Sort of radwaste from nuclear power plants

Breakdown of radwaste according

   
SOLID RADIOACTIVE WASTE
Solid radwaste is generated in nuclear power plants in two ways:
1. in contact of solid materials used in the appropriate installation with active fluids such as reactor coolant (contamination).
2. under the effect of radioactive radiation when solid materials become sources (activation).
     

  
Certain facilities can be used notwithstanding their contamination (e.g., primary piping, components of reactor, and so on), others have to be cleaned from radionuclides prior their use, i.e., decontaminated (e.g., tools). A part of these materials, due to their activity, cannot be used in the operation further. They are mainly filters, parts of machinery worn in various degree, damaged and contaminated measurement devices, tools, cuts of valves, laboratory aids, paper, textile, wood, glass, plastic materials, insulation materials, and so on. Activated parts of equipment and contaminated parts of civil constructions that will have to be disposed of during nuclear power plant decommissioning represent a special category.

    
If we consider spent nuclear fuel as radwaste, then it also represents solid radioactive waste generated periodically during reactor normal operation.
Solid radwaste (except spent nuclear fuel) generated during nominal operation can be categorized as soft radwaste, hard radwaste, parts of reactor protection equipment and aerosol filters. In Table data outline about the activity and amount of solid radwaste from the V-2 Bohunice plant, as planned in a design supplement to the plant, are shown.

    
Solid radwaste generated in nuclear power plants with VVER-440 reactors is stored in storage facilities made out of reinforced concrete which provide a part of the auxiliary building.

LIQUID RADIOACTIVE WASTE
Liquid radwaste from nuclear power plants with VVER-440 reactors represent a broad range of wastewater with various chemical composition, various specific activity, and so on. Waste is generated not only during nuclear power plant operation, but also during maintenance and various repairs. This liquid radwaste representing the largest volume of operational radioactive waste can be broken into the following groups:
a) liquid waste that can be discharged from nuclear power plant site after cleaning,
b) liquid waste that can be reused in nuclear power plant after cleaning,
c) liquid waste that can be neither discharged from nuclear power plant site, nor reused.
Waste water contaminated above the authorized level evan after after its cleaning ("clean" condensate from the primary system of nuclear power plant and waste water from special washing facility and sanitary loops) can be discharged into the environment.
Waste water from decontamination, drain water from equipment and piping systems, leakages from reactor coolant system and waste water from washing facility with the activity exceeding the authorized standard are categorized as reusable liquid waste. It is characteristic for this group of liquid waste that the water can be reused for plant needs after its treatment (evaporation, ion exchange, chemical treatment).
    

  
The liquid radwaste non-useable and non-dischargeable from plant site is concentrate from evaporation station, saturated ion exchangers, and slugs. It is characteristic for this waste that it is produced as secondary radwaste in the course of processing of reusable water, and it is predominantly low- and medium-level active concentrated residues. A small part of it is also high-level active concentrated residues. This waste is sometimes designated as wet solid or semi-liquid radwaste. With regard to its composition and activity, it is conditioned into a form suitable for long-term storage in appropriate repositories (cementation, bitumination), vitrification, and so on).

The amounts and the chemical and isotope compositions of liquid radwaste depend on a number of technologic factors (service water used, character and modes of operation, use of various decontamination solutions and of various washing means, and so on), and data from various nuclear power plants thus differ. Outline of data about the amount of liquid radwaste from a plant with VVER-440 reactor is shown in Table.

   
The amount of non-organized coolant leaks from reactor system depends on the conditions of plant process equipment and is in the range of 5 to 200 dm3/hour (authorized level). The estimated amount of concentrates (220 t/annually) thus can contain a significant amount of boric acid that has to be accounted for in the subsequent treatment of liquid radwaste.  

The activity of annual discharges from the plant site (limiting conditions for the operation of four Mochovce units) is as follows:

Liquid discharges:

Volumetric activity:

The amount of radionuclides in discharges is by two orders of magnitude lower than in normal surface water. The only exception is tritium as a hydrogen isotope; however, its concentration in discharges is significantly lower than the authorized value in drinking water. Tritium cannot be removed from waste water, and a network of monitoring stations and regular measurements of samples from plant vicinity thus ensures its continual control.
    

GASEOUS RADWASTE
During the operation of nuclear power plant, a relatively large amount of gaseous radwaste is generated which is released from ventilation stack after its partial capture. This gaseous radwaste represents gaseous radioactive elements, dispersed particles or aerosols. Its amount and composition is determined mainly by the activity from the ventilation systems of production process equipment and operational rooms. The activity from the ventilation systems of operational rooms depends on the air activity in reactor cavity and on the activity of coolant released from reactor coolant system. 
Gaseous radwaste - in comparison with other sorts of radwaste - obviously represents the least problem due to its relatively short decay half-time of the radionuclides included and to its low biologic effectiveness.
An outline of annual values of activity discharged from the ventilation stack is shown in Table (limiting conditions for the operation of two Mochovce units):

  
The actual releases from our nuclear power plants represent only a few tenths of percent from the limiting values shown.
Air from plant internal areas passes through ventilation systems via special filters consisting of a set of coarse pre-filters and aerosol HEPA filters (High Efficiency Particulate Air Filter). These filters are able to capture up to 99.9% of solid aerosol particles. Radioactive gaseous iodine is captured at filters made from active charcoal. Contaminated air is cleaned from most of radioactive materials by purification systems.

   
The radiological character of discharged gaseous radwaste and the significant dilution in the atmosphere (for the stack height of 120 m, the dilution factor in relation to the rate of release is 10-6 up to 5 x 10-5 at the point of peak concentration) means the these releases do not impose any danger for the population. Nevertheless it will be necessary in the future to continue in permanent reduction of the level of activity of gaseous radioactive discharges from nuclear power plants.