ML24008A131
| ML24008A131 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  (SNM-2506) |
| Issue date: | 03/05/2024 |
| From: | Storage and Transportation Licensing Branch |
| To: | Northern States Power Company, Minnesota, Xcel Energy |
| Shared Package | |
| ML24008A128 | List: |
| References | |
| Download: ML24008A131 (5) | |
Text
Enclosure 3 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION REPORT INDEPENDENT SPENT FUEL STORAGE INSTALLATION SPECIAL NUCLEAR MATERIAL (SNM) LICENSE NO. 2506 AMENDMENT NO. 12 1.0
SUMMARY
This safety evaluation report (SER) documents the review and evaluation of a license amendment request (L-PI-23-018) (Agency Document Access Management System Accession No. ML23195A187) to Special Nuclear Material (SNM) License No. 2506 for the Prairie Island (PI) Independent Spent Fuel Storage Installation (ISFSI). By letter dated July 14, 2013, Northern States Power Company - a Minnesota Corporation doing business as Xcel Energy (NSPM) submitted license amendment request L-PI-23-018 to the U.S. Nuclear Regulatory Commission (NRC) in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 72.56, to amend the technical specifications (TS) of SNM License No. 2506, to allow use of a code alternate needed to provide additional non-destructive examination options during fabrication of the TN-40HT casks at the PI ISFSI by allowing use of an equivalent method for examination of weld edge preparation surfaces.
2.0 REVIEW CRITERIA Staff's evaluation of the requested changes is based on ensuring the PI ISFSI continues to meet the applicable requirements of 10 CFR Part 72 for independent storage of spent fuel and of 10 CFR Part 20 for radiation protection. Staff followed the guidelines provided in NUREG-2215 Standard Review Plan for Spent Fuel Dry Storage Facilities in conducting the evaluation.
Staffs evaluation focused only on changes to SNM-2506 requested in the licensees amendment request and did not reassess previously approved portions of the license, TS, the final safety analysis report (FSAR) or those areas of the FSAR modified by the licensee as allowed by 10 CFR 72.48 which are not associated with this amendment request. The objectives for the following review disciplines are as described below for the requested change.
3.0 MATERIALS EVALUATION
3.1 DESCRIPTION
NSPM requested an alternative to the surface examination requirements of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code [1], section III, Division 1, subsection NB, Paragraph NB-5130 for their TN-40HT casks. The proposed alternative, contained in Technical Specification section 4.4, Codes and Standards for the TN-40HT Casks, table 4.4-1, TN-40HT ASME CODE EXCEPTIONS, of their ISFSI license, is requested only for the shell flange, specifically the shell flange to inner shell weld. No other components of the TN-40HT casks are included.
3.2 CODES AND STANDARDS As stated in NUREG-2215, Standard Review Plan for Spent Fuel Dry Storage Systems and Facilities, issued in April 2020, section 17.4.4, Design Features, proposed alternatives to the ASME codes may be used when the proposed alternatives are authorized by the Director of the Office of Nuclear Material Safety and Safeguards, or designee. NSPMs request should demonstrate that the proposed alternative provides an acceptable level of quality and safety, or compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Paragraph NB-5130 of the ASME code requires that all full penetration weld edge preparation surfaces for joint categories A, B, C, D, and similar joints in material two inches (in.) (50 millimeters [mm]) or more in thickness shall be examined by the magnetic particle or liquid penetrant method. The need for the alternative was identified because TN-40HT casks 52 and 53, which are still undergoing fabrication, contain category B inner shell welds of material two in.
or greater, but did not receive this non-destructive examination (NDE) prior to welding.
NSPM states, in the Technical Evaluation section of its license amendment request letter, that the purpose of this NDE is to detect cracks or discontinuities (laps, seams, cold shuts, laminations, and porosity) on, near, or open to the surface of the material to be welded, that could prorogate during welding and result in rejection of the weld in later weld examination.
NSPM also noted that laminar defects are the greatest concern and would result in extensive repairs to the weld joint.
As an alternative to the NDE required by paragraph NB-5130, NSPM proposes a two-pronged approach to address these possible effects of laminar and non-laminar defects and assure the final quality of the welds. First, NSPM will restrict the fabrication of the shell flange to forgings, which are not susceptible to laminar defects, but could still have non-laminar defects. Second, to ensure non-laminar defects are identified, NSPM proposes either an enhancement of the already required radiographic testing (RT) with more stringent acceptance criteria and greater image quality or performing additional NDE in the form of phased array ultrasonic testing (PAUT), both of which would cover the final weld and 0.5 in. (12.7 mm) of base metal on the forging side.
NSPM, in their pre-application meeting with the NRC staff, stated that they performed both the enhanced RT examination and the PAUT on the two affected casks 52 and 53, and the results of both tests were satisfactory. Additionally, NSPM stated that their PAUT was first qualified using a mockup containing embedded flaws to ensure the efficacy of the testing methodology.
NSPM states that these additional proposed NDE requirements, along with the other existing tests and examinations required by ASME code and contained in its license, ensure that weld defects do not exceed maximum allowable size, the weld has been properly fabricated, and no significant leak paths exist in the weld that could jeopardize confinement functions.
The staff finds that NSPM has demonstrated the proposed alternative provides an acceptable level of quality and safety for the reasons stated below. The staff has reviewed the proposed alternatives to the required NDE of paragraph NB-5130 and verified that NSPM provided a sufficient description and technical basis for the proposed alternative NDE, consistent with the guidance of NUREG-2215, Section 8.5.3, for welding processes that are not fully consistent with ASME code. The staff has determined either the enhanced RT or the PAUT using a mockup of the affected area, along with the existing tests and examinations contained in their license, is sufficient to ensure the quality and structural integrity of the shell flange to inner shell welds, for the TN-40HT design at Prairie Island.
