Non-high-level waste

The goal of non-high-level waste treatment is primarily volume reduction. This, however, does not hold for alpha-bearing waste, often called TRU waste. f Effective immobilization may 

Process waste (aqueous solutions, slurries, ion-exchange resins, organic liquids) 

There are three basic steps in treating these wastes, which may be applied in sequence or individually  

The methods available for volume reduction are different for liquid and solid waste. For liquid waste evaporation, ion exchange, and flocculation are used for solid waste incineration, baling and surface decontamination are the most common processes. 

Evaporation. Evaporation is a process whereby a solution or a slurry is concentrated by vaporizing the solvent, normally water. Then a residue with a high solids content, usually a sludge, will be formed that is handled as the radioactive waste concentrate. 

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

It should also be obvibus that actinide reduction in HLW is reasonable only if an equivalent reduction of actinides in non-high-level waste, such as refabrication waste, can also be achieved. Also, 1 must be considered in a long-term hazard balance. 

The wiped-film evaporator is a special type of evaporator that permits evaporation to a much higher concentration of solids than do other evaporators. Liquid is fed into a heated cylinder that contains rotating blades or wipers to reduce the liquid to a film, thereby improving the heat-transfer efficiency. Wiped-film evaporators can also be operated as dryers. Other equipment that can be used for drying and calcining non-high-level waste is the same as for HLW, e.g., spray calciners, fiuidized-bed calciners, and rotary kilns. 

Volume reduction as described above usually leads to a product that still contains considerable quantities of water or that is quite easily leached or dissolved by water. The policy as to the degree of immobilization required for final disposal varies in different countries. As yet, there is no official regulation in the United States requiring that non-hi -level waste be inunobilized before disposal. It is, however, practiced in many places. In West Germany, by regulation, any non-high-level waste has to be immobilized before disposal in such a way that low leachability is warranted over a sufficient period of time. 

There is no doubt that immobilization at least of alpha-bearing waste must generally be required and will be in the future. It has been mentioned before that the total transuranic inventory of alpha-bearing non-high-level waste will be in the same order of magnitude as that of HLW. 

The range of suitable immobilization products for non-high-level waste is broader than that for HLW because there will be no significant heat generation. It includes glasses as well as cement, bitumen, and polymers. 

Solidification. In principle, any solid that contains firmly bound water may be suitable as a solidification form for HTO. This includes drying agents, such as silica gel, molecular sieves, and calcium sulfate, as well as hydraulic cement and organic polymers. Most experience is available with cement, which has been used to solidify non-high-level waste for quite a while. 

Cooley, C. R., and D. E. Clark Treatment Technologies for Non-High-Level Wastes (USA), Proceedings of the International Symposium on the Management of Wastes fivm the LWR Fuel Cycle, Denver, 1976, Report CONF-76-0701, p. 250. 

High-level waste (HLW), intermediate-level waste (ILW), and low-level waste (LLW) are produced at all stages of the nuclear fuel cycle as well as in the non-nuclear industry, research institutions, and hospitals. The nuclear fuel cycle produces liquid, solid, and gaseous wastes. Moreover, spent nuclear fuel (SNF) is considered either as a source of U and Pu for re-use or as radioactive waste (Johnson Shoesmith 1988), depending on whether the closed ( reprocessing ) or the open ( once-through ) nuclear fuel cycle is realized, respectively (Ewing, 2004). 

Requirements for Disposal. The National Security and Military Applications of Nuclear Energy Authorization Act (NSMA, 1980) established the current DOE program for disposal of defense transuranic waste at the WIPP facility in New Mexico. The Act specifically authorized test emplacements of waste for purposes of research and development. WIPPLWA (1992) then authorized permanent disposal of defense transuranic waste at this facility. The Act specifies that the WIPP facility may not be used for disposal of high-level waste, commercial transuranic waste, or any DOE non-defense transuranic... 

In this chapter, the primary emphasis will be on HLW. Non-high-level alpha waste, tritium, 1, and Kr wiU be treated to some extent. Volumes and radioactivity concentrations of these wastes to be expected from a 1400 MT/year reprocessing plant according to a German design are given in Table 11.1 [D2]. 

Flocculation. Flocculation is the least costly procedure to concentrate non-hlgh-level waste. The principles are unspecific adsorption of radionuclides on a carrier, such as Fej 03(07) or calcium phosphate, or cocrystallization with a suitable crystalline precipitate, such as strontium with CaCOa. The sludge has to be collected by settling or filtering and is handled as the radioactive waste concentrate. This technique, because of its rather poor decontamination effect, is suitable only for LLW. Usually, the concentrate has a high water content. 

Glass. For liquid non-high-level alpha-bearing wastes with sufficiently high activity concentration, glass may be a suitable fixation product as it is for high-level waste. 

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