AECM-82-603, Comments on BWROG-8260, NUREG-0737,Item II.K.3.18,Mod of Automatic Depressurization Sys Logic. Option 4,providing Bypass Timer Delay,Will Assure Adequate Core Cooling During Worst Case Conditions

Comments on BWROG-8260, NUREG-0737,Item II.K.3.18,Mod of Automatic Depressurization Sys Logic. Option 4,providing Bypass Timer Delay,Will Assure Adequate Core Cooling During Worst Case Conditions

ML20070E475
Person / Time
Site:	Grand Gulf
Issue date:	12/14/1982
From:	Dale L MISSISSIPPI POWER & LIGHT CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.3.18, TASK-TM AECM-82-603, TAC-56447, TAC-61039, NUDOCS 8212170278
Download: ML20070E475 (2)

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MISSISSIPPI POWER & LIGHT COMPANY Helpin$ Build Mississippi P. O. B O X 16 4 0, J A C K S O N, MIS SIS SIP PI 3 9 2 0 5 December 14, 1982 NUCLEAR PRooUCTioN DEPARTMENT U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D. C. 20555 Attention: Mr. Harold R. Denton, Director

SUBJECT:

Grand Gulf Nuclear Station Units 1 and 2 Docket Nos. 50-416 and 50-417 License No. NPF-13 File 0260/L-334.0/L-860.0 ADS Logic Modifications AECM-82/603

REFERENCES:

1. AECM-82/358 " Comments and Status on Grand Gulf Operating License and Safety Evaluation Report"

2. AECM-82/492 " Status on License Condition 2.C. (44)(1)(a) ADS Logic Modification"

3. Letter, BWROG-8260, T. J. Dente (BWROG) to D. G. Eisenhut (NRC), "NUREG-0737 Item II.K.3.18 ' Modification of Automatic Depressurization System Logic'", October 28, 1982 The following information represents Mississippi Power & Light Company's (MP&L) response to Operating License Condition 2.C. (44)(1)(a). This License Condition required MP&L to submit its evaluation of the BWR Owners' Group report on Automatic Depressurization System (ADS) Logic Modification and its proposed modifications by November 1, 1982. Due to a delayed Owners' Group submittal, MP&L requested that the date for its submittal be moved to December 1, 1982, (Reference 1). It was subsequently requested that the date be changed to December 15, 1982, (Reference 2).

MP&L has participated in a BWR Owners' Group study to modify Automatic Depressurization System (ADS) actuation logic. The study was made in response to NUREG-0737, Item II.K.3.18, and the results were submitted to the NRC on October 29, 1982 (Reference 3). Eight alternatives, including retaining the current design, were considered.

The current design, given implementation of the BWR Emergency Procedure Guidelines (Revision 2), is adequate for all design basis events which require RPV depressurizations to maintain adequate core cooling. However, to further assure adequate core cooling for the events which do not directly produce a high drywell pressure signal, Grand Gulf Nuclear Station will utilize Option 4 of the Owners' Group tcport. This option includes the addition of a timer that bypasses the existing high drywell pressure trip logic if RPV water level /

is low for a sustained period of time, plus the addition of a manual inhibit switch.

8212170278 821214 Aember Middle South Utilities System PDR ADOCK 05000416 P PDR

• AECM-82/603 Ml201221PPI POWER Q Ll2HT COMPANY These modifications will be accomplished by installing a bypass timer that is activated on low RFV water level (Level 1). When the timer runs out, the high drywell pressure trip is bypassed, and the ADS is initiated on low water level signal, provided other system prerequisites for ADS actuation are met. Starting the bypass timer at low RPV water level (Level 1) allows the operator adequate time to recover the water level manually, yet still assures automatic depressurization in time to prevent excessive fuel heatup, even under the worst-case conditions. In addition to the bypass timer, a manual inhibit switch for the automatic depressurization system will be installed.

This modification would allow certain operator actions specified in the Emergency Procedure Guidelines to be performed more reliably. Principally, automatic initiation of the ADS following boron injection or while restoring RPV water level manually could be prevented.

NUREG-0737 Item II.K.3.18 states "The Automatic Depressurization System (ADS) actuation logic should be modified to eliminate the need for manual actuation to assure adequate core cooling." MP&L believes that implementation of the Option 4 modifications and of the Emergency Procedure Guidelines will assure adequate core cooling in even the worst-case conditions.

Analysis supporting the selection of the proper bypass timer delay will be provided prior to implementation. This analysis and work on the design change package will begin following NRC approval of the Option 4 modifications and Revision 2 of the Emergency Procedure Guidelines. Implementation of the ADS modifications will be performed prior to startup following the first refueling outage assuming such NRC approval.

If additional information is required, please advise.

Yours truly, m-iv ,a' _ ,

,f' L. F. Dale

' Manager of Nuclear Safety MSAW/ RAW /SHH/JDR: sap cc: Mr. N. L. Stampley Mr. R. B. McGehee Mr. T. B. Conner Mr. G. B. Taylor Mr. Richard C. DeYoung, Director Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Mr. J. P. O'Reilly, Regional Administrator Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region II 101 Marietta St., N.W., Suite 3100 Atlanta, Georgia 30303 I

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