IR 05000346/2021091

NRC Inspection Report (05000346/2021091) Preliminary Greater than Green Finding

ML21348A767
Person / Time
Site:	Davis Besse
Issue date:	12/17/2021
From:	Hayes M Division of Reactor Safety III
To:	Tony Brown Energy Harbor Nuclear Corp
References
EA-21-176 IR 2021091
Download: ML21348A767 (8)

Text

December 16, 2021

SUBJECT:

DAVIS-BESSE - NRC INSPECTION REPORT (05000346/2021091);

PRELIMINARY GREATER THAN GREEN FINDING

Dear Mr. Brown:

This letter transmits the NRCs preliminary determination of the safety significance of an inspection finding described in NRC inspection report 05000346/2021050. The finding has preliminarily been determined to be of greater than very low safety significance resulting in the need for further evaluation to determine the final significance. As described in the previous inspection report, the finding involved the failure to develop a preventative maintenance schedule for the inspection of the emergency diesel generator (EDG) field flash selector (FFSS)

switch. The switch was not inspected from the time it was installed in the plant in 2006. The failure to inspect the switch contributed to the long-term degradation of the switch electrical contacts and ultimately contributed to an EDG failure during fast start testing on May 27, 2021.

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.

After the special inspection concluded and during the development of the preliminary significance determination you provided the perspective, based on a vendor analysis, that the EDG FFSS failure during the fast start test was most likely the result of foreign material between the switch electrical contacts as evidenced by the presence of nickel on the contact surface.

You concluded that the failure was not caused by the lack of inspection and long-term switch electrical contact degradation. The NRC has preliminarily determined this vendor analysis does not rule out contact degradation due to lack of inspection as a significant contributing cause of the failure. There is sufficient operating experience on electrical contact failure due to contamination to reasonably consider this degradation mechanism to be credible. Therefore, we continued to conduct our significance determination with this assumption.

The basis for the staffs significance determination is provided in the enclosure. Important assumptions used in the staffs significance determination include the period of time the EDG was unavailable to automatically provide emergency power (i.e., the exposure period), the feasibility and reliability of actions to recover the EDG if it failed, and the contribution of fire risk scenarios to the safety significance of the finding. On November 30, you informed the NRC that you had conducted a risk evaluation of the degraded condition and that while you maintained the failure was not related to the performance deficiency identified by the NRC, you believed the risk of the degraded condition itself was of low to moderate safety significance. The NRC was not able to review your evaluation prior to completing the preliminary determination enclosed in this letter but will review it and consider your position as we make our final decision on this matter.

The NRC significance determination is subject to several uncertainties which could affect the outcome of the significance determination. Therefore, before we make a final decision, we invite you to provide any additional information on the docket to help in our evaluation of the significance of the finding. Specifically, we would like any information or perspectives you can provide in the following areas:

The assumed exposure period used in the NRC preliminary evaluation.

Actions that can be taken by operators to recover from a fast start failure of the EDG, including operator training on the FFSS.

The feasibility and reliability of the operator actions to recover from the fast start failure of the EDG, particularly during the dominant fire risk scenarios.

Conservatisms or non-conservatisms in your fire Probabilistic risk assessment (PRA)

that could affect the outcome of this evaluation.

Why you believe the contact contamination is not a credible cause of the FFSS that occurred during testing, including how inspection and preventive maintenance would not prevent the failure.

This finding does not represent a current safety concern because the FFSS on both EDGs have been replaced and procedures have been put in place to perform monthly continuity checks on the contacts. 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, 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.

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, or (2) submit your position on the finding to the NRC in writing, or (3) if you choose not to submit information or attend a Regulatory Conference, accept the NRCs final significance determination. 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-21-176)" 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 630-464-3344 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. 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 12/16/21 Michelle Hayes, Acting Deputy Director Division of Reactor Safety Docket No. 05000346 License No. NPF-3 Enclosure:

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