A1 NPP Decommissioning
At the time of the final shutdown of the A1 NPP, the required procedures and equipment to secure all necessary decommissioning activities were not yet in place.
In Czechoslovakia, at that time, there was no applicable legislation specifying the frames of the nuclear facilities decommissioning or technical conditions for implementation of such activities. Apart from legislative and administrative conditions and staffing required for these activities, specific technological facilities for management of radioactive waste (RAW) and spent nuclear fuel, including the repository for final disposal of RAW and related transport means were being gradually designed and constructed.
Works executed by 1994 were focused primarily on elimination of consequences of the operational events. Subsequently, the pre-decommissioning activities were in progress by 1999. These activities included dismantling of several technological facilities, creation of areas required for installation of technological facilities intended for management of radioactive materials, decontamination of selected areas/premises, mainly in the main reactor building and transport of spent nuclear fuel used in the A1 NPP reactor outside the territory of the Slovak Republic.
The process of decommissioning commenced after the license for decommissioning was obtained in 1999. This process has been divided into five, subsequent stages with time schedule specified by 2033.
First Stage of Decommissioning
The objective of the 1st stage of decommissioning was to secure a safe radiation state of the A1 NPP. Activities implemented in this stage addressed the following tasks: long-term storage, processing of liquid RAW in external buildings, contaminated waters and technological facilities in the plant main reactor building. Preparation of future projects focusing on decontamination and removal of the primary circuit systems/equipment and also revision of priorities focused on extended monitoring of the heavy-water and gas circuit reactor.
Second Stage of Decommissioning
The activities of this stage are focused on removal of environmental loads from the A1 external buildings, removal and sorting of contaminated soil and concrete debris and monitoring and treatment of underground and leaking water, treatment and conditioning of historical RAW and RAW from the A1 NPP decommissioning, decommissioning of technological equipment and civil units of external buildings and buildings of A1 main reactor building and decommissioning of long-term storage for spent nuclear fuel.
Within the second stage, the disposal facility for very low level waste in nuclear facility of NRR Mochovce is also to be erected, within the scope of first module erection, designated for disposal of very low level waste from the A1 NPP decommissioning.
Third and Fourth Stage of Decommissioning
After the second stage, it is continually proceeded to the connected third and fourth stage. Activities will be focused on decommissioning of long-term storage for A1 NPP nuclear spent fuel, processing of sludge from long-term storage, casks of long-term storage of nuclear spent fuel and liquid RAW from the external tanks of storage place for liquid RAW, decommissioning of mutually connected technological parts, (steam generators with accessories, turbo compressors, section valves).
Fifth Stage of Decommissioning
The subject of the final stage of A1 NPP decommissioning is the nuclear reactor itself and connected equipment in reactor shaft, short-term storage, long-term storage pool for spent nuclear fuel and equipment situated in Reactor Hall, which were installed and used for the decommissioning process itself. From the previous stages, decommissioning of remaining steam generators with accessories will continue. From decommissioning of such equipment, certain quantity of RAW cannot be disposed of at the National Repository for low level waste and will be stored in the Interim Storage of RAW until the deep geological repository is erected.
Impact of activities of A1 NPP decommissioning on environment during the individual decommissioning phases is prior to its beginning publicly assessed within the EIA process in accordance with the Act No. 24/2006 Coll. on Environmental Impact Assessment. In the process of A1 NPP decommissioning are the elements influencing the environment mainly gaseous and liquid discharges of radioactive waste, of which values reach units or fractions of percentage from the allowed limits by legislation for free release of radioactive substances into environment.
Majority of waste meets the limits for disposal at the National Repository of RAW, part of waste will be in the future stored in deep geological repository and large amount of material is after its decontamination, pursuant to rigid legislation limits for free release of radioactive material, free released into environment.
A1 NPP decommissioning process is continual and regarding the concept of operation termination, it is a very complex and specific process. During its demanding implementation, safety is the main criterion of all activities, and therefore, in respect of nuclear safety and radiation protection, no substantial negative impact of such activities on the environment was recorded. Decommissioning works are implemented continually pursuant to strategic document approved by the Slovak Government “The proposal of national policy and national programme for spent fuel management and radioactive waste in the Slovak Republic” as an update of the strategic document “The Strategy of final stage of peaceful use of nuclear energy in the Slovak Republic” in accordance with procedure of EC 2011/70/Euratom with an objective to fully free release the plant site for its further industrial use.