ONS-2014-071, 3 - Request for Exemption from Certain Requirements of 10 CFR 72.212(a)(2), 72.212(b)(5), 72.212(b)(11) and 72.214

3 - Request for Exemption from Certain Requirements of 10 CFR 72.212(a)(2), 72.212(b)(5), 72.212(b)(11) and 72.214

ML14255A005
Person / Time
Site:	Oconee, 07200040, 07201004
Issue date:	08/28/2014
From:	Batson S Duke Energy Carolinas
To:	Document Control Desk, NRC/NMSS/SFST
References
ONS-2014-071
Download: ML14255A005 (10)

Text

SCOTT L.BATSON Vice President Oconee Nuclear Station ENERGY. Duke Energy ONO I VP / 7800 Rochester Hwy Seneca, SC 29672 864-873-3274 864-873-4208 fax ONS-2014-071 Scott.Batson@duke-energy.com August 28, 2014 10 CFR 72.7 ATTN: Document Control Desk Director, Division of Spent Fuel Storage and Transportation, Office of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001 Duke Energy Carolinas, LLC Oconee Nuclear Station, Units 1, 2, and 3 Docket Nos. 72-40, 50-269, 50-270, 50-287

Subject:

Request for Exemption from Certain Requirements of 10 CFR 72.212(a)(2), 72.212(b)(5), 72.212(b)(11) and 72.214

Reference:

NRC Certificate of Compliance for Spent Fuel Storage Casks Issued to Transnuclear, Inc., Certificate No. 1004, Standardized NUHOMS Horizontal Modular Storage System for Irradiated Nuclear Fuel, Amendment No. 9, Effective Date: April 17, 2007.

Duke Energy Carolinas, LLC (Duke Energy) requests U. S. Nuclear Regulatory Commission (NRC) approval of an exemption to certain requirements of 10 CFR 72.212(b)(3) and 72.212(b)(1 1) pursuant to 10 CFR 72.7. The regulations require, in part, compliance to the terms and conditions of the NUHOMS Certificate of Compliance (CoC) 1004 (Reference).

The CoC conditions require the general licensee to meet the requirements of the Technical Specifications (TS) for the NUHOMS storage system (Attachment A to the CoC).

This requested exemption pertains to Amendment 9 of Technical Specification (TS) 1.2.4a, "Technical Specifications, Functional and Operating Limits - 61 BT, 32PT, 24PHB and 24PTH DSC Helium Leak Rate of Inner Seal Weld," and is associated with five (5) dry storage containers (DSCs) where it was discovered that the seal weld helium leak check was performed using an incorrect temperature correction coefficient. The five (5) DSCs were loaded under Amendment 9.

For these DSCs, with the correct temperature coefficient applied, the TS 1.2.4a limit needs to be increased from < 1.0 x 10-07 to < 1.02 x 10-07 reference cc/sec. Pursuant to 10 CFR 72.7, Duke Energy requests a permanent exemption from the TS acceptance value as the reduction in both the risk of a cask handling accident and substantial personnel exposure during cask re-test activities outweigh the risk associated with the very small increase in the TS acceptance value. A detailed discussion of this exemption request is provided in the Enclosure and Attachment to this letter.

I U. S. Nuclear Regulatory Commission August 28, 2014 Page 2 There are no regulatory commitments contained within this exemption request. Duke Energy respectively requests NRC approval of this exemption by the end of December 2014.

If you have any questions or require additional information, please contact Stephen C. Newman, Lead Engineer, Oconee Nuclear Station Regulatory Affairs Group, at (864) 873-4388.

Sincerely, Scott L. Batson Site Vice President Oconee Nuclear Station Enclosure

U. S. Nuclear Regulatory Commission August 28, 2014 Page 3 xc: w/enclosure Mr. Victor McCree Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 Mr. James R. Hall, Senior Project Manager (by electronic mail only)

Office of Nuclear Reactor Regulation, Mailstop: O-8G9A U. S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852 Mr. Eddy Crowe NRC Senior Resident Inspector Oconee Nuclear Station Ms. Susan E. Jenkins, Manager Radioactive & Infectious Waste Management SC Dept. of Health and Environmental Control 2600 Bull St.

