National Report of the Slovak Republic - Radiation and Nuclear Safety , September 1998

2.6.1 Brief Description of Technologies


  1. Bitumenation plant
  2. The principal equipment of the bitumenation plant is a rotor evaporator with a capacity of approx. 120 dm 3 /h of evaporated water depending on the radiochemical composition of the concentrate to be treated. The main function of the evaporator is to evaporate water from RAW concentrate and to embed the dry fine crystals of the dried salts with bitumen serving as fixation medium. Both components (bitumen and concentrate) are dosed into the evaporator over the heated zone in tangential direction. The resulting product is then drained into galvanized drums with 200 dm 3 capacity; the drums are sealed and stored at intermediate RAW storage sites.

    After purification at oil-removing plant, vapex and coal filter, bride condensate is repumped to active water purification plant for post-purification (radioactivity reduction to below-limit values).

    Following non-active, active tests and elimination of identified faults, the bitumenation plant PS 44 was put into permanent operation in 1995; by that time, 252 m 3 concentrates from NPP A-1 had been processed. The line processed 6 m 3 concentrates from NPP V-1 in 1997. It has continued processing concentrates from NPP V-1, V-2 in 1998.

     

  3. Active Waters Purification Plant at Building 41
  4. It serves to accept and treat contaminated waters from MGU NPP A-1, from buildings 809, 28, and will also capable to waters from BSC (building 808) as soon as put into operation, with an overall gamma volume activity of up to 3.7.10 6 Bq/dm 3 .

    Mechanically, chemically and radiochemically contaminated waters are treated by evaporation on a boiler evaporator with an external heating element. The designed capacity of the evaporator is 2.5 m 3 /h evaporated water. The actual capacity is dependent on the composition of the water treated.

    Bride concentrate is subsequently purified on ion-exchange filter until the volume activity of radionuclides drops below the limit values. The concentrate is moved to the bitumenation plant to fix its salts in bitumen matrix.

    The purification plant was put into operation along with other technologies upon the commissioning of NPP A-1, and has been operated, with several breaks needed for modernization, until now.

  5. VICHR Vitrification Line
  6. The vitrification line serves the purpose of fixation of radioactive chrompik into glass matrix of boron-silicate type, aimed at significantly reducing the volume and increasing the safety of storage of this specific radioactive liquid waste. The technology is a combined one (being neither a single-step nor a two-step process). From the storage flasks chrompik is pumped into the measuring tank having a volume of 128 dm 3 , from where it is dosed into the evaporator, where a concentrate of 3 dm 3 is prepared at 143 O C . This is subsequently drained to a melting induction furnace to which melt glass is added. The concentrate is left to dry out and the mixture is melt and then drained into a thimble which is loaded into the intermittent storage site. The remaining humidity of the mixture flows into the condenser and the separation unit. Having condensed, the condensate is returned to the beginning of the vitrification process. The activity of breed condensate vapors from the evaporator is reduced on sorbents. Parts of the line are cooled using an interposed cooling circuit which at the same time represents an antiradioactive leakage barrier. Minimum value of the leachability index for the vitrified product is L i = 9.0 and/or 10 -6 g/cm 2 .day (according to the US national standard ANSI/ANS 16/1/1986).

  7. V┌JE Bitumenation Plant
  8. The principle of the V┌JE bitumenation plant is identical with what has been mentioned with respect to the bitumenation plant under 2.6.1.1. The line processes smaller amounts of media. It was installed in building 28 in 1985, a changed use of which was approved by the authority in 1990 allowing the use of the line. There was an adjustment of the technological equipment of the V┌JE bitumenation plant in 1995, following the terms of the CSKAE Decree No. 436/90.

    During the period mentioned, this line of V┌JE served the purposes of a variety of experimental works aimed at setting up the recipe for bitumen embedding of A-1, V-1 concentrates, dowtherm, non-active sorbents, test of bitumen embedding of ground sorbents. Experimental works started with non-active, so-called model preparations and were followed by active real media as soon as procedures were successfully verified.

    Concentrates from A-1, V-1, V-2 and dowtherm are being currently processed on the V┌JE bitumenation plant.

