Decommissioning of NPP A-1 and innovative technologies in the decommissioning

The first operated NPP in Slovakia was NPP A-1 Jaslovske Bohunice. Its reactor was cooled by CO2, and moderated by heavy water, and natural uranium was used as fuel (HWGCR type). It was in operation since 1972 and was finally shutdown in 1977 after the second accident (level 4 according to the International Nuclear Event Scale). NPP A-1 unit is in the preparation for decommissioning. The NPP A-1 decommissioning project started in 1998 and its first stage will end in 2007. The radiologically safe state of NPP A-1 is defined, in the plan as such state of the NPP A-1 at which it would be ensured that up to the time, when the NPP A-1 will be in a safe enclosure or in other stage of decommissioning, neither uncontrolled release of activity into environment would occur, nor other risks for environment or to NPP personnel could be reasonably expected from normal ageing of materials, equipment and barriers of the NPP A-1. Decommissioning was realised by Slovak electric P.l.c., now by GovCo, P.l.c., and VUJE, P.l.c., which has been chosen as a general supplier for the NPP A-1 decommissioning Project from 1999 to 2005. In the project these problems were solved: initial status characterization, determination of the task objectives, analysis and comparison of available methods for the task solution, choice of the method - justification, alternatives, research and development requirements, specification of requested equipment and other resources, radioactive waste (RAW) arisings - characteristics, RAW management, safety - doses, impact on environment, quantitative characteristics: time schedule, required personal, costs, doses etc. All spent fuel from NPP A-1 has been transported to Russia. Low and intermediate level radioactive waste has been partially treated and conditioned. Several innovative technologies were developed in the Project. Some of the most interesting ones are the following: 1. Treatment of radioactive sludge stored in underground storage tanks at NPP A-1 by movable open air cementation facility (OACF) developed for fixation of radioactive liquid waste in 200 l drums. The developed OACF allows waste immobilization in different kinds of inorganic matrixes. It has employed in drum mixing and thus the final product is waste fixed in stable matrix stored in 200 l drums; 2. Treatment of spent aerosol filters (HEPA) on workstation for treatment spent aerosol filters (WTSAF). WTSAF operates using the shredding technology for volume reduction and separation of cartridge filters parts to metallic and aluminium parts from HEPA filters. After separation process, antimicrobial inhibitors are added to organic cartridge filters and all system is compacted in 200 l drums. WTSAF is in test operation now. The decommissioning Project and innovative technologies used for treatment of radwaste from decommissioning have been fully described in poster presentation. (author)