ML23062A594

Enclosure - NRC SQN Exemption Rsi Response Staff Follow Up Questions

ML23062A594
Person / Time
Site:	Sequoyah
Issue date:	02/27/2023
From:	Tilda Liu Storage and Transportation Licensing Branch
To:	Kitts Z Tennessee Valley Authority
Shared Package
ML23062A592	List: ML23062A594 ML23062A595
References
Download: ML23062A594 (1)

Text

Follow-up Questions to TVAs Response to NRCs Request for Supplemental Information (RSI)

Related to August 4, 2022, Sequoyah ISFSI Exemption Request 1 2/27/2023 Material Discipline

1. Provide supporting information confirming that all repairs were performed on the outside diameter of the multipurpose canister (MPC) on weld #21. [RSI-M1, RSI-M2]

2. Provide supporting information confirming that the 7.5 inches of missing radiographic testing (RT) is approximately located between XX inches to YY inches (e.g., 15 inches to 22.5 inches) from the base of the MPC on the longitudinal weld. [RSI-M2]

3. Provide supporting information explaining the rationale that the 0.327 inches lack of fusion (LOF) indication located in view 0-1 in approximately 8 inches to 14 inches zone extended to be a 16.5 inches excavation that extended approximately from 8 inches to 24 inches. [RSI-M2]

4. Provide supporting information on the identification (e.g., location and type) of any acceptable indications in the available RT examinations for weld #21 views 0-1 and 1-2.

[RSI-M1, RSI-M2]

Structural Discipline

1. Provide the resultant safety factor for the combined effects of local membrane plus primary bending stress at the sections of the MPC longitudinal shell-to-shell weld where the RT was missed. [RSI-S3]

In its December 19, 2022, response to RSI-S3, the applicant stated that the contributions from local membrane plus primary bending and secondary stresses are expected to be minimal given the separation distance from the shell-to-baseplate or shell-lid discontinuities. The response further states that the presented safety analysis considers the effects of local membrane plus primary bending stress since the maximum stress intensity values are compared conservatively with the applicable primary membrane stress limits (which are lower than local membrane plus primary bending stress and secondary stress limits) to compute the safety factors.

During the review of Holtec HI-2094418, Revision 20, Structural Calculation Package for HI STORM FW System, it was noted that the structural analysis followed the methodology in Regulatory Guide (RG) 7.6, Design Criteria for the Structural Analysis of 1 By letter dated August 4, 2022 (ML22216A078), Tennessee Valley Authority (TVA) submitted an exemption request for the Sequoyah Nuclear Plant (SQN) Independent Spent Fuel Storage Installation (ISFSI), requesting deviation from the conditions of the NRC Certificate of Compliance (CoC) No. 1032, Amendment No. 3 (ML17214A039), Appendix B, Section 3.3, "Codes and Standards." By letter dated November 18, 2022 (ML22318A147), the NRC staff provided a request for supplemental information (RSI) to TVA as part of the acceptance review process. By letter dated December 19, 2022 (ML22353A066), TVA provided its response to NRCs RSI.

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Shipping Cask Containment Vessels. In this analysis, both the primary membrane stress AND the local membrane plus primary bending stress were considered, and the safety factors evaluated, in accordance with the regulatory position no. C.2 in RG 7.6.

The regulatory position states that, for normal conditions, the value of the stress intensity resulting from the primary membrane stress should be less than the design stress intensity, Sm, and the stress intensity resulting from the sum of the primary membrane stresses and the primary bending stresses should be less than 1.5 Sm. However, the analysis in Section 1.5 of Holtec RRTI 3087 007, Revision 2, only includes the calculated safety factor from stress intensity resulting from the primary membrane stress.

In addition, the exemption request does not contain adequate information in demonstrating the safety factor available/remaining at the shell, as resulted from the effects of local membrane plus primary bending stress remains within acceptable limits, after considering a reduction factor for the RT that was missed at the MPC longitudinal shell-to-shell weld.

This information is necessary to evaluate the requested exemption, under 10 CFR 72.7, from the requirements of 10 CFR 72.154(b), 10 CFR 72.212(a)(2), 72.212(b)(5)(i),

72.212(b)(11) and 72.214.

EPID No.: L-2022-LLE-0027 Docket No.72-034 2