27th Annual Report, Executive Summary, Conclusions and Recommendations

History and Introduction

The Diablo Canyon Independent Safety Committee (DCISC) was established as part of the June 24, 1988, settlement agreement which arose from the rate proceedings for the Diablo Canyon Nuclear Power Plant (DCPP). The DCISC was formed in late 1989 with the appointments of Committee Members and began formal review activities and meetings on January 1, 1990. The original settlement agreement (D.88-12-083) was terminated by the California Public Utilities Commission (CPUC) in its decision to open the state electricity markets to competition on January 1, 1998; however, under the provisions of the Commission’s Decisions 97-05-088, issued on May 21, 1997, and 04-05-055, issued on May 27, 2004, the DCISC will continue to function and fulfill its responsibilities as established under the terms of the 1988 settlement agreement.

The original settlement agreement provided for a three-member Independent Safety Committee for the purpose of““reviewing and assessing the safety of operations of DCPP”. The members serve three-year staggered terms and remain on the DCISC until a new appointment or their reappointment is made. To fill an expired term or a vacancy, the CPUC issues a public notice soliciting applications from interested persons or nominations by others of prospective candidates. Under the revised process in accordance with the restated charter, candidates are selected by the CPUC from the applications plus the incumbent, if willing to serve.

The candidates must be “persons with knowledge, background and experience in the field of nuclear power facilities and nuclear safety issues.” From the list of candidates, the new or returning member is appointed by the Governor of California, the Attorney General of California or the Chairperson of the California Energy Commission (CEC), whichever made the original appointment.

On May 27, 2004, the CPUC issued Decision 04-05-055. In its decision, the CPUC changed the nomination procedures by eliminating from the process the participation of PG&E and the Dean of Engineering at the University of California at Berkeley; modified the requirements for membership on the DCISC to add “knowledge and background in nuclear safety issues” to the “experience in the field of nuclear power facilities” and modified the DCISC’s mandate to require it to undertake public outreach in the community. The Decision concluded the DCISC should retain the discretion to determine how best to accomplish its mandate and that the DCISC shall otherwise continue to exist and to operate and continued funding through cost-of-service rates. To implement this directive the DCISC has continued to expand its public outreach as described in Section 8.0 Public Input and Outreach and continues to consider additional outreach activities.

On January 25, 2007, the CPUC issued Decision 07-01-028. The CPUC had previously adopted new practices and expectations for the DCISC without concurrently restating the Committee’s charter to reflect the changes. In its decision, the CPUC granted the DCISC application for authority to restate its charter including the incorporation into the Restated Charter of several terms, conditions, changes and clarifications necessitated by, and previously authorized by, the CPUC which govern the composition, responsibilities and operations of the Committee. In its decision, the CPUC found the Restated Charter to be in the public’s interest as it reflects the latest authority and obligations of the DCISC. The Committee’s application was unopposed. On June 21, 2016, PG&E announced a Joint Proposal with Friends of the Earth, the Natural Resources Defense Council, Environment California, the International Brotherhood of Electrical Works Local 1245, Coalition of California Utility Employees, and the Alliance for Nuclear Responsibility to retire DCPP at the expiration of the current operating licenses. On August 11, 2016, PG&E filed an Application with the California Public Utilities Commission (CPUC) for approval of the retirement of DCPP, implementation of the Joint Proposal, and for recovery of associated costs through proposed ratemaking.

Under the Joint Proposal, PG&E will continue to operate DCPP at current levels through the current license periods. If the Application is approved by the CPUC, in 2024 PG&E would retire Unit-1, and in 2025 would retire Unit-2. To replace DCPP power, the Joint Proposal provides specific greenhouse gas (GHG)-free procurement requirements beginning in 2018 and continuing through 2031. The Committee will follow developments and activities at DCPP to assure continued nuclear safety during the remaining years of operation, if the joint proposal is adopted.

The Committee Members during this period were as follows:

Overview of Activities during the Current Period

The DCISC held three public meetings in the vicinity of the Diablo Canyon Power Plant and one public meeting at Berkeley, CA on the following dates:

The Committee regularly performs the following activities:

The DCISC issues a report for each reporting year, which runs from July 1 to June 30. The report is approved by the Committee Members at the fall public meeting following the end of the reporting period. The first six-month interim report and subsequent twenty annual reports covered the periods January 1, 1990–June 30, 2016.