Columbia, SC 29201 C. Haney, Director Office of Nuclear Material Safety and Safeguards U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop E1D2M Rockville, MD 20852-2738 Michele Sampson - Chief, Division of Spent Fuel Storage and Transportation Office of Nuclear Material Safety and Safeguards U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop E3 D2M Rockville, MD 20852-2738 Jennifer Davis, Project Manager, Division of Spent Fuel Storage and Transportation Office of Nuclear Material Safety and Safeguards U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop E3 D2M Rockville, MD 20852-2738

U. S. Nuclear Regulatory Commission August 28, 2014 Page 4 xc: w/enclosure (continued)

Robert P. Carrion, Division of Reactor Safety U. S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, GA 30303-1257

Enclosure Request for Exemption from Certain Requirements of Title 10 of Code of Federal Regulations Parts 72.212(a)(2), 72.212(b)(5), 72.212(b)(1 1) and 72.214

Enclosure - Request for Exemption August 28, 2014 Page 2

1. Request for Exemption Duke Energy hereby requests an exemption from certain requirements of 10 CFR 72.212(b)(3) and 72.212(b)(1 1) (Reference 1) that require compliance with the terms and conditions of the NUHOMS Certificate of Compliance (CoC) (Reference 2). This exemption, if approved, would apply only to DSCs 93, 94, 100, 105, and 106, each -

24PHB systems loaded under CoC No. 1004, Amendment No. 9.

2. Background The NUHOMS system provides for the horizontal, dry storage of canisterized spent fuel assemblies (SFAs) in a concrete horizontal storage module (HSM). The cask storage system components for NUHOMS consist of a reinforced concrete HSM and a dry shielded canister (DSC) containment vessel with an internal basket assembly which holds the SFAs.

The HSM is a low profile, reinforced concrete structure designed to withstand all normal condition loads as well as the abnormal condition loads created by earthquakes, tornadoes, flooding, and other natural phenomena. The HSM is also designed to withstand abnormal condition loadings postulated to occur during design basis accident conditions such as a complete loss of ventilation.

The structural features of the DSC design depend, to a large extent, on the postulated design basis transfer cask drop accident. The DSC shell, the redundant closures on each end, and the DSC internals are designed to ensure that the intended safety functions of the system are not impaired following a postulated transfer cask drop accident. The limits established for equivalent decelerations due to a postulated drop accident are intended to be bounding. They envelop a range of conditions such as the transfer cask handling operations, the type of handling equipment used, the transfer cask on-site transport route, the maximum feasible drop height and orientation, and the conditions of the impacted surface.

Each NUHOMS system model type is designated by NUHOMS-XXY. The two digits (XX) refer to the number of fuel assemblies stored in the DSC, and the character (Y) is a P for PWR, or B for BWR, to designate the type of fuel stored. A fourth character (T) is added, if applicable, to designate the DSC is intended for transportation in a 10 CFR 71 approved package (Reference 3). The number of HSMs to be erected at any one time depends on individual plant discharge rates and storage capacity needs, and will be addressed by the licensee.

Certificate of Compliance 1004, Amendment 9 (Reference 2) conditions require the general licensee to meet the requirements of the Technical Specifications (TS) for the NUHOMS System (Attachment A to the CoC). The two (2) objectives of TS 1.2.4a, "Technical Specifications, Functional and Operating Limits - 61 BT, 32PT, 24PHB and 24PTH DSC Helium Leak Rate of Inner Seal Weld," are to: (1) demonstrate that the top cover be "leak tight," as defined in "American National Standard for Leakage Tests on Packages for Shipment of Radioactive Materials," ANSI N14.5-1997 (Reference 4), and (2) to retain helium cover gases within the DSC. The helium improves the heat dissipation characteristics of the DSC and minimizes oxidation of the fuel cladding. This

Enclosure - Request for Exemption August 28, 2014 Page 3 specification is applicable to the inner top cover seal weld of the 61 BT, 32PT, 24PHB and 24PTH DSC only.

