ML25323A008
| ML25323A008 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 01/14/2026 |
| From: | Hipolito Gonzalez Plant Licensing Branch IV |
| To: | Wolf Creek |
| References | |
| EPID L-2024-LLE-0026 | |
| Download: ML25323A008 (0) | |
Text
NUCLEAR REGULATORY COMMISSION Docket No. 50-482 Wolf Creek Nuclear Operating Corporation Wolf Creek Generating Station, Unit 1 Exemption I. Background Wolf Creek Nuclear Operating Corporation (the licensee) is the holder of Renewed Facility Operating License No. NPF-42, which authorizes operation of Wolf Creek Generating Station, Unit 1 (Wolf Creek). The license provides, among other things, that the facility is subject to all rules, regulations, and orders of the U.S. Nuclear Regulatory Commission (NRC, the Commission) now or hereafter in effect. The facility consists of a pressurized-water reactor (PWR) located in Coffey County, Kansas.
The license amendment request (LAR) incorporates Technical Specifications (TS) Task Force (TSTF) Traveler TSTF-567, Revision 1, Add Containment Sump TS to Address GSI
[Generic Safety Issue]-191 Issues, dated August 2, 2017 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML17214A813). The NRC issued a final safety evaluation approving TSTF-567, Revision 1, on July 3, 2018 (ML18109A077). The proposed amendment would revise TS 3.5.2, ECCS [Emergency Core Cooling System] - Operating, and TS 3.5.3, ECCS - Shutdown. The proposed changes would also add a new TS 3.6.8, Containment Sumps, to Section 3.6, Containment Systems.
II. Request/Action By letter dated September 12, 2024 (ML24260A071), as supplemented by letter dated August 28, 2025 (ML25240B584), the licensee submitted a LAR, exemption request, and an updated response to Generic Letter (GL) 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors
2 (ML042360586) for Wolf Creek. The amendment would modify the Wolf Creek TSs. The amendment would allow the use of a risk-informed approach to address safety issues discussed in GSI-191, Assessment of Debris Accumulation on PWR Sump Performance.
The specific exemption request pertains to requirements associated with the ECCS function for core cooling following a postulated loss-of-coolant accident (LOCA).
Approval of the exemption will allow the use of a risk-informed method to account for the probabilities and uncertainties associated with mitigation of the effects of debris following postulated LOCAs. The method evaluates concerns raised by GSI-191 related to the effects of post-accident debris on the containment sump recirculation strainers and reactor core blockage due to debris in the recirculating fluid. To confirm acceptable sump design, the risk associated with loss of core cooling due to the effects of debris is evaluated. The risk-informed approach is designed to be consistent with the guidance in Regulatory Guide (RG) 1.174, Revision 3, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis, dated January 2018 (ML17317A256).
The licensees approach is the risk-informed part of an overall graded approach that is based on the amount of debris in the plant, as discussed in SECY-12-0093, Closure Options for Generic Safety Issue-191, Assessment of Debris Accumulation on Pressurized Water Reactor Sump Performance, dated June 9, 2012 (ML121310648). The licensees risk-informed approach addresses the five key principles in RG 1.174. The resulting risk metrics (i.e., core damage frequency (CDF), large early release frequency (LERF), CDF, and LERF) are used to determine whether plant modifications are warranted to ensure acceptable sump performance. The Wolf Creek risk quantification shows that CDF and LERF are below the threshold for RG 1.174 Region Ill, Very Small Changes, without further plant or procedure modifications. Therefore, the risk-informed approach provides an equivalent level of assurance for sump performance without incurring significant cost and occupational dose associated with
3 removing, replacing, or reinforcing insulation in containment. Approval of the requested exemption will support the application of the risk informed approach.
III. Discussion Pursuant to 10 CFR 50.12, Specific exemptions, the licensee submitted this request for exemption from certain requirements of 10 CFR 50.46, Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors, paragraph (a)(1), other properties, as it relates to using a specific deterministic methodology to evaluate the effects of debris on long-term core cooling. The regulation under 10 CFR 50.46(a)(1) in the other properties portion for which exemption is requested, states in part:
ECCS cooling performance must be calculated in accordance with an acceptable evaluation model and must be calculated for a number of postulated loss-of-coolant accidents of different sizes, locations, and other properties sufficient to provide assurance that the most severe postulated loss-of-coolant accidents are calculated. Except as provided in paragraph (a)(1)(ii) of this section, the evaluation model must include sufficient supporting justification to show that the analytical technique realistically describes the behavior of the reactor system during a loss-of-coolant accident.
Pursuant to 10 CFR 50.12, the NRC may, upon application by any interested person or upon its own initiative, grant exemptions from the requirements of 10 CFR Part 50 when: (1) the exemptions are authorized by law, will not present an undue risk to public health or safety, and are consistent with the common defense and security; and (2) special circumstances are present. Under 10 CFR 50.12(a)(2)(ii), special circumstances include, among other things, when
[a]pplication of the specific regulation in the particular circumstance would not serve, or is not necessary to achieve, the underlying purpose of the rule. The requested exemption satisfies the criteria as described below.
