ML13155A140

Response to Request for Additional Information Regarding Proposed Technical Specifications Changes for Spent Fuel Storage

ML13155A140
Person / Time
Site:	Millstone
Issue date:	05/28/2013
From:	Grecheck E Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
13-283
Download: ML13155A140 (5)

Text

Dominion Nuclear Connecticut, Inc.

5000 Dominion Boulevard, Glen Allen, VA 23060 FDomininn Web Address: www.dom.com May 28, 2013 U.S. Nuclear Regulatory Commission Serial No.13-283 Attention: Document Control Desk NLOS/WDC RO Washington, DC 20555 Docket No. 50-336 License No. DPR-65 DOMINION NUCLEAR CONNECTICUT. INC.

MILLSTONE POWER STATION UNIT 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING PROPOSED TECHNICAL SPECIFICATIONS CHANGES FOR SPENT FUEL STORAGE By letter dated December 17, 2012, Dominion Nuclear Connecticut, Inc. (DNC) submitted a license amendment request (LAR) for Millstone Power Station Unit 2 (MPS2). The proposed amendment would revise Technical Specification (TS) 1.39 "Storage Pattern," TS 3.9.18, "Spent Fuel Pool - Storage," TS 3.9.19, "Spent Fuel Pool - Storage Patterns," TS 5.3.1 "Fuel Assemblies," TS 5.6.1, "Criticality," and TS 5.6.3, "Capacity" with conforming changes to Technical Specifications Bases (TSB) 3/4.9.18 and 3/4.9.19. The proposed changes would reflect the results and constraints of a new criticality safety analysis for fuel assembly storage in the MPS2 fuel storage racks.

In a letter dated February 11, 2013, the NRC provided DNC an opportunity to supplement the LAR identified above. The NRC requested the justification for the continued credit for Boraflex. DNC provided the supplement in a letter dated February 25, 2013.

In a letter dated April 26, 2013, the NRC transmitted a request for additional information (RAI) to DNC related to the LAR. DNC agreed to respond to the RAI by June 10, 2013. provides DNC's response to the NRC's RAI.

Should you have any questions in regard to this submittal, please contact Wanda D. Craft at (804) 273-4687.

Sincerely, VICKI L.HULL Notary Public Eugene S. Grecheck Commonwealth of Virginia Vice President - Nuclear Engineering and Development 140542 My Commission Expires May 31, 2014 COMMONWEALTH OF VIRGINIA ))

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COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Eugene S. Grecheck, who is Vice President - Nuclear Engineering and Development of Dominion Nuclear Connecticut, Inc. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this 1ý/'ay of .2013.

My Commission Expires: - 31 Notary Public vt)tP-gp-

Serial No.13-283 Docket No. 50-336 Page 2 of 2 Commitments made in this letter: None

Attachment:

1. Response to Request for Additional Information Regarding Proposed Technical Specifications Changes For Spent Fuel Storage cc: U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd Suite 100 King of Prussia, PA 19406-2713 Nadiyah S. Morgan Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08 C2 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station Director Bureau of Air Management Monitoring and Radiation Division Department of Environmental Protection 79 Elm Street Hartford, CT 06106-5127

Serial No.13-283 Docket No. 50-336 Attachment 1 Response to RAI Regarding Proposed Technical Specifications Changes For Spent Fuel Storage DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2

Serial No.13-283 Docket No. 50-336 Attachment 1, Page 1 of 2 By letter dated December 17, 2012, Dominion Nuclear Connecticut, Inc. (DNC) submitted a license amendment request (LAR) for Millstone Power Station Unit 2 (MPS2). The proposed amendment would revise Technical Specification (TS) 1.39 "Storage Pattern,"

TS 3.9.18, "Spent Fuel Pool - Storage," TS 3.9.19, "Spent Fuel Pool - Storage Patterns,"

TS 5.3.1 "Fuel Assemblies," TS 5.6.1, "Criticality," and TS 5.6.3, "Capacity" with conforming changes to Technical Specifications Bases (TSB) 3/4.9.18 and 3/4.9.19. The proposed changes would reflect the results and constraints of a new criticality safety analysis for fuel assembly storage in the MPS2 fuel storage racks. In a letter dated April 26, 2013, the NRC transmitted a request for additional information (RAI) to DNC related to the LAR. This attachment provides DNC's response to the NRC's RAI.