Reason for Exemption Request There are two methods used to verify an adequate inner top cover plate seal weld for the dry shielded canisters loaded at the Oconee Nuclear Station (ONS). Both methods are required by the Independent Spent Fuel Storage Installation (ISFSI) Technical Specifications (TSs). The first is a dye penetrant test, and the second is a helium leak check.

In January 2014, a discrepancy was identified on a test report processed from the helium leak rate instrument vendor. The discrepancy was that the linear temperature coefficient was stated as four (4) percent per degree Celsius (%/°C) when previously, this value was three (3) %/PC. A follow-up call with the instrument vendor confirmed that the three (3) %/°C coefficient had historically been incorrect for this instrument.

With the incorrect temperature correction coefficient, canisters loaded at ambient temperatures greater than (>) 23°C would have had a non-conservative correction applied to the helium leak rate measurement. There was no safety concern since the dye penetrant test results were found to be acceptable for the affected population of canisters. Additionally installation of the outer top cover plate negates any concern over a potentially high leak rate. The canisters affected were DSCs 85 through 131.

Forty-two (42) of the 47 DSCs affected were either recertified (DSCs loaded at < 23 0C) or re-evaluated (DSCs loaded at > 23 0C) using the proper temperature correction factor.

These canisters were found to be in compliance by reviewing the ambient temperature when they were loaded and applying the appropriate temperature correction coefficient.

However, the actual temperature correction value datasheets could not be found for DSCs 93, 94, 100, 105, and 106. These canisters were loaded in the summer months when ambient conditions during helium leak testing would likely have exceeded 23 0C, so the temperature correction factor would have been applicable. For these DSCs, without evidence of the actual ambient temperature or test value, confirmation that the TS had been satisfied with the revised correction factor was not possible. For these DSCs, with the correct temperature coefficient applied and assuming worst case ambient temperatures, the TS 1.2.4a limit would have to be increased to 1.02 x 10-07 reference cc/sec.

Duke Energy's exemption request is for DSCs 93, 94, 100, 105, and 106 only. Pursuant to 10 CFR 72.7, Duke Energy requests an exemption from the TS acceptance value as the reduction in both the risk of a cask handling accident and substantial personnel exposure during cask re-test activities outweigh the risk associated with the very small increase in the TS acceptance value. Duke Energy also requests that this exemption remain in-effect until the spent nuclear fuel in the canisters is relocated from its' DSC to an appropriate transportation cask prior to transport to a permanent storage repository.

Enclosure - Request for Exemption August 28, 2014 Page 4

3. Justification for Granting the Exemptions The specific requirements for granting exemptions to 10 CFR Part 72 licensing requirements are set forth in 10 CFR 72.7, "Specific Exemptions," which states: "The Commission may, upon application by any interested person or upon its own initiative, grant such exemptions from the requirements of the regulations in this part as it determines are authorized by law and will not endanger life or property or the common defense and security and are otherwise in the public interest."

The following factors are relevant to this exemption request:

A. The ISFSI regulations cited in this exemption request, 10 CFR 72.212(a)(2),

72.212(b)(5), 72.212(b)(11) and 72.214, are contained within 10 CFR Part 72 of the Commission's regulations. The Commission has the legal authority to issue exemptions for the ONS ISFSI as provided in §72.7.

B. There is reasonable engineering assurance that there is no safety concern by granting the exemption and that the helium leak test results for the five (5) DSCs in question would have been found acceptable. This is based on the following considerations:

• Results of the dye penetrant test were found to be acceptable for the affected canisters, and welded outer top cover plates were installed. This essentially assures the leak tight configuration of the sealed DSCs.

• No leaking fuel assemblies loaded into affected DSCs. All fuel assemblies were discharged from "clean" cores or were inspected by Ultrasonic Test or vacuum sipping after discharge (ONEI -0400, -259, -260, 286, -303, -304).

