ML20211H975

Submits Basis on Which Determination Made,Based Upon New Analysis of Loading Requirements Re Asymmetrical Loading of Spent Fuel Racks

ML20211H975
Person / Time
Site:	Oyster Creek
Issue date:	09/30/1997
From:	Roche M GENERAL PUBLIC UTILITIES CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
6730-97-2235, NUDOCS 9710070231
Download: ML20211H975 (3)

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GPU Nuclear ine, y

U s. Route (9 South orked ve NJ 731 0388 Tel 609 9714000 September 30,1997 U. S. Nuclear Regulatory Commission 6730-97-2235 Attn.: Document Control Center Washington, DC 20555 Gentlemen:

Subject:

Asymmetrical Loading of Spent Fuel Racks Oyster Creek Nuclear Generating Station Docket No. 50-219 GPU Nuclear has an administrative control in place to ensure that each quadrant of the racks in the spent fuel pool is symmetrical in nature. This administrative control was put in place as a result of a commitment in a September 2,1983 submittal entitled " Technical Specification Change Request No.111 and Facility Description and Safety Analysis Report Amendment No. 79". It should be noted that the NRC safety evaluation report (SER) and the appended Technical Evaluation Report did not specify or discuss the symmetrical loading.

GPU Nuclear has determined that it is acceptable to revise that commitment based upon a new analysis of the loading requirements. This correspondence is the formal notification of GPU Nuclear's intention to revise that commitment. The basis on which the determination was made is contained in Attachment I to this letter, Should you have any questions or require additional information, please contact Dennis Kelly of our Licensing stafTat (609) 971-4246.

Sincerely, f(0 0

Michael B. Roche Vice President & Director Oyster Creek cc: Administrator,RegionI NRC Project Manager

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4 WHOLE POOL MULTI RACK ANALYSIS OF OYSTER CREEK NUCLEAR GENERATING STATION RACKS Holtec Intemational, under contract to GPU Nuclear, has performed a new analysis of the

- loading in the Oyster Creek N.G.S. spent fuel pool. Holtec also prepared the original analysis in support of Technical Specification Change Request (TSCR) 111. At the time the original analysis was prepared, the sophisticated analytical tools used in the new l

analysis ivere not available. Based on the original analysis and as a conservative measure, it was committed to the NRC that the racks be balanced for all fuel evolutions.

In symmetrical loading of the spent fuel racks, the centroid of the totality of the fuel in L

each of the ten racks must be aligned with the rack metal cross section centroid within a 10% tolerance.

The original analysis, prepared at the time the racks were installed, was a three dimen:ional simulation of a single rack. That method requires definition of the motion of adjacent racks and/or walls as moving 180 degrees out of phase in relation to the subject rack, in the new analysis, Whole Pool Multi Rack (WPMR), all racks in the pool are modeled without any pre-imposed pattem of motion between the racks and/or walls.

There are several other differences between the two analyses. The original analysis used the then current Housner response spectra to generate time history spectra at the pool slab. GPU Nuclear has developed a new response spectra with the assistance of EQE International, a seismic engineering consulting firm. That spectra, which has been approved by the NRC and constitutes the current licensing basis, was used in the new

= analysis. In addition, the original analysis projected that the racks were loaded symmetrically, and full, half full and empty load cases were analyzed with either 0.2 or

. 0.8 friction coefficients at the base. In the new analysis various full and half full (non-symmetrical) load cases were analyzed with 0.2,0.8 or Gaussian coefficients of friction at the bases.

Comparison of the two analytical methods determined that the results of the WPMR analysis are bounded by the original analysis and that for the non symmetrical load cases, the racks are kinematically stable. Also, the combined load to the pool slab is reduced.

For the dead load case, the new analysis determined that load restrictions are necessary for racks D and H. For the remaining eight racks, the procedural loading restrictions can be remeved.

The computer algorithm on which the new analysis is based has been used in every Holtec licensing submittal to the USNRC and to foreign regulatory agencies since 1986.

All submittals have been approved. The code and the methodology have been reviewed

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- by Franklin Research Labs and by Brookhaven National Laboratory.' Both organizations were under contract to the NRC at the time.

A detailed safity evaluation was prepared in accordance with the provisions of 10 CFR ~

~ 50.59 that considered all the points discussed above. Based on that analysis, GPU Nuclear has determined that the loading restrictions contained in the governing procedure can be modified to apply only to racks D and 11.

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