency

, The cables were incorrectly designated by the responsible design personnel.

The error was not detected and corrected by the site personnel.

Safety Implications The deficiency in units 1 and 2 could allow a fault in the Division II RHR logic control power to affect the Division I RHR logic control power for the minificw valve, FCV 74-7, and cause a loss of function of the valve.

Loss of this valve would be critical only if the valve is required to be open to allow recirculation of water through the RHR pu=p when all other valves are closed. This limited recirculatten is lecessary to cool the i RHR pump. This case would only arise if there were a small line LCCA which did not cause a rapid depressurization of the reactor pressure vessel, but which would cause an automatic start of the RHR system in the LICI code.

However, there is no credible single failure following a LOCA that could

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lead to the loss of the Division II RHR logic control power and the mini-flow valve FCV 74-7 The deficiency in unit 3 could allow a fault in the RHR logic control power of either electrical division to affect the other division. Such a fault could cause the loss of all RHR logic control power. If it were necessary to use the RHR system for torus cooling and such a fault had occurred, it would still be possible to manua ly start the appropriate EdiR pu=ps from

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,,.,loSal contrcl station and to canually alicn the val . This could be l done quickly enough revent c threat to the healt nd safety of tha public. However, there is no credible single failure that could causa this type of fault follcuing a ILCA.

Both deficiencies have safety implications that could cause operational difficulties, but neither deficiency uould directly endanger the integrity cf the plant or threaten the health and safety of the public.

Description of Correct 8ve Action .

The incorractly designated and routed wires have been disconnected, removed, and replaced with wires from the correct electrical divisions.

The physical separation of the connections to the valve limit switches in unit 3 has been improved to meet the Browns Ferry separations criteria.

Means Taken to Prevent a Recurrence As a result of an earlier similar deficiency, a memorandum has been issued from the Director of Engineering Design requesting Project Managers -

to reevaluate existing controls on drawing verification. This memo-randum also instructed Project Managers to make appropriate changes, or additions, to detailed project level engineering procedures to ensure compliance with EN DES-EP 310, " Design Verification Methods and Per-formance of Design Verifications." TVA believes that compliance with this memorandum reduces to an acceptable level the chance of recurrence cf a similar deficiency. .

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