A.
The Exemption is Authorized by Law The NRC has authority under the Atomic Energy Act of 1954, as amended, to grant exemptions from its regulations if doing so would not violate the requirements of law. This exemption is authorized by law as 10 CFR 50.12 provides the NRC authority to grant
4 exemptions from 10 CFR Part 50 requirements with provision of proper justification. Approval of the exemption from 10 CFR 50.46(a)(1), would not conflict with any provisions of the Atomic Energy Act of 1954, as amended, any of the Commissions regulations, or any other law.
Therefore, the NRC concludes that there is no statutory prohibition on the issuance of the requested exemption, and the NRC is authorized to grant the exemption by law.
B.
The Exemption Present no Undue Risk to Public Health and Safety The provision of 10 CFR 50.46 is to establish acceptance criteria for ECCS performance to provide a high confidence that the system will perform its required functions. The requested exemption does not involve any modifications to the plant that could introduce a new accident precursor or affect the probability of postulated accidents, and therefore the probability of postulated initiating events is not increased. The probabilistic risk assessment (PRA) and engineering analysis demonstrate that the calculated risk is very small (attachment VII of the letter dated September 12, 2024) and consistent with the intent of the Commissions safety goal policy statement, which defines an acceptable level of risk that is a small fraction of other risks to which the public is exposed. As discussed in previous 10 CFR 50.46 rulemaking, the probability of a large break LOCA is sufficiently low. Application of a risk-informed approach shows a high probability with low uncertainty that the ECCS will meet 10 CFR 50.46 requirements (attachment VII of the letter dated September 12, 2024), rather than using deterministic methods to achieve a similar understanding. This is applicable to evaluating acceptable containment sump design in support of ECCS and containment spray system recirculation modes.
The proposed change is to apply a risk-informed method rather than a deterministic method to establish a high probability of success for performance of ECCS in accordance with the requirements in 10 CFR 50.46(a)(1). The risk-informed approach involves a complete evaluation of the spectrum of LOCAs up to and including double ended guillotine breaks
5 (DEGBs) on the largest pipe in the reactor coolant system, as described in attachment VII of the letter dated September 12, 2024.
The risk-informed approach analyzes LOCAs, regardless of break size, using the same methods, assumptions, and criteria in order to quantify the uncertainties and overall risk metrics (attachment VII of the letter dated September 12, 2024). This ensures that large break LOCAs with a low probability of occurrence and smaller break LOCAs with higher probability of occurrence are both considered in the results. Because the design-basis requirement for consideration of a DEGB of the largest pipe in the reactor coolant system is retained, the existing defense-in-depth and safety margin established for the design of the facility are not reduced.
This exemption only affects 10 CFR 50.46(a)(1), other properties, requirements that a licensee is able to demonstrate, using a bounding calculation or other deterministic method, that the ECCS and CSS are capable of functioning during a design basis event. This exemption does not impact the adequacy of the acceptance criteria for cladding performance, which is important to maintain adequate safety margins.
C.
The Exemption is Consistent with Common Defense and Security This exemption involves a change to the licensing basis for the plant that has no relation to the control of licensed material or any security requirements that apply to Wolf Creek.
Therefore, the exemption is consistent with the common defense and security.
D.
Special Circumstances The regulation under 10 CFR 50.12(a)(2) states, in part, that [t]he Commission will not consider granting an exemption unless special circumstances are present, and describes, in 10 CFR 50.12((a)(i)-(vi), the conditions under which special circumstances are present.
Relevant to this exemption, special circumstances are present under 10 CFR 50.12(a)(2)(ii) whenever application of the regulation in the particular circumstances would not serve the underlying purpose of the rule or is not necessary to achieve the underlying purpose of the rule.
6 The underlying purpose of 10 CFR 50.46(a)(1) is to ensure adequate evaluation of safety, pertaining to ECCS cooling performance during LOCA. Since the underlying purpose of 10 CFR 50.46(a)(1) is achieved using the Wolf Creek risk analysis, as discussed above, the special circumstances required by 10 CFR 50.12(a)(2)(ii) for the granting of an exemption from 10 CFR 50.46 exist.
IV. Conclusion Accordingly, the Commission has determined that, pursuant to 10 CFR 50.12, the exemption is authorized by law, will not present and undue risk to the public health and safety, and is consistent with the common defense and security, and special circumstances are present pursuant to 10 CFR 50.12(a)(2)(ii). Therefore, the NRC grants Wolf Creek Nuclear Operating Corporation a one-time exemption from the requirements of 10 CFR 50.46(a)(1) other properties, which requires deterministic calculations or other analyses to address the concerns raised by GSI-191to acceptable plant performance during the recirculation mode following a LOCA.
This exemption is effective upon issuance.
Dated: January 14, 2026 For the Nuclear Regulatory Commission.
Hipólito González, Acting Deputy Director, Division of Operating Reactor Licensing, Office of Nuclear Reactor Regulation.
HIPOLITO GONZALEZ Digitally signed by HIPOLITO GONZALEZ Date: 2026.01.14 15:01:10 -05'00'