This twenty-seventh annual report covers the period July 1, 2016—June 30, 2017.

The technical items covered during these public meetings were selected by the DCISC based on the DCISC’s own priorities concerning which technical issues are important to cover. PG&E then responds by providing presentations and experts to participate in the public meetings as requested. The following significant items were reviewed:

Individual Committee Members and consultants reviewed many other items in nine fact-finding visits, inspections and tours at DCPP. The DCISC keeps track of past, current and future items for review in its Open Items List (Section 6.0 and Volume II, Exhibit F).

A DCISC Member, visited officials from the California Energy Commission to provide updates on DCISC activities, to discuss agency concerns and comments, and to provide copies of the Committee’s Annual Report.

Public input and questions were received at the public meetings, and by telephone, letter, and e-mail. Members of the public spoke at each of the three DCISC public meetings held in San Luis Obispo. The DCISC has responded to all of their questions and requests during this period.

Overall Conclusion
The DCISC concludes that PG&E operated DCPP safely during the period July 1, 2016—June 30, 2016.

Specific Conclusions

Based on its activities, the DCISC has the following specific conclusions from the major review topics examined during the current reporting period (references to sections of this report are shown in parentheses). Conclusions are based on, but may vary from, information contained in Committee Fact-finding Reports in Exhibit D in Volume II of this report.

