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Category:Enforcement Action
MONTHYEARIR 05000346/20230902023-08-0101 August 2023 EA-23-002 Davis-Besse Nuclear Power Station - NRC Inspection Report No. 05000346/2023090 (Public) IR 05000346/20210922022-03-0101 March 2022 EA-21-155 Davis Besse - Final Significance Determination of White Finding, Notice of Violation and Assessment Follow Up Letter, NRC Inspection Report 50000346/2021092 ML22031A1712022-01-31031 January 2022 EA-21-105; Davis-Besse Final Determination for a Greater than Green Finding Letter and Enclosure 1 (Public) IR 05000346/20210912021-12-17017 December 2021 NRC Inspection Report (05000346/2021091) Preliminary Greater than Green Finding ML21340A2212021-12-0909 December 2021 NRC Inspection Report (05000346/2021090) Preliminary White Finding ML20275A0482020-10-0101 October 2020 EA-20-068 Davis Besse Licensee Closure Letter ML18099A0742018-04-10010 April 2018 EN-18-006, Issuance of Final Significance Determination and Notice of Violation (EA-18-008) L-16-347, Action for Confirmatory Order EA-16-0222016-12-0101 December 2016 Action for Confirmatory Order EA-16-022 ML16077A3722016-03-17017 March 2016 EA-15-215; Results of Nuclear Regulatory Commission Investigation Report 3-2015-002 IR 05000346/20144072014-10-22022 October 2014 EA-14-129 Final Significance Determination for a Security-Related Greater than Green Finding and Notice of Violation; NRC Inspection Report No. 05000346/2014407; Davis-Besse Nuclear Power Station (Cover Letter Only) ML12314A2812012-11-0808 November 2012 EA-12-179, Davis-Besse, Final Significance Determination of a Security-Related Greater than Green Finding and Notice of Violation - Cover Letter Only IR 05000346/20124052012-11-0808 November 2012 EA-12-179, Davis-Besse, Final Significance Determination of a Security-Related Greater than Green Finding and Notice of Violation - Cover Letter Only IR 05000346/20100072010-04-30030 April 2010 EA-09-332, Davis-Besse Nuclear Power Station, Notice of Violation, NRC Inspection Report No. 05000346-10-007(DRS) IR 05000346/20095032009-12-28028 December 2009 IR 05000346-09-503(DRS), on 08/04/2009 - 11/23/2009; Davis-Besse Nuclear Power Station; Event Follow-up Inspection ML0936208142009-12-28028 December 2009 IR 05000346-09-503(DRS), on 08/04/2009 - 11/23/2009; Davis-Besse Nuclear Power Station; Event Follow-up Inspection IR 05000346/20060052007-01-30030 January 2007 IR 05000346-06-005; 10/1/2006 - 12/31/2006; Davis-Besse Nuclear Power Station; Maintenance Risk Assessments and Emergent Work Control, As-Low-As-Reasonably-Achievable (ALARA) Planning and Controls ML1026701392005-02-25025 February 2005 Choice Letter - Apparent Violation of Employee Protection Requirements (Office of Investigations Report Nos. 3-2004-006 and 3-2004-018), Davis Besse ML0406411712004-03-0808 March 2004 EA-03-214, CAL No. 3-02-001, Approval to Restart the Davis-Besse Nuclear Power Station Closure of Confirmatory Action Letter, and Issuance of Confirmatory Order ML0328017062003-10-0707 October 2003 EA-03-131, Davis-Besse, Notice of Violation IR 05000346/20020162003-01-0707 January 2003 IR 05000346-02-016, IR 05000346-02-006, on 09/30-12/13/2002, Davis-Besse, Special Inspection - Substantial Potential for an Overexposure of Occupational Workers and Uncontrolled Release of Radioactive Material to the Environment 2023-08-01
[Table view] Category:Inspection Report
MONTHYEARIR 05000346/20243012024-02-0202 February 2024 NRC Initial License Examination Report 05000346/2024301 IR 05000346/20230042024-01-31031 January 2024 Integrated Inspection Report 05000346/2023004 IR 05000346/20234022023-12-19019 December 2023 Cyber Security Inspection Report 05000346/2023402 ML23338A3172023-12-0606 December 2023 Notification of NRC Baseline Inspection and Request for Information; Inspection Report 05000346/2024001 IR 05000346/20234032023-11-0202 November 2023 Security Baseline Inspection Report 05000346/2023403 IR 05000346/20234012023-09-13013 September 2023 Security Baseline Inspection Report 05000346/2023401 (Public) IR 05000346/20230112023-08-30030 August 2023 Biennial Problem Identification and