Nuclear Regulation:

NRC Needs to More Aggressively and Comprehensively Resolve Issues Related to the Davis-Besse Nuclear Power Plant's Shutdown

GAO-04-415: Published: May 17, 2004. Publicly Released: May 18, 2004.

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In March 2002, the most serious safety issue confronting the nation's commercial nuclear power industry since Three Mile Island in 1979 was identified at the Davis- Besse plant in Ohio. After the Nuclear Regulatory Commission (NRC) allowed Davis-Besse to delay shutting down to inspect its reactor vessel for cracked tubing, the plant found that leakage from these tubes had caused extensive corrosion on the vessel head--a vital barrier preventing a radioactive release. GAO determined (1) why NRC did not identify and prevent the corrosion, (2) whether the process NRC used in deciding to delay the shutdown was credible, and (3) whether NRC is taking sufficient action in the wake of the incident to prevent similar problems from developing at other plants.

NRC should have but did not identify or prevent the corrosion at Davis- Besse because its oversight did not generate accurate information on plant conditions. NRC inspectors were aware of indications of leaking tubes and corrosion; however, the inspectors did not recognize the indications' importance and did not fully communicate information about them. NRC also considered FirstEnergy--Davis-Besse's owner--a good performer, which resulted in fewer NRC inspections and questions about plant conditions. NRC was aware of the potential for cracked tubes and corrosion at plants like Davis-Besse but did not view them as an immediate concern. Thus, NRC did not modify its inspections to identify these conditions. NRC's process for deciding to allow Davis-Besse to delay its shutdown lacks credibility. Because NRC had no guidance specifically for making a decision on whether a plant should shut down, it used guidance for deciding whether a plant should be allowed to modify its operating license. NRC did not always follow this guidance and generally did not document how it applied the guidance. The risk estimate NRC used to help decide whether the plant should shut down was also flawed and underestimated the amount of risk that Davis-Besse posed. Further, even though underestimated, the estimate still exceeded risk levels generally accepted by the agency. NRC has taken several significant actions to help prevent reactor vessel corrosion from recurring at nuclear power plants. NRC has required more extensive vessel examinations and augmented inspector training. However, NRC has not yet completed all of its planned actions and, more importantly, has no plans to address three systemic weaknesses underscored by the incident. Specifically, NRC has proposed no actions to help it better (1) identify early indications of deteriorating safety conditions at plants, (2) decide whether to shut down a plant, or (3) monitor actions taken in response to incidents at plants. Both NRC and GAO had previously identified problems in NRC programs that contributed to the Davis-Besse incident, yet these problems continue to persist.

Status Legend:

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  • Review Pending-GAO has not yet assessed implementation status.
  • Open-Actions to satisfy the intent of the recommendation have not been taken or are being planned, or actions that partially satisfy the intent of the recommendation have been taken.
  • Closed-implemented-Actions that satisfy the intent of the recommendation have been taken.
  • Closed-not implemented-While the intent of the recommendation has not been satisfied, time or circumstances have rendered the recommendation invalid.
    • Review Pending
    • Open
    • Closed - implemented
    • Closed - not implemented

    Recommendations for Executive Action

    Recommendation: To ensure that NRC aggressively and comprehensively addresses the weaknesses that contributed to the Davis-Besse incident and could contribute to problems at nuclear power plants in the future, the NRC commissioners should develop specific guidance and a well-defined process for deciding on when to shut down a nuclear power plant. The guidance should clearly set out the process to be used, the safety-related factors to be considered, the weight that should be assigned to each factor, and the standards for judging the quality of the evidence considered.

    Agency Affected: Nuclear Regulatory Commission

    Status: Closed - Implemented

    Comments: Although NRC believes that the risk-informed decision-making process set out in its Regulatory Guidance 1.174 is generally applicable to a wide range of decisions that NRC makes, it agreed that it would be useful to develop additional risk-informed guidance on how to address emergent issues. NRC said that therefore it will develop additional regulatory guidance to expand the application of risk-informed decision-making. NRC also agreed that it lacked sufficient and appropriate documentation of its decision on Davis-Besse and said that it was committed to making sure future decisions are documented in a proper and timely manner. As a result of this effort, NRC developed a process that provides guidelines for making and documenting risk-informed decisions for those issues that are not addressed by current NRC processes. In addition to providing specific guidelines for taking regulatory actions, this office instruction emphasizes the need to document and communicate the results from analyses performed as part of this process, including any uncertainties in the analyses, to support fully informed and timely management action. In September 2005, the process was released for trial use as an Office of Nuclear Reactor Regulation Instruction LIC-504, "Integrated Risk-Informed Decision Making Process for Emergent Issues." Based on comments received during the initial trial period, the process was revised to provide additional clarity and re-released as a final document in December 2005.

