Cleaning of radioactively contaminated soils

One of the activities of VNIINM, JSC in the field of environmental technologies is cleaning of radioactively contaminated soil.

Today, the topic of recovery of territories as part of decommissioning of nuclear and radiation-hazardous facilities (NRHF) is becoming particularly relevant. This process involves generation of a large amount of soil contaminated with radionuclides whose level of specific activity of radionuclides is below the threshold to classify these materials as radioactive waste. According to the Basic sanitary rules of radiation safety SP 2.6.1.2612-10 (OSPORB-99/2010), such soils are classified as materials of limited use, and its handling requires substantiation of measures of radiation safety for the population and personnel. VNIINM possesses a technology and an installation designed for cleaning radioactively contaminated soil (RCS). We are testing and developing cleaning processes for various types of RCS provided by customers.

The principles of treatment of soil are as follows:

the technical procedure of soil purification by means of hydroseparation comprises a number of processes: dispersion of soil in an aqueous solution, its separation into gravel and sand components, separation of mineral particles by size, and conditioning of secondary refinement products. Up to 80% of pollutants are concentrated within a fine fraction with a particle size of 5 to 150 microns, whose mass fraction does not exceed 20%. Removing the fine fraction reduces soil contamination significantly, and makes it possible to use the remaining larger part of soil as a building material. The contaminated part of the soil is subject to thickening, dehydration, and storage as waste. Water solutions are reusable, and may be used repeatedly.

The scope of the technology:

The technology of soil purification using the hydroseparation method is used in combination with other soil reclamation techniques applied at NRH facilities. This makes it possible to reduce the volume of radioactively contaminated soil and low-level radioactive waste, and hence the cost of handling them, several times over.

In addition to removing radionuclides, the hydroseparation method can be used to clean soil contaminated with mercury, petroleum products and other dispersed industrial pollutants.

The hydroseparation method is versatile, and can be used for cleansing soils of different types. However, the installation options and the process must be elaborated depending on the task, soil types and the nature of contamination. For this reason, it is necessary to conduct studies of the properties of soil and refine the process in a laboratory environment.

Infrastructure required by the RCS treatment site:

At VNIINM, JSC, the ground cleaning unit is installed in a temporary easily erected shelter. The installation equipment has a high level of automation. A radiation monitoring system and an self-contained ventilation system are installed. Random from the site leaks are collected by gravity.

Hardware:

The equipment of the soil treatment plant is a complex of six modules that ensure decontamination of contaminated soils by separating and removing fine fractions by means of gravity separation in an aqueous medium, cleaning water-soil pulps, extracting and removing fine solid fractions and returning purified water to the technological cycle, obtaining a stable decontaminated product and secondary waste in a compact form (cake or cement compound). The modules of the soil treatment plant are mobile and can be transported by a truck to the site of RCS.

Each module is encased in a load-bearing transport frame welded from channel beams and coated with a paint coating resistant to decontaminating solutions. Lifting lugs are provided for handling the frames.

Any vehicle capable of transporting a standard 20-foot container can be used to transport the modules.

After delivery to the required location, the modules are unloaded from the vehicles using lifting mechanisms and are placed at a specially prepared work site.

Products and services:

VNIINM, JSC is ready to offer its customers:

• testing of the efficiency of hydroseparation soil cleaning processes on customer samples;
• development of soil cleaning technology involving the preparation of initial technical requirements for the design of installations;
• pilot testing of the hydroseparation soil cleaning process on the customer soil samples.