  9. B ohunice RAW Processing Center
  10. The Bohunice Processing Center is expected to process RAW which can be classified into the following categories:

    This center includes the following technologies for processing and treatment of RAW:

    1. Evaporator
    2. The concentration equipment will be used to treat liquid incombustible RAW from NPP A-1, V-1 and V-2 which, after having been concentrated or directly, will be brought to the cementing line.

      The evaporator itself is of flow-through type, and consists of 3 U-shaped units. The capacity of the evaporator is 500 dm 3 /h at a salt concentration of the dosed waste of 200 ¸ 300 g/l.

      Bride condensate may be used to flush the equipment or within the incinerator flue gases purification system.

      The output product - the concentrate shall be collected in a tank from where it will be transferred into the cementing plant.

    3. Cementing Line
    4. RAW (concentrates) will enter the dosage tank of the cementing line directly from the concentration plant or from the flask (chrompik) or via inlet tanks (resins - ionex and/or sludge).

      RAW shall be dosed according to verified recipes from dosage tank or ashes from the dosage tank will be dosed from incinerator, along with additives and cement from oblique mixer (volume 500 dm 3 ).

      After thorough mixing, the cement product will be introduced into a concrete container of high integrity (volume 3 m 3 ). Six batches from the mixer are needed to fill the container. Containers with aged and hardened concrete will be transported to the National Repository at Mochovce.

    5. Sorting
    6. Unsorted solid RAW will be transported on Europalettes :

        • as bulk foil-wrapped material,
        • in 200 dm 3 sacks,
        • in 200 dm 3 drums (2 pcs)

      into the sorting plant. They will be transported to the sorting box by turning drums upside down or directly via open lid of the box manhole.

      RAW sorted in box and packaged in 200 dm 3 drums will be transported according to category as follows:

        • uncombustible pressable materials into the press plant,
        • uncombustible non-pressable materials to the delivery point to be cemented,
        • combustible materials wrapped in 25 l sacks packed in 200 dm 3 drums to the tilting device of the incinerator inlet box.

      Also, fragmentation workplace is a part of the sorting plant.

       

    7. Incinerator
    8. The incinerator will be used to incinerate the existing and the generated solid and liquid wastes from NPP JaslovskÚ Bohunice and Mochovce. The capacity of the plant is 30 kg/h solid wastes incinerated together with liquid wastes, or 50 kg/h of solid wastes only. Solid wastes are dosed via a box system into the feeding box which represents a safety feedtrough - loop.

      The incinerator furnace itself is constructed as a pit furnace, with upper feeding and no internal built-in parts. Incineration goes on in two zones. In the bottom zone, material is incinerated in a steam/air mixture thus providing for a burning material temperature of 900 ° C and no bottom ashes or agglomerates are formed on the furnace walls. In the upper zone, the main air inflow will be directly over the burning material (excess oxygen operation) with the air volume being set so as to achieve incineration temperatures of 800 ¸ 1050 ° C.

      Flue gases from the furnace will be post-burnt at the post-incineration chamber at 850 ¸ 1200 ° C. Water injected into the bottom part of the post-incineration chamber will bring the temperature down to 850 ° C; the necessary amounts of NO x -Out will be added to this water to reduce the share of NO x in smoke gases.

      The temperature of flue gases will be brought down in the mixer to 300░ C by adding fresh air. The sudden cooling quickly spans the temperature range of 600 ¸ 350 ° C, thus substantially reducing dioxin formation. Subsequently, flue gases are washed in washers and purified on HEPA-filters which separate radioactive particles with a 99.9 % efficiency.

      Ashes formed in the incinerator are grinned, filled into 200 dm 3 drums and transported into the cementing plant similarly as water from flue gases washer.

       

    9. Storage and Transport Facilities
    10. These facilities are intended for handling between the individual storage spaces and facilities of:

        • concrete containers,
        • 200 dm 3 drums,
        • Europalettes.

    11. Press Plant
    12. Wastes from the sorting plant are pressed and packed in the press plant into 200 dm 3 drums. The drums are pressed at the press plant high pressure presses at 20,000 kN. At each insertion step, presswork is shifted outside on removal slide and put to storage site. The presswork is then put into concrete containers and embedded into cement mix at the cementing plant.


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