3.3 Evaluation Findings
The applicant has met the requirements in 10 CFR 72.24(c)(4) and 10 CFR 72.122(a).
The use of codes and standards, quality assurance programs, and control of special processes are demonstrated to be adequate to ensure that the design, testing, fabrication, and maintenance of materials support structures, systems, components intended functions.
The staff concludes that the PI lSFSI license amendment adequately considers material properties, environmental degradation and other reactions, fuel clad integrity, material quality controls such that the design is in compliance with 10 CFR Part 72. This finding is reached on the basis of a review that considered the regulation, itself, appropriate regulatory guides, applicable codes and standards, and accepted engineering practices.
4.0 OPERATION PROCEDURES AND SYSTEMS EVALUATION 4.1 ACCEPTANCE CRITERIA AND MAINTENANCE PROGRAM EVALUATION The objective of this review is to ensure that NSPMs FSAR and TS includes the appropriate acceptance criteria/tests and maintenance programs for the system. A clear, specific listing of these commitments will help avoid ambiguities concerning design, fabrication, and operational testing requirements when the NRC staff conducts subsequent inspections. The acceptance criteria/tests demonstrate that the cask has been fabricated in accordance with the design criteria and that the initial operation of the cask complies with regulatory requirements.
Two TN40-HT casks, 52 and 53, which are still in fabrication, did not receive the required NDE of the shell flange to inner shell weld edge preparation surface prior to welding and machining; therefore, an alternative is needed to complete fabrication of these casks. NSPMs proposed conservative changes to the NDE of the final shell flange to inner shell to an equal or greater level of quality of the final weld. Specifically, the proposed alternative is to perform an alternate examination consisting of a restricted RT or a PAUT examination. The staff determined for this amendment; the proposed change is relevant to conduct of operations associated with acceptance testing.
The staff finds that the alternate proposed NDE for the TN40-HT cask system is in compliant with 10 CFR 72.158, Control of special processes, and that the applicable examination acceptance criteria have been satisfied. The evaluation of the acceptance test provides reasonable assurance that the TN40-HT casks will allow safe storage of spent fuel throughout its licensed or certified term. This finding is reached based on a review that considered the applicable regulations, appropriate regulatory guides, using qualified procedures in accordance with applicable codes and standards, specifications, criteria, and accepted practices.
4.2 OPERATING PROCEDURES The operating procedures review ensures that NSPM presents acceptable operating sequences, guidance, and generic procedures for key operations. The review also ensures that the application incorporates and is compatible with the applicable operating control limits in the technical specifications. For this amendment, NSPM proposed no changes that are relevant to operating procedures.
4.3 QUALITY ASSURANCE EVALUATION NSPM did not propose any changes that affect the staffs quality assurance evaluation provided in the previous SERs to SNM License No. 2506 for the PI ISFSI. Therefore, the staff determined that a new evaluation was not required. There are no changes to the quality assurance program associated with the current license.
4.4 Evaluation Findings
NSPM has met the requirements in 10 CFR 72.158. The revised TS provides reasonable assurance that the PI ISFSI will continue to allow safe storage of spent fuel.
NSPM has met the requirements in 10 CFR 72.122. The revised TS provides reasonable assurance that the PI ISFSI are designed to permit inspection, maintenance, and testing.
5 REQUIREMENTS FOR NOTICING PROPOSED ACTION In accordance with 10 CFR 72.16, a Notice of Proposed Action and a Notice of Opportunity for Hearing was published in the Federal Register (FR) on September 8, 2023 (88 FR 62108). No requests for a hearing or leave to intervene were submitted. Accordingly, pursuant to 10 CFR 72.46(d), action can be taken on this license amendment request.
6 ENVIRONMENTAL REVIEW The licensee stated that the amendment request met the categorical exclusion criteria in 10 CFR 51.22(c)(11). Per 10 CFR 51.22(c)(11), a categorical exclusion for an amendment which is administrative, organizational, or procedural in nature - or which results in a change in process operations or equipment - is allowed provided the amendment: (i) would not produce a significant change in either the types or significant increase in the amounts of any effluents that may be released offsite, (ii) would not produce a significant increase in individual or cumulative occupational radiation exposure, (iii) would not have significant construction impact, and (iv) would not produce a significant increase in the potential for or consequences from radiological accidents..
After evaluating the amendment request, staff made the following determinations: (i) the amendment would not produce a significant change in either the types or significant increase in the amounts of any effluents that may be released offsite because the amendment did not alter the confinement boundary components as documented in Section 3, (ii) the amendment would not produce a significant increase in individual or cumulative occupational radiation exposure because, as shown in Section 3, the likelihood of fuel cladding failure would not be increased by the requested changes, (iii) the amendment would not have significant construction impact because the amendment only provided additional non-destructive examination options during fabrication of the TN-40HT casks by allowing use of an equivalent method for examination of weld edge preparation surfaces, and (iv) the amendment would not produce a significant increase in the potential for or consequences from radiological accidents because the change did not alter confinement boundary components as documented in Section 3. Consequently, staff finds the amendment request meets the categorical exclusion criteria in 10 CFR 51.22(c)(11).
7 CONCLUSION Based on its review of license amendment request L-PI-23-018, staff determined there is reasonable assurance that: (i) the activities authorized by the amended license will be conducted without endangering the health and safety of the public, and (ii) these activities will be conducted in compliance with the applicable regulations. Staff further determined that the issuance of the amendment will not be inimical to the common defense and security. As such, the staff concludes that SNM License No. 2506, as amended, meets the requirements of 10 CFR Part 72. Therefore, the amendment should be approved.
Issued with Materials License No. SNM-2506.
Dated: March 5, 2024