Neutralization of liquid radioactive waste
One of the main problems of the nuclear industry is the neutralizationl of liquid radioactive waste resulting from the operation of fission reactors, the use of isotopic products, the reprocessing of nuclear fuel and the dismantling of spent nuclear facilities.
The variety of LRW in terms of radiation hazard, as well as chemical and nuclide composition, cause big problems for the development of a technology for neutralizing LRW, suitable for widespread use.
The proposed method for concentrating LRW to a salinity of 600-800 g / l, followed by cementing the concentrate in a cement matrix, may become the most acceptable from both an economic and a technological point of view.
This method consists of two main steps:
- Separation of LRW into clean water (suitable for discharge into an open water network) and a radioactive concentrate with a high salt content (600-800 g / l);
- Cementing the radioactive concentrate and creating a reliable package for the cement compound, capable of providing long-term isolation of radionuclides from the environment for many millennia.
The first stage of concentration can be performed using special heat and mass transfer equipment, for which patents have been obtained. This equipment is a Drum Film Evaporator (patents RU2488421C1 and RU2619768C1) and a Horizontal Heat and Mass Transfer Apparatus (patent RU2750492C1). Conventional equipment is used during the cementing stage of the concentrate.
The use of DFE makes it possible to concentrate LRW solutions using mechanical vapor recompression (MVR) technology with continuous cleaning of heating surfaces from salt deposits to the required level of salt content in a continuous mode.
Secondary steam is compressed and converted into heating steam in a Roots pump. A simplified diagram of the evaporator operation is shown in Figure 1.
Figure 1
To reduce the cost and simplify the concentration system, compressed steam supplied tangentially into the housing of the Drum Film Evaporator can be used as a working medium for the rotation drive, made in the form of a turbine-type pneumatic motor.
Figure 2
Thermal parameters of the specific performance of DFE drums at 60 kPa steam compression, as well as a simplified process flow diagram, are shown in Figure 3.
Figure 3
Concentration of liquid radioactive waste containing surfactants, such as radioactive water from special laundries, causes problems with foaming and entrainment of aerosols with secondary vapor. To purify steam from radioactive aerosols, you can use a horizontal heat-mass transfer apparatus (patent RU2750492C1). As a drive for rotation of the nozzle structure, this apparatus can also use the kinetic energy of steam directed to a turbine-type pneumatic motor (Figure 4).
Figure 4
The use of a heat-mass transfer apparatus in an evaporator is shown in a simplified technological scheme of Figure 5. In this case, pure distillate (reflux) is used to remove aerosols from steam, which, after contamination, is sent for re-evaporation (Figure 5).
Figure 5
A simplified scheme for LRW concentration and concentrate cementing is shown in Fig. 6.
Figure 6
If you are interested in the use and development of this technology for LRW neutralization, you can contact us for additional information by e-mail: Vitaly Uzikov, uzikov62@mail.ru