2016-06-30 – NRC – Chairman’s Response to OSC – ML16195A368

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Carolyn N. Lerner
Special Counsel
UNITED ST ATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, O.C. 20555-0001
June 30, 2016
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U.S. Office of Special Counsel –
1730 M Street, N.W. , Suite 218
Washington, D.C. 20036-4505
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Re: OSC File No. Dl-15-5254
Dear Ms. Lerner:
By letter dated April 12, 2016, you referred a whistleblower disclosure to me. Pursuant
to 5 U.S.C. § 12.13(c)(1 ), the U.S. Office of Special Counsel (OSC) requested that I, as the
Chairman of the U.S. Nuclear Regulatory Commission (NRC), investigate the whistleblower’s
allegations and submit a written report setting forth my findings to OSC. OSC requested an
investigation of the whistleblower’s allegations that the NRC has failed to:
• require Oconee Nuclear Station in South Carolina to take corrective measures to
safeguard the plant from potential flooding should the Lake Jocassee Dam fail; and
• require 18 other nuclear power stations to take appropriate measures to protect against
the risk of flooding in the event of upstream dam failures.
OSC also requested that the investigation address five additional questions related to NRC
actions with respect to flooding hazards at nuclear power plants. As discussed below, the
referred allegations were not substantiated.
The NRC’s organic statute, the Atomic Energy Act of 1954, as amended (AEA),
“requires the NRC to provide ‘adequate protection’ for the health and safety of the public, which
the NRC seeks to ensure on an ongoing basis through an ‘evolving set of requirements and
commitments for a specific plant that are modified as necessary over the life of a plant to ensure
continuation of an adequate level of safety.”‘1 Adequate protection is not a fixed standard, but
rather involves a case-by-case application of technical judgment of the Commission.2 Adequate
protection does not equate to zero risk from regulated activities, and the courts have long held
that the NRC’s adequate protection standard permits the acceptance of some level of risk.3
When exercising engineering and scientific judgment in the light of all relevant and material
information, the NRC reviews credible hazards identified by license applicants (following NRC
published guidance), then requires that designs be able to cope with such hazards with
sufficient safety margins and reliable backup systems. The NRC has previously determined that
1 Massachusetts v. NRC, 708 F.3d 63, 67 (1s1 Cir. 2013) (citations omitted).
2 Union of Concerned Scientists v. NRC, 880 F.2d 552, 558 (D.C. Cir 1989).
3 Public Citizen v. NRC, 473 F.3d 916, 918 (1 51 Cir. 2009) (quoting Union of Concerned Scientists v. NRG,
824 F.2d 108, 118 (D.C. Cir. 1987)).
C. N. Lerner – 2 –
compliance with the NRC’s regulations provides “reasonable assurance of adequate protection ,”
but has also concluded that “failure to comply with one regulation or another is [not] an
indication of the absence of adequate protection … where the Commission has reviewed the
noncompliance and found that it does not pose an ‘undue risk’ to the public health and safety.”4
The NRC’s regulatory regime is discussed in more detail in Section 3 of the Investigative
Report.
Given the technical nature of the allegations, I convened a working group to initiate the
inquiry that resulted in the development of the enclosed Investigative Report, which addresses
the matters identified in your letter. I have reviewed the Investigative Report and adopt its
content and findings. As is detailed in the Report, the allegations referred by OSC are
unsubstantiated. Contrary to the whistleblower’s allegations, the NRC has taken the actions
that the agency has determined to be necessary to ensure that the public health and safety is
adequately protected from potential flooding caused by credible upstream dam failures at the
Oconee Nuclear Station5 and the other 18 nuclear power stations identified by OSC. In
addition, as detailed in the report the NRC’s actions have:
• been in accordance with the NRC’s functions and authorities under the AEA;
• been in conformance with NRC programs, processes, and procedures, including those
for addressing differing staff views; and
• followed normal NRC processes for resolution of technical issues and response to
operating events.
The whistleblower’s disagreement with the actions taken by the NRC does not equate to
inaction.
I also note that it is not clear that there is necessarily disagreement between the
whistleblower and the agency over whether the NRC has acted appropriately to address
potential flooding hazards. During his interview the whistleblower acknowledged that his
primary concern pertains to the non-public nature of certain NRC and other federal agency
documents and not whether the NRC has fulfilled its statutory obligation regarding the identified
facilities. In its regulation of nuclear power facilities and other licensed activities, the NRC
endeavors to make a substantial portion of its documentation available to the public.
Nonetheless, some information may be legitimately withheld from public disclosure to protect,
for example, inter-agency information, proprietary information, or security-related information.
The whistleblower has frequently availed himself of the processes afforded under the Freedom
of Information Act to seek access to NRC non-public (FOIA) documents, and has been
4 In the Matter of All Reactor Licensees with Installed Thermo-Lag Fire Barrier Material, DD-96-3, 43 NRC
183, 195 (1996) (quoting In the Matter of Ohio Citizens for Responsible Energy, DPRM-88-4, 28 NRC 411
(1988)).
s The Investigative Report indicates that the NRC staff would not make a final determination on whether
the licensee for Oconee had met the commitments of a June 22, 2010 Confirmatory Action Letter (CAL)
completed until the permanent modifications were completed. On June 20, 2016, the NRC staff issued a
follow-up inspection report documenting the NRC’s determination that Oconee has satisfied the terms of
the CAL and that the June 22, 2010 CAL is now closed. The June 20, 2016, letter also noted that
additional ongoing external flooding issues will be addressed separately. Catherine Haney, NRC, letter
to Scott Batson, Duke Energy Carolinas, LLC, “Oconee Nuclear Station – Confirmatory Action Letter
Followup Inspection Report 05000269/2016009, 05000270/2016009, and 05000287/2016009, dated
June 20, 2016. ADAMS Access No. ML 16168A176.
C. N. Lerner – 3 –
informed that under FOIA the agency may permissibly withhold certain information from public
disclosure. The whistleblower’s dissatisfaction with the NRC’s lawful use of FOIA withholding
exemptions cannot be remedied through the OSC’s disclosure process. Please note, however,
that the Investigative Report being provided to you today does not contain any personally
identifiable information, sensitive unclassified security-related information, or classified
information that would require it to be withheld from the public.
Under 5 U.S.C. § 1213(d)(5), the investigative report provided in response to the OSC
referral is to include a description of any action taken or planned as a result of the investigation.
As I previously noted, the whistleblower’s allegations were not substantiated and, therefore, no
further action is warranted.
If you have any questions regarding this matter, please contact my Legal Counsel,
Tracey Stokes, at (301) 415-1747.
