Medium level waste

The above discussion applies to low level activity liquid wastes. Inorganic membranes have also been tested for treating medium level liquid wastes containing approximately 100 times the activity of the aforementioned low level wastes [Gutman et al., 1986]. The same type of zirconia membranes with a MWGO of 10,000 daltons used in treating low level wastes docs not perform as well (in terms of the permeate flux and decontamination factor), but can function acceptably when processing medium level wastes. The problem is particularly pronounced if there are some defects in the... 

Non-high-level waste (medium-level waste, MLW low-level waste waste, LLW) shielding may be required. 

In 1976 pilot-scale testing with simulated commercial high- and medium-level waste feedstock composition was conducted to demonstrate the feasibility of the process for this type of waste. Currently expected commercial waste compositions do not seem to present major problems in fluidized-bed calcination [M2]. A conceptual flow sheet for fluidized-bed solidification of commercial waste is shown in Fig. 11.16. 

Development and implementation of methods of extracting high- and medium-level waste from the tanks of storage facilities ... 

The cylindrical masses of radioactive wastes are enclosed in containers, separated from one another by smectite-rich clays. These containers are placed in vertical boreholes or long horizontal bored or blasted tunnels. For high-level radioactive wastes, the containers are stored at a depth of 300-800 m. Low- and medium-level waste has shorter lifetimes and can be stored at smaller depth. 

There are two main approaches to such land disposal by burial either in near surface facilities for low and non heat generating medium level wastes or in deep imderground repositories in geological environments. Low and medium level wastes were disposed of in U countries in near surface facilities in France, United Kingdom and recently in Spain and in deep disposal facilities in Germany. 

Deep geological disposal concepts, in particular for alpha bearing (low or medium level) waste and heat generating high level waste, were developed mainly based on the multi-barrier concept. In this concept, the protection of humans and the environment should be guaranteed by an optimal combination of a number of barriers consisting of the waste matrix, container, buffer and backfill material, the repository structures and the geological environment. 

The wide chemical variation of radioactive wastes which are extremely complex in composition require different methods of immobilisation and containment. The waste forms range from Low Level Waste (LLW), Medium Level Waste (MLW) through to High Level Waste (HLW). MLW can be embedded in cement or bitumen whereas HLW is either reprocessing waste immobilised in borosilicate type glasses or is the spent fuel when declared as waste. 

Regarding the external fuel cycle, all spent fuel will be stored on-site below the reactor in spent fuel tanks. Upon final discharge of the last spent fuel load, i.e. after 40 years of operation the fuel can be placed in safe store for a further 40 years. After this period has lapsed the spent fuel could be suitably classified as medium level waste, which can be packaged for final disposal in a suitable repository. It is foreseen that this waste will be treated... 

Nomura, I., Nagaya, K. Hashimoto. Y. 1985. Vitrification of low- and medium-level nuclear waste. Transactions of the American Nuclear Society, 49, 74. 

The most important liquid wastes are the high-level effluents, containing fission products from fuel reprocessing. They contain >99% of the fission products in the fuel with small quantities of U and Pu. Medium-level liquid waste has an activity of 4 GBq/L and results from various steps in fuel reprocessing. Low-level (<0.1GBq/m3) waste is treated or concentrated. Liquid organic waste is usually incinerated or chemically destroyed. 

The standard and legal base in the area of managing low-level and medium-level Solid Radioactive Waste (SRW) needs further development and extension. 

Andrezej, G. et al., Concentration of low and medium level radioactive wastes with three stage reverse osmosis pilot plant, Sep. Sci. Technol. 36, 1117, 2001. 

In Table 30.15, decontamination factors for different processes for low- and medium-level radioactive waste treatment are shown. Membrane distillation with its high decontamination factors is a competitive method in this field. However, it has to be mentioned that these high-decontamination factors are achieved from low-volatile solute after adequate pretreatment. 

DFs for Most Common Methods of Low- and Medium-Level Radioactive Wastes Processing... 

Since 1995, the Chemical and Nuclear Engineering Department of the Polytechnic University of Valencia in Spain has been working on the application of membrane technology to the treatment of low and medium level radioactive liquid wastes. In this chapter, we describe two practical cases of radioactive liquid waste treatment using membrane processes the treatment of Cs-contaminated water generated after a radioactive incident in a stainless steel production factory, and the treatment of 1 liquid wastes from nuclear medicine services at hospitals. 

Medium-active wastes of low-salt content can be treated by distillation in the same way as described above for highly active liquid waste. The small volume of concentrate produced from medium-active waste distillation can be combined with high-level waste arisings and the very low low-active condensate can be disposed of to sea in accordance with government authorizations. 

The medium level liquid waste (MLLW) results essratially from evaporating various streams from the chemical process, such as solvent clean-up, off-gas scrubbers, product concentration, etc Table 21.8. It may contain up to 0.5 % of the uranium and up to 0.2%... 

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. 

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. 

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