GO2-22-049, Supplement to Licensing Amendment Request to Adopt 10CFR50.69, Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Rectors
| ML22130A591 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 05/10/2022 |
| From: | Dittmer J Energy Northwest |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GO2-22-049 | |
| Download: ML22130A591 (5) | |
Text
J. Kent Dittmer Vice President, Engineering P.O. Box 968, PE01 Richland, WA 99352-0968 Ph. 509.377.4248 l F. 509.377.2354 jkdittmer@energy-northwest.com 10 CFR 50.90 GO2-22-049 10 CFR 50.69 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
COLUMBIA GENERATING STATION, DOCKET NO. 50-397 SUPPLEMENT TO LICENSE AMENDMENT REQUEST TO ADOPT 10 CFR 50.69, "RISK-INFORMED CATEGORIZATION AND TREATMENT OF STRUCTURES, SYSTEMS AND COMPONENTS FOR NUCLEAR POWER REACTORS
Reference:
- 1. Letter from J. K. Dittmer (Energy Northwest) to U.S. Nuclear Regulatory Commission, License Amendment Request to Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors, dated November 9, 2021 (ADAMS Accession No. ML21314A224)
- 2. Letter from U.S. Regulatory Commission to Mr. Robert Schuetz (Energy Northwest), Columbia Generating Station - Audit Plan and Setup of Online Reference Portal for License Amendment Request to Adopt 10 CFR 50.69, Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors (EPID L-2021-LLA-0207), dated February 9, 2022
Dear Sir or Madam:
In Reference 1, Energy Northwest requested an amendment to the Columbia Generating Station (Columbia) Operating License. The proposed amendment would modify the Columbia licensing basis, by the addition of a License Condition, to allow for the implementation of the provisions of Title 10 of the Code of Federal Regulations (10 CFR), Part 50.69, Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors.
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May 10, 2022 ENERGY NORTHWEST
GO2-22-049 Page 2 of 2 In Reference 2, the Nuclear Regulatory Commission (NRC) requested a virtual audit to improve the efficiency of staff reviews. As a result of this regulatory audit that was conducted on March 30, 2022, Energy Northwest is supplementing the License Amendment Request (LAR) to support the NRC staffs review of the proposed change.
The enclosure to this letter provides information requested by the NRC staff during the regulatory audit to amend Reference 1.
The information contained in the enclosure does not affect the Technical Analysis or No Significant Hazards Consideration conclusions contained in the LAR. Additionally, the information provided in this supplement does not affect the bases for concluding that neither an environmental impact statement nor an environmental assessment needs to be prepared in connection with the proposed amendment.
In accordance with 10 CFR 50.91, Energy Northwest is notifying the State of Washington of this amendment supplement by transmitting a copy of this letter and enclosure to the designated State Official.
This letter and its enclosure contain no new commitments.
If there are any questions or if additional information is needed, please contact Mr. R.M. Garcia, Licensing Supervisor, at 509-377-8463.
I declare under penalty of perjury that the foregoing is true and correct.
Executed this ______ day of ___________ 2022.
Respectfully, J. Kent Dittmer Vice President, Engineering
Enclosure:
Supplemental Information cc:
NRC RIV Regional Administrator NRC NRR Project Manager NRC Senior Resident Inspector/988C CD Sonoda - BPA/1399 EFSECutc.wa.gov - EFSEC E Fordham - WDOH R Brice - WDOH L Albin - WDOH
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GO2-22-049 Enclosure Page 1 of 3 Enclosure Supplemental Information
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GO2-22-049 Enclosure Page 2 of 3 The following supplemental information, which includes responses to audit questions APLA-02 and APLC-02, is in response to the regulatory audit held between the U.S.
Nuclear Regulatory Commission (NRC) and Energy Northwest on March 30, 2022, as requested by the NRC in Reference 2.
Audit Item APLA-02 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, provides the risk acceptance guidelines for total core damage frequency (CDF) and large early release frequency (LERF) (1E-04 per year and 1E-05 per year, respectively). NRC staff notes based on RG 1.174 and Section 6.4 of NUREG-1855, Revision 1, Guidance on the Treatment of Uncertainties Associated with PRAs in Risk-Informed Decisionmaking, for a Capability Category II risk evaluation, the mean values of the risk metrics (total and incremental values) need to be compared against the risk acceptance guidelines. The mean values referred to are the means of the probability distributions that result from the propagation of the uncertainties to the probabilistic risk assessment (PRA) input parameters and model uncertainties that are explicitly input to the PRA models, including explicit consideration of the state-of-knowledge correlation (SOKC) between events. In general, the point estimate CDF and LERF obtained by quantification of the cutset probabilities using mean values for each basic event probability do not produce a true mean of the CDF and LERF. Under certain circumstances, a formal knowledge of SOKC is not important (i.e., the risk results are well below the acceptance guidelines).
of Reference 1 provides the CDF and LERF values for Columbia that appear to be point estimates which are likely lower than the mean CDF and LERF values. The total LERF value of 8.66E-06 per year does approach the RG 1.174 guideline of 1E-05 per year for LERF. In consideration of this information, the NRC requested that Energy Northwest demonstrate that the total mean probabilistic results for internal events (including internal flooding), fire, and seismic LERF remain in conformance with RG 1.174 risk acceptance guidelines (i.e., LERF < 1E-05 per year).
Table A-1 below addresses the mean of the LERF probability distributions that result from the propagation of uncertainties to the PRA input parameters, including explicit consideration of the SOKC. This is provided to supplement the information previously provided in Attachment 2 of Reference 1.
Table A-1 Columbia Mean LERF Source Contribution per year Internal Events/Internal Flood 1.62E-07 Seismic 4.30E-06 Fire 3.48E-06 TOTAL Mean LERF 7.94E-06
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GO2-22-049 Enclosure Page 3 of 3 Audit Item APLC-02 From Attachment 4, External Hazards Screening, of Reference 1, the sand or dust storm hazard was determined to be bounded by a postulated volcanic ash event.
During the March 30, 2022 regulatory audit, the NRC requested clarification of how a volcanic ash event bounds a sand/dust storm event, or how a sand/dust storm is bounded within the design basis.
The initial preliminary screening for a sand/dust storm determined that the event damage potential is less than events for which the plant is designed, and that the event is included in the definition of another event. For sand/dust storm specifically, this event is considered included in a volcanic ash event due to multiple factors, including smaller accumulation of particles, and shorter duration of a sand/dust storm.
Section 5.5.2, Severe Storms, of the Individual Plant Examination of External Events (IPEEE) Report for Columbia documents that the worst-case dust storm is considered to have an average dust concentration of 8.9 mgm/m3 with a duration of 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />, while the design basis volcanic ash fall has an average dust concentration of 174 mgm/m3 and a 20-hour duration. Therefore, the volcanic ash fall event is considered for worst case effects on safety related equipment and heating, ventilation, and air conditioning (HVAC) systems.
In the event of sand storm conditions, station procedures direct Operations personnel to re-align the diesel generator HVAC systems to a room recirculation mode. If the ventilation for the Control Room is blocked, degraded, or cannot be restored, Operations personnel are directed to advance the inlet air filters, or cut down the air filters if the air flow restriction is not resolved.
Table B-1 is provided to amend the information previously provided in Attachment 4 of Reference 1.
Table B-1 Updated External Hazards Screening External Hazard Screening Result Screened?
(Y/N)
Screening Criterion (Note a)
Comment Sand or Dust Storm Y
C1 C4 Sand or dust storm is bounded by a postulated volcanic ash event.
See also IPEEE Section 5.5.2, Severe Storms.
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