Question I Discuss if the neutron absorbing capability of the borated stainless steel rodlets will be maintained such that degradation of the material does not exceed the assumptions made in the criticality analysis of record.

a. Describe how long each borated stainless steel rodlet may be used in the spent fuel pool over the life of the spent fuel pool.

b. Discuss whether a removed borated stainless steel rodlet can be reused in other fuel assemblies. In addition, describe how there is reasonable assurance that the re-used rodlet maintainsthe criticalityanalysis' assumed boron content of 2 percent.

Include in the discussion, the expected maximum calculated fluence over the life of the spent fuel pool which includes time after the reactoris decommissioned; and if there would be any significant change in the material properties at this calculated fluence.

c. Is the program for surveillance and inspection of the poison rodlets describedin the letter dated July 16, 1993, currently used at Millstone? If so, discuss in more detail the visual inspection aspect of the program including the parameters to be monitored and acceptance criteria to ensure that there is no material degradation occurring and that the boron content in the rodlets remains at the criticality analysis' assumed boron content of 2 percent.

DNC Response

a. Borated stainless steel rodlets have been in continuous service since 1994 and are expected to be in use throughout the service life of the Millstone Power Station Unit 2 (MPS2) spent fuel pool.

Serial No.13-283 Docket No. 50-336 Attachment 1, Page 2 of 2

b. Rodlets are removed from assemblies that are stored in dry storage casks and are available for re-use in other fuel assemblies in the spent fuel pool. A 1992 Electric Power Research Institute (EPRI) study determined the maximum fluence over a 40-year service life in a spent fuel pool is 1 x 1012 neutron/cm 2 . Extending the service life an additional 40 years to account for a 20-year plant operating license extension and an additional 20 years of storage could result in maximum fluence of less than 2 x 1012 neutrons/cm2 . The maximum fluence is equivalent to less than one second of in-reactor exposure, therefore, no measurable depletion of rodlet boron will occur over the lifetime of the rodlets. Tests performed by EPRI, to an upper bound of 1 x 1017 neutrons/cm 2 , determined that there was no significant change in borated stainless steel material properties. No significant change in material properties is projected over the lifetime of the rodlets, providing high confidence that the material and neutronic characteristics of the rodlets will remain within the assumptions of the criticality analysis.

c. DNC's current program for surveillance and inspection of the poison rodlets is consistent with that which was described in the July 16, 1993 letter (Reference 1).

There are 2491 rodlets available for use, of which 27 rodlets installed in 9 selected fuel assemblies are designated as surveillance rodlets. These 27 rodlets, which have been in continuous use since installation, are representative of all rodlets installed in the spent fuel pool. Following initial selection as surveillance rodlets, the same rodlets are re-inspected during subsequent periods of inspections to permit trending of rodlet material condition.

Beginning in 1999, inspections have been performed at 5-year intervals. Each surveillance rodlet is removed from the spent fuel pool and a detailed visual inspection is performed to identify any cracks, blisters, missing pieces of surface material, corrosion, or pitting. Any observed material abnormality would result in a more detailed assessment to evaluate the significance. In 2004, a small nick was identified on one rodlet. The size of the indication was approximately 1/16" x 1/8".

The assessment of this abnormality concluded that "minimal, if any, material has been removed" and it "does not affect the boron content of the rodlet." The 2009 inspection found no indication of degradation for any of the 27 rodlets. Therefore, the boron content in the rodlets remains at the criticality analysis assumed boron content of 2 percent.

References:

1. J. F. Opeka, Northeast Nuclear Energy Company to the Nuclear Regulatory Commission, "Millstone Nuclear Power Station Unit 2, Response to Request for Additional Information," July 16, 1993