Design information verification (DIV) of conditioning plant for geological repositories (SAGOR activity 3a)

Following IAEA Advisory and Consultants Group meetings in September 1988 and in May 1991 respectively an IAEA multi-national Support Programme Task was initiated to consider the 'Development of Safeguards for Final Disposal of Spent Fuel in Geological Repositories' (SAGOR). A Technical Coordination Committee (TCC) was set up with invited representatives from those Member State Support Programmes wishing to be involved. The joint programme, through the TCC, was given the task of studying the safeguards requirements in: conditioning plant (where the spent fuel is prepared for transfer to the repository); operating repositories (i.e. those in which the fuel is being emplaced); closed repositories. At the first meeting of the TCC in Washington in July 1994 the UK undertook to provide a study of the Design Information Verification (DIV) required in all three areas. For this activity the requirements, techniques and procedures for the Design Information Verification (DIV) of conditioning plant have been considered. In completing the study the findings reported for Activities 1a and 2a (descriptions of a Model Facility and Potential Diversion Paths, respectively) have been used in formulating any conclusions reached. The findings of Activity 1a show that a conditioning plant will be far simpler in concept than is a reprocessing plant. From this it must be concluded that DIV is unlikely to present any significant problems; experience based on reprocessing plant shows that it can be done both efficiently and effectively using proven techniques. In section 3.2, however, a number of valuable techniques which are currently being developed are also described. These have potential for effecting better DIV and could provide further evidence that the declared designs are (or are not) being fully complied with. More general DIV requirements are described in section 4. Like the detailed considerations mentioned above, these are no different from those already being applied in reprocessing plant and, in conditioning plant, the requirements will be less arduous. For section 5 the possible diversion routes identified in Activity 2a have been considered in detail. Figures 1a, 1b, and 1c are the same as those in the report for Activity 2a but have been modified to indicate three types of area: those where it is considered that DIV is the only means of identification; those areas where DIV will provide essential help to other techniques, such as Containment and Surveillance (C and S); those areas where DIV cannot help. In section 6 a draft Quality Plan for the completion of the DIV of a conditioning plant is provided. This is a check list of the activities which the IAEA will have to undertake from the initial inception of the project to its becoming an active plant. Any ongoing DIV needed during the active life of the plant is not included although, as suggested in section 2.7, this will be necessary in much the same way as now done in reprocessing plant. Finally, the relative simplicity of conditioning plant must not be allowed to hide the one salient feature where it differs from reprocessing plant. Once the spent fuel has been sealed in a canister it becomes very difficult, and almost prohibitively expensive, to reverify. 'Continuity-of-Knowledge' from its receipt at the plant right up to final emplacement in a repository, backfilling, and beyond is paramount. DIV of the conditioning plant, and the containers and casks used to hold the spent fuel, must ensure that all of the other C and S techniques which are used are as effective as it is possible to make them. This, it is believed, can best be implemented by ensuring that the involvement of the IAEA is started at as early a stage as possible and not left until the 180 days before the plant becomes active. This early stage is referred to as being that of 'informal' DIV but it is hoped that it will eventually become a formal requirement. This should lead to improved safeguards and potential savings to the operator as changes made at a late stage can be difficult and costly to implement