Enclosures:
NRC Investigative Report Re: OSC File No. 01-15-5254
cc: Commissioner Svinicki
Commissioner Ostendorff
Commissioner Baran
NRC FORM SC
(7-94)
NRCMD 3.57
COVER SHEET FOR CORRESPONDENCE
USE THIS COVER SHEET TO PROTECT ORIGINALS OF
MUL Tl-PAGE CORRESPONDENCE

United States Nuclear Regulatory Commission
Protecting People and the Environment
INVESTIGATIVE REPORT TO THE
CHAIRMAN OF THE U.S. NRC
RE: OSC FILE NO. 01-15-5254
OSC File No. Dl-15-5254
EXECUTIVE SUMMARY
This report documents the activities of the U.S. Nuclear Regulatory Commission (NRC)
Flooding Working Group, which was established by NRC Chairman Stephen G. Burns to inquire
into whistleblower disclosures provided to the Office of Special Counsel (OSC) with respect to
the risk from flooding at nuclear power plants located downstream from dams. The specific
allegations to be investigated are:
1. NRC has failed to require the Oconee Nuclear Station in South Carolina [referred to as
Oconee] to take corrective measures to safeguard the plant from potential flooding
should the Lake Jocassee Dam fail.
2. NRC has also failed to require 18 other nuclear power stations to take appropriate
measures to protect against the risk of flooding in the event of upstream dam failures.
In addition, the Flooding Working Group considered whether any NRC action or inaction could
be considered a failure to fulfill the agency’s statutory obligation to provide reasonable
assurance of adequate protection to public health and safety, such that it could constitute a
violation of law, rule, or regulation; gross mismanagement; or abuse of authority.
During the investigation, the Flooding Working Group developed a practical understanding of,
and significant insights into, the evolving scientific and engineering state of knowledge related to
dam safety, dam failure likelihood, dam failure analysis, consequential flooding scenarios, and
their implications for the health and safety of the public. The Flooding Working Group
determined that it had sufficient knowledge and experience with NRC safety decision-making,
regulatory programs, and legal processes; time and resources; access to both public and nonpublic
information; and access to knowledgeable individuals to make an informed judgement on
the matters referred to the NRC by OSC.
The report contains a sufficient amount of material to support the findings and conclusions while
avoiding the disclosure of any personally identifiable information, sensitive unclassified securityrelated
information, or classified information. It includes a summary of information investigated
and a description of the conduct of the investigation. In addition, the report presents the
evidence collected through a transcribed interview of the whistleblower, interviews of NRC staff
directly involved in the evaluation of potential dam failures and their consequences, and NRC
and licensee documents that described dam failure analyses, related NRC actions, and licensee
modifications to their facilities and operations.
The report also provides responses to five specific questions posed by OSC:
1. Has NRG required [Oconee] to take adequate corrective measures to safeguard the
plant from potential flooding in the event of a failure of the Lake Jocassee Dam? If so,
describe the measures and when they were taken.
Yes. Section 4.1 documents the NRG-required actions and related activities, both
complete and ongoing, taken with respect to Oconee.
2. Has NRG required the 18 other nuclear power stations identified in Appendix A [to the
OSG referral] to take appropriate measures to protect against the risk of flooding in the
event of upstream dam failures? If so, describe the measures and when they were
taken.
OSC Fi le No. Dl-15-5254
Yes. Section 4.2 documents the NRC-required actions and related activities taken with
respect to the nuclear power plants at the other 18 sites identified.
3. What action has been taken to address the risk of flooding from upstream dam failures?
Are there actions planned that have not yet been completed?
Section 4.3 provides a summary of the numerous NRC and licensee actions related to
the issue of potential dam failures and consequential flooding. Five specific and relevant
topics are addressed for each plant. Further details are provided in Appendix B to this
report for each topic for the 19 sites evaluated.
4. What is the current risk to public health and safety from potential flooding of the 19
nuclear power plants identified in Appendix A [to the OSC referral letter]?
Section 4.4 presents the working group’s views and conclusions on the current risk to
from dam-failure-related flooding. In short, the current risks to public health and safety
are very small and within the Commission’s mandate to provide adequate protection.
5. Would the risk to public health and safety from potential flooding of nuclear power plants
identified in Appendix A [to the OSC referral letter] have been reduced if NRG had
required those plants to take action to protect against flooding in 2013?
Section 4.5 presents information concluding that risk reductions were achieved before
2013, have been achieved since 2013, and are expected to be further enhanced upon
completion of ongoing licensee actions that resulted from NRC requirements.
The report concludes the following with respect to the allegations regarding the NRC’s response
to the potential failure of dams upstream from Oconee and the other 18 sites:
• The NRC has required Oconee and the plants at the other 18 sites to take appropriate
action to provide adequate protection to public health and safety from rare but credible
upstream dam failures.
• The NRC actions have been in accordance with the functions and authorities of the
Atomic Energy Act, as amended. No violation of law, rule, or regulation; gross
mismanagement; or abuse of authority was found.
• The NRC actions, including orders, requests for information, enforcement actions, and
rulemaking activities, have been in conformance with NRC programs, processes, and
procedures. including those for addressing differing staff views.
• The NRC actions followed normal NRC processes for resolution of technical issues and
response to operating events and were independent of the whistleblower disclosure.
• Continued timely, efficient, and effective use of these programs, processes, and
procedures by NRC staff, implementing Commission decisions and considering all
available information and technical viewpoints. provides the best and most appropriate
means of bringing the ongoing dam failure and flooding reviews to appropriate
conclusions. In addition, these programs. processes, and procedures constitute an
appropriate and effective means of addressing emerging issues of potential safety
significance in the future.
