25th 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.

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.

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 interested persons. 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.

The Committee Members during this period were as follows:

Overview of Activities during the Current Period

The DCISC held four 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, 2014.

This Twenty-fifth Annual report covers the period July 1, 2014—June 30, 2015.

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).

Dr. Peter Lam, a DCISC Member, visited the Chairman of 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 email. 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, 2014—June 30, 2015.

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.
  2. The Committee notes that, although the NRC concluded that, “Overall, Diablo Canyon Nuclear Power Plant, Units 1 and 2, operated in a manner that preserved public health and safety…,” it identified 10 Non-cited Violations of “very low safety significance” and one item of “Low to moderate safety significance.” The number of violations has remained about the same as in the previous period and shows a trend downward (3.2.2), and DCPP has initiated strong actions to improve its regulatory performance. The number of Licensee Event Reports (LERs) has decreased dramatically (3.1.7).
  3. The DCISC is following this closely, specifically, review of DCPP NRC regulatory performance during the next reporting period, paying attention to the number of DCPP License Event Reports. (Section 3.5)
  1. DCPP Operations Department performance on component mispositions and reactivity management has been good and improving. DCPP’s Chemistry Program is effective and achieving good results. Primary and Secondary System chemistry levels are generally within specifications. Discharge of liquid radioactive waste is well within plant and regulatory limits. Although DCPP has expressed no intent to implement flexible power operation at this time, it has been examining the potential impacts that could arise from such a change to its operating practices, safety, and reliability. Flexible operation will have a different impact on plant safety and reliability than does steady state operation. The DCISC will continue to follow this topic. During this past winter, there were no Pacific Ocean winter storms, which impacted DCPP. DCPP appears to have performed its Operability Decision Making process satisfactorily. follow-up effectiveness evaluations were performed appropriately, concluding that the ODMs were effective. (4.1.3)
  2. Considerable management attention is being directed at minimizing maintenance risk and the need for maintenance rework, and improvements appear to be emerging in this area. Likewise, Foreign Material Exclusion Events appear to be more effectively avoided. Delays in taking corrective action to prevent recurrence of identified problems appear to have been a recent, short term problem, but should be of continued focus. Actions taken with respect to emerging issues appear to be appropriate. Positive engagement with the work force appears to be a significant contributor to this improvement. The DCPP Trouble-Shooting Program appears effective, and two DCPP troubleshooting cases appeared to have been performed satisfactorily as reviewed by the DCISC. (4.2.3)
  3. Overall, DCPP’s Engineering Program continued to be strong. DCPP’s Design Quality measures showed satisfactory performance based on scores of final designs released for installation.
  1. Recent improvements in Human Performance at DCPP reflect noticeable resources that the station has devoted to this important topic. The Operations group in particular has achieved commendable improvements in Component Mispositionings. The DCISC will reexamine these performance areas no later than the third quarter of 2016 to determine the degree to which these improvements are being sustained. (4.4.3)
  2. DCPP is organizationally focused on fostering a safety conscious work environment from the standpoints of both nuclear and industrial safety. The station appears to be in the early stages of implementing an enhanced process for observing station work activities. This includes obtaining feedback from employees being observed, occasionally conducting an observation with more than one observer, and expanding the amount of data that are retrieved and analyzed. The DCISC will continue to follow this area actively. (4.5.3)
  3. DCPP’s Performance Improvement Program appears to be effective in improving performance at the station. The program meets all requirements of the Nuclear Regulatory Commission and industry guidance. (4.6.3)
  4. DCPP appeared to have successfully implemented the second and third versions of the Meteorological Information and Dose Assessment System (MIDAS), utilizing seven meteorological towers and several sonic detection and ranging (SODAR) units, which provides more accurate offsite radiation release consequence predictions. The NRC Level III violation on Emergency Preparedness is White, or low-to-moderate level of safety significance. DCPP addressed the violation with appropriate corrective actions. (4.7.3)
  5. The DCPP Probabilistic Risk Assessment (PRA) group’s development work today is emphasizing the completion of new PRA models in the seismic and internal-flooding areas. Its applications work continues with applying PRA methods in several safety-significant areas at the plant. The DCISC concludes that the PRA group is doing fine work, as its competence and its recent accomplishments attest. The DCISC will continue to follow developments in the seismic-PRA area closely. On the other PRA topics the DCISC will undertake a further review about a year hence, when the plant anticipates it will have achieved additional major milestones in its PRA development effort. (4.8.3)
  6. Attending NSOC meetings is an excellent way for the DCISC to learn about various plant issues, and therefore the DCISC should plan to attend them regularly. The DCISC believes that the DCPP Nuclear Safety Oversight Committee is effective in advising plant management on items of nuclear safety and operational improvement. (4.9.3)
  7. DCPP’s 2013 total liquid and gaseous radiological releases were very small fractions of amounts permitted by regulations and Technical Specifications. The Radiological Environmental Monitoring Program confirmed that the operation of DCPP had no significant radiological impact on the environment in 2013. The results of the program were also compared to preoperational data and showed no unusual trends. Minute and diminishing traces of radioactivity from the radioactive releases that occurred in the March 2011 accident at Japan’s Fukushima Nuclear Plant were detected in one of DCPP’s four monitoring wells. (4.10.3)
  8. The QV audits reviewed by the DCISC Fact-finding Team were clear, detailed, and focused. (4.11.3)