    Recommendation: To ensure that NRC aggressively and comprehensively addresses the weaknesses that contributed to the Davis-Besse incident and could contribute to problems at nuclear power plants in the future, the NRC commissioners should develop a methodology to assess licensees' safety culture that includes indicators of and inspection information on patterns of licensee performance, as well as on licensees' organization and processes. NRC should collect and analyze this data either during the course of the agency's routine inspection program or during separate targeted assessments, or during both routine and targeted inspections and assessments, to provide an early warning of deteriorating or declining performance and future safety problems.

    Agency Affected: Nuclear Regulatory Commission

    Status: Closed - Implemented

    Comments: In July 2006, NRC implemented changes to incorporate safety culture into its process for overseeing nuclear power plant operations. In doing so, it used two overall approaches. First, it issued additional guidance for identifying and addressing cross-cutting issues, which relate to aspects of safety culture. Second, it provided a structured way to determine the need to evaluate plants' safety culture. While the three cross-cutting issues (problem identification and resolution, human performance, and safety conscious work environment) did not change, NRC developed new definitions for them to more fully encompass safety culture aspects. Also, NRC developed additional guidance on the cross-cutting issues' treatment once they have been identified. If the same substantive cross-cutting issue is identified in three consecutive assessment periods, NRC may request a plant to formally evaluate its safety culture. In certain circumstances, NRC may request a plant to independently evaluate its safety culture, with any deficiencies identified entered into the corrective action program.

    Recommendation: To ensure that NRC aggressively and comprehensively addresses the weaknesses that contributed to the Davis-Besse incident and could contribute to problems at nuclear power plants in the future, the NRC commissioners should develop a management control approach to track, on a long-term basis, implementation of the recommendations made by the Davis-Besse lessons-learned task force and future task forces. This approach, at a minimum, should assign accountability for implementing each recommendation and include information on the status of major actions, how each recommendation will be judged as completed, and how its effectiveness will be assessed. The approach should also provide for regular--quarterly or semiannual--reports to the NRC commissioners on the status of and obstacles to full implementation of the recommendations.

    Agency Affected: Nuclear Regulatory Commission

    Status: Closed - Implemented

    Comments: NRC agreed with the recommendation and the importance of having a management control approach to tracking, on a long-term basis, implementation of recommendations made by the Davis-Besse and future task forces. According to NRC, the management control approach that NRC is using was set forth in the implementation plan for the Davis-Besse Lessons-Learned Task Force recommendations submitted to the NRC Commissioners in 2003. Furthermore, NRC has taken some additional actions since issuance of GAO's report. A detailed effectiveness review of the actions taken in response to past lessons learned reviews was completed in August 2004 and the results are being evaluated. Moreover, a process for proposing and approving any deviations to the Davis-Besse Lessons Learned implementation plan was recently developed. The plan includes the development of four action plans and semiannual status reports to the Commissioners. The action plans included scheduled completion dates and designations of accountability. In addition, a column was added to the semiannual status reports to the Commissioners to track the status of the effectiveness reviews for each recommendation. According to NRC, this management control approach will be used for future task force recommendations.

    Recommendation: To ensure that NRC aggressively and comprehensively addresses the weaknesses that contributed to the Davis-Besse incident and could contribute to problems at nuclear power plants in the future, the NRC commissioners should determine the resource implications of the task force's recommendations and reallocate the agency's resources, as appropriate, to better ensure that NRC effectively implements the recommendations.

    Agency Affected: Nuclear Regulatory Commission

    Status: Closed - Implemented

    Comments: NRC developed an overall plan to implement the recommendations of the Davis-Besse Lessons Learned Task Force and resources were reallocated to implement the high-priority recommendations. In addition, resources were allocated to implement the other recommendations. NRC has implemented almost all the task force's recommendations.

    Recommendation: To ensure that NRC aggressively and comprehensively addresses the weaknesses that contributed to the Davis-Besse incident and could contribute to problems at nuclear power plants in the future, the NRC commissioners should improve NRC's use of probabilistic risk assessment estimates in decision making by (1) ensuring that the risk estimates, uncertainties, and assumptions made in developing the estimates are fully defined, documented, and communicated to NRC decision makers; and (2) providing guidance to decision makers on how to consider the relative importance, validity, and reliability of quantitative risk estimates in conjunction with other qualitative safety-related factors.

    Agency Affected: Nuclear Regulatory Commission

    Status: Closed - Implemented

    Comments: NRC agreed with our recommendation, stating that it remains committed to continuous improvement in using probabilistic risk assessment (PRA) estimates in decision-making. To further implement its Regulatory Guide 1.174, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to Licensing Bases," NRC, in February 2004--as we were nearing issuance of our report--issued Regulatory Guide 1.200, "An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities," for trial use. Subsequently, in October 2005 the Office of Nuclear Reactor Regulation issued office instruction LIC-504, "Integrated Risk-Informed Decision-Making Process for Emergent Issues," and revised this instruction in December 2005 and February 2007. NRC continues to focus on developing improved methods for calculating risk in support of the risk-informed regulatory decision making by (1) developing and evaluating alternative formal methods for using risk information in decision-making, (2) improving methods and practices for implementing human reliability analysis, and (3) developing methods and tools for quantifying and assessing uncertainties in a complex engineering assessment.

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