ii
OSC File No. 01-15-5254
TABLE OF CONTENTS
1 Summary of Information Investigated ………………………….. ………………. ……. 1
2 Conduct of Investigation ……………………………………………………………………. 2
2.1 Summary of the Testimonial Evidence ………… ………………………………………. ………… 2
2.2 Weighing of the Evidence .. …… …… ……….. …. ……… …………. ….. ………. …….. ……. ….. … 6
2.3 Standard of Proof ………… ………………………………… ……. ….. ……………. …………. .. …….. 7
3 NRC Regulatory Context ………………………………………… …………………………. 8
4 Response to OSC Questions ……………………………………………………………. 10
4.1 Question 1: Evaluation of NRG-Required Actions at Oconee … ……….. ………………. 10
4.2 Question 2: Evaluation of NRG-Required Actions at Other Power Stations ………… 13
4.3 Question 3: Summary of Actions Taken to Address Risk … …….. …………. ……. .. …… 13
4.4 Question 4: Evaluation of Current Risk ………………. …………………….. …….. ……. .. …. 27
4.5 Question 5: Evaluation of Risk Reduction Potential ……… ………………… … …….. .. …. 28
5 Conclusions ……………………………………………………………………………………. 29
Appendix A: Background on Regulatory Approach ……………………………………… 30
A.1 Agency Responsibilities …………. ………. ………… … ……. .. ………. … …… …. … … .. ….. ……. 30
A.2 Agency Regulatory Approach ……….. ………… .. …….. ……… …….. … ……. ……. …. ……. … 30
A.3 Evaluation of Flooding Hazards ….. …… .. … ………… .. ….. ……. .. …….. ……….. … …… … … 32
A.4 Generic Issues Program … .. …………… .. … … … … ……. ………….. …….. .. … … .. ………. …… 33
A.5 Response to Fukushima Dai-ichi Accident ……………. ………… … …….. … …. ….. ……….. 34
A.6 Programs for Addressing Differing Views … ……… ………. … …… ………….. .. ….. ………… 36
Appendix B: Additional Detail on Actions Taken at Sites ……………………………… 38
B.1 Arkansas Nuclear One …………………………………. …….. ….. .. …… ………. ….. ……………. 38
B.2 Beaver Valley .. …………………. .. ………………. .. … …. ………… ………. .. ……….. .. ….. ……. .. 43
B.3 Browns Ferry ….. ….. …………….. ……….. .. … …… ……. .. ………………… …………. … … ….. … 46
B.4 Columbia ……………………………….. ….. ………….. …. .. …… ……… ……………………………. 51
B.5 Cooper …… …. … .. …… …… …………… …….. … .. …………. ….. ………… ……………………. …. .. 53
B.6 Fort Calhoun …………… ……………….. …………………………….. ….. ………. …. … ………… … 58
B.7 H.B. Robinson …………………………………………………………………. ….. .. …. … …….. …. .. 65
B.8 Hope Creek I Salem …………… …… …. … ……….. …… …. .. .. ……… …….. …….. …………… .. 68
B.9 Indian Point. ….. ……. .. ….. ….. ……. …… ……. .. … .. ….. .. … ………… ……………… … … …….. … 74
B.10 McGuire ………………………………… ……….. …………… ………………………….. …………….. 79
B.11 Oconee ……………. … ………………. …… ….. ……………… ……… … ……. .. …………………. ….. 82
B.12 Peach Bottom .. ………………. … ………. ……. ……………………. …….. .. …….. …… ………… … 93
B.13 Prairie Island ……….. .. ……………………………… …… … ……. …….. …… .. .. ……. .. ………… … 97
B.14 Sequoyah ….. ……. .. …….. .. ………. .. … …… ……. …… …. ….. ……. .. …. ………. … …….. ……… 101
B.15 South Texas Project ……. ………… ………….. …….. …. ………… …………………… ….. …….. 110
B.16 Surry … …………. ……………………………………….. .. …………… .. ……….. ………….. … …….. 114
B.17 Three Mile Island ……… … ….. …… …… …….. ………… ……. ……. …….. … …. ………. …… … .. 119
B.18 Waterford … .. …… ………………………. …………….. … ……………… ……… …. … ……. …….. … 125
B.19 Watts Bar ……………. .. ……. …. …. ………………. …………. ……………… … …………….. .. …… 129
iii
OSC File No. Dl-15-5254
1 Summary of Information Investigated
This report documents the investigation of the following two allegations transmitted to the
Chairman of the U.S. Nuclear Regulatory Commission (NRC) by the Special Counsel of the
United States.1
1. NRC has failed to require the Oconee Nuclear Station2 in South Carolina to take
corrective measures to safeguard the plant from potential flooding should the Lake
Jocassee Dam fail.
2. NRC has also failed to require 18 other nuclear power stations to take appropriate
measures to protect against the risk of flooding in the event of upstream dam failures.
The report also answers the following five questions that were also included in the letter from
the Office of Special Counsel (OSC).
1. Has NRC required [Oconee] to take adequate corrective measures to safeguard the
plant from potential flooding in the event of a failure of the Lake Jocassee Dam? If so,
describe the measures and when they were taken.
2. Has NRC required the 18 other nuclear power stations identified in Appendix A [to the
OSC referral letter] to take appropriate measures to protect against the risk of flooding in
the event of upstream dam failures? If so, describe the measures and when they were
taken.
3. What action has been taken to address the risk of flooding from upstream dam failures?
Are there actions planned that have not yet been completed?
4. What is the current risk to public health and safety from potential flood ing of the 19
nuclear power plants identified in Appendix A [to the OSC referral letter]?
5. Would the risk to public health and safety from potential flooding of nuclear power plants
identified in Appendix A [to the OSC referral letter] have been reduced if NRC had
required those plants to take action to protect against flooding in 2013
1 Carolyn N. Lerner, U.S. Special Counsel, letter to Stephen G. Burns, NRC, “OSC File No. Dl-15-5254,” dated
April 12, 2016.
2 Referred to in the remainder of the report as Oconee.
1
OSC File No. Dl-15-5254
2 Conduct of Investigation
After receiving the April 12, 2016, letter from OSC, Chairman Stephen G. Burns convened a
Flooding Working Group to inquire into the whistleblower disclosure provided to OSC and to
provide a report to the Chairman of the working group’s findings. The working group consists of
the following senior NRC staff members3 who were assigned to the Chairman’s office to conduct
the investigation: Sara Kirkwood (legal team lead), Gary Holahan (technical team lead), and
Theresa Clark (technical staff).
The working group began the investigation by reviewing the referral letter from the OSC. The
working group also examined hundreds of public and non-public documents in the NRC’s
Agencywide Documents Access and Management System (ADAMS), as well as documents
provided to the working group by the whistleblower and other interviewed employees.4 These
documents are summarized and referenced in the sections that respond to the OSC questions.
In addition, the working group considered testimonial evidence provided in interviews with four
NRC staff members, including the whistleblower. The interview with the whistleblower was
transcribed, and the working group prepared summaries of the other interviews (which the
interviewees were given an opportunity to review). The working group used these documents
as references in considering the insights gained from the interviews.
2.1 Summary of the Testimonial Evidence
2.1.1 Summary of Evidence from Whistleblower Interview
On May 19, 2016, the working group interviewed the whistleblower, Mr. Lawrence Criscione, in
a transcribed interview. Mr. Criscione was accompanied by his attorney, Mr. Thomas Devine.
Mr. Criscione stated that he became involved in the evaluation of flooding from upstream dam
failures in February 2010. At the time, colleagues in his branch in the Office of Nuclear
Regulatory Research (the generic issues branch) were working on a screening analysis on
upstream dam failures for what later became Generic Issue 204. He was not assigned to this
project, but stated that they consulted with him because of his experience as an operator at
commercial nuclear power plants. Mr. Criscione also stated that the authors of the screening
analysis report felt pressure to not include certain information in their documents, but that they
submitted the report they wanted to submit in the end. Mr. Criscione did not know what
information the authors felt pressured to exclude from the report, and encouraged the working
group to speak with the authors of the report. Mr. Criscione stated that he was satisfied that the
screening analysis report was complete and had all the necessary information.
