AECM-85-0038, Informs of Commencement of Effort to Perform Addl 1/10 Scale Tests W/Existing Facility & Specific Encroachment Dimensions to Address Humphrey Containment Concerns.Schedule Identifying Pertinent Milestones Encl

Informs of Commencement of Effort to Perform Addl 1/10 Scale Tests W/Existing Facility & Specific Encroachment Dimensions to Address Humphrey Containment Concerns.Schedule Identifying Pertinent Milestones Encl

ML20099C940
Person / Time
Site:	Grand Gulf
Issue date:	03/07/1985
From:	Dale L MISSISSIPPI POWER & LIGHT CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
AECM-85-0038, AECM-85-38, TAC-56303, NUDOCS 8503110480
Download: ML20099C940 (3)

Text

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MISSISSIPPI POWER & LIGHT COMPANY

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Helping Build Mississippi P. O. B O X 164 0, J A C K S O N, MIS SIS SIP PI 39215-1640 March 7, 1985 NUCLEAR LICENSING & $AFETY DEPARTMENT U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation  ;

Washington, D. C. 20555 l l

l Attention: Mr. Harold R. Denton, Director

Dear Mr. Denton:

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SUBJECT:

Grand Gulf Nuclear Station Units I and  ?.

Docket Nos. 50-416 and 50-417 License No. N'F-29 File: 0260/0272/L-860.0 Humphrey Containment Concerns AECM-85/5038 On November 16, 1984, the Containment Issues Owner's Group (CIOG) met with members of your staff to discuss the generic methodology for defining the loads produced from encroached pool swell and the plant unique approach that each member was going to take to resolve the encroached pool issue. During this meeting, CIOG presented the details of the generic load definition methodology that will be used to apply the test results from 1/10-scale tests. The preliminary evaluation of your staff members, based on the information supplied and discussed in the meeting, was that the generic encroachment load definition methodology seemed to be reasonable and adequate.

In the discussion of plant specific approaches, Mississippi Power & Light (MP&L) stated that the plant unique load definition for Grand Gulf Nuclent Station (GGNS) was almost complete. MP&L also indicated that its architect engineer was currently analyzing the affected structures and components for which loads had been defined. The staff noted that in at least one area, the calculated pressure using the encroached pool load methodology appeared considerably higher than the original design load and recommended that MP&L consider performing, in parallel with the analytical approach, additional sub-scale tests using a GGNS specific encroachment. MF&L indicated that test options were being investigated but that no firm decision had been made at that time. MP&L also agreed to advise the staff on whether additional testing would be performed within a week.

On November 21, 1984, Mr. S. H. Hobbs of MP&L called Mr. M. B. Fields of your staff to inform the staff that MP&L intended to perform additional 1/10-scale tests with the existing facility and GGNS specific encroachment dimensions. This effort has commenced and a schedule identifying pertinent milestones in included as Attachment 1 to this letter.

It should be noted that because of the complexity and amcant of effort required to finalize the structural analysis of load definitions from the 8503110480 850307 Sh}

PDR ADOCK 05000416 P PDR 's Member Middle South Utilities System J0P14AECM85020402 - 1

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.' AECM-85/0038 Page 2 original 1/10-scale tests, MP&L has stopped this effort. Work has continued on the development of the structural analytical model which will be used in the structural analysis. The load definitions from the GGNS plant specific 1/10-scale tests will be utilized for the structural analysis. MP&L fcals that this is a more effective use of limited resources since this information is now available.

MP&L remains committed to assuring that encroached pool swell does not adversely affect plant equipment or structures. Although MP&L does not believe that this issue has any immediate safety significance, MP&L is proceeding on an expedited schedule to complete this confirmatory effort and resolve this issue.

Yours truly, L. F. Dale Director GWS/SHH:rw Attachment ec: Mr. J. B. Richard (w/a)

Mr. R. B. McGehee (w/a)

Mr. N. S. Reynolds (w/a)

Mr. G. B. Taylor (w/o)

Mr. James M. Taylor, Director (w/a)

Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555

, Dr. J. Nelson Grace, Regional Administrator (w/a) l U. S. Nuclear Regulatory Commission Region II l

101 Marietta St., N. W., Suite 2900 Atlanta, Georgia 30323 I

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e i Attachmsnt I to AECM-85/0038 '

4 GGNS SPECIFIC ENCROACHED POOL SWELL ISSUE CLOSURE SCHEDULE

1. GE completes load definition from Week of February 4, 1985 plant specific tests and transmits to MP&L/Bechtel  !

2. GE complete and issue Draft Final Week of March 11, 1985 Test Report to MP&L

3. Submit Final Test Report to NRC Week of April 1, 1985

4. Bechtel completes evaluation of Week of April 15, 1985 plant specific loads

5. -MP&L submits Summary of Bechtel Week of May 15, 1985 Evaluation and identifies any additional course of action t -

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