Resolution Inspection Report 05000346/2023011 IR 05000346/20230052023-08-24024 August 2023 Updated Inspection Plan for Davis-Besse Nuclear Power Station (Report 05000346/2023005) IR 05000346/20230502023-08-0303 August 2023 Special Inspection Report 05000346/2023050 IR 05000346/20230902023-08-0101 August 2023 EA-23-002 Davis-Besse Nuclear Power Station - NRC Inspection Report No. 05000346/2023090 (Public) IR 05000346/20230022023-07-27027 July 2023 Integrated Inspection Report 05000346/2023002 IR 05000346/20235012023-06-13013 June 2023 Emergency Preparedness Biennial Exercise Inspection Report 05000346/2023501 IR 05000346/20230102023-05-0909 May 2023 Commercial Grade Dedication Inspection Report 05000346/2023010 IR 05000346/20230012023-05-0101 May 2023 Integrated Inspection Report 05000346/2023001 and 07200014/2022001 ML23096A1382023-04-11011 April 2023 Review of the Spring 2022 Steam Generator Tube Inspection Report IR 05000346/20220062023-03-0101 March 2023 Annual Assessment Letter for Davis-Besse Nuclear Power Station, Unit 1 (Report 05000346/2022006) IR 05000346/20220912023-02-10010 February 2023 NRC Inspection Report 05000346/2022091 and Apparent Violation IR 05000346/20220042023-02-0909 February 2023 Integrated Inspection Report 05000346/2022004 and 07200014/2022001 IR 05000346/20224042023-02-0808 February 2023 Material Control and Accounting Program Inspection Report 05000346/2022404 IR 05000346/20224032023-01-23023 January 2023 Security Baseline Inspection Report 05000346/2022403 IR 05000346/20220112023-01-0505 January 2023 Triennial Fire Protection Inspection Report 05000346/2022011 IR 05000346/20220032022-11-10010 November 2022 Integrated Inspection Report 05000346/2022003 IR 05000346/20220402022-11-10010 November 2022 95001 Supplemental Inspection Report 05000346/2022040 and Follow-Up Assessment Letter IR 05000346/20220102022-11-0202 November 2022 Design Basis Assurance Inspection (Programs) Inspection Report 05000346/2022010 IR 05000346/20224402022-10-0404 October 2022 NRC Supplemental Inspection (95001) Interim Report 05000346/2022440 IR 05000346/20220052022-08-25025 August 2022 Updated Inspection Plan for Davis-Besse Nuclear Power Station (Report 05000346/2022005) IR 05000346/20220022022-08-11011 August 2022 Integrated Inspection Report 05000346/2022002 ML22208A0652022-07-27027 July 2022 Notification of NRC Fire Protection Team Inspection Request for Information: Inspection Report 05000346/2022011 IR 05000346/20220122022-06-30030 June 2022 Phase III 71003 License Renewal Report 05000346/2022012 IR 05000346/20224012022-05-17017 May 2022 Security Baseline Inspection Report 05000346/2022401 IR 05000346/20220012022-05-12012 May 2022 Integrated Inspection Report 05000346/2022001 IR 05000346/20223012022-04-12012 April 2022 NRC Initial License Examination Report 05000346/2022301 IR 05000346/20210062022-03-0202 March 2022 Annual Assessment Letter for Davis-Besse Nuclear Power Station, Unit 1 (Report 05000346/2021006) IR 05000346/20210922022-03-0101 March 2022 EA-21-155 Davis Besse - Final Significance Determination of White Finding, Notice of Violation and Assessment Follow Up Letter, NRC Inspection Report 50000346/2021092 IR 05000346/20210042022-02-0909 February 2022 Integrated Inspection Report 05000346/2021004 and Exercise of Enforcement Discretion ML22032A3142022-02-0101 February 2022 Notification of NRC Design Bases Assurance Inspection (Programs) and Initial Request for Information Inspection Report 05000346/2022010 IR 05000346/20210122022-01-31031 January 2022 Temporary Instruction 2515/194 Inspection Report 05000346/2021012 IR 05000346/20210912021-12-17017 December 2021 NRC Inspection Report (05000346/2021091) Preliminary Greater than Green Finding IR 05000346/20210902021-12-16016 December 2021 Reissue Davis-Besse NRC Inspection Report (05000346/2021090) Preliminary White Finding IR 05000346/20214042021-12-0909 December 2021 Security Baseline Inspection Report 05000346/2021404 ML21340A2212021-12-0909 December 2021 NRC Inspection Report (05000346/2021090) Preliminary White Finding IR 05000346/20210502021-11-19019 November 2021 Special Inspection Reactive Report 