Mr. Criscione stated the he provided to OSC the list of 19 sites, and that the list came from the
Generic Issue 204 screening analysis report. He stated that he did not have any specific
concerns about any of the 19 sites, but that they were just the ones in the screening analysis
report. Mr. Criscione indicated that he had no insights into these matters other than what he
had read in the Generic Issue 204 report, and that he believed that his colleagues thought that
3 In this report, “NRG staff’ is used as a collective term for the staff of the NRG, as distinct from the Commission. The
Commission has delegated authority to the NRG staff to take certain actions, and “NRC staff’ actions reflect agency
positions on these matters. It does not imply action taken by an individual; in specific cases (such as the statement of
a differing view from the agency position), the term “NRG staff member” is used instead.
4 The publicly available version of ADAMS is accessible via http://adams.nrc.gov/wba/ and the hyperlinked accession
numbers within this document.
2
OSC File No. Dl-15-5254
flooding issues were not being appropriately addressed. Mr. Criscione stated that he did not
know the current status of Generic Issue 204. Mr. Criscione stated that he thought Fort
Calhoun had a particularly credible hazard from dam failure. He said that he knew the NRC had
a study on Fort Calhoun, but that he had not been given access to the study. He further stated
that he had heard that H.B. Robinson, Watts Bar, Browns Ferry, and Sequoyah were of concern
to some people, but he did not know specifics for any of these sites. He stated that he had
observed dams leak in the past while hiking on the Appalachian Trail. He stated that he was not
a civil engineer or a hydrologist and did not know if seepage through a dam is acceptable or not.
Specifically with respect to Oconee, Mr. Criscione stated that he did not know if the NRC had
completed its review of the potential for dam failure to affect the site. He stated that he has
never been assigned to work on Oconee. Mr. Criscione could not specifically identify what
provisions he would view as sufficient to protect Oconee and suggested that the working group
speak with Mr. Jeffrey Mitman. He stated that technical staff members felt pressured to “pencilwhip”
their calculations to the point that the risk estimates were acceptable. Mr. Criscione
stated that he had not personally experienced this pressure. Mr. Criscione stated that he did
not think he had read any documents on Oconee that were written after 2012, but that he had
heard a rumor that the NRC was accepting a lower flood height. He referred the working group
to Dr. Michelle Bensi for further information. Mr. Criscione stated that Oconee had committed to
shut down the plant if the reservoir water level in Lake Jocassee goes over a certain height, but
that he was concerned that still today it was not in the plant procedures. He believes that this
shows that the potential for dam failure flooding at Oconee had not been adequately addressed.
Mr. Criscione stated that he did not know at what water level Oconee should shut down, and he
was not sure in what document Oconee committed to a plant shut down. He suggested that
Mr. Mitman would have more information on this topic
Mr. Criscione stated that, in his view, adequate protection could not be provided by mitigation
measures. He based this on his 22 years working in nuclear power. He defined adequate
protection as meaning that the installed safety equipment could survive the flood, and mitigation
as meaning that the installed safety equipment might not survive, but that other equipment could
prevent the reactor core from melting. He further stated that adequate protection meant that the
reactor core had to be cooled with installed equipment.
Mr. Criscione stated that he believed the working group had all of the documents it needed to
investigate his concerns. He was not aware of any documents that were wrong or inaccurate.
Mr. Criscione stated that he had not closely followed the issues regarding flooding from dam
failures since 2013, and that the working group should speak with others who were more
involved with this issue than he was. Mr. Criscione provided the names of several other
individuals who he believed had concerns. He stated that Dr. Bensi had concerns that she
would not share with Mr. Criscione because he did not have a need to know. He stated that Mr.
Jacob Philip had concerns about the walkdowns that had been done. He stated that Mr. Joseph
Kanney expressed a willingness to speak with the working group, but Mr. Criscione did not
identify any specific concerns that Mr. Kanney would share. He stated that Mr. Mitman could
describe a concern that the Oconee analysis was not conservative because Mr. Mitman
believed that it was possible for the dam to fail by erosion if flood waters exceed the dam height
(generally referred to as overtopping). Mr. Criscione relayed what he believed these concerns
to be, as well as his view on Oconee’s planned actions to avoid overtopping.
3
OSC File No. Dl-15-5254
Additionally, Mr. Criscione stated the following concerns that were outside the scope of the
investigation:
1. Mr. Criscione stated that he believed that the NRC had not appropriately considered
whether there was sufficient security around dams. His basis for this was that he had
sent a request to the NRC Inspector General under the Freedom of Information Act ·
requesting any studies on the topic; he was told that there were no records that met his
request in the Inspector General’s office. Mr. Criscione stated that in his position he
would not have any way of knowing whether or not such a study had ever been done.
2. Mr. Criscione believes that the NRC should communicate to the public that the NRC is,
in his view, relying on mitigation rather than adequate protection and that, in his view,
this communication had not been done. He believes that it needs to be unequivocally
stated to Congress and the public that the agency is not going to ensure adequate
protection for a dam failure.
3. Mr. Criscione stated that his main concern is that the documents concerning these
issues needed to be publicly available.
4. Mr. Criscione stated that staff members were restricted from speaking to people even
within their own branch, claiming they did not have a need to know. Mr. Criscione
believes this is affecting the open and collaborative work environment in the agency.
Mr. Devine stated that he believes that the suppression of necessary work-related
communications is within the scope of the disclosure.
2.1.2 Summary of Evidence from Dr. Michelle Bensi
The working group met with Dr. Bensi at the suggestion of Mr. Criscione, who had indicated
multiple times that she was in a better position than he was to speak to the technical aspects of
his concerns. Dr. Bensi has a doctorate in civil engineering and works primarily in the area of
seismic risk. She was involved in Generic Issue 204 while she was in the Office of Nuclear
Regulatory Research. Dr. Bensi later transferred to the Office of New Reactors, where she
became involved in the reviews of flooding information submitted by licensees after the
Fukushima Dai-ichi accident. Dr. Bensi expressed that there was significant technical
disagreement within the NRC staff regarding the appropriate way to resolve flooding concerns.
She stated that she found her division director, Mr. Scott Flanders, to be an amazingly
supportive person, and stated that while she has not always agreed with the ultimate technical
conclusion, she believes that she has been heard.
