[en] Prototype nuclear power plant A-1 located at Jaslovske Bohunice, was a HWGCR with channel type reactor KS 150 (refuelling during operation) and capacity of 143 MWe. Single unit has been constructed with reactor hall building containing reactor vessel, heavy water system and equipment for spent fuel handling. Another compartment of main building contents coolant system piping, six steam generators and six turbo compressors, the turbine hall was equipped by three turbines. Unit also shares liquid radwaste treatment and storage buildings and ventilation systems including chimney. It started operation in 1972 and was shutdown in 1977 after primary coolant system integrity accident. In 1979 a final decision was made to decommission this plant. The absence of waste treatment technologies and repository and not sufficient storage capacity affected the planning and realization of decommissioning for NPP A-1. The decommissioning policy for the first stage is for lack of regulations based on 'case by case' strategy. For these reasons and for not existence of Decommissioning Found until 1995 the preferred decommissioning option is based on differed decommissioning with safe enclosure of confinement. Transfer of undamaged spent fuel cooled in organic coolant to Russia was finished in 1990. It was necessary to develop new technology for the damaged fuel preparation for transport. The barriers check-up and dismantling of secondary circuit and cooling towers was performed during 1989/90. The complex plan for the first phase of A-1 decommissioning - the status with treated operational radwaste, removed contamination and restored treated waste and spent fuel (in case of interruption of transfer to Russia) was developed in 1993-1994. Under this project bituminization of all liquid operational radwaste (concentrates) was performed during 1995/96, vitrification of inorganic spent fuel coolant started at 1996, decontamination of spent fuel pool coolant occurs (under AEA Technology support) in 1997 as well as preparation for bituminization of organic spent fuel coolant. The new equipment for spent fuel handling including new storage (semi dry) for spent fuel was projected and should be built up in 1997. The decontamination and dismantling of auxiliary equipment (radwaste tanks, evaporation plant and original solid storage) should start after the commissioning of conditioning centre and bituminization plant with new evaporation plant in 1998 and finish at 2000. The decontamination and dismantling of original spent fuel storage should finish at 2007/8. Supporting activities to these works started at 1994/95. (author)