05000346/2021050 and Apparent Violation IR 05000346/20210032021-11-10010 November 2021 Integrated Inspection Report 05000346/2021003 IR 05000346/20210112021-11-0101 November 2021 Design Basis Assurance Inspection (Teams) Inspection Report 05000346/2021011 IR 05000346/20214032021-10-14014 October 2021 Security Baseline Inspection Report 05000346/2021403 IR 05000346/20210102021-10-0707 October 2021 Biennial Problem Identification and Resolution Inspection Report 05000346/2021010 IR 05000346/20214012021-10-0707 October 2021 Cyber Security Inspection Report 05000346/2021401 and Premliminary Greater than Green Finding and Apparent Violation IR 05000346/20210052021-09-0101 September 2021 Updated Inspection Plan for Davis-Beese Nuclear Power Station (Report 05000346/2021005) IR 05000346/20210022021-08-12012 August 2021 Integrated Inspection Report 05000346/2021002 and 07200014/2021001 IR 05000346/20215012021-06-15015 June 2021 Emergency Preparedness Inspection Report 05000346/2021501 2024-02-02
[Table view] Category:Letter
MONTHYEARIR 05000346/20243012024-02-0202 February 2024 NRC Initial License Examination Report 05000346/2024301 IR 05000346/20230042024-01-31031 January 2024 Integrated Inspection Report 05000346/2023004 ML23313A1352024-01-17017 January 2024 Authorization and Safety Evaluation for Alternative Request RP 5 for the Fifth 10 Year Interval Inservice Testing Program ML23353A1192023-12-19019 December 2023 Operator Licensing Examination Approval Davis Besse Nuclear Power Station, January 2024 L-23-260, Corrections to the 2022 Combined Annual Radiological Environmental Operating Report and Radioactive Effluent Release Report for the Davis-Besse Nuclear Power Station2023-12-0707 December 2023 Corrections to the 2022 Combined Annual Radiological Environmental Operating Report and Radioactive Effluent Release Report for the Davis-Besse Nuclear Power Station L-23-243, Independent Spent Fuel Storage Installation - Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation2023-12-0606 December 2023 Independent Spent Fuel Storage Installation - Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation ML23338A3172023-12-0606 December 2023 Notification of NRC Baseline Inspection and Request for Information; Inspection Report 05000346/2024001 IR 05000346/20234032023-11-0202 November 2023 Security Baseline Inspection Report 05000346/2023403 ML23293A0612023-11-0101 November 2023 Letter to the Honorable Marcy Kaptur, from Chair Hanson Responds to Letter Regarding Follow Up on Concerns Raised by Union Representatives During the June Visit to the Davis-Besse Nuclear Power Plant L-23-215, Changes to Emergency Plan2023-10-19019 October 2023 Changes to Emergency Plan ML23237B4222023-09-28028 September 2023 Energy Harbor Nuclear Corp. - Vistra Operations Company LLC - Letter Regarding Order Approving Transfer of Licenses and Draft Conforming License Amendments ML23269A1242023-09-27027 September 2023 Request for Withholding Information from Public Disclosure IR 05000346/20234012023-09-13013 September 2023 Security Baseline Inspection Report 05000346/2023401 (Public) L-23-205, Supplement to Application for Order Consenting to Transfer of Licenses and Conforming License Amendments2023-09-12012 September 2023 Supplement to Application for Order Consenting to Transfer of Licenses and Conforming License Amendments L-23-172, Quality Assurance Program Manual2023-08-31031 August 2023 Quality Assurance Program Manual IR 05000346/20230112023-08-30030 August 2023 Biennial Problem Identification and Resolution Inspection Report 05000346/2023011 ML23129A1722023-08-25025 August 2023 Request for Withholding Information from Public Disclosure for Beaver Valley Power Station, Units 1 and 2; Davis Besse Nuclear Power Station, Unit 1; and Perry Nuclear Power Plant, Unit 1 IR 05000346/20230052023-08-24024 August 2023 Updated Inspection Plan for Davis-Besse Nuclear Power Station (Report 05000346/2023005) L-23-188, Energy Harbor Nuclear Corp., Supplement to Application for Order Consenting to Transfer of Licenses and Conforming License Amendments2023-08-0707 August 2023 Energy Harbor Nuclear Corp., Supplement to