Dr. Bensi identified herself as an author of the screening analysis for Generic Issue 204. She
denied ever being asked to remove anything from the screening analysis for Generic Issue
204.5 She stated that the list of plants was included in the Generic Issue 204 screening analysis
report to indicate that those sites had an upstream dam; therefore, multiple sites had the
potential to be affected by an upstream dam failure, establishing that upstream dam failures was
a potential generic issue rather than a plant-specific issue.
5 On Friday, June 10, 2016, Dr. Bensi contacted the working group and clarified that there had been discussion
regarding whether some of the detailed information for Gl-204 was necessary. The ultimate resolution was to create
a public and a non-public version.
4
OSC File No. Dl-15-5254
Dr. Bensi stated that she was responsible for the NRC review of the seismic failure analysis for
Jocassee Dam upstream from Oconee and agreed that seismic failure could be appropriately
screened out.
Dr. Bensi stated that the NRC staff has not been restricted in what they write in their reports as
a result of security concerns; however, portions of those reports have been withheld from the
public because of the security sensitivity of certain information. She further stated that she
believes the security concerns have restricted the free flow of information among NRC staff, but
she has not been personally affected by this.
2.1.3 Summary of Evidence from Mr. Jeffrey Mitman
The working group met with Mr. Jeffrey Mitman at the suggestion of Mr. Criscione. Mr. Mitman
is a Senior Reliability and Risk Analyst. He has 35 years of experience in the nuclear industry
and 20 years of probabilistic risk assessment experience. Mr. Mitman stated that his
involvement in the Oconee dam flooding issues occurred when his division was asked to look at
the dam failure frequency following an inspection finding at Oconee in 2006. Once the
probabilistic portion of the NRC staff’s assessment was complete, he was no longer involved in
the review.
Mr. Mitman filed a non-concurrence in 2011 on the NRC staffs assessment of the licensee’s
dam failure flooding analysis, because he did not find the assumptions used to eliminate an
overtopping failure of the Oconee dam to be sufficiently conservative. In the interview, Mr.
Mitman provided clarifying information on the basis for this non-concurrence that facilitated the
working group’s evaluation of available documents.
2.1.4 Summary of Evidence from Dr. Christopher Cook
The working group met with Dr. Christopher Cook since his staff is responsible for many of the
documents that the working group has been reviewing. Dr. Cook is the supervisor of a
hydrology and meteorology group in the NRC’s Office of New Reactors. He has a doctorate in
civil engineering and has over 16 years of experience working with dams.
Dr. Cook was not involved with reviews of Oconee prior to the flooding reviews conducted in
response to the Fukushima Dai-ichi accident in Japan in 2011 . He was generally aware of the
issues at Oconee and has always thought the licensee’s dam failure flooding analysis accepted
by the NRC staff in 2011 was very conservative. Dr. Cook stated that the NRC staff suggested
to the licensee that they could simply use this earlier flooding evaluation to respond to the
NRC’s request for information after the Fukushima Dai-ichi accident, rather than doing a new
hazard reevaluation, but that the licensee opted to do the reeval uation.
Dr. Cook stated that in reviewing the flooding hazard reevaluation, the NRC staff carefully
considered the different potential failure modes of Jocassee Dam. He stated that he was not
aware of any disagreement among the review team regarding the appropriate flood level at
Oconee. He stated that he was not familiar with Mr. Mitman’s 2011 non-concurrence, but that
he was thoroughly convinced that an overtopping failure did not need to be further evaluated.
He provided additional background on the NRC staff’s visits to Oconee, discussions with staff of
the licensee and the Federal Energy Regulatory Commission, and independent evaluations that
provided the basis for the NRC staff to conclude that the flood level was reasonable. In
particular, he described the conservatisms in the modeling of the water inflow to Jocassee
Reservoir during an extreme storm and the reasonableness of the assumptions on outflow
based on the operation of the dam.
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Furthermore, Dr. Cook stated that the NRC staff’s assessment was a collaborative effort with
input from Dr. Nebiyu Tiruneh (another hydrologist in his branch), Dr. Bensi, consultants from
the Center for Nuclear Waste Regulatory Analysis, contractors at Oak Ridge National
Laboratory, staff of the Federal Energy Regulatory Commission, and Dr. Tony Wahl (a
researcher at the U.S. Bureau of Reclamation). All of these individuals and groups had free
access to all the information they needed to review the hazard analysis. He stated that the
other plant reviews had a similar level of collaboration and emphasized that his staff had not
raised any safety concerns to him regarding the flooding assessments that had been completed
to date.
Dr. Cook stated that all dams leak, and leakage alone does not indicate a problem with the dam.
Dr. Cook stated that there is a tremendous amount of engineering judgment involved in
determining how a dam fails and how floods develop. In order to do the analysis, calculations
are performed in multiple analytical models and ranges of parameters and results are
considered.
2.2 Weighing of the Evidence
No person who was interviewed identified any concerns with the validity of the documents
reviewed by the working group, and none expressed a concern that any specific document had
been altered or modified. Thus, the working group relied on the documents as the primary
source of information for this report.
The working group credited the testimony of individuals within the scope of their own personal
knowledge and expertise. For issues regarding dam failures, the working group primarily
credited the testimony of Dr. Cook, due to his academic degrees in a related field (civil
engineering related with a focus on hydrology issues), his lengthy experience with dams, and
his personal involvement with the reviews at issue. Similarly, the working group credited the
testimony of Dr. Bensi and Mr. Mitman for the reviews they were personally involved in.
Mr. Criscione testified that he was not personally involved in any of the reviews at issue.
Moreover, Mr. Criscione does not have an academic background or professional experience in
seismology, hydrology, or civil engineering. Thus, to the extent that his testimony conflicted with
others’, the other testimony was given more weight.
While the working group has carefully reviewed actions taken related to all 19 sites identified in
the OSC referral letter, the working group specifically notes the testimony of Mr. Criscione that
he obtained the list of sites from the Generic Issue 204 screening analysis report, and that he
did not have any specific concerns about those sites. The working group also noted the
testimony of Dr. Bensi that the list of 19 sites in the Generic Issue 204 screening analysis report
was included to establish that upstream dam failures was a generic issue, not to indicate any
particular concern with any of those sites.
From the testimony, it was clear that reasonable people can come to different conclusions
regarding technical and regulatory questions. In some areas, such as the standards to be used
for licensing plants or the use of mitigation versus protection, the Commission has taken
relevant positions. In other areas, technical judgment may differ, such as in estimating the
likelihood of a dam failure and how a dam failure would progress and result in a flood that could
affect a nuclear power plant. This is a complex technical issue, and there is not a uniformly
accepted technical model.
