XI.M40 (NUREG-2191 R0)
XI.M40 MONITORING OF NEUTRON-ABSORBING MATERIALS OTHER THAN BORAFLEX
Program Description
Many neutron‐absorbing materials are used in spent fuel pools. This aging management program (AMP) addresses aging management of spent fuel pools that use materials other than Boraflex, such as Boral, Metamic, boron steel, and Carborundum. Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report AMP XI.M22, “Boraflex Monitoring,” addresses aging management of spent fuel pools that use Boraflex as the neutron-absorbing material. When a spent fuel pool criticality analysis credits both Boraflex and materials other than Boraflex, the guidance in both AMPs XI.M22 and XI.M40 applies.
A monitoring program is implemented to assure that degradation of the neutron-absorbing material used in spent fuel pools that could compromise the criticality analysis will be detected. The AMP relies on periodic inspection, testing, monitoring, and analysis of the criticality design to assure that the required 5 percent subcriticality margin is maintained during the period of subsequent license renewal.
Evaluation and Technical Basis
- 1. Scope of Program: The AMP manages the effects of aging on neutron-absorbing components/materials other than Boraflex used in spent fuel racks.
- 2. Preventive Actions: This AMP is a condition monitoring program. Therefore, there are no preventative actions.
- 3. Parameters Monitored or Inspected: For these materials, gamma irradiation and/or long-term exposure to the wet pool environment may cause loss of material and changes in dimension (such as gap formation, formation of blisters, pits and bulges) that could result in loss of neutron-absorbing capability of the material. The parameters monitored include the physical condition of the neutron-absorbing materials, such as in-situ gap formation, geometric changes in the material (formation of blisters, pits, and bulges) as observed from coupons or in situ, and decreased boron-10 areal density, etc. The parameters monitored are directly related to determination of the loss of material or loss of neutron absorption capability of the material(s).
- 4. Detection of Aging Effects: The loss of material and the degradation of neutron absorbing material capacity are determined through coupon and/or direct in-situ testing. Such testing should include periodic verification of boron loss through boron-10 areal density measurement of coupons or through direct in-situ techniques. In addition to measuring boron content, testing should also be capable of identifying indications of geometric changes in the material (blistering, pitting, and bulging). The frequency of the inspection and testing depends on the condition of the neutron-absorbing material and is determined and justified with plant-specific operating experience (OE) by the licensee. The maximum interval between inspections for polymer-based materials (e.g., Carborundum, Tetrabor), regardless of OE, should not exceed 5 years. The maximum interval between inspections for nonpolymer-based materials (e.g., Boral, Metamic, Boralcan, borated stainless steel), regardless of OE, should not exceed 10 years.
- 5. Monitoring and Trending: The measurements from periodic inspections and analysis are compared to baseline information or prior measurements and analysis for trend analysis. The approach for relating the measurements to the performance of the spent fuel neutron absorber materials is specified by the applicant, considering differences in exposure conditions, vented/nonvented test samples, and spent fuel racks, etc.
- 6. Acceptance Criteria: Although the goal is to ensure maintenance of the 5 percent subcriticality margin for the spent fuel pool, the specific acceptance criteria for the measurements and analyses are specified by the applicant.
- 7. Corrective Actions: Results that do not meet the acceptance criteria are addressed in the applicant’s corrective action program under those specific portions of the quality assurance (QA) program that are used to meet Criterion XVI, “Corrective Action,” of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix B. Appendix A of the GALL-SLR Report describes how an applicant may apply its 10 CFR Part 50, Appendix B, QA program to fulfill the corrective actions element of this AMP for both safety-related and nonsafety-related structures and components (SCs) within the scope of this program.
- Corrective actions are initiated if the results from measurements and analysis indicate that the 5 percent subcriticality margin cannot be maintained because of current or projected future degradation of the neutron-absorbing material. Corrective actions may consist of providing additional neutron-absorbing capacity with an alternate material, or applying other options, which are available to maintain the subcriticality margin.
- 8. Confirmation Process: The confirmation process is addressed through those specific portions of the QA program that are used to meet Criterion XVI, “Corrective Action,” of 10 CFR Part 50, Appendix B. Appendix A of the Appendix A of the GALL-SLR Report describes how an applicant may apply its 10 CFR Part 50, Appendix B, QA program to fulfill the confirmation process element of this AMP for both safety-related and nonsafety-related SCs within the scope of this program.
