- Nuclear Installations in Slovakia
- Basic Data on Radioactivity
- Radiological Situation Monitoring
- Classification of Events
National Radioactive Waste Repository (RÚ RAO)
RÚ RAO Mochovce is a multi-barrier surface-type repository designed for the final disposal of solid and solidified low and very low-activity radioactive waste produced from the operation and decommissioning of nuclear facilities, research institutes, laboratories and hospitals in the Slovak Republic.
The appropriate location of the repository was selected on the basis of engineering, geological and hydrogeological survey. The selection criteria corresponded to the legislation in force, the IAEA safety guides, the requirements for the siting of nuclear facilities and the proposed disposal project, the properties and form of disposed radioactive waste were also taken into account. Construction work on the repository began in 1986 with the construction of clay seal, an important element separating disposed radioactive waste from the environment. The inclusion of the repository among the nuclear installations entailed increased requirements for the quality of the works carried out. For this reason, and based on the recommendations of the IAEA mission, a number of changes have been proposed and implemented in the next period aimed at improving the nuclear safety of the disposal system. The repository was put into operation in 2001.
Protective barriers against the leakage of radioactivity into the environment represent all structures engineered and natural, which are used to separate disposed radwaste from the environment and to prevent the migration of radionuclides into the environment. The multi – barrier concept for the repository for the disposal of low-activity radioactive waste consist of a matrix in which the waste is fixed, a wall of fibre concrete containers (FCCs), reinforced concrete construction of the repository, the backfilling, multi-layered final cap and clay basin. The last barrier is the low-permeable geological formation. In case of extremely unfavourable conditions with water penetration into the interior of the disposal boxes, within the clay basin, the repository is equipped with a drainage system designed for the collection and control of water. The drainage system is one of the engineering barriers that help to prevent negative environmental impacts of the repository.
The low-level radioactive waste (LLRAW) repository consists of a set of disposal boxes arranged in rows and double rows. Double rows are covered with a movable steel hall. The boxes are made of reinforced concrete with dimensions of 18 x 6 x 5.5 m, the wall thickness is 600 mm. One double row consists of 40 boxes and each box can take 90 fibre concrete containers with dimensions of 1.7 x 1.7 x 1.7 m and a wall thickness of 0.1 m. The total capacity of the three double-rows built so far is 10,800 fibre concrete containers which corresponds to the volume of 33,480 m3. Currently, the second double row is being filled. The second double row is expected to be fully filled by the end of 2024. The third double row is expected to be filled by the end of 2032. The repository is designed up to 7.5 double rows, which will be completed gradually according to the production levels of low-activity radioactive waste.
Conditioned low-level radioactive waste (LLRAW) is transported to the repository, fixed with cement mixture in fibre-concrete containers from the Bohunice Treatment Centre and also from the treatment facility of FS KRAO in Mochovce. After the initial inspection, the marked containers shall be transferred from the transport vehicle to the disposal box to a predetermined location.
Due to the early shutdown of two units of NPP V1 in Jaslovské Bohunice, the need to build additional disposal capacities within the existing RÚ RAO Mochovce area for the efficient and safe disposal of very low-activity radioactive waste (VLLRAW) from decommissioning, has increased. Only solidified VLLRAW waste are accepted for disposal in trenches. No liquid or gaseous waste can be admitted to the repository.
VLLRAW handling packages are grouped into different groups, taking into account the origin of the radwaste, their characteristics and treatment. Typical very low-level radioactive waste includes contaminated soil, contaminated concrete debris, contaminated insulating material, etc. in big-bags or MEVA drums.
The VLLRAW repository is designed and implemented for a total capacity of 68,000 m3 and the disposal areas of the repository are built gradually in three phases:
- Phase I: 1 construction of part 1 – module for 20,000 m3 from decommissioning of NPP A1 (this part has been in operation since 2016)
- Phase II: construction of part 2 – module for 9,000 m3 (+100 m3 reserve) for decommissioning of NPP V1 (this part has been in operation since 2017)
- Phase III envisages the construction of the 3rd part for the remaining volume of disposal capacity in the future (39,000 m3), respectively, as appropriate, according to the production of VLLRAW waste
Part of the disposal area is also the roofing of the currently loaded disposal trench to protect against adverse weather conditions and auxiliary, directly related equipment such as drainage, shafts and leakage control tanks.
VLLRAW disposal is carried out by gradual filling of the module, which is formed by the bottom and walls of the module. When the disposal trench is full, the roofing is moved to the next (adjacent) part of the disposal module.
As of 14 September 2019, the second PSR of RÚ RAO was initiated after 10 years from the date on which the previous periodic review was carried out. On 24 July 2020, a final report on the PSR of the facility was submitted to the Authority. In 2020, inspection activities in RÚ RAO were mainly focused on checking the confirmation of compliance of the submitted results of the periodic review for selected areas with the facts and safety requirements defined in the methodology for the PSR RÚ RAO, as well as physical inspection of the parts for disposal of VLLRAW and LLRAW. The Authority’s team inspection confirmed compliance with the safety requirements in question and notes that there are all prerequisites for maintaining a high level of safety in the period up to the next PSR.
The disposing of LLRAW in the FCCs to the 2nd double row was carried out standardly. By the end of the first half of 2021, a total of 6,412 pcs of FCCs were disposed, of which 206 pcs were disposed in the first half of 2021. In the first half of 2021, 1,457.80 m3 of handling packages with VLLRAW (MEVA drums and big-bags) were placed in the VLLRAW disposal section. A total of 15,720.50 m3 VLLRAW has been disposed.
Based on the inspection activities of the ÚJD SR and the results of monitoring of the environmental impact of the RÚ RAO on the environment, it can be concluded that the current operation of RÚ RAO as safe, with negligible impact on the environment. Reports on the environmental impact of the operation of the RÚ RAO are published on the website of the licensee.