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There was testimony from Mr. Mitman, Dr. Bensi, and Mr. Criscione that restrictions on
dissemination of information regarding dam failure was restricting the free exchange of ideas
within the NRC staff. Mr. Criscione expressed this particularly forcefully. However,
Mr. Criscione was not able to identify any projects to which he was assigned wherein he was
not allowed free access to all information he needed. Similarly, Dr. Bensi testified that these
restrictions had not inhibited her work. Mr. Mitman identified that he requested but did not
receive a copy of a specific detailed flooding analysis for Oconee in the context of preparing his
non-concurrence in 2011 . However, Mr. Mitman was later told that the NRC staff did not
actually have the report. Dr. Cook testified credibly that all staff members assigned to a project
had access to all the information they needed. Similarly, he testified that the reviews were done
in a collaborative manner, and involved multiple NRC staff members, as well as contractors and
staff from other Federal agencies. Since Dr. Cook has the most personal knowledge of how
these reviews are being conducted, the working group credited his testimony on this issue. The
working group does not find that concerns regarding a “need to know” have adversely affected
the conclusions the NRC staff has drawn regarding the likelihood or consequences of dam
failures either at Oconee or the other 18 sites identified by OSC.
2.3 Standard of Proof
As explained above, the working group did not have significant factual or legal disputes to
resolve in answering the questions in the OSC referral. The working group did find that there
were examples of significant technical and regulatory disputes among NRC staff regarding what
actions the NRC should take on these issues. The working group did not attempt to resolve
these individual technical or regulatory disputes, or to apply a standard of proof to their
resolution. Rather, the working group developed its responses to the OSC questions by
considering the overall agency actions and positions that were taken or are planned to be taken.
In the view of the working group, resolution of these technical and regulatory disputes has been
addressed and is best achieved within the agency using existing agency processes.
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3 NRC Regulatory Context
A brief summary of the NRC’s regulatory approach is provided below as context for
understanding the agency’s actions regarding dam failures. More detailed background,
including definitions and additional references, is presented in Appendix A.
The NRC is provided authority under the Atomic Energy Act6 to execute its mission: to license
and regulate the Nation’s civilian use of radioactive materials to protect public health and safety,
promote the common defense and security, and protect the environment. This mission is
primarily implemented through licensing, oversight, rulemaking, and research. The NRC
licenses commercial nuclear power plants using an “adequate protection” standard, which is a
case-by-case judgment using all relevant engineering and scientific information. One aspect of
licensing reviews is the evaluation of natural hazards, including flooding, to determine that a
proposed site is a safe place to build a nuclear power plant.
After a license is issued, the NRC has various processes for addressing new information and
taking appropriate action. Steps in these processes include collecting appropriate information,
evaluating the information for safety significance (including whether immediate action is
warranted), considering the legal and procedural implications of the new information,
considering any differing technical views, soliciting public input as appropriate, and taking
necessary regulatory action. These deliberative processes can take significant time and
technical and regulatory resources to complete. The NRC strives to make well-informed
decisions in a timeframe appropriate to the safety significance of the various issues it considers.
The NRC has a formal office procedure to determine whether an immediate plant shutdown is
warranted given new information.7 If so, the process for issuing a safety order would generally
be implemented. If not, this decision is documented, along with an appropriate justification for
continued operation while the issue is resolved. Often, licensees implement interim
compensatory measures while resolution of the issue is pursued. This report includes several
examples of such measures.
In considering whether it should require changes at a plant as a result of new information, the
NRC uses a structured process referred to as the “backfit” process. The NRC considers
whether changes are necessary to provide adequate protection to the public health and safety,
to ensure compliance with the plant’s licensing basis, or to provide a substantial safety
enhancement for which the costs are justified. Licensees also voluntarily make plant changes
to enhance safety. Some of these enhancements are formalized by NRC action after they are
implemented.
An example of this deliberative approach is the NRC’s response to the Fukushima Dai-ichi
accident, flooding aspects of which are described in detail in this report. The NRC’s Near Term
Task Force charged with evaluating this accident recommended several safety enhancements
that ultimately resulted in orders and formal requests for information.8 However, the Near Term
Task Force also concluded that “continued operation and licensing activities do not pose
6 The Atomic Energy Act of 1954, as amended. Public Law 83-703. The full text of the Act is provided in NUREG-
0980, Volume 1, Number 10, “Nuclear Regulatory Legislation – 1121h Congress; 2nd Session,” dated September 2013.
ADAMS Accession No. ML 13274A489.
7 LIC-504, Revision 4, “Integrated Risk-Informed Decision-Making Process for Emergent Issues,” dated June 2, 2014.
ADAMS Accession No. ML 14035A143.
8 The authority to issue such requests is included in Section 182a of the Atomic Energy Act and implemented in
Title 10 of the Code of Federal Regulations (10 CFR), Section 50.54, “Conditions of licenses,” paragraph f, which is
referred to as 10 CFR 50.54(f) in this report.
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imminent risk to public health and safety,” and the later orders included the same statement
about continued operation. The requests for information that were issued inherently recognize
the safety of continued operation, since the request is for information “to enable the Commission
to determine whether or not the license should be modified, suspended, or revoked” in the
future. As the NRC completes its evaluation of the information obtained through these requests,
actions already implemented by licensees-both voluntarily and as a result of other NRC
requirements-provide further confidence in the safety of the operating fleet.
In addition, throughout the NRC staff activities related to dam failure analysis, the NRC has
implemented various processes to ensure that differing views were raised and addressed, such
that well-informed technical decisions were made. These processes range from informal
conversations among staff and management to formal reconsideration of a final agency
position. These processes, all of which were used in addressing the issues discussed in this
report, are described in Section A.6 of this report.
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4 Response to OSC Questions
This section presents the answers to the five specific questions contained in the OSC referral.
These answers also form the basis for the overall findings with respect to the whistleblower
disclosure, which are presented in Section 5 of this report.
4.1 Question 1: Evaluation of NRC-Required Actions at Oconee
Question 1 in the OSC letter asked:
Has NRC required Oconee to take adequate corrective measures to safeguard
the plant from potential flooding in the event of a failure of the Lake Jocassee
Dam? If so, describe the measures and when they were taken.
Yes, the NRC has taken appropriate regulatory action as the state of knowledge developed and
potential safety implications were identified.
4.1.1 2012 NRC Orders and Information Requests
As described in detail in Appendix B, on March 12, 2012, the NRC issued an immediatelyeffective
order (designated Order EA-12-0499 ) to Oconee and all other reactor licensees “with
regard to requirements for mitigation strategies for beyond-design-basis external events.” Order
EA-12-049 required licensees to develop a three-phase approach to an extended loss of all
electrical power as a result of a beyond-design-basis external event. Order EA-12-049 also
required licensees to address flooding from dam failure or from other sources as a category of
external events.
