Since 1980, the National Agency ONDRAF/NIRAS has been responsible by law for the safe management of all radioactive waste produced in Belgium, including decommissioning waste. In 1991, its responsibility was extended by Royal Decree of 16.10.91 to the field of decommissioning, its main specific assignments being: • The collection and evaluation of data (physical and radiological inventories) from nuclear plants; • The approval of decommissioning programmes, including decommissioning cost evaluations and mechanisms of funding. Already in the early 90s, ONDRAF/NIRAS started with the implementation of its own integrated data processing system, recording the physical and radiological inventories of nuclear plants and allowing the evaluation of the quantities of decommissioning materials and waste as well as of the decommissioning costs of the plants. In 1997, the law on the inventory of nuclear liabilities of 12.12.97 completed and enforced the decree of 1991, stating that the agency will: • Draw up a register specifying the location and condition of all nuclear facilities and all sites containing radioactive substances on Belgian territory; • Estimate the cost of decommissioning and cleaning up these facilities and sites; • Evaluate the availability of sufficient funds to carry out these future or ongoing operations; • Update the inventory every five years. As a result, during these last few years, ONDRAF/NIRAS had to deal with an increasing amount of decommissioning data (submission of inventories, new decommissioning plans and also a first batch of five-yearly revisions) concerning a larger diversity of facility types (enlargement of activities to “smaller” licensees, like universities, hospitals, etc). Simultaneously and consequently, ONDRAF/NIRAS faced the need to integrate a larger range of field-experienced decontamination and dismantling techniques, performed by different decommissioning companies, in order to obtain more refined and “pertinent” cost evaluations. For the same purposes, it appeared necessary to consider alternative waste processing possibilities, especially for very low-level waster arising from decommissioning activities. In 2000, ONDRAF/NIRAS started to upgrade its Decommissioning Management System (DMS) in order to enhance the quality of the database (integrity, intrinsic validity, extrinsic validity, completeness and accuracy) and simultaneously to develop the flexibility and the abilities of the evaluation functions. This paper presents and describes the latest version of the ONDRAF/NIRAS DMS (the data model, interface facilities, and the calculation and reporting possibilities) putting emphasis on experience gained and on some of the first lessons learned. The two first sections of this paper give an overview of the National Agency’s main missions and outline the information and data collection process in the framework of decommissioning and inventory. Indeed, the context in which the updated DMS was developed and the difficulties encountered during the data collection process should inform the reader about the way the upgrading of the data system has been thought out and the alternatives the National Agency had to deal with. In the third section, the main functionalities of the DMS modules are set out in concrete terms, the main modules being: • The “Inventories” module, recording their physical and radiological inventories for the sites that fall within the scope; • The “Techniques” module, integrating measurement, decontamination, dismantling and special recycling techniques, as well as their unit cost elements; • The “Waste” module, integrating standard and special waste categories, their packaging, transportation and processing possibilities, as well as their unit cost elements; • The “Nominal Forecast” module, linking an inventory to selected techniques and waste costs, associated with the “best estimate” reference calculation scenario; • The “Scenario” module, dealing with the storage and evaluation of alternative scenarios (pessimistic or optimistic ones, deferred dismantling, etc). The last section focuses on experience gained through developing the upgraded DMS and putting it into operation. Some potentialities of the upgraded DMS are also discussed.

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