Medium-active radioactive wastes

Sato et al. studied the removal efficiency of four pot-type water purifiers, two of which consisted of activated carbon and ceramic hollow fibers [62]. Iodide, iodate, cesium, and barium were removed with efficiencies of 85%, 40%, 75%-90%, and 85%, respectively, by all purifiers. In another study, Zakrzewska-Trznadel et al. have presented work concerning liquid waste treatment, in particular, the processing of low- and medium-level radioactive waste treatment [63]. After discussing various methods, they concluded that RO and tvSm ceAIseeded UF are the most basic methods to be applied. The other methods such as MF, MD, and NF can be considered as supplementary methods for the preliminary stages of raw radioactive waste processing or the final processing of the effluents. They also proposed a hybrid process, in which RO, UF, and MD are combined, based on their experiences with each individual process. 

In relation to future trends of the membrane treatments described in this chapter, they are expected to be applied for medical and research wastes of low-medium activity contaminated with Cs, or other radioisotopes with similar characteristics. Furthermore, membrane treatment has been proved as an efficient and quick treatment in an incident that generates low-medium radioactive wastes. 

The last stage in the disposal of nuclear power station waste is long-term secure permanent storage of the solidified high, medium and low activity waste. Annually 5000 m- of radioactive waste is produced in the Federal Republic of Germany, of which only half comes from nuclear power stations. 

Medium-active waste also can be treated by floe precipitation processes similar in character to those widely used in water treatment. Precipitants are required which will remove the unwanted radioactive species from the waste solution and quickly settle, carrying the radioactivity into a small bulk of sludge. The supemate can be treated as a low-active waste and discharged locally to the environment. Typical precipitants for common cations are as follows. 

Nuclear fuel reprocessing operations produce both high and medium level activity liquid wastes (HLW/MLW). The major nuclides in these radioactive wastes are those with long half-lives, mainly / /7 emitters such as Tc, I, Zr, Se, Cs, etc., or a emitters such as transuranics Np, Pu, Am, Cm, etc. [1]. That is why great efforts have been devoted throughout the world to propose harmless storage of these wastes. 

The plant possesses a duly issued license for types of activity related to processing of nuclear materials and the equipment of temporary storage facilities for medium- and high-level liquid waste, and to the handling of radioactive substances as individual units of the temporary storage facility for medium- and high-level waste are decommissioned. It holds a temporary permit from the Russian Federation State Academy of Sciences for all types of activity. 

Low Environmental Impact Plant discharges of all types, including chemicals and radioactive isotopes must be minimal. A comprehensive waste management scheme (low, medium and high activity) must be included. 

Water is the main transport medium for migration of radioactivity from the disposed waste. Therefore effective measures need to be taken to ensure that water will not come in contact with the disposed waste for periods till the activity in the waste decays to safe levels. Experience has shown that the portions of the disposal structure which are exposed to the atmosphere are the vulnerable... 

The radioactive material in the waste solutions consists mainly of the corrosion products containing radionuclides such as Co, Co, Cr, Fe, Mn. This material arises from the decontamination of components, of contaminated areas, of reusable protective clothing and possibly also of personnel (see paras 4.41-4.50) in the facilities that are provided to remove radioactive contamination from the surfaces. Whereas the activity concentrations in the waste arising from the decontamination of personnel and of clothing are low, concentrations may be medium or high in solutions arising from the decontamination of components before major repair work. 

Medium and high activity waste is stored at the Cadarache Center. High activity waste consists mainly of parts from the nickel and steel reflector assemblies or from control-rod mechanisms and irradiation devices. These account for the major part of the total radioactivity (4800 TBq) which has been removed from the reactor. The liquid effluent produced by washing and decontaminating operations was transferred to the Liquid Waste Treatment Facility at Cadarache where it has been neutralized, concentrated by evaporation and encapsulated in bitumen or cement. Furthermore, on completion of the partial dismantling work, about 300 tons of material (steel and lead in particular) will been returned to service. Much of this will be turned into biological radiation shielding. 

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