The specific flooding events to be addressed by the mitigation strategies are being established
for each site (including Oconee) through reevaluations of flooding hazards using insights from
state-of-the-art information and techniques similar to those used to assess new reactor
sites. The hazard reevaluations were required by the NRC as part of the information request
(referred to as a 10 CFR 50.54(f) letter) issued to Oconee and all other reactor licensees on
March 12, 2012.10 Enclosure 2 to the 10 CFR 50.54(f) letters provided detailed instructions on
the required evaluation, including a hazard reevaluation report and an integrated assessment
report to be prepared if “the current design basis floods do not bound the reevaluated hazard for
all flood causing mechanisms.”
Duke Energy, the licen$ee for Oconee, submitted its reevaluation of potential flooding events on
March 6, 2015.11 The NRC completed its review and approval of the reevaluated hazard on
April 14, 2016.12
9 EA-1 2-049, “Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for
Beyond-Design-Basis External Events,” dated March 12, 2012. ADAMS Accession No. ML 12054A735.
10 “Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54{f) Regarding
Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights From the Fukushima Dai-ichi
Accident,” dated March 12, 2012. ADAMS Accession No. ML 12053A340.
11 Scott L. Batson, Duke Energy, letter to NRC, “Oconee, Units 1, 2 and 3 – Submittal of Revised Flood Hazard
Reevaluation Report per NRC”s Request for Additional Information,” dated March 6, 2015. ADAMS Accession
No. ML 15072A 106.
12 Jack R. Davis and Anne Boland, NRC, letter to Scott Batson, Duke Energy Carolinas, LLC, “Oconee Nuclear
Station, Units 1, 2, and 3 – Staff Assessment of Response to 10 CFR 50.54(f) Information Request Flood-Causing
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In addition, the 10 CFR 50.54(f) letter included a request for licensees to perform flooding
“walkdowns” (physical verification of the state of the plant with respect to flood protection
features) using an NRG-endorsed methodology. Licensees were expected to identify conditions
of concern, identify actions taken or planned to enhance flood protection, and verify the
adequacy of maintenance and monitoring for flood protection features. Specific information on
the conduct and findings of the flooding walkdowns at Oconee is included in the response to
Question 3 below.
The facility changes that resulted from the NRC’s actions in issuing this order and information
request are detailed in the response to Question 3.
4.1.2 Additional NRC Actions
The NRC, and its predecessor the Atomic Energy Commission, always considered and
addressed the potential for dam failures to affect reactor safety. The state of knowledge
associated with the likelihood and causes of dam failures has evolved over the last half century,
within the NRC and in the scientific community in general
1994-1995 NRC Inspection and Risk Assessment
NRC inspection activities at Oconee during 1994 and discussions of newly available flooding
information led to a licensee commitment to study the safety significance of the issues more
fully. That study was conducted as part of the Individual Plant Examination for External Events
(IPEEE) performed in response to NRC Generic Letter 88-20, an NRC program requesting
licensees to conduct more thorough probabilistic risk assessments for reactors.13 In 1995, the
licensee concluded that a flood level above the barrier around key equipment housed in a
“standby shutdown facility”14 had a frequency of approximately once in 75,000 years. Since the
IPEEE showed that dam fai lures were very unlikely, no additional action was determined to be
necessary, and the NRC issued a letter closing the IPEEE project for Oconee.
2005-2006 NRC Inspection and Enforcement
In June 2005, during a periodic risk-informed flood inspection under the NRC’s Reactor
Oversight Process, NRC inspectors identified a breach in the flood-protection wall of the
standby shutdown facility. In April 2006, the NRC staff concluded that the licensee failed to
effectively control maintenance activities associated with removing a fire suppression refill
access cover (an element of a flood protection barrier) in the standby shutdown facility south
wall to facilitate installation of temporary electrical power cables. The NRC staff also noted that
the licensee may not have appropriately addressed the potential consequences of flooding
based on information in a 1992 study of inundation from dam fa ilures conducted by the Federal
Energy Regulatory Commission.
Mechanism Reevaluation (CAC Nos. MF1012, MF1013, and MF1014) and Path Forward on Confirmatory Action
Letter,” dated April 14, 2016. ADAMS Accession No. ML 15352A207.
13 Generic Letter 88-20, “Individual Plant Examination for Severe Accident Vulnerabilities,” dated November 23, 1988,
requested plants to perform a systematic examination to identify any plant-specific vulnerabilities to severe accidents
and report the results to the Commission. Five supplements to Generic Letter 88-20 provided additional guidance,
notably Supplement 4, dated June 8, 1991, which requested that plants perform an IPEEE. The initial Generic Letter
and its supplements are available on the NRC Web site at http://www.nrc.gov/reading-rm/doc-collections/qencomm/
gen-letters/1988/.
14 More information on this facility is provided in Appendix 8 to this report.
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2007-2008 NRC Independent Analysis and Information Request
Following this inspection finding, the NRC staff conducted an independent review of the
Jocassee Dam failure frequency that the licensee had used in developing its probabilistic risk
assessment in the 1980s. From that review, the NRC staff concluded that a higher frequency
estimate of Jocassee Dam failure was more appropriate and that the licensee’s estimate was
not adequately supported by operating experience and actual performance data of similar rockfilled
dam structures. The NRC staff also concluded that the licensee had an inadequate basis
for applying a reduction factor to further reduce the risk estimate (i.e .• the assumption that only
20 percent of floods would exceed the existing standby shutdown facility flood wall). On
August 15, 2008, an 10 CFR 50.54(f) letter was issued to the licensee to obtain further
information on the hazard from the potential failure of Jocassee Dam.15
2010 NRC Confirmatory Action Letter
In 2010, the NRC issued a Confirmatory Action Letter to assure that licensee commitments to
interim and compensatory actions to strengthen flooding protections were taken and
maintained.16
2015 NRC Rulemaking on Mitigation of Beyond-Design-Basis Events
On August 27, 2015, the Commission approved the NRC staff recommendation to promulgate
an NRC regulation to incorporate all of the NRC post-Fukushima Dai-ichi accident actions into
the NRC regulations.17 The previously issued orders would be written into the NRC”s
permanent regulations, so that their requirements would apply to any future reactors. The
proposed regulation would apply the requirements of both Order EA-12-049 and an additional
order on spent fuel pool instrumentation18 (EA-12-051) to all operating or future U.S. nuclear
power plants.19 The proposed rule also incorporates many other recommendations of the
Fukushima Dai-ichi accident Near-Term Task Force, including requirements re lated to:
• onsite emergency response capabilities
• emergency plans to address prolonged station blackout and multiunit events
• command and control structure and qualification
• enhanced onsite emergency response resources
15 Joseph G. Giitter, NRC, letter to Dave Baxter, Duke Energy Carolinas, LLC, “Information Request Pursuant to
1 O CFR 50.54(F) Related to External Flooding, Including Failure of the Jocassee Dam at Oconee Nuclear Station,
Units 1, 2, and 3 (TAC Nos. MD8224, MD8225, and MD8226),” dated August 15, 2008. ADAMS Accession
No. ML081640244.