Application for Order Consenting to Transfer of Licenses and Conforming License Amendments IR 05000346/20230502023-08-0303 August 2023 Special Inspection Report 05000346/2023050 IR 05000346/20230902023-08-0101 August 2023 EA-23-002 Davis-Besse Nuclear Power Station - NRC Inspection Report No. 05000346/2023090 (Public) ML23178A2742023-08-0101 August 2023 Letter to the Honorable Marcy Kaptur from Chair Hanson Responds to Letter Regarding the License Transfer Application for the Davis-Besse Nuclear Power Station L-23-175, Submittal of Fifth Ten Year Inservice Testing Program2023-08-0101 August 2023 Submittal of Fifth Ten Year Inservice Testing Program IR 05000346/20230022023-07-27027 July 2023 Integrated Inspection Report 05000346/2023002 ML23193A7842023-07-13013 July 2023 Information Request for the Cyber-Security Baseline Inspection, Notification to Perform Inspection 05000346/2023402 ML23178A2422023-06-28028 June 2023 Reassignment of the U.S. Nuclear Regulatory Commission Branch Chief in the Division of Operating Reactor Licensing for Plant Licensing Branch III ML23160A2342023-06-13013 June 2023 Confirmation of Initial License Examination L-23-034, 2022 Annual 10 CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models2023-06-13013 June 2023 2022 Annual 10 CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models IR 05000346/20235012023-06-13013 June 2023 Emergency Preparedness Biennial Exercise Inspection Report 05000346/2023501 L-23-135, Response to Regulatory Issue Summary 2023-01, Preparation and Scheduling of Operator Licensing Examinations2023-05-31031 May 2023 Response to Regulatory Issue Summary 2023-01, Preparation and Scheduling of Operator Licensing Examinations L-23-065, Annual Financial Report2023-05-22022 May 2023 Annual Financial Report ML23124A1742023-05-17017 May 2023 Energy Harbor Fleet Vistra License Transfer - Request for Withholding Information from Public Disclosure for Commance Peak Plant, Units 1 & 2, Beaver Valley Station, Units 1 & 2, Davis Besse Station, Unit 1 and Perry Plant, Unit 1 ML23129A0112023-05-16016 May 2023 Notice of Consideration of Approval of Indirect and Direct License Transfer for Comanche Peak Plant, Units 1 & 2, Beaver Valley Station, Units 1 & 2, Davis Besse Station, Unit 1 and Perry Plant, Unit 1 (EPID L-2023-LLM-0000) (Letter) ML23131A2732023-05-15015 May 2023 Notification of NRC Supplemental Inspection 95001 and Request for Information L-23-101, Combined Annual Radiological Environmental Operating Report and Radioactive Effluent Release Report for the Davis-Besse Nuclear Power Station - 20222023-05-12012 May 2023 Combined Annual Radiological Environmental Operating Report and Radioactive Effluent Release Report for the Davis-Besse Nuclear Power Station - 2022 L-23-131, Readiness for Resumption of NRC Supplemental Inspection2023-05-12012 May 2023 Readiness for Resumption of NRC Supplemental Inspection IR 05000346/20230102023-05-0909 May 2023 Commercial Grade Dedication Inspection Report 05000346/2023010 ML23123A1272023-05-0303 May 2023 Information Request to Support Upcoming Problem Identification and Resolution Inspection at Davis-Besse Nuclear Power Station IR 05000346/20230012023-05-0101 May 2023 Integrated Inspection Report 05000346/2023001 and 07200014/2022001 L-23-092, Occupational Radiation Exposure Report for Year 20222023-04-27027 April 2023 Occupational Radiation Exposure Report for Year 2022 ML23111A1972023-04-26026 April 2023 Information Meeting with Question and Answer Session to Discuss NRC 2022 End-of-Cycle Plant Performance Assessment of Davis-Besse Nuclear Power Plant Station ML23114A1062023-04-25025 April 2023 Information Request to Support the NRC Annual Baseline Emergency Action Level and Emergency Plan Changes Inspection CP-202300181, ISFSI, Beaver Valley, Units 1 and 2, ISFSI, Davis-Besse, Unit 1, ISFSI, Perry, Unit 1, ISFSI, Corrected Affidavit for Application for Order Consenting to Transfer of Licenses and Conforming License Amendments2023-04-20020 April 2023 ISFSI, Beaver Valley, Units 1 and 2, ISFSI, Davis-Besse, Unit 1, ISFSI, Perry, Unit 1, ISFSI, Corrected Affidavit for Application for Order