ML20216B909
| ML20216B909 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 04/06/1998 |
| From: | Hughey W ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-96-04, GL-96-4, GNRO-98-00039, GNRO-98-39, NUDOCS 9804140176 | |
| Download: ML20216B909 (3) | |
Text
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Entt y ritions, Inc.
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Port Gason, MS 39150 Tel 601437 6470 W.K.Hughey Dm; tor i Of.il bil!Oly b NMJIdIOfy April 6. 1998 U.S. Nuclear Regulatory Commission Mail Station P1-37 Washington, D.C. 20555 Attention:
Document Control Desk l
Subject:
Grand Gulf Nuclear Station Unit 1 Docket No. 50-416 License No. NPF-29 GGNS Spent Fuel Pool Silica Evaluation GNRO-98/00039 Gentlemen:
Pursuant to your letter of May 14,1997, "Cornpletion of Licensing Action Review For Generic Letter 96-04, 'Boraflex Degradation in Soent Fuel Pool Storage Racks,' For Grand Gulf Nuclear Station, Unit 1"., we are submitting the requested 90 day response (Attachment 1). Your letter requested that we provide the resu;ts of the detailed silica concentration evaluation of the GGNS spent fuel pool (SFP) to be performed for the refueling outage.
The RACKLIFE evaluation demonstrates that GGNS racks have relatively low silica loss and a correspondingly low B C loss. Tne loss projected to the end of Cycle (EOC) 9 is 4
approximately 2.8% which is well below the 10% value assumed in the criticality safety analysis. Also, the test area Boraflex panel accumulated doses continue to bound the other areas of the SFP rack through EOC 10.
If additionalinformation is needed, please contact Rita Jackson at 601-437-2149.
Yours truly, r
i WKH/RRJ/rrj h$
attachment:
Summary of GGNS SFP RACKLIFE Silica Evaluation cc:
(See Next Page) 900A140176 980406 PDR ADOCK 05000416 P
GNRO-98/00039 Page 2 of 2 cc:
Ms. J. L. Dixon-Herrity, GGNS Senior Resident (w/a)
Mr. L. J. Smith (Wise Carter) (w/a)
Mr. N. S. Reynolds (w/a)
Mr. H. L. Thomas (w/o)
Mr. E. W. Merschoff (w/a)
Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 Mr. J. N. Donohew, Project Manager (w/2)
Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Comrnission Mail Stop 13H3 Washington, D.C. 20555
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Attachm:nt 1 to:
GNR0-98/00039 Page 1 of 1 ATTACHMENT 1 Summary of GGNS SFP RACKLIFE Silica Evaluation In response to the NRC Generic Letter 96-04, Grand Gulf Nuclear Station (GGNS) committed to perform Spent Fuel Pool (SFP) silica evaluations based on the EPRI RACKLIFE computer system.
The commitment requires an initial evaluation to be completed prior to the start of RFO-9 with additional evaluations each cycle prior to new fuel receipt. The RACKLIFE model performs SFP silica evaluations and provides results conceming Boraflex panel degradation and dose.
Projections have been made to the estimated end of Cycle (EOC) 10. In order to ensure continued Boraflex performance through Cycle 10 operation, assumptions in the criticality safety analysis (CSA) were confirmed, with respect to Boraflex panel degradation and doses (as related to gap size and shrinkage).
The RACKLIFE model results, provided in Table 1, demonstrate that the CSA used conservative values when predMting Boraflex panel degradation allowances. The criticality analysis assumed a 10% boron cartOe loss from the minimum boron carbide manufacturing tolerance. The maximum RACKLIFE value,'or projected SFP operation through Cycle 10 is 3.13%, significantly smaller than 10%.
Table 1 Summary of GGNS RACKLIFE Results Peak Panel Dose Peak Boraflex (cell / rads)
Panel B4C Loss Test Area SPF 1
End of RFO9 Z20 NNN56 2.76 %
3.11E10 1.11E10 EOC10 Z20 NNN56 3.13%
3.t 1E10 1.14E10 I
The CSA Boraflex gap assumptions were established to bound the most recent (July,1996) gap measurements. Since gamma fluence has been strongly correlated to gaps in Boraflex, the test area viill lead other areas of the racks in the formation of gaps. The RACKLIFE dose results for the SFP test area, corresponding to these measurements, confirm that the test area dose will continue j
to bound the balance of the pool through EOC 10 as shown by Table 1. This confirms that the mos!
recent gap measurements will remain bounding through EOC 10 for the SFP. This is expected since the test area was purposely managed to induce higher doses in these panels than the remainder of the SFP. In Table 1, the leading panel for accumulated dose inside the test area does not show an increase in accumulated dose since that location is conservatively assumed to be l
empty during Cycle 10 operation and that location leads the other panels enough to remain the leading panel for dose accumulation. In actuality, some additional dose accumulation will occur as the test area is exposed in preparation for the Cycle 10 blackness testing campaign. However, projections are that the peak Boraflex loss will not appreciably incresse above the 3.13% value shown in Table 1.
Therefore, the Boraflex assumptions employed in the CSA are conservative and continue to be applicable through Cycle 10.
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