October 6, 2000

The Future of Uranium Enrichment Operations

Japan Nuclear Fuel Limited

Japan Nuclear Fuel Limited (JNFL) has conducted a review of some of the specifications for a component of the lower section of the centrifugal separator’s rotator. That review was conducted as part of preparations for the introduction of an enhanced centrifuge* in the latter half of the second phase (450 t SWU/a) of uranium enrichment plant construction. In the process of performance testing of the rotator component, a uranium compound was found adhering to the surface of the component, as was evidence of corrosion. (Notification was provided on March 31, 2000.) As a result of a comprehensive evaluation and study of the test results, we determined that the evidence of corrosion on the component opens the possibility that stress corrosion cracks may form. In addition, we have ascertained that stress corrosion cracks may be preventable by modifying the structure of the component. It should be noted, however, that because those structural modifications will be major, approximately nine years will be required before the modified component can be used. That is based on a minimum of approximately five years of work, including reconfirmation of their overall functioning, followed by testing to verify their practical applicability. It also includes the time required for obtaining the necessary permissions and approvals, manufacturing, and other steps. Meanwhile, since fiscal 1992 the Japan Nuclear Cycle Development Institute (JNC) has been engaged in ongoing development of a centrifugal separator (the advanced centrifugal separator*) to achieve higher performance. Its high separation performance, confirmed at 4 to 5 times that of the enhanced centrifugal separator, which itself features 2.5 to 3 times the performance of the unit currently in operation. Further verification testing is required to perfect the system for actual application. Through comprehensive analysis of the situation described, JNFL has decided to shift its development work to a different type of unit, called the new-model centrifuge*. We will accomplish that by taking over the enrichment technology of JNC, and combining that with the know-how gained in development of the enhanced centrifuge. By so doing, we believe that we can develop a high-performance and very economical new type of centrifugal separator. What's more, we expect to be able to accomplish that about a year earlier than would have been required if structural modifications were made to the enhanced centrifuge. As part of the development project, we have gathered together technicians from JNC, the Nuclear Fuel Machinery Co., Ltd., and our organization, and will establish the Uranium Enrichment Technology Development Center in the town of Rokkasho on November 1. The Development Center embodies the fruits of previous centrifuge development and know-how. Its test facility, now under construction in Rokkasho, will provide the focal point for the development of Japan's nuclear enrichment technology, and its work will be devoted to the new-model centrifuge. As for the centrifugal separator now in operation, we will work to make a smooth transition to a production system based on the new-model centrifuge. We will do so by applying what we have learned in our ongoing autopsy of the present unit, and we will continue to study methods of extending its operating life. We place the highest priority on not only achieving safety, but also on attaining long-term reliability. To realize those goals, we will make use of the lessons learned in the development of the enhanced centrifuge. We will first work to strengthen our systems for development, and then begin production using the new-model centrifuge, with a target date of around 2010. Thus approximately ten years will be spent with the aim of attaining 1,500 t SWU/a. The amount of time required for each phase of development will be as follows: Approximately two years for testing the technologies that will comprise the unit, approximately four years in testing to confirm the basic specifications, then about four more years in verification testing, final decision-making as to whether or not to adopt it, obtaining permissions and approvals, and construction.

