Sort of radwaste from nuclear power plants

Special type of radwaste at the A-1 plant

   
A specific situation has occurred in the first Czechoslovak nuclear power plant A-1 Bohunice during the time period following its shutdown in 1977. The last spent nuclear fuel was transported to the Russian Federation in summer 1999, but still it is necessary to handle certain special types, mainly liquid radwaste that is not known from plants with VVER-440 reactors. The most significant of it is the liquid radwaste of dowtherm and chrompik.

  
Dowtherm is an organic liquid with a high boiling point used for fuel storage. Total volume of dowtherm represents about 50 m3 and its maximum specific activity is about 300 MBq/dm3. The high activity of dowtherm is mainly caused by a damage of cladding in some fuel assemblies, and it also depends on the level of burn-up of the fuel stored in the past in this liquid radwaste. Some fuel assemblies stored had damaged cladding, and dowtherm was thus also contaminated by alpha nuclides.
    

One of the methods for dowtherm conditioning is bitumination based on the fixation of dowtherm with molten asphalt.
Another method of dowtherm conditioning is incineration in the incineration facility of the Bohunice Radwaste Treatment and Conditioning Center.
Chrompik is a water solution of potassium dichromate compound with the concentration in the range 3 to 5%. Chrompik was used - in the same way as dowtherm - for storage of spent fuel, and it should also have prevented corrosion of fuel element cladding. Since some fuel assemblies under storage had cladding damaged, its contamination by alpha nuclides occurred as well.
The total volume of chrompik is about 38 m3, with its peak activity higher by three orders of magnitude than that of dowtherm. Since it is a liquid radwaste with such a high activity, it is conditioned by the vitrification method. The method consists in the production of special glass or glass-ceramic mass from liquid radioactive waste and glass materials at the temperature of 900 up to 1200 °C. From the total removed amount of chrompik, not more than 2.5 m3 of ultimate product in glass form should be generated due to high volumetric reduction in vitrification. 

Bitumination of dowtherm is carried out in the bitumination facility of VÚJE Trnava (experimental facility). Vitrification of chrompik is carried out in the vitrification facility of the VYZ plant in Bohunice.