ML21334A306
| ML21334A306 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 11/30/2021 |
| From: | Mary Woods NRC/OGC |
| To: | Atomic Safety and Licensing Board Panel |
| SECY RAS | |
| References | |
| 50-269-SLR, 50-270-SLR, 50-287-SLR, ASLBP 22-973-01-SLR-BD01, RAS 56315 | |
| Download: ML21334A306 (5) | |
Text
November,
UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of DUKE ENERGY CAROLINAS, LLC (Oconee Nuclear Station, Units,, and )
Docket No. -, -,
and --SLR NRC STAFF RESPONSE TO THE ATOMIC SAFETY AND LICENSING BOARDS NOVEMBER
, MEMORANDUM AND ORDER On November,, the Atomic Safety and Licensing Board issued a Memorandum and Order requesting the supporting basis for the following statement in the Nuclear Regulatory Commission (NRC) Staffs letter dated January,, where Staff closed issues associated with a Confirmatory Action Letter regarding the mitigation of external flooding hazards at Oconee resulting from the postulated failure of the Jocassee Dam: The random sunny-day failure scenario was selected after evaluation of the failure modes determined that the potential failure of the Jocassee Dam from either an overtopping event or seismic event was not credible.1 The supporting bases for the NRC Staffs findings and conclusions as stated in its January,, letter are provided in the January, Safety Evaluation as well as the supporting documents cited within the evaluation.2 Additional details beyond those identified within the NRC Staffs January,, letter and Safety Evaluation may be found in the Non-Concurrence on Oconee Assessment Letter, 1 Staff Assessment of Dukes Response to Confirmatory Action Letter Regarding Dukes Commitments to Address External Flooding Concerns at the Oconee Nuclear Station, Units,, and (ONS) (TAC NOS.
ME, ME, AND ME) (Jan., ) (Agencywide Documents Access Management System (ADAMS) Accession No. ML) ( Safety Evaluation).
2 See Safety Evaluation, Section., References at.
which was used to inform the January,, letter and Safety Evaluation.3 Notably, the Non-Concurrence on Oconee Assessment Letter includes, among other things, the Staff Response To Non-Concurrence On The Initial Starting Reservoir Level Of The Jocassee Dam For The Flooding Inundation Study Of The Oconee Nuclear Site For Demonstrating Reasonable Assurance, dated January,, which provides the Staffs detailed assessment and finding that the overtopping event and the seismic event failure modes were deemed to be not credible.4 Concerning overtopping, the January,, Staff Response states in part that:
[A] failure of a saddle dike would avert an overtopping failure of the Jocassee Dam. Failure of a single saddle dike would drain the lake down to an elevation of approximately ft msl, fully averting a catastrophic draining of the entire lake, thereby protecting the Keowee Dam and [Oconee] from damage. Based on the discussion above, the NRC staff concluded that overtopping of the Jocassee Dam is not a credible event.5 Addressing seismic event failure, the January,, Staff Response describes how the seismic attributes of the Jocassee Dam were analyzed by the NRC staff experts, and they have determined that a seismic failure of the Jocassee Dam is not a credible event,6 and further describes how the NRC staff, consisting of subject matter experts in geotechnical engineering and geology, performed a qualitative evaluation of the seismic stability of the Jocassee Dam. The qualitative evaluation was based on the following: a review of the available information in the technical literature pertaining to the performance of rock filled dams; the review and certification by Duke's Consulting Board of the quality control performed during construction; and finally based on the overall condition of the Jocassee Dam as certified by [the Federal Energy Regulatory Commission]
FERC's annual inspections. The NRC staff verified that the original construction 3 Non-Concurrence on Oconee Assessment Letter (Jan. ) (ADAMS Accession No. ML)
(Non-Concurrence on Oconee Assessment Letter).
4 Staff Response To Non-Concurrence On The Initial Starting Reservoir Level Of The Jocassee Dam For The Flooding Inundation Study Of The Oconee Nuclear Site For Demonstrating Reasonable Assurance (Jan., ) (ADAMS Accession No. ML) (January,, Staff Response).
5 Id. at.
6 Id. at.
data, including the compaction data, were reviewed and approved by FERC at the time of construction.7 Finally, the Staff notes that, in, the NRC Chairman issued an Investigative Report reaffirming the January,, Staff Response that overtopping and seismic failures of the Jocassee Dam are not credible.8 The Investigative Report addressed, in part, a whistleblower's allegations that NRC has failed to require [that] [Oconee] [] take corrective measures to safeguard the plant from potential flooding should the Lake Jocassee Dam fail.9 Notably, the Investigative Report reaffirmed the Staffs prior conclusion that the failure modes of seismic and overtopping of the Jocassee Dam were not credible, stating:
The NRC staff documented its acceptance in a January,,
safety evaluation.[10] An NRC staff member did not agree with the NRC staff evaluation of the licensee's response to the Confirmatory Action Letter and documented the concerns in a detailed non-concurrence.[11] The non-concurring individual specifically noted that the reservoir levels used by the licensee were based on normal operating limits, rather than bounding values. If higher starting reservoir levels were used, the effects of the dam failure would be greater. The non-concurring individual proposed that the licensee be required to perform a sensitivity analysis that used a "technically defendable most severe limit." The NRC staff response to this concern noted that these reservoirs were evaluated by NRC staff hydrologists, as well as consultants from the U.S.
Bureau of Reclamation, and determined to be appropriate for a sunny-day failure of the dam. This sunny-day scenario that was selected after NRC technical experts determined that overtopping and seismic failures were not credible; the NRC staff response also included the basis for excluding these other failure modes. The NRC staff clarified that its use of the word "bounded" in the Confirmatory Action Letter was meant to be in reference to conditions that bound the sunny-day failure of the Jocassee Dam, not the absolute worst case. Some clarifications were made to the 7 Id. at.
8 Investigative Report to the Chairman of the U.S. NRC RE: OSC [U.S. Office of Special Counsel] File No.
-- (June ) ( Investigative Report) (available at:
https://osc.gov/Documents/Public%Files/FY/DI--/DI--%Agency%Report.pdf).
9 Id. at.
10 Safety Evaluation.
11 Non-Concurrence on Oconee Assessment Letter.
assessment letter as a result of the non-concurrence, and it was issued as noted above.12
/Signed (electronically) by/
Mary Frances Woods Counsel for NRC Staff Mail Stop: O--A U.S. Nuclear Regulatory Commission Washington, DC -
Telephone: () -
E-mail: Mary.Woods@nrc.gov Dated in Rockville, MD this th day of November 12 Investigative Report, Appendix B, Additional Detail on Actions Taken at Sites at.
UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of DUKE ENERGY CAROLINAS, LLC (Oconee Nuclear Station, Units,, and )
Docket No. -, -,
and --SLR Certificate of Service Pursuant to C.F.R §., I hereby certify that copies of the foregoing NRC STAFF RESPONSE TO THE ATOMIC SAFETY AND LICENSING BOARDS NOVEMBER,
MEMORANDUM AND ORDER, dated November,, have been served upon the Electronic Information Exchange (the NRCs E-Filing System), in the captioned proceeding, this th day of November.
/Signed (electronically) by/
Mary Frances Woods Counsel for NRC Staff Mail Stop: O--A U.S. Nuclear Regulatory Commission Washington, DC -
Telephone: () -
E-mail: Mary.Woods@nrc.gov Dated in Rockville, MD this th day of November