  9. DCPP’s nuclear fuel has continued to function without any fuel failures since DCISC’s prior review of this topic in November 2011. Implementation of the Electric Power Research Institute’s (EPRI) guidelines for nuclear fuel management appears to have contributed positively to nuclear fuel performance and is aiding the continued preparation for transfer of used fuel to the Independent Spent Fuel Storage Installation. (4.12.3)
  10. DCPP appears to be sustaining its reduction of Critical Event Clock Resets since October 2012. Only two such resets have occurred since that time.
  1. Considerable attention and effort have been devoted during 2014 to enhancing DCPP’s Management Observation Program. This includes changing the basic approach from being somewhat critical of observed workers to being more supportive. The cooperative aspect of this program thus far has resulted in the identification of barriers to error free work, which can either be eliminated or addressed during the performance of work. This enhanced program is still in too early a stage to accurately evaluate its effectiveness with respect to worker performance. The results from DCPP Refueling Outage 2R18, which should be available in early 2015, may provide preliminary indications. (4.14.3)
  2. DCPP has dealt effectively with most equipment and system problems and is focused on improving system health. Systems that are the sources of emergency electrical power to the station’s vital electrical equipment, the station’s Emergency Diesel Generators and the 230 kV system that is supplied from the offsite electrical grid, were found to be operational but have been a focus of station and NRC attention. DCPP has been continuing to pursue preventive measures that are designed to strengthen the capabilities of exterior electrical equipment to better withstand the effects of high salinity in the local atmosphere and as aggravated by prolonged dry spells that have been interspersed with periods of light rain. 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. The System Engineer/Component Program continues to be effective. DCPP has improved its performance with Safety System Functional Failures. (4.15.3)
  3. The DCPP Steam Generators (SGs) have been performing as expected since their replacement in 2008 and 2009. The most important SG parameter, tube integrity, has been shown to meet all criteria as a result of visual inspection and Eddy Current testing. (4.16.3)
  4. DCPP’s statistical performance, in general, in refueling outage 1R18 reflected continuing improvement over that of earlier outages. Also, DCPP’s intended future outage focus on the reliability of electrical equipment appeared to be reasonable. The DCPP 2R18 Outage Safety Plan, used to assure nuclear safety during the outage, appeared comprehensive and clearly written, assuring the Defense-in-Depth philosophy to prevent accidents and to mitigate the effects of accidents, if they were to occur. DCPP’s 2R18 Refueling Outage met essentially all goals and was considered a success by DCPP. The DCISC considered 2R18 to be a success from a nuclear safety perspective. DCPP has a good clearance program, which continues to show effective protection of personnel and components. (4.17.3)
  5. The Safety-Security Interface appears to be satisfactorily implemented at DCPP. (4.18.3)
  6. The DCISC believes that DCPP is prudent in its planned campaigns to expand its Independent Spent Fuel Storage Installation (ISFSI) and move its spent fuel from the Spent Fuel Pools to the ISFSI in a timely manner. The potential chloride stress corrosion cracking issue in stainless steel spent fuel casks, which is not an urgent issue, is being addressed by the NRC and nuclear industry. The DCISC plans to monitor this issue. (4.19.3)
  7. DCPP’s progress on resolving its Workplace Personnel Seismic Safety issues has been satisfactory and responsive to the DCISC’s concerns. PG&E’s technical work on tsunami hazards at the DCPP site is well-planned, proceeding very well so far, and working on the correct set of problems. The DCISC concluded that the full DCISC should be engaged in reviewing whether the controversy over the plant’s seismic licensing basis raises a safety concern. The DCISC finds that the current project to develop probabilistic seismic hazard information about the Diablo Canyon site is going well. The DCISC will continue to follow the progress of this important work. (4.20.3)
  8. DCPP appears to be appropriately transitioning from its current “deterministic” Fire Protection Program (FPP) to the new “deterministic and risk-informed” National Fire Protection Association Standard NFPA-805. The DCISC learned in December 2013 that 16 impaired fire doors would not be repaired or replaced until 2017 due to funding deferrals and found this unacceptable. Following up in March 2014, the DCISC found that six doors had been repaired or replaced, and the remaining ten were the highest priority on the Plant Door Life Cycle Management Plan. The ten impaired doors are compensated for by fire watches, which, while acceptable, are not desirable. This is an acceptable start, and the DCISC will follow up on this issue. (4.21.3)
  9. The refresher training on Time Critical Operator Actions (TCOAs) for Licensed and Senior Licensed operations personnel was an exemplary training session. The instructor was highly knowledgeable and employed a variety of effective training techniques to keep the students engaged throughout the entire training period. Students from all areas of the classroom actively participated in the training. This training session could serve as a model for other refresher training sessions if the need should ever arise. The engineering training session on DC Power Systems was extensive and detailed. However, the interaction between the new instructor for this topic and the students was subdued, and the training session consumed considerably more time than had been planned for this topic. DCISC’s Maintenance Training Program was extensive and rigorous. The number and variety of inputs to training, both in-house and external to DCPP, contribute to the rigor of this program. DCISC’s future focus will be on individual, or related, issues that arise at DCPP and may have ties to training. (4.22.3)
  10. During this DCISC reporting period, the DCPP License Renewal Project to obtain NRC approval for a twenty-year extension of the operating license for each unit remained on hold for completion in 2015. The DCISC will resume its review upon the restart of Licensing Renewal activities. (4.23.3)
  11. The DCISC has found a number of potential nuclear safety issues with the use of cooling towers at DCPP. The DCISC intends to follow this issue over the next year or more and to review the operational safety implications of any proposal that would replace Once Through Cooling with cooling towers or different technologies
  1. The DCPP responses on Fukushima to NRC and the FLEX Initiative (post-Fukushima analysis and modifications) appeared well resourced, comprehensive, and on schedule to meet NRC and industry requirements. The DCISC will follow up periodically to assess DCPP’s progress. (4.25.3)