  1. The DCISC received regular reports on the Nuclear Regulatory Commission (NRC) Performance Indicators, DCPP License Event Reports (LERs) sent to NRC, and NRC Inspection Reports and Enforcement Actions (violations) at each of its Public Meetings as well as copies of these documents throughout the reporting period. The DCISC investigated selected reports at its fact-finding meetings. The number of LERs has decreased significantly and was one during this period. This is the same as the previous period.
  1. The Committee notes that, although the NRC concluded that DCPP operated acceptably, it identified seven Non-cited Violations of “very low safety significance.” This is a significant improvement from previous periods. The one negative is the “White” violation received during this period.
  2. The DCISC will continue to review DCPP’s NRC regulatory performance during the next reporting period, paying particular attention to the number and significance of DCPP violations and LERs. (3.0)
  1. Operations continued to perform well at DCPP by successfully changing power levels through several Pacific winter storms, effectively performing regular plant rounds, developing appropriate operability determinations, correcting low level human errors, managing a continued low level of “no solo” licenses, implementing its Department Excellence Plan, and properly planning for assuring adequate numbers of operators will be available in the future. (4.1)
  2. DCPP’s use of electronic work orders was just beginning in 2016. These work orders are primarily used for preventive maintenance and simpler work not involving many drawings. Although not used extensively, the electronic work orders appear to be a step in the direction of a more effective and efficient process of work direction. (4.2)
  3. Overall, DCPP’s Engineering Programs appear to be healthy and effective. Design Quality, an issue for the past several years, has improved due to corrective actions to tighten the design process. Design Quality measures showed satisfactory performance based on scores of final designs released for installation. The DCISC will continue to monitor Design Quality. (4.3)
  4. The DCPP Safety and Wellness Expo was well implemented. The earthquake-simulating shake trailer was particularly helpful in showing why it is important to brace furniture. (4.4)
  5. DCPP’s nuclear safety culture appears strong according to its Nuclear Safety Dashboard and from early results of its latest Nuclear Safety Culture Survey. The DCISC will follow up on the latter during its next operating period. (4.5)
  6. DCPP’s Self-Assessment Program appears to be implemented satisfactorily in that many self-assessments are performed; however, the quality of some of them is somewhat questionable as some are determined to need changes by the Performance Improvement Review Board before becoming final. (4.6)
  7. The three-day DCPP November 2, 2017 Ingestion Pathway Emergency Preparedness Exercise successfully achieved its objectives. The exercise involved multiple local, state and Federal agencies and organizations. Drill critiques and evaluations were positive. The DCPP Emergency Response Organization was proficient in its implementation of the exercise. (4.7)
  8. Probabilistic Risk Assessment is an effective tool in understanding and determining nuclear reactor safety. PG&E has established an effective PRA Program staffed by experienced personnel and utilizes PRA to the full extent in analyzing and operating DCPP safely. (4.8)
  9. Attending Nuclear Safety Operating Committee (NSOC) meetings is an excellent way for the DCISC to learn about various plant issues, and therefore the DCISC will continue to attend them regularly. The DCISC believes that the DCPP NSOC is effective in advising plant management on items of nuclear safety and operational improvement. DCPP is satisfied that DCPP is taking its Institute of Nuclear Power Operation/World Association of Nuclear Operators evaluation seriously and satisfactorily working to resolve the evaluation areas for improvement. (4.9)
  10. DCPP radioactive releases have been measured to be a very small fraction of allowable releases. This has been confirmed by environmental sampling around the plant. (4.10)
  11. DCPP Quality Verification Audit Program procedures appeared satisfactory as did program implementation. Quality Verification was actively identifying quality problems and following them to resolution. DCPP’s pre-Nuclear Industry Evaluation Program self-assessment was a good practice. (4.11)
  12. DCPP nuclear fuel has performed well for many years with no leaks or failures. DCPP’s programs for assuring nuclear fuel integrity appear effective. (4.12)
  13. Although the DCISC did not review Equipment Reliability per se during this period, it concluded that DCPP equipment performed reliably based on plant operating data, monthly equipment reliability performance measures, and the absence of equipment problem reports. (4.13)
  14. The DCISC concluded that Organizational Effectiveness at DCPP continues satisfactorily. (4.14)
  15. DCPP has dealt effectively with most equipment and system problems and is focused on improving system health. DCPP’s Plant Health Committee has been improved to focus more on system/component health and meets more frequently, and overall system health has improved. DCPP has improved its performance with Safety System Functional Failures. (4.15)
  16. Although the DCISC did not specifically review Steam Generator performance, it concluded that the performance was satisfactory in its reviews of secondary water chemistry and refueling outage results. (4.16)
  17. The DCPP 1R20 Outage Safety Plan and Safety Schedule appeared comprehensive and effective to prevent the plant safety level from dropping below acceptable safety standards. DCPP 1R20 Outage work proceeded in a controlled, professional manner with careful pre-planning and management. The DCISC tour of DCPP Containment was well planned and executed, permitting the DCISC Fact-finding Team to observe practically all outage work in progress while achieving very low radiation dose. The DCPP Containment Equipment Hatch Closure Team performed their work within the required time, moving swiftly but methodically and safely. (4.17)
  18. The DCPP Safety/Security Interface Program appears to be implemented effectively. The accidental or negligent discharge of weapons in a way that could affect nuclear safety at DCPP does not appear to be a concern. (4.18)
  19. The 2016 Independent Spent Fuel Storage Installation (ISFSI) cask loading campaign was successfully completed. Spent fuel loading requirements for casks have been changed to a single thermal loading requirement to simplify loading and preserve cask limits. Although there are no immediate corrosion concerns, DCPP is continuing to participate in an industry initiative to determine the impact of atmospheric chlorides on cask corrosion. The DCISC will continue to follow DCPP’s efforts in analyzing and responding to this potential problem. DCPP will be submitting a request for license renewal for the ISFSI in 2022, two years before its scheduled expiration in 2024 and will be analyzing acceleration of the movement of spent fuel to the ISFSI as required by the Joint Proposal as a part of its decommissioning planning process. (4.19)
  20. DCPP is proceeding satisfactorily with its analyses on seismic, intense precipitation, tsunami and seismic interaction issues. The DCISC will continue to follow the progress of this important work. (4.20)
  21. DCPP continues to make good progress in the repair or replacement of its impaired fire and Equipment Control Guideline doors. DCPP is proceeding satisfactorily on its implementation of National Fire Protection Association (NFPA) Standard 805. DCPP’s procedures and process for transferring control to the Remote Hot Shutdown Panel and maintaining control of unit from the panel in the event of a need to evacuate the Control Room appear to be sound. The level of attention to DCPP’s Fire Protection Program and Systems has increased significantly, and numerous improvements have been accomplished. DCPP has aggressively moved to improve the control of transient combustible materials at the station. (4.21)
  22. DCPP FLEX training for operators has begun and is ongoing. DCPP’s licensed operator continuing training on Storm Season and Intake Management appeared satisfactory. The Continuing Training session referred to as a Human Performance Dynamic Learning Activity was useful for improving the use of Human Performance tools by Operators. The activity was well conducted by the station Human Performance Lead and other members of the Training staff. (4.22)
  23. In 2011 DCPP had requested that NRC pause its review of license extension pending completion and submittal of its seismic evaluations. These evaluations were completed and submitted in March and April 2015. In June 2016 PG&E had participated in a Joint Proposal to shut the plant down at the end of its original licensed life in 2024 for Unit 1 and 2025 for Unit 2. PG&E on June 21, 2016 requested that the NRC suspend its review of the PG&E License Renewal application. The NRC initiated its suspension on July 18, 2016. (4.23)
  24. Because of the Joint Proposal, the issue of closed look cooling is moot because the plant would cease operations in mid-2025, and any required closed loop cooling would have had to be installed by that time for license and plant operation continuation. Because of this, the DCISC will not pursue this issue further. (4.24)
  25. The DCPP Emergency Auxiliary Saltwater (EASW) Pump test was successfully performed with no debris buildup blocking flow. The DCISC believes this test was important in showing that the EASW system can operate without blockage from kelp and other potential debris. (4.25)
  26. The DCPP Joint Proposal to end DCPP operation in 2025 is beginning to work its way through the California Public Utilities Commission hearing process. PG&E expects to have the final CPUC decision in late 2017. PG&E is using the DCPP Excellence Plan to track and implement the high-level actions necessary to support the retirement of Diablo Canyon at the expiration of its current NRC operating licenses under the Joint Proposal. DCPP has formed a Project Review Working Group using experienced staff from Operations, Engineering, and Work Control to perform an initial review of the entire portfolio for future capital projects in light of the Joint Proposal. DCPP’s plan for decommissioning has begun with the process of developing its decommissioning organization, which will determine what type of decommissioning to use and a detailed cost estimate. The DCISC should follow closely the progress of the Joint Proposal, the DCPP Excellence Plan, and DCPP’s decommissioning planning through regular updates during both Fact-finding Meetings and Public Meetings. (4.26)