- 9. Administrative Controls: Administrative controls are addressed through the QA program that is used to meet the requirements of 10 CFR Part 50, Appendix B, associated with managing the effects of aging. Appendix A of the GALL-SLR Report describes how an applicant may apply its 10 CFR Part 50, Appendix B, QA program to fulfill the administrative controls element of this AMP for both safety-related and nonsafety-related SCs within the scope of this program.
- 10. Operating Experience: Applicants for license renewal reference plant-specific OE and industry experience to provide reasonable assurance that the program is able to detect degradation of the neutron absorbing material in the applicant’s spent fuel pool. Some of the industry OE that should be included is discussed in Information Notice 2009-26, Degradation of Neutron-Absorbing Materials in the Spent Fuel Pool, and listed below:
- Loss of material from the neutron absorbing material has been seen at many plants, including loss of aluminum, which was detected by monitoring the aluminum concentration in the spent fuel pool. One instance of this was documented in the Vogtle license renewal application Water Chemistry Program B.3.28.
- Blistering has also been noted at many plants. Examples include blistering at Seabrook and Beaver Valley.
- The significant loss of neutron-absorbing capacity of the plate-type Carborundum material has been reported at Palisades.
- The coupon testing program at Kewaunee has observed loss of boron-10 areal density of Tetrabor.
- The coupon testing programs at Calvert Cliffs Unit 1 and Crystal River Unit 3 have observed weight loss of sheet-type Carborundum.
- The applicant should describe how the monitoring program described above is capable of detecting the aforementioned degradation mechanisms.
- The program is informed and enhanced when necessary through the systematic and ongoing review of both plant-specific and industry OE including research and development such that the effectiveness of the AMP is evaluated consistent with the discussion in Appendix B of the GALL-SLR Report.
References
10 CFR Part 50, Appendix B, “Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants.” Washington, DC: U.S. Nuclear Regulatory Commission. 2016.
Franke, Jon A., Progress Energy, letter to the U.S. Nuclear Regulatory Commission, Crystal River Unit 3–Response to Request for Additional Information for the Review of the Crystal River Unit 3, Nuclear Generating Plant, License Renewal Application. Agencywide Documents Access and Management System (ADAMS) Accession No. ML100290366. January 2010.
US NRC. Information Notice 2009-26, “Degradation of Neutron-Absorbing Materials in the Spent Fuel Pool.” Washington, DC: U.S. Nuclear Regulatory Commission. October 2009.
_____. License Renewal Interim Staff Guidance LR-ISG-2009-01, “Aging Management of Spent Fuel Pool Neutron-Absorbing Materials Other Than Boraflex.” Washington, DC: U.S. Nuclear Regulatory Commission. 2010.
Ostrowski, Kevin L., FirstEnergy Nuclear Operating Company, letter to the U.S. Nuclear Regulatory Commission, Supplemental Information for the Review of the Beaver Valley Power Station, Units 1 and 2, License Renewal Application (TAC Nos. MD6593 and MD6594) and License Renewal Application Amendment No. 34. ADAMS Accession No. ML090220216. Washington, DC: U.S. Nuclear Regulatory Commission. January 2009.
Schwarz, Christopher J., Entergy Nuclear Operations, Inc., Palisades Nuclear Plant, letter to the U.S. Nuclear Regulatory Commission, Commitments to Address Degraded Spent Fuel Pool Storage Rack Neutron Absorber. ADAMS Accession No. ML082410132. Washington, DC: U.S. Nuclear Regulatory Commission. August 2008.
Southern Nuclear Operating Company. “License Renewal Application Vogtle Electric Generating Plant Units 1 and 2.” ADAMS Accession No. ML071840360. Birmingham, Alabama: Southern Nuclear Operating Company, Inc. June 2007.
Spina, James A., Constellation Energy Nuclear Generation Group, letter to the U.S. Nuclear Regulatory Commission, Calvert Cliffs 1 Response to Request for Additional Information–Long- Term Carborundum Coupon Surveillance Program. ADAMS Accession No. ML080140341. Washington, DC: U.S. Nuclear Regulatory Commission. January 2008.
Warner, Mark E., FPL Energy Seabrook Station, letter to the U.S. Nuclear Regulatory Commission, Seabrook Station Boral Spent Fuel Pool Test Coupons Report Pursuant to 10 CFR Part 21.21. ADAMS Accession No. ML032880525. Washington, DC: U.S. Nuclear Regulatory Commission. October 2003.