Abstract

Performance indicators have been assuming an increasingly important role in the nuclear industry. An integrated methodology is proposed in this research for the identification and validation of performance indicators for assessing and predicting nuclear power plant overall performance (i.e., both economic and safety performance) in a systematic and quantitative way. The methodology consists of four steps: the selection of target sites/plants, the identification and refinement of candidate indicators, the collection of historical operating records of selected indicators, and the identification and evaluation of correlations between selected indicators and plant performance through data analysis. The methodology is centered upon individual plants, using plant-specific operation records to identify and validate plant-specific correlations. It can also be applied to multiple plants and the results from different plants can be compared to identify and analyze commonalities and differences in plant operations across-plant.

Case studies of the proposed methodology were performed at three target plants. A list of candidate performance indicators was identified through a sensitivity analysis on a quantitative model of nuclear power plant operation. The list was validated and supplemented through interviews with plant personnel and a refined, plant-specific list was obtained for each target plant. Historical operating records of candidate indicators in the lists were collected from target plants. Data analyses, including correlational analysis, multivariate regression analysis, and lead/lag time analysis, were performed using the historical data collected.

The methodology was originally intended for the identification of leading indicators, which can provide advance warnings of deterioration of performance before the direct outcome indicators are affected. A regression-based lead/lag time analysis method was proposed and applied in the case studies to evaluate lead/lag relationships between candidate indicators and plant performance. However, the method did not produce stable and reliable results by using the data currently available at the target plants and was not able to identify leading indicators with certainty. As a result, we shifted the focus of our data analysis to identifying correlations between candidate indicators and plant performance through correlational analysis and multivariate regression analysis.

Several findings are noteworthy: (1) Data analysis results were sensitive to the indicators and data points used, mainly due to the small number of data points (30~60) available for use in the analyses; (2) Data analysis results generally agreed with our knowledge and expectation, with a few exceptions; (3) Correlations showed large variations from plant to plant; (4) Correlations varied from time to time at most target plants; (5) The outcome indicators with smoother patterns (e.g., the INPO performance index) tended to correlate better with candidate indicators than the outcome indicators that measured relatively rare events and had sharp changes in their patterns (e.g., unplanned capability loss factor); (6) Work order backlogs stood out as important indicators for all three target plants; corrective maintenance generally showed a negative correlation with plant performance, while preventive maintenance generally showed a positive correlation with plant performance; (7) Supervisor availability and indicators measuring minor events were also identified to be important performance indicators.

A major finding of the project effort is that the data currently available at NPPs are not sufficient to validate and support formulation of industry-wide performance indicators. The data are too sparse and inconsistently formulated among different plants. In order for future analyses to produce more reliable results, the NPP operators need to adopt more extensive and more standardized data collection programs in order to improve the quality of the data set. Recommendations are provided on how these improvements should be made.

Abstract

A renewed interest in new nuclear power generation in the United States has spurred interest in developing advanced reactors with features which will address the public’s concerns regarding nuclear generation. However, it is economic performance which will dictate whether any new orders for these plants will materialize. Economic performance is, to a great extent, improved by maximizing the time that the plant is on-line generating electricity relative to the time spent off-line conducting maintenance and refueling. Indeed, the strategy for the advanced light water reactor plant IRIS (International Reactor, Innovative & Secure) is to utilize an eight year operating cycle.

This report describes a formalized strategy to address, during the design phase, the maintenance-related barriers to an extended operating cycle. The top-level objective of this investigation was to develop a methodology for injecting component and system maintainability issues into the reactor plant design process to overcome these barriers. A primary goal was to demonstrate the applicability and utility of the methodology in the context of the IRIS design.

The first step in meeting the top-level objective was to determine the types of operating cycle length barriers that the IRIS design team is likely to face. Evaluation of previously identified regulatory and investment protection surveillance program barriers preventing a candidate operating PWR from achieving an extended (48 month) cycle was conducted in the context of the IRIS design. From this analysis, 54 known IRIS operating cycle length barriers were identified. The resolution methodology was applied to each of these barriers to generate design solution alternatives for consideration in the IRIS design.

The methodology developed has been demonstrated to narrow the design space to feasible design solutions which enable a desired operating cycle length, yet is general enough to have broad applicability. Feedback from the IRIS design team indicates that the proposed solutions to the investigated operating cycle length barriers are both feasible and consistent with sound design practice.

Abstract

The objective of this report is to clarify the ways that organizational factors influence nuclear power plant performance in order to improve performance. Therefore, this report studied the nuclear power plant organizational environment by identifying and detailing its important work processes. These work processes are: the Work Request Work Process; the Condition Reporting Work Process; the External Operating Experience Work Process; the Design Change Process; and the Procedure Change Work Process. Using this information, a methodology of incident investigation that targets organizational deficiencies contributing to events was developed. Using this methodology to analyze recent significant incidents, a list of important organizational factors and the context within which they influence the successful completion of tasks was identified. These factors are: 1) Communication - Pervasive – Most important between different units and departments; 2) Formalization -Execution; 3) Goal Prioritization - Prioritization; 4) Problem Identification - Planning, scheduling, and return to normal line-up; 5) Roles and Responsibilities - Execution; and 6) Technical Knowledge (job specific knowledge and broad based knowledge) - Job specific knowledge – execution/ Broad based knowledge –prioritization, planning, scheduling, and other tasks.

Although safety culture and organizational learning are not listed, they are important. The reason for their exclusion is that they are not single organizational factors useful when cited in incident investigations. Rather, safety culture is a term used to describe all organizational factors, including organizational structure, that impact performance. Similarly, organizational learning was excluded because it is a collection of programs, processes, individual attitudes and culture responsible for learning. Although organizational learning was not listed, it was studied resulting in the development of the Utilization of Operating Experience Work Process. The Utilization of Operating Experience Work Process consists of the following seven steps: 1) Identification; 2) Screening/Prioritization/Dissemination; 3) Investigation/Evaluation; 4) Development; 5) Implementation; 6) Closeout; and 7) Verification/Validation. Since prioritization was identified as important in the above work process and the analysis of significant events, a methodology for the prioritization of work activities at nuclear power plants was developed. This methodology produces a prioritization tool that assigns a numerical performance index to each item requiring prioritization. Applying the methodology at Seabrook Station produced a tool that allowed those who prioritize external operating experience to more efficiently and accurately do so. In addition to the success of the application at Seabrook, a workshop was held at MIT with experts in prioritizing external operating experience. These experts further validated the methodology and the resulting tool.

The final piece of work in this report is an analysis of the NRC's revised oversight process as it relates to safety culture. The performance-based regulatory approach is appropriate for regulating safety culture. However, the NRC should continue the analysis of operating experience to identify additional organizational factors and the context within which they influence performance. Furthermore, they should develop performance indicators and measurement instruments for each organizational factor so that plants would be better able to take responsibility to proactively manage their safety culture.