CNL-24-031, Supplement to Request for Exemption from Various Part 72 Regulations Resulting from Fuel Basket Design Control Compliance

Supplement to Request for Exemption from Various Part 72 Regulations Resulting from Fuel Basket Design Control Compliance

ML24078A257
Person / Time
Site:	Watts Bar
Issue date:	03/18/2024
From:	Hulvey K Tennessee Valley Authority
To:	Office of Nuclear Material Safety and Safeguards, Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-24-031
Download: ML24078A257 (1)

Text

1101 Market Street, Chattanooga, Tennessee 37402

CNL-24-031

March 18, 2024

10 CFR 72.7

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001

Watts Bar Nuclear Plant, Units 1 and 2 Facility Operating License Nos. NPF-90 and NPF-96 NRC Docket Nos. 50-390, 50-391, and 72-1048

Subject:

Watts Bar Nuclear Plant - Supplement to Request for Exemption from Various Part 72 Regulations Resulting from Fuel Basket Design Control Compliance

References:

1. TVA letter to NRC, CNL-24-012, "Watts Bar Nuclear Plant - Request for Exemption from Various Part 72 Regulations Resulting from Fuel Basket Design Control Compliance," dated February 28, 2024 (ML24059A369)

2. NRC presentation, Public Meeting with Holtec, Holtec Users Group, and General Licensees - Path Forward for General Licensees affected by the Continuous Basket Shims basket design change, dated March 6, 2024 (ML24065A118)

In Reference 1, Tennessee Valley Authority (TVA) submitted a request for exemption from various requirements of Title 10 of the Code of Federal Regulations (10 CFR) Part 72 for the Watts Bar Nuclear Plant (WBN), Units 1 and 2. The requested exemption from certain requirements of 10 CFR 72.212 and 10 CFR 72.214 would allow future loading of Holtec multi-purpose canisters with continuous basket shim design at WBN.

Subsequent to the submittal of this request, the Nuclear Regulatory Commission (NRC) held a public meeting with general licensees on March 6, 2024, in which expectations for exemption requests were presented to general licensees to support expedient NRC reviews for urgent licensee needs (Reference 2). The enclosure to this letter provides additional information to assist the NRC staff in a timely review of the WBN exemption request. This supplement does not change any information provided by TVA in Reference 1.

U.S. Nuclear Regulatory Commission CNL-24-031 Page 2 March 18, 2024

There are no new regulatory commitments associated with this submittal. Please address any questions regarding this request to Stuart L. Rymer, Senior Manager, Fleet Licensing, at slrymer@tva.gov.

Respectfully, Digitally signed by Edmondson, Carla Date: 2024.03.18 12:20:01 -04'00' Kimberly D. Hulvey Director, Nuclear Regulatory Affairs

Enclosure:

Supplemental Information to the Watts Bar Nuclear Plant Request for Exemption from Various Part 72 Regulations Resulting from Fuel Basket Design Control Compliance

cc (Enclosure):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Watts Bar Nuclear Plant NRC Director - Division of Spent Fuel Management, NMSS

Enclosure

Supplemental Information to the Watts Bar Nuclear Plant Request for Exemption from Various Part 72 Regulations Resulting from Fuel Basket Design Control Compliance

On February 28, 2024, Tennessee Valley Authority (TVA) requested an exemption for Watts Bar Nuclear Plant (WBN)(Reference 1) from the requirements of Title 10 of the Code of Federal Regulations (10 CFR) 72.212(a)(2), 72.212(b)(3), 72.212(b)(5)(i), 72.212(b)(11) and 72.214 for Holtec Certificate of Compliance (CoC) No. 1032. The exemption would allow WBN to continue to store loaded Holtec MPC-37CBS multi-purpose canisters (MPC) with a continuous basket shim (CBS) design at the WBN Independent Spent Fuel Storage Installation (ISFSI) and load MPC-37CBS canisters during future campaigns.

On March 6, 2024, the Nuclear Regulatory Commission (NRC) held a public meeting with Holtec, the Holtec Users Group, and general licensees where NRC expectations for exemption requests were presented to general licensees with urgent needs (Reference 2).

The information below is provided to supplement the request in Reference 1 in order to support an expedient review by NRC staff.

Will not Endanger Life or Property or the Common Defense and Security

In Section III.b of Reference 1, TVA stated:

The NRC has performed a safety assessment (Reference 3) to evaluate the loading and storage of the MPC-37CBS variant without an approved tip-over analysis. This evaluation (detailed below) assumed basket failure due to the tip-over event but []

concluded that the consequences of a basket failure have a very low safety significance provided the confinement boundary is maintained and the fuel is kept in a dry storage condition. As these conditions are demonstrated to be met during a tip-over event, the staff determined that there was no need to take an immediate action with respect to loaded HI-STORM FW and HI-STORM 100 dry cask storage systems with the continuous basket shim (CBS) fuel basket designs. Based on the NRC safety assessment detailed below and summarized here, the proposed exemption does not endanger life or property or the common defense and security.

