Getting ready for final disposal in Finland - Independent verification of spent fuel

Full text: Final disposal of spent nuclear fuel has been known to be the solution for the back-end of the fuel cycle in Finland already for a long time. This has allowed the State system for accounting and control (SSAC) to prepare for the safeguards requirements in time. The Finnish SSAC includes the operator, the State authority STUK and the parties above them e.g. the Ministry for Trade and Industry. Undisputed responsibility of the safe disposal of spent fuel is on the operator. The role of the safety authority STUK. is to set up detailed requirements, to inspect the operator plans and by using different tools of a quality audit approach to verity that the requirements will be complied with in practice. Responsibility on the safeguards issues is similar with the addition of the role of the regional and the international verification organizations represented by Euratom and the IAEA, As the competent safeguards authority, STUK has decided to maintain its active role also in the future. This will be reflected in the future in the increasing cooperation between the SSAC and the IAEA in the new safeguards activities related to the Additional Protocol. The role of Euratom will remain the same concerning the implementation of conventional safeguards. Based on its SSAC role, STUK has continued carrying out safeguards inspections including independent verification measurements on spent fuel also after joining the EU and Euratom safeguards in 1995. Verification of the operator declared data is the key verification element of safeguards. This will remain to be the case also under the Integrated Safeguards (IS) in the future. It is believed that the importance of high quality measurements will rather increase than decrease when the frequency of interim inspections will decrease. Maintaining the continuity of knowledge makes sense only when the knowledge is reliable and independently verified. One of the corner stones of the high quality of the Finnish SSAC activities is based on the active independent verification of declared data One of the difficulties that may be related to the final disposal will be old fuel, especially fuel with missing verified knowledge or fuel with poorly maintained continuity of knowledge. The Finnish SSAC has avoided this potential future problem in time by carrying out NDA verification measurements of spent fuel in a systematic manner since the beginning of the interim storing 1987. Data and spectra of the measurements have been stored into a spent fuel measurement database FISDAM (Finnish Safeguards Database of Measurements) maintained by the safeguards office of STUK. The NDA methods used are based on the detection of spent fuel specific signals i.e. fission product gamma rays or passive neutron emission from actinides. Final verification of spent fuel upon the final disposal is planned to be based on the FISDAM data followed by partial defect/rod level verification of all declared irradiated nuclear material. This will allow the SSAC to gain very high assurance that the data of the disposed material will be correct and complete. The SSAC verification activities may also form of close future cooperation with the IAEA and Euratom according to the principles of the Additional Protocol. Systematic and accurate measurements are an essential feature of the Finnish SSAC understanding of good safeguards. All present and future questions concerning declared data will be verified in time. The approach selected ensures that no undue burden is transferred to the future generations due to partially or poorly filled safeguards obligations The paper discusses the activities and results gained by the SSAC in addition to the programs and plans related to preparing for the final disposal safeguards needs, with special emphasis on the spent fuel NDA verification issues. (author)