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. Electricity load growth in the geographic region around DCPP has resulted in voltage fluctuations on the 230kV system. DCPP is planning to compensate for these voltage fluctuations by installing VAR compensators in the 230kV switchyard on site. However, this load growth has also necessitated that DCPP transfer some nonessential 4kV loads to other power sources in order to maintain confidence that the 230kV system will be able to supply vital loads when called upon. It appears to the DCISC that the issue of 230kV system reliability extends beyond DCPP and also may involve the PG&E corporate organization. (4.15)
  2. The discovery in 2008 of a new earthquake fault just west of the plant site, the “Shoreline Fault,” has resulted in a multi-year technical effort to understand the fault and its possible effect on the plant’s ability to remain safe during a potential earthquake on that fault. The tentative conclusion of the NRC is that the plant’s current design is adequate, and the DCISC concurs. However, important technical work is ongoing to provide additional information about this fault and its potential effects. The DCISC has followed this issue from the start and will continue to do so. (4.20)
  3. Although the studies examining the possible replacement of a Once Through Cooling capability for DCPP’s main condensers are still in progress, the DCISC expressed a significant initial concern regarding the potential impact that such a modification would have on nuclear plant safety and reliability. (4.24)
  4. Though DCPP is performing well in implementing Fukushima initiatives, the significant number of changes will be challenging to learn, implement, and operate effectively. (4.25)

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.