Consenting to Transfer of Licenses and Conforming License Amendments CP-202300157, ISFSI, Beaver Valley, Units 1 and 2, ISFSI, Davis-Besse, Unit 1, ISFSI, Perry, Unit 1, and ISFSI, Application for Order Consenting to Transfer of Licenses and Conforming License Amendments2023-04-14014 April 2023 ISFSI, Beaver Valley, Units 1 and 2, ISFSI, Davis-Besse, Unit 1, ISFSI, Perry, Unit 1, and ISFSI, Application for Order Consenting to Transfer of Licenses and Conforming License Amendments ML23096A1382023-04-11011 April 2023 Review of the Spring 2022 Steam Generator Tube Inspection Report L-23-061, Submittal of the Decommissioning Funding Status Reports2023-03-31031 March 2023 Submittal of the Decommissioning Funding Status Reports L-23-037, and Perry Nuclear Power Plant - Independent Spent Fuel Storage Installation Changes, Tests, and Experiments2023-03-29029 March 2023 and Perry Nuclear Power Plant - Independent Spent Fuel Storage Installation Changes, Tests, and Experiments L-23-066, Annual Notification of Property Insurance Coverage2023-03-21021 March 2023 Annual Notification of Property Insurance Coverage ML23066A2892023-03-14014 March 2023 Request for Threshold Determination Under 10 CFR 50.80 and 10 CFR 72.50 for an Amendment to the Voting Agreement ML23066A2592023-03-14014 March 2023 Request for Withholding Information from Public Disclosure for Beaver Valley Power Station, Units 1 and 2, Davis Besse Nuclear Power Station, Unit 1, and Perry Nuclear Power Plant, Unit 1 2024-02-02
[Table view] |
See also: IR 05000346/2021090
Text
December 9, 2021
EA-21-155
Mr. Terry Brown
Site Vice President
Energy Harbor Nuclear Corp.
Davis-Besse Nuclear Power Station
5501 N. State Rte. 2, Mail Stop A-DB-3080
Oak Harbor, OH 43449-9760
SUBJECT: DAVIS-BESSE - NRC INSPECTION REPORT (05000346/2021090);
PRELIMINARY WHITE FINDING
Dear Mr. Brown:
This letter transmits the NRCs preliminary detailed risk evaluation of the safety significance of
an inspection finding described in NRC inspection report 05000246/2021050. The finding has
preliminarily been determined to be of low to moderate increased safety significance
(i.e., White) that may require additional NRC inspections. As described in the previous
inspection report, the finding involved the failure to select a suitable replacement part for the
emergency diesel generator (EDG) speed switch. The speed switch design was not compatible
with the stations 125/250 Volts direct current (Vdc) battery system. The switch design
contained a subcomponent that was rated for 170 Vdc but was exposed to a voltage potential of
201 Vdc. The long-term exposure to this voltage potential caused the switch subcomponent to
fail and, combined with another unrelated ground on the 125/250 Vdc system, resulted in failure
of the switch. The failure of the switch resulted in the failure of the EDG to start during testing
on September 4, 2020. This finding was assessed based on the best available information,
using the applicable Significance Determination Process (SDP). The final resolution of this
finding will be conveyed in separate correspondence.
The basis for the staffs significance determination is provided in the enclosure. This finding
does not represent a current safety concern because the speed switches on both EDGs have
been replaced and interim measures have been put in place until a new design is procured.
However, the finding is also an apparent violation of NRC requirements and is being considered
for escalated enforcement action in accordance with the Enforcement Policy, which can be
found on the NRCs Web site at http://www.nrc.gov/about-nrc/regulatory/enforcement/enforce-
pol.html.
In accordance with NRC Inspection Manual Chapter 0609, we intend to complete our evaluation
using the best available information and issue our final determination of safety significance
within 90 days of November 19, 2021, the date of the issuance of the special inspection report
that initially documented the finding. The SDP encourages an open dialogue between the NRC
staff and the licensee; however, the dialogue should not impact the timeliness of the staffs final
determination.