In addition, as documented in the WBN 10 CFR 72.212 evaluation report for the HI-STORM FW system (Reference 3), the calculated total values for annual dose to any real individual who is located beyond the controlled area are shown to be well below the limits required by 10 CFR 72.104(a).

The HI-STORM FW MPC storage system does not create any radioactive materials or have any radioactive waste treatment systems. Therefore, specific operating procedures for the control of radioactive effluents are not required. There are no radioactive effluents from the spent fuel storage casks. Accordingly, operational restrictions to meet 10 CFR 72.104(b) as low as reasonably achievable objectives for radioactive effluents are not required for the HI-STORM FW system, and 10 CFR 72.104(c) operational limits for radioactive materials in effluents from the HI-STORM FW system are not required.

Due to the large size of the WBN site, the exclusion area boundary (EAB) is smaller than, and is completely within, the site boundary. Regarding 10 CFR 72.106, the EAB is considered the controlled area boundary for the purposes of evaluating the plant dose contribution during a design basis accident. The distance from the ISFSI pad to the EAB is about 871 meters. Site

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specific evaluation determined no accidents result in damage to an overpack. As such, analysis of an accident scenario and demonstration of compliance with 10 CFR 72.106 is met by the HI-STORM FW system and by location of the ISFSI being greater than 100 meters from the EAB.

As noted in the NRC safety determination of the HI-STORM FW (Reference 4), the likelihood of a tip-over during handling operations is administratively controlled using the technical specifications (TS) for the HI-STORM FW system, which are used at WBN. The NRC staff considers the type of handling accident that could challenge the fuel basket to not be credible when following HI-STORM FW TS procedures.

Furthermore, handling activities involving the transport cask and/or overpack when loaded or empty outside of the Part 50 structure are performed with the vertical cask transporter (VCT).

The WBN VCT has redundant drop protection features and was designed, fabricated, and tested in accordance with the applicable codes described in CoC No. 1032.

Otherwise in the Public Interest

In Section III.c of Reference 1, TVA stated:

It is in the publics interest to grant an exemption, since dry storage places the fuel in an inherently safe, passive system, and the exemption would permit this continued storage of already loaded canisters to bring them back into compliance most quickly and efficiently. This exemption would also allow upcoming loading campaigns to proceed on time to move fuel into the dry storage condition and maintain the ability to offload fuel from the reactor, thus allowing continued safe reactor operation.

To give additional detail to that statement, the most significant impact of not being able to load CBS type canisters in future campaigns relates to the ability to manage the margin for full core reserve (FCR) in the WBN spent fuel pool (SFP).

Dry cask storage (DCS) Campaign 6 was originally scheduled to begin January 29, 2024, but was postponed until July 2024 due to regulatory uncertainty. SFP FCR is currently maintained by 179 cells. If DCS Campaign 6 is not performed as scheduled in July 2024, FCR margin is reduced to 87 SFP cells after new fuel receipt for WBN Unit 1 in September 2024. Once Unit 1 new fuel receipt begins, refuel floor and personnel resources are allocated for the Unit 1 refueling outage until the end of 2024. New fuel receipt for WBN Unit 2 is scheduled to begin in February 2025, immediately followed by the Unit 2 refueling outage. Once Unit 2 new fuel receipt is complete, FCR margin is lost by five SFP cells. At that point, the Unit 2 refueling outage cannot be performed due to insufficient space for core offload, leading to the shutdown of WBN Unit 2 until sufficient space in the SFP is made available to accommodate a full core offload. To prevent that scenario, at least one canister must be loaded prior to the Unit 2 new fuel receipt in February 2025. This means DCS Campaign 6, scheduled to begin July 8, 2024, cannot be fully cancelled until the next planned campaign in July 2025.

As described above, the planned July 8 start date is the latest, and only, opportunity for cask loading to avoid loss of FCR in 2025.

CNL-24-031 E2 of 3 Enclosure

References

1. TVA letter to NRC, CNL-24-012, "Watts Bar Nuclear Plant - Request for Exemption from Various Part 72 Regulations Resulting from Fuel Basket Design Control Compliance," dated February 28, 2024 (ML24059A369)

2. NRC presentation, Public Meeting with Holtec, Holtec Users Group, and General Licensees - Path Forward for General Licensees affected by the Continuous Basket Shims basket design change, dated March 6, 2024 (ML24065A118)

3. Holtec International, Watts Bar Nuclear Plant 10 CFR 72.212 Evaluation Report for the HI-STORM FW System, Revision 5, dated July 8, 2022

4. NRC Memorandum, Safety Determination of a Potential Structural Failure of the Fuel Basket During Accident Conditions for the HI-STORM 100 and HI-STORM Flood/Wind Dry Cask Storage Systems, dated January 31, 2024 (ML24018A085)

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