• Radiological Protection (RP) Group surveys of the affected HSMs confirm no detectable leakage of radioactive materials.

• Even if a leak rate of 1.02 x 10-07 reference cc/sec were assumed, vendor calculation confirms the helium environment will be maintained for 100 years and fuel oxidation would not be a concern (Reference 7).

Consequently, the requested exemption items introduce no undue risk to the public health and safety.

C. If granted, the requested exemption will reduce both the risk of a cask handling accident and substantial personnel exposure that would be experienced if the canisters were unloaded from the HSM, transported back to the cask handling area, opened, rewelded, and retested.

D. The requested exemption items are consistent with providing for the common defense and security. The ONS ISFSI will continue to be physically protected under Duke Energy's Physical Security Plan, and the exemption request does not affect the confinement of the spent fuel stored at the ISFSI facility.

Enclosure - Request for Exemption August 28, 2014 Page 5

4. Conclusion Duke Energy concludes that the requested exemption from certain requirements of the 10 CFR 72.212(a)(2), 72.212(b)(5), 72.212(b)(11) and 72.214 regulations, allowing for the continued storage of DSCs 93, 94, 100, 105, and 106, is justified. Such an exemption meets the specific exemption requirements of 10 CFR 72.7. The requested exemption item is authorized by law, will not endanger life or property, and is consistent with the common defense and security. Furthermore, granting this exemption will result in the reduction in both the risk of a cask handling accident and substantial personnel exposure.

5. Environmental Consideration Pursuant to the provisions of 10 CFR 72.7, Duke Energy is requesting an exemption from certain requirements under the 10 CFR 72.212(a)(2), 72.212(b)(5), 72.212(b)(1 1) and 72.214 regulations. For the five (5) DSCs involved, results of the initial inner seal weld dye penetrant test were found to be acceptable and welded outer top cover plates were installed. This substantiates the leak tightness of the DSC. Additionally, Radiological Protection Group surveys of affected HSMs have confirmed there is no leakage occurring from the affected canisters.

The proposed exemption does not affect the type of radioactive effluents or the quantity or type of nonradioactive effluents entering the environment; Therefore, there is no significant environmental effect associated with the proposed exemption.

6. Precedent Although no previous examples of an NRC-approved exemption request that dealt with a similar issue could be found, by letter dated July 16, 2014, the Staff received an exemption request associated with a nonconforming TS condition related to dye penetrant examinations which were performed on six (6) dry shielded canisters (Reference 5).

On April 12, 2012 (Reference 6), the Staff approved an exemption request associated with the storage of NUHOMs HD dry shield canisters at North Anna Power Station's ISFSI. The issue involved 12 fuel assemblies that had been loaded into seven (7) DSCs with decay heat greater than specified in the CoC.

7. References

1. 10 CFR Part 72.212, "Conditions of general license issued under § 72.210."

2. NRC Certificate of Compliance for Spent Fuel Storage Casks Issued to Transnuclear, Inc., Certificate No. 1004, Standardized NUHOMS Horizontal Modular Storage System for Irradiated Nuclear Fuel, Amendment No. 9, effective date April 17, 2007.

3. 10 CFR Part 71, "Packaging and Transport of Nuclear Material."

4. American National Standard for Leakage Tests on Packages for Shipment of Radioactive Materials," ANSI N14.5-1997.

Enclosure - Request for Exemption August 28, 2014 Page 6

5. Xcel Energy, Monticello Nuclear Generating Plant, "Exemption Request for Dry Shielded Canisters 11-16 Due to Nonconforming Dye Penetrant Examination," dated July 16, 2014.

6. NRC Letter, "Exemption from Parts of 10 CFR 72.212 - Storage of the NUHOMS HD Dry Shielded Canisters at North Anna Power Station Independent Spent Fuel Storage Installation," dated April 12, 2012.

7. AREVA Calculation 13922-0402, "Helium Leak Rate Evaluation for 24PHB DSC," August 13, 2014.