Reference

1. Characteristics of the Centrifugal Separators (1) Enhanced centrifuge This is a centrifuge that, instead of a traditional metal centrifuge, employs a rotator composed of a new material (composite). In addition, by increasing the speed of rotation and the dimensions, it provides improved separation capability. In fact, its separation performance is 2.5 to 3 times that of a metal centrifuge. (2) Advanced centrifuge This is a centrifugal separator that JNC has been developing since fiscal 1992 with the aim of providing higher performance. (3) New-model centrifuge This is a centrifugal separator that seeks to achieve higher performance and economy. It seeks to do so by leveraging the know-how gained in the operation of uranium enrichment plant, and in the enhanced centrifuge and advanced centrifuge development projects. 2. History of the Enhanced Centrifuge Development * Starting in 1993, the former Power Reactor & Nuclear Fuel Development Corporation (the present JNC), electric power companies, and JNFL commenced joint research. * In March 1998, long-term reliability testing was commenced. That was prompted by the shut-down of the metal centrifuge, caused by what was surmised as the adherence of uranium compounds. * In April 1998, it was announced that the enhanced centrifuge would be used in the latter half of the second phase of plant construction. That centrifuge offered the promise of high separation capability and improved economy. Approval was requested in advance from the prefecture and town governments for the facilities expansion plans for the latter half of the second phase. * In July 1998, approvals were obtained from the prefecture and town governments. * In October 1998, a change was made in the time period for applying for a change in business operations (from October 1998 to March 1999). That was due to the fact that more time was needed for the long-term reliability testing. * In March 1999, the time period for applying for a change in business operations was again extended. * In September 1999, the results of long-term reliability testing of a component of the lower section of the rotator revealed that by revising some of the specifications, long-term reliability could be achieved. Thus upgraded rotator was incorporated in the centrifugal separator, and the start of performance tests using the group mounting was announced. * In March 2000, the following were announced: - Performance tests using the group mounting revealed that the initial goals for separation performance of the centrifuge had been achieved. - Long-term reliability tests revealed evidence of the adherence of uranium compounds and corrosion on the component of the lower section of the rotator. - Comprehensive evaluation and study was again started to determine the long-term reliability of the relevant component. 3. Results of Investigation Conducted during the Current Fiscal Year (1) Investigation of test conditions It was confirmed that the temperature and pressure conditions of the long-term reliability tests replicated those of an actual production machine, and that the test conditions were appropriate. It was confirmed that the component used in the tests had identical specifications to those of the component in the lower section of the rotator in the production machine. (2) Results of investigation into events that occurred We have determined that under the current specifications for the component in the lower section of the rotator, there is a possibility of damage due to cracks caused by stress corrosion on the component prior to the end of the operating life of the unit. (3) Description and results of countermeasures Modifying the method of processing the surface of the component in the lower section of the rotator did not produce satisfactory results. However, we now believe that the occurrence of stress corrosion cracks can be prevented by making structural changes. 4. Outline of the Uranium Enrichment Technology Center (1) Purpose of establishment Expert technicians required for the development of uranium enrichment technology will be recruited to create a centralized development system. The Enrichment and Disposal Office Centrifuge Test Facility, scheduled for completion in December of this year, will be utilized to aggressively pursue development of the new-model centrifuge. (2) Organization and staffing - Under the leadership of the Superintendent and Deputy Superintendent of the Uranium Enrichment Technology Center, the following groups and sections will be established for the conduct of research and development: Management Group, Engineering Group, Structural Design Group, Separation and Current Analyzing Group, Materials Development Group, and Testing Section - Technicians expert in enrichment will be hired from JNC, the Nuclear Fuel Machinery Co., and JNFL. (Development staff will be approximately 60 in number.) (3) Outline of the Enrichment and Disposal Office Centrifuge Test Facility - Location: Enrichment and Disposal Office at the Rokkasho Uranium Enrichment Plant - Characteristics: The only private facility in Japan possessing the equipment necessary for the development of enrichment technology. - Size of the facility: (1) Main building: Approximately 69 m x approximately 39 m (2) Power station: Approximately 17 m x approximately 7 m - Major facilities: (1) Test facilities Cascade testing facilities, continuous operation testing facilities, single centrifuge facilities, and materials testing facilities (2) Ancillary facilities UF6 handling facilities, on-site electrical facilities, ventilation and air conditioning facilities, radiation control facilities, controlled drainage processing facilities, storage facilities, analytic facilities, and others - History of construction: Start of Test Facility construction: August 1998 Scheduled completion: December 2000