T. Brown 2
Before we make a final decision on this matter, we are providing you with an opportunity to
(1) attend a Regulatory Conference where you can present to the NRC your perspective on the
facts and assumptions the NRC used to arrive at the finding and assess its significance,
(2) submit your position on the finding to the NRC in writing, or (3) accept the finding as
documented in the enclosure. If you request a Regulatory Conference, it should be held within
40 days of the receipt of this letter, and we encourage you to submit supporting documentation
at least one week prior to the conference in an effort to make the conference more efficient and
effective. The focus of the Regulatory Conference is to discuss the significance of the finding
and not necessarily the root cause(s) or corrective action(s) associated with the finding. If a
Regulatory Conference is held, it will be open for public observation. If you decide to submit
only a written response, such submittal should be sent to the NRC within 40 days of your receipt
of this letter. If you decline to request a Regulatory Conference or to submit a written response,
you relinquish your right to appeal the final SDP determination, in that by not doing either, you
fail to meet the appeal requirements stated in the Prerequisite and Limitation sections of
Attachment 2 of NRC Inspection Manual Chapter 0609.
If you choose to send a response, it should be clearly marked as a "Response to An Apparent
Violation; (EA-21-155)" and should include for the apparent violation: (1) the reason for the
apparent violation or, if contested, the basis for disputing the apparent violation; (2) the
corrective steps that have been taken and the results achieved; (3) the corrective steps that will
be taken; and (4) the date when full compliance will be achieved. Your response should be
submitted under oath or affirmation and may reference or include previously docketed
correspondence, if the correspondence adequately addresses the required response.
Additionally, your response should be sent to the U.S. Nuclear Regulatory Commission,
ATTN: Document Control Center, Washington, DC 20555-0001 with a copy to Laura Kozak,
acting Branch Chief, U.S. Nuclear Regulatory Commission, Region III, 2443 Warrenville Road,
Suite 210, Lisle, IL 60532, within 40 days of the date of this letter. If an adequate response is
not received within the time specified or an extension of time has not been granted by the NRC,
the NRC will proceed with its enforcement decision or schedule a Regulatory Conference.
Please contact Laura Kozak at 630-829-9604 and in writing within 10 days from the issue date
of this letter to notify the NRC of your intentions. If we have not heard from you within 10 days,
we will continue with our significance determination and enforcement decision. The final
resolution of this matter will be conveyed in separate correspondence.
Because the NRC has not made a final determination in this matter, no Notice of Violation is
being issued for these inspection findings at this time. In addition, please be advised that the
characterization of the apparent violation described in the enclosed inspection report may
change as a result of further NRC review.
T. Brown 3
In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter and its
enclosure will be made available electronically for public inspection in the NRC Public
Document Room and in the NRCs Agencywide Documents Access and Management System
(ADAMS), accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html.
Sincerely,
Signed by Hayes, Michelle
on 12/09/21
Michelle Hayes, Acting Deputy Director
Division of Reactor Safety
Docket No. 05000346
License No. NPF-3
Enclosure:
As stated
cc: Distribution via LISTSERV
T. Brown 4
Letter to Terry Brown from Michelle Hayes dated December 9, 2021.
SUBJECT: DAVIS-BESSE - NRC INSPECTION REPORT (05000346/2021090);
PRELIMINARY WHITE FINDING
DISTRIBUTION:
Jessie Quichocho
Robert Williams
RidsNrrDorlLpl3
RidsNrrPMDavisBesse Resource
RidsNrrDroIrib Resource
John Giessner
Mohammed Shuaibi
Jamnes Cameron
Shelbie Lewman
Allan Barker
DRPIII
DRSIII
ROPassessment.Resource@nrc.gov
ADAMS Accession Number: ML21340A221
Publicly Available Non-Publicly Available Sensitive Non-Sensitive
OFFICE RIII RIII RIII RIII
NAME JHanna:mb LKozak JCameron MHayes
DATE 12/08/2021 12/08/2021 12/09/2021 12/09/2021
OFFICIAL RECORD COPY
Summary of the Detailed Risk Evaluation for the Davis-Besse Speed Switch Finding and
Basis for Preliminary Significance Determination
Exposure Time - From late August 28 or early August 29, 2020, until September 7, 2020,
Emergency Diesel Generator-2 (EDG) was unavailable; a time window of 9 days. This was
when the engine was reasonably known to be in a failed condition. A factor of
9 days/365 days/year, or 0.0246 was applied to the annualized results.