Concerns are items, which, while not necessarily warranting recommendations, need enhanced continuing Committee review and scrutiny or attention by PG&E. Concerns are monitored more actively and frequently by the Committee than other items. The DCISC concerns are as follows:

  1. PG&E entered into an agreement, the Joint Proposal, to close DCPP at the end of its original operating license (2024 for Unit 1 and 2025 for Unit 2). As a result, the DCISC has specific interest/concerns in two areas and will follow them closely:
  1. Retention of qualified, experienced personnel necessary to operate DCPP at an appropriate level of safety
  2. Adequate spending on programs and equipment to sustain an appropriate level of nuclear safety
  1. The DCISC is interested in further analysis of the potential effects on DCPP of tsunamis generated from submarine landslides.
  2. The DCISC is interested in continuing to monitor PG&E’s ongoing program of working with local, state, and Federal agencies to assure adequate emergency preparedness in the event of a significant accident.


PG&E should perform additional study of submarine landslide-induced tsunami hazards at DCPP and its environs.

Basis for Recommendation:
The DCISC believes that a probabilistic analysis would provide the annual frequency of various tsunami “sizes” at the DCPP site, including estimates of the various uncertainties. Here the word “size” might have one of several meanings, including tsunami maximum height, tsunami run-up, tsunami volume (related to its force on structures), or other possible endpoints. The DCISC endorses developing an estimate (or a useful upper bound) on the annual frequency of a tsunami-caused core-damage accident at DCPP. Such a Core-damage Frequency (CDF) estimate could be used by decision-makers and the public to understand whether the overall CDF risk from tsunamis is (or is not) an important contributor to the total CDF from all accidents at DCPP. Developing a probabilistic “understanding” does not, in the DCISC’s view, necessarily mean performing a full-blown quantitative probabilistic analysis of the tsunami hazard. Instead, it might involve something less, such as a demonstrably conservative bounding analysis of the annual probabilities of various tsunami “sizes,” or an analysis that aims for a realistic probabilistic description but might have very large uncertainties, if that is the best that can be accomplished. Perhaps the desired upper-bound CDF estimate would be easier to develop in a defensible way than a quantified realistic CDF. (4.20.3)

For more information contact:

Diablo Canyon Independent Safety Committee
Office of the Legal Counsel
857 Cass Street, Suite D, Monterey, California 93940
Telephone: in California call 800-439-4688; outside of California call 831-647-1044
Send E-mail to: dcsafety@dcisc.org.