Management of the radioactive waste generated from refurbishment of research reactor (IRT-2000)

Objectives: The main objective of the management of the radioactive waste (RAW) generated from refurbishment of research reactor IRT-Sofia is to achieve a condition not allowing occurrence of radiation impact on the staff, population and environment now and in the future. Meanwhile, it aims to reduce RAW quantities and types subject to treatment, control, storage and expansion of the capabilities to reuse equipment and material. The main objective of RAW treatment is their exemption of radiation control on the part of National Regulatory Authority. Results: RAW quantities are classified according to their activity and material type based on the effective Regulation No. 7 of the Nuclear Regulatory Agency. The equipment decontamination methods are in conformity with: the equipment type and selection of decontamination solutions; equipment overall dimensions; capabilities for higher decontamination rate; capabilities to use smaller amounts of decontamination solutions and generate less waste quantities; decontamination period. When selecting the technical solutions for safety assurance during dismantling of equipment and temporary storage of RAW generated from the refurbishment of IRT-Sofia the Regulations in Bulgaria are considered. Also, the experience of other countries performing reconstruction and decommissioning of such types of research reactors is taken into account. Also, the Kozloduy NPP experience in this regard as well as the ideas set out in the existing operation instructions of Kozloduy NPP for RAW treatment are implemented. The objective of each technical solution is related to the minimum dose exposure of the personnel involved in dismantling activities as well as to the finding out of the most suitable form of final storage of the obtained waste. The necessity of localization of the radioactive contamination in the compartments where dismantling activities are performed and in the auxiliary compartments designated for decontamination and storage before RAW treatment, packaging and transportation is taken into account in the development of the technical solutions. The suitability of the available compartments and their ensuring systems for temporary storage of the generated RAW is taken into account too. These compartments are provided with special vents, decontamination and other auxiliary systems. Transportation and temporary storage packages for decontaminated waste solid RAW are indicated. Conclusions: The classification of RAW generated and expected in the future from dismantling activities according to the table classification show that RAW activity levels regardless the long reactor operation life time are not getting higher. After the equipment decontamination is performed a reiterated reduction of activity is anticipated. The reason is the main specific activity is caused by isotopes, which are piled up in the surface oxide layer of the metal. The objective of the present paper is to indicate the treatment way for the Low and Intermediate RAW which will be accumulated during IRT - Sofia research reactor refurbishment as well as the RAW accumulated during the future reactor operation. The suitable first circuit water chemistry regime will lead to lower equipment activity levels during the operation of the reconstructed and modernized IRT-2000 research reactor. A conclusion could be made that there are some methods and means for radioactive equipment decontamination and treatment, which enable avoiding environment pollution and not imposing undue burdens on future generations. (authors)