Failure Mechanism - The failure of EDG-2, during a hypothetical demand, would be in the first
few seconds of an attempted start of the engine. Consequently, the basic event in the
Davis-Besse Standardized Plant Analysis Risk (SPAR) model basic event Diesel Generator 1-2
Fails to Start was set to True. All other basic events were left at their nominal failure
probabilities, except for the Mitigating Strategies equipment, which is discussed below.
Common Cause Implications - The two safety-related EDGs at Davis-Besse are similar in all
respects, and the performance deficiency affected both engines. The potential for common
cause failure was used in the NRCs evaluation. However, it is important to note that the
Davis-Besse Station Blackout EDG was sufficiently different in design, vintage, and other
material properties such that it was not part of the Common Cause Component Group with the
two safety-related engines in the SPAR model.
Mitigating Strategies - The Mitigating Strategies equipment and response procedures
(commonly and collectively known as FLEX) were credited in this analysis. Given that the
performance deficiency affected the safety-related EDGs, and the accident sequences of
concern were station blackout sequences that become extended losses of AC power scenarios,
FLEX was included in the internal and external events analysis. However, the analyst adjusted
the failure probabilities in the SPAR model for the FLEX basic events using a 3x multiplier to
more accurately reflect the higher unreliability of portable equipment. The analyst also
compared the FLEX unavailability/unreliability values used in the licensee Probabilistic risk
assessment (PRA) model with the NRC SPAR model (using the 3x multiplier). No significant
differences were identified.
Repair/Recovery of Failed Components - The diagnosis and replacement of the failed speed
switch following the surveillance testing failure was three days in duration. The analyst
concluded that the recovery of the failed speed switch during a postulated event, i.e., during a
loss of offsite power that progresses to a station blackout for the non-conforming case was not
credible.
Internal Events Risk - The dominant internal event accident sequence is a weather-related
loss of offsite power sequence and contributes 46% of the total internal events risk. However,
the overall results were dominated by fire and internal events only represented 12% of the total.
External Events Risk -
Fire - Fire was the dominant contributor to the overall change in core damage frequency
(CDF) result and was included quantitatively using the licensees all hazard model. The
dominant fire sequence are large damaging fires, or high energy arc faults, which cause
a loss of offsite power (LOOP) with a subsequent loss of decay heat removal via the
once-through steam generators with subsequent failure of makeup/high pressure
injection (HPI) cooling. These scenarios contribute 54% of the fire risk. FLEX
Enclosure
equipment/strategies were credited in both the base and non-conforming cases. The
analyst sampled the top 20 dominant cutsets and verified that bounding and/or
unrealistic assumptions were not being used, however, further reviews or discussions
with Energy Harbor staff may be needed to either confirm or refute this assumption.
Tornados/High Winds and External Flooding - External flooding or tornados leading to a
LOOP, though credible, was determined to be several orders of magnitude less frequent
than the LOOP values used in the internal events model. No further analysis was
performed.
Seismic - Seismic-induced events were quantified using the licensees all hazard model,
though they were not a significant contributor to the overall result.
Uncertainty - With all risk evaluations, there are both aleatory (randomness) and epistemic
(lack of knowledge) uncertainties. The aleatory uncertainty was assessed using the
Davis-Besse SPAR model. The 5% and 95% values for the consolidated results (both internal
and external events) were 9E-7/year to 4E-6/year. The remaining epistemic uncertainties with
the results were centered on the fire results generated from the licensees model. Specifically, it
was unknown at the time of completion of the risk analysis whether substantial conservatism
were present in the fire model, though some efforts had been taken to address this question as
described above.
Item of Merit - The risk contribution for the two most commonly used items of merit, delta-CDF
and delta large early release frequency (LERF), were quantified in the analysis. Delta-CDF
remained the item of merit.
Consolidated Results -
Base Non-Conforming Delta Risk
Case Case (change in CDF)
Internal Events (NRC Results) 1.3E-7 3.6E-7 2.2E-7
Seismic (Licensee Results) 3.1E-7 3.4E-7 3.2E-8
Fire (Licensee Results) 1.3E-6 2.9E-6 1.6E-6
Total = 1.7E-6 3.6E-6 1.9E-6
The quantitative and qualitative inputs described above support the treatment of this finding as
low to moderate safety significance (i.e., White).
2