RAW management system

Russia adheres to the principles of safe RAW management [18] , involving the following basic stages of the process:

1. Pretreatment

• collection

• segregation

• chemical adjustment

• decontamination.

2. Treatment

• volume reduction

• removal of radionuclides from the waste

• change of composition.

3. Conditioning

• solidification

• immobilization

• overpacking.

RAW is divided into categories based on its origin; its physical, chemical and biological properties; its state of aggregation; and level of activity. The different properties of different types of RAW make it necessary to use different RAW management technologies for different sorts of waste. In Russia, a number of technological methods have been developed to allow the optimal processing of RAW. The basic methods used for RAW process­ing [19] are presented in Table 10.5 and Fig. 10.5.

LRAW constitutes the majority of all RAW in Russia, with 90% of LRAW made up of aqueous solutions originating from (a) technological drains, which are produced at industrial and research centres, including medical and biological laboratories; and (b) decontamination drains from the decontamination of equipment and overalls. These aqueous solutions are highly varied in their chemical and radionuclide composition, and include such diverse forms as ions, dissolved complexes of organic sub­stances, colloidal particles and micelles, suspended solids, and liquid emulsi­fied oil products. Solid RAW includes different materials contaminated with radionuclides such as construction materials, dismantled equipment, spent filters and resin, corpses of experimental animals, and silts and soils from contaminated territories.

The basic aim of RAW treatment is to reduce the physical volume of the waste and to transfer this waste into a monolithic, chemically and mechani­cally stable form, suitable for long-term storage in containers.

RAW Type

Processing methods

Solid

Combustible

Combustion in furnaces on fire grates at 900°C, plasma treatment, thermochemical treatment, vitrification, acid decomposition

Compactable

Compaction at low and high pressure, super-compaction

Metallic

Compaction, melting

Incombustible and non-compactable

Direct placement into containers

Liquid

Organic combustible

Combustion, joint combustion with SRAW, encapsulation in cement matrix

Organic incombustible

Absorption using powders and encapsulation in cement matrix, thermochemical treatment

Liquid low salinity

Purifying (concentration) by evaporation, by chemical precipitation, by absorption, by selective absorption, by a membrane separation process, by cementation

Liquid high salinity

Purifying by selective absorption, cementation, bituminization, vitrification

Gaseous

Trapping by absorption and through the use of chemical reagents

Table 10.5 The basic methods for RAW processing

image158,image159

10.5 Basic methods of RAW treatment at MosNPO ‘Radon’ [19].

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