16 Luis A. Reyes, NRC, letter to David A. Baxter, Duke Energy Carolinas, LLC, “Confirmatory Action Letter – Oconee
Nuclear Station, Units 1, 2, and 3 Commitments to Address External Flooding Concerns (TAC Nos. ME3065,
ME3066 and ME3067),” dated June 22, 2010. ADAMS Accession No. ML 101730329.
17 Annette L. Vietti-Cook, NRC, memorandum to Mark A. Satorius, NRC, “Staff Requirements – SECY-15-0065 –
Proposed Rule: Mitigation ofBeyond-Design-Basis Events (RIN 3150-AJ49),” dated August 27, 2015. ADAMS
Accession No. ML15239A767.
18 EA-12-051 , “Order Modifying Licenses with Regard to Reliable Spent Fuel Pool Instrumentation.” ADAMS
Accession No. ML 12056A044.
19 Information on the proposed rule issued in November 2015 is available at
https://www.requlations.gov/#!documentDetail;D=NRC-2014-0240-0003.
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4.2 Question 2: Evaluation of NRC-Required Actions at Other
Power Stations
Question 2 in the OSC letter asked:
Has NRC required the other 18 nuclear power stations identified in Appendix A
[to the OSC letter] to take adequate measures to protect against the risk of
flooding in the event of upstream dam failures? If so, describe the measures and
when they were taken.
Yes, the NRC issued immediately-effective orders to the facilities at each of these 18 sites on
March 12, 2012, requiring licensees to provide mitigation strategies for beyond-design-basis
external events. All licensees were required to develop a three-phase approach to an extended
loss of all electrical power as a result of a beyond-design-basis external event, including
flooding events that could credibly be caused by an upstream dam failure.
In addition, the plants at each of the 18 sites were issued requests for information under
10 CFR 50. 54(f) on March 12, 2012, requiring analysis of external hazards, including potential
flooding caused by failure of upstream dams. They were also requested to identify actions
taken or planned.
The response to Question 3 includes sections for each site listed in Appendix A, on plantspecific
actions taken, as well as activities related to this order and 10 CFR 50.54(f) letter.
4.3 Question 3: Summary of Actions Taken to Address Risk
Question 3 in the OSC letter asked:
What action has been taken to address the risk of flooding from upstream dam
failures? Are there actions planned that have not yet been completed?
The NRC and licensees have taken a large number of actions in response to the risk of flooding
from potential upstream dam failures at each of the 19 sites listed in Appendix A to the OSC
letter. A summary of these actions is provided in this section, and additional details are
provided in Appendix B to this report. While additional sites may have dams upstream that were
considered either in the original licensing of the plant or in more recent evaluations, the general
approach and actions taken are the same; therefore, these 19 sites can be seen as examples
representing the spectrum of issues.
Many of the actions discussed address prevention and mitigation of flooding from all external
sources, including upstream dam failures. For a given plant, upstream dam failure may be the
cause of the most significant flooding, or another flooding source may be more significant than a
dam failure, or some combination of dam failure and other flooding sources may be most
significant.
The NRC’s responsibility to provide reasonable assurance of adequate protection of public
health and safety involves a continuous process in which the original licensing process is
complemented by an ongoing evaluation of operating experience, and new engineering and
scientific information that is collected and evaluated for its safety significance. As such, some of
these actions were included in the original licensing documents; others were taken in response
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to NRC requirements such as orders or as part of licensees’ response to NRC requests for
information, generic communications, or inspection findings.
The five subjects presented in detail for each site in Appendix B to this report are described
below. In general, the topics are addressed in Appendix Busing this order and scope; for some
sites, there have been significant changes to the facility or analyses that necessitate a deviation
from this structure to present the information more clearly. Table 1 summarizes the actions
taken for each site after initial plant licensing, as well as actions planned to be taken.
4.3.1 Initial Plant Design and Licensing
Flooding was considered in the initial design and licensing of every plant, as supplemented by
later changes, as appropriate. For some older plants, the NRC requirements and guidance at
the time of licensing may not have necessitated consideration of an upstream dam failure in
establishing design-basis flood. In some cases, the potential for flooding from dam failures was
revised in the plant’s design or licensing basis as new information emerged.
4.3.2 Plant-specific Regulatory Actions
Depending on the site, there may have been specific actions taken related to potential flooding
or dam failures as a result of inspections, licensee-identified issues, generic evaluations, or
other reasons. While not every action related to external flooding throughout the licensed
history of the plants is presented, the most significant actions identified by the Flooding Working
Group (particularly those relating to dam failures) are included. Plant-specific actions in
response to the Fukushima Dai-ichi accident are described separately in the following sections,
as they are relevant to every site.
4.3.3 Flooding Walkdowns
As noted above, after the Fukushima Dai-ichi accident, the NRC issued a request for
information under 10 CFR 50.54(f). Response to this request required performing walkdowns
using an NRC-endorsed methodology, identifying conditions of concern, identifying actions
taken or planned to enhance flood protection, and verifying the adequacy of maintenance and
monitoring for flood protection features.
The licensees for all 19 sites completed these walkdowns and took action to address any
identified deficiencies. For each site, the NRC staff has issued assessments documenting the
sufficiency of the actions taken.
4.3.4 Reevaluation of Flooding Hazard and Related Actions
The NRC’s request for information also asked all licensees to reevaluate the flooding hazards
for their sites based on present-day methodologies and guidance, establish interim actions if the
reevaluated hazard were found to be higher than the design-basis hazard, and conduct, as
appropriate, an integrated assessment (including additional protection and mitigation features)
to address the reevaluated hazard. The submittal dates for the flooding hazard reevaluation
reports was prioritized based on the complexity of analyses and available industry and staff
resources.2° For a small number of sites, the hazard reevaluation is not yet complete because
20 Eric J . Leeds, NRC, letter to all power reactor licensees and holders of construction permits, “Prioritization of
Response Due Dates for Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f)
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the U.S. Army Corps of Engineers is fi nalizing its inputs to the analysis (particularly for the dams
that for which it has responsibility). After the licensee’s flooding hazard reevaluation report is
received, the NRC staff reviews it and provides an interim response once it determines that the
reevaluated flood levels are appropriate for use in further assessments, including the evaluation
of mitigating strategies described in the next section. The NRC staff then issues a staff
assessment to document in more detail its review of the reevaluation.
As indicated in the initial request for information, licensees are expected to assess how the plant
would respond to reevaluated flood levels that exceed the design basis-an activity that is
referred to as “Phase 1.” The