SVPLTR 13-0024, Supplement to Dresden Nuclear Power Station Written Response to Preliminary White Finding from NRC Integrated Inspection Report 2013-002

Supplement to Dresden Nuclear Power Station Written Response to Preliminary White Finding from NRC Integrated Inspection Report 2013-002

ML13191A944
Person / Time
Site:	Dresden
Issue date:	06/21/2013
From:	Czufin D Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation, NRC/RGN-III
References
SVPLTR: #13-0024, EA-13-079
Download: ML13191A944 (2)

Text

Dresden Nuclear Power Station Exe!.on Generation@

6500 North Dresden Road Morris, IL 60450 815 942 2920 Telephone www.exeloncorp.com SVPLTR: #13-0024 June 21,2013 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-19 and DPR-25 NRC Docket Nos. 50-237 ard 50-249 Subject. Supplement to Dresden Nuclear Power Station Written Response to Preliminary White Finding from NRC Integrated Inspection Report 2013-002

Reference:

Letter from D. Czufin (EGC) to U. S. NRC, "Dresden Nuclear Power Station Response to Preliminary White Finding from NRC Integrated Inspection Report 2013-002," dated June 6,2013 In the referenced letter, Dresden Nuclear Power Station provided a written response to the NRC regarding the preliminary White finding that was identified in Inspection Report 2013-002. The response noted that a human reliability analysis was performed to assess the probability of successfully injecting into the reactor pressure vessel during a flood. The base SPAR-H assessment, used In the referenced letter, assumed that both Units 2 and 3 would be shutdown 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to water levels reaching grade elevation.

Although reasonable, a reactor shutdown 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to flood water reaching grade elevation Is not the most conservative flood timeline. Therefore, a sensitivity study has been performed using the SPAR-H methodology assuming an even more conservative flood timeline where both Units 2 and 3 would be shutdown seven hours prior to flood waters reaching grade elevation.

The flood timetine for the sensitivity study Is consistent with the probable maximum flood. The sensitivity study shows that the later shutdown has a negligible Impact on the time available for diagnosis and execution, and has a negligible impact on other performance shaping factors.

Further, the results of this sensitivity study show that the original SPAR-H PSF multipliers and calculated HEP are not affected by the change in timing.

Even with applying a more conservative flooding assumption for reactor shutdown (i.e.. 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> versus 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) prior to water reaching grade elevation, the operator action to provide inventory make-up remains highly likely as demonstrated by the SPAR-H analysis. The sensittvity study has been provided to the Senior Reactor Analysis for review.

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June 21, 2013 U. S. Nuclear Regulatory Commission Page 2 This letter does not contain any new regulatory commitments.

Should you have any questions concerning this letter, please contact Mr. Riley Ruffin, DNPS Regulatory Assurance Manager, at (815) 416-2815.

Respectfully, David M. Czufin Site Vice President Dresden Nuclear Power Station cc: Regional Administrator, NRC Region III NRC Senior Resident Inspector, Dresden Nuclear Power Station Chief, Division of Reactor Projects Branch 6, NRC Region III