ML20148T658

Forwards Generic Safety Evaluation Summarizing Results of NRC Review of BWR Scram Discharge Sys,Resulting from Browns Ferry 3 Control Rod Sys Failure.Updates NRC

ML20148T658
Person / Time
Site:	Hatch, Browns Ferry, Brunswick
Issue date:	01/09/1981
From:	Ahearne J NRC COMMISSION (OCM)
To:	Udall M HOUSE OF REP., INTERIOR & INSULAR AFFAIRS
Shared Package
ML20148T662	List: ML20148T658 ML20148T781
References
NUDOCS 8102270508
Download: ML20148T658 (1)

Text

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Dear Mr. Chairman:

In an earlier letter to you dated October 23, 1980, we provided an assessment of the causes of the Browns Ferry Unit 3 control rod systen e failure, and the consequences had a control rod failure occurred under other conditions. In addition to a description of those actions taken to that date, we stated that a report of all actions taken in response to the Browns Ferry event was being prepared and would be provided. E:. closed is a copy of that report. We will keep you infonned regarding what actions we decide to take based on this report. Sincerely, Original Signeu et gehny.Ahearne John F. Ahearne

Enclosure:

As stated .. cc: -Rep;-Steven Syms

s-, My?Q &e} % (s,v Cleared with all Cmrs. ' Offices by SECY C/R.

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l i ME.TRhiDUM FOR: Gus C. Lainas, Assistant Director for Safety Assessment. 00L - Thomas H. Novak, Assistant Director for Operating Rectors, 00L Robert L. Tecesco, Assistant Director for Licensing. 00L FROM: Paul S. Check, Assistant Director for Plant Systems, OSI

SUBJECT:

BWR SCRAM OISCHARGE SYSTEM SAFETY 7 VALUATION The enclosed report sunnarizes the results of our review and evaluation of the BWR scram discharge system. The report deals with Browns Ferry 3 partial scram event of June 28,1980; subsequent investigations, tests, and analyses involving a numoer of operating BWRs; and f ailums of the scram level in'struments at Brunswick and Haten plants. Our review has considered licensee response to IE Bulletin requirements and the BWR Owners' Group proposed criteria for scram discharge volume (SOV) designs. The report specifies acceptabie bases for continued SWR plant operation and provides design criteria for the 50V system. The findings of this report should be transmitted to BWR licensees and applicants for implemen-tation. Also included as an appendix to the SER are plant-specific evalu-ations for each onerating BWR. These evaluations provide the basis for continued operation while needed permanent modifications are being designed - and implemented which will probably take about two years. Our review has identified two additional requirements beyond those proposed by the Owners Group. The first addresses the potential for fast fill of the 50V oa decaying air system pressure. An automatic air header dumo will be reouired to initiate control rod insertion on low pressure in the con-t trol air header. This should prevent loss of scram tunction during certain low procability loss of air cressure events. This reouirement is apoli-caole to all licensees ioentified in Table 1 of the SER. It should oe installed within about two months. Meanwnile tne operator action to scram on low air pressure alarm, backed up by the same action on rod drift alarms and other indications, is acceptable. ' The second added requirement deals with the 50V level instrumentation and addresses potential comon-cause f ailures. It is descriced in Section 4.2.2.3 of the SER. This aequ1rement Jogether with the criteria for scram system design orovide an acceptacle basis for scram discnarge system cesign, (new plants) and design modifications (operating plants). h0ll

December 1, 1980 We have suggested acceptable ways of complying with the requirenants and criteria. If a licenser or applicant chooses to enploy these approved neans, no further review by MRR is needed. Under separate cover, I will shortly transmit this SER to Dave Waters, Chairaan of the SWR Owners Group. j* $ Paul S. Check Assistant Director for Plant Systens Division of Systens Integration

Enclosure:

As stated cc: D. Ross ACRS(3) O. Eisenhut A. Bates . E. Jordan D. Zukor S. Hanauer F. Schroeder T. Ippolito R. Reid D. Crutchfield G. Lainas F. Coffman S. Rubin G. Lanik J. Huang O. Thatcher J. Wilson R. Youngblood W. Mills J. Hannon T. Speis T. Loomis M. Mencones V. Panciera M. Goocman R. Satterfield A. Thomas A. Thadani W. Miners C. Graves J. Stolz M. dagner Contacc:

          . V. P anciera x28164
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