Quantitative Performance Comparison of Japanese and American Nuclear Power Industries

Report Date: January 2004
Appendices: No

Executive Summary

There are significant differences in the performance of US and TEPCO BWRs. The US has steadily improved reaching energy availability values of 93 % while TEPCO plants are at levels in the 80 % range. Upon reviewing the reasons for the difference, it was observed that the TEPCO lost capacity is largely due to refueling outages (20% lost capacity) while the comparable US figure is about 5 %. Outages due to other factors (forced or other scheduled) are about the same in the 2% to 2.5 % levels.

It is quite clear that there are opportunities for TEPCO to reduce outage durations based on the performance of US BWRs. From a Japanese perspective the reduction in refueling outage is the most important matter to understand. In this study, the basic performance data of US BWRs was analyzed, interviews were held with outage management staff from the Pilgrim Nuclear Power Station and the Seabrook Nuclear Station, staff from the Nuclear Regulatory Commission and other industry officials, TEPCO management through the good services of Mr. Sakuragi to better understand the practices of each country that affect overall operating performance. This study does not include the recent extended outages of TEPCO units, thus it provides a good representation of TEPCO performance prior to 2002.

The reasons for US improvement were briefly analyzed. The results suggest that there are at least five significant factors that influenced and motivated improved performance. These factors are economic deregulation that forced utilities to review their operation for efficiencies; industrial cooperation in which all aspects of the industry work together to improve performance by applying benchmarks and best practices; with 900 reactor years of experience , the industry is able to address numerous technology problems by sharing the cost of developing solutions; information technology advances that allowed utilities to use this data in developing quantitative measures and tools for assessing performance; and finally regulatory changes largely driven by the trend to use Probabilistic Safety Analysis tools in risk informed performance based regulation.

There are also many significant differences in outage practices in Japan and the US that lead to the difference in operating performance especially during refueling outages. Part of it is driven by the regulatory requirements for maintenance, overhauls, and regulatory inspections. Part is due to utility and industry practices. The work scope in TEPCO outages is considerably higher due to utility choices and regulatory requirements for maintenance and upgrades. TEPCO has shown that when work scope is controlled and management focus is provided they can execute short (32 day) outages similar to US plants. This is not the norm, however.

The US uses risk informed tools to manage risk during operations and during outages. This has lead to opportunities to reduce work scope by shifting outage work to on line and manage outage activities to allow for more efficient work flow. US also uses outage planning and scheduling tools to plan and manage the outages which is not used in TEPCO. TEPCO also has a large number of special projects which take a significant amount of outage time. In the US such large projects have not been experienced recently. The US practice is to maintain plant components based on safety significance and operating performance of the component. In TEPCO, the approach is to maintain all equipment regardless of performance in the expectation that this will improve operating reliability.

In reviewing outage performance data, there are three major observations which identify the differences between the US and TEPCO. The first is there are many regulatory driven work items and practices such as inspections that lengthen the outage. The second is that the utility chooses many special projects and upgrades. The third is that for specific outage activities, TEPCO usually takes longer than comparable US plants. The reasons for the latter have not been investigated but they should be to determine whether benchmarking and the use of planning and scheduling tools might be of value to reduce the outage length..

While not all of the differences in outage performance can be attributed to the regulator, regulatory requirements and regulatory involvement during outages is very different in Japan and the United States. The difference in the regulatory practices of the two countries can be summarized as the Japanese regulations require significantly more work during the outages than the US regulator. They also have a more involved role during the outages in terms of requiring the witnessing of tests and inspections which can cause critical path delays. The regulatory approach in Japan is not risk informed, performance based which allows US utilities to make determinations on the need for maintenance and how and when that maintenance is performed.

Despite all these differences, the key indicator is whether the safety performance or operating reliability of the plants is materially different. The safety metrics of both the US and Japan show excellent performance at equally good operating reliability. This implies that despite the difference in maintenance philosophies and regulatory requirements, the performance of US plant equipment leading to problems is quite similar to TEPCO while taking shorter outages resulting in high operating performance.

It would appear that a careful review of Japanese regulatory requirements would be useful to determine which add value to the overall safety and reliability of the plants. Based on the US experience, introducing risk informed tools to this decision making process would be helpful in improving operational performance and reducing costs without compromising safety.

Program:     NSP Nuclear Systems Enhanced Performance

Type:     TR 

RPT. No.: 18