Decontamination resulting radioactive waste

The results of radioactive waste sample C treatment with 3RO are shown in Figure 30.5. The feed radioactivity is 2,200 Bq/dm. After processing permeate has radioactivity below discharge limits (3.9 Bq/dm ) and can be discharged the concentrate of radioactivity 16,000 Bq/dm can undergo further processing. The average decontamination factor for entire plant is 564. 

In decontaminating a reactor component, there is always the problem that after a relatively short period of continued plant operation redistribution of radionuclides from the non-decontaminated surfaces of the other circuits and components will result in a recontamination of the cleaned regions. This effect can only be reliably precluded by decontamination of the whole reactor system, possibly with the fuel in place. Such decontamination operations require additional preparatory work as compared with the decontamination of components, due to the large volumes to be treated which require large amounts of decontamination solution, resulting in large amounts of radioactive waste. Further, additional preparatory work is necessary because different materials are exposed simultaneously to the decontamination solution. Since the mid-1960 s, a number of reactors have been decontaminated in this way more details will be given in Section 4.5.3. 

There is an abiding interest in reducing the concentrations of the chemicals in the decontamination solutions, not only to further improve materials compatibility but also to minimize the resulting volume of radioactive waste. To this end, a simple reduction in concentration alone is not sufficient, since such a measure... 

Calix[4]-W5-crowns 1-7 are used as selective cesium-carriers in supported liquid membranes (SLMs). Application of the D esi diffusional model allows the transport isotherms of trace level Cs through SLMs (containing calix[4]-6/5-crowns) to be determined as a function of the ionic concentration of the aqueous feed solutions. Compound 5 appears to be much more efficient than mixtures of crown ethers and acidic exchangers, especially in very acidic media. Decontamination factors greater than 20 are obtained in the treatment of synthetic acidic radioactive wastes. Permeability coefficient measurements are conducted for repetitive transport experiments in order to determine the SMLs stability with time. Very good results (over 50 days of stability) and high decontamination yields are observed with l,3-calfac[4]-Aw-crowns 5 and 6. 

H2O. Thus, a pressure vessel of a decommissioned reactor could, after chemical decontamination, be cut into smaller sections, some of which would only be slightly radioactive. The resulting scrap can either be encapsulated in concrete and put in a repository for normal reactor waste (Swedish plans), or melted to be used as raw material for new reactor parts where the remaining level of activity is acc table (France). 

Surface contamination from radioactively contaminated lead can be removed by dipping the contaminated lead into a solution of 1 M hydrochloric acid. After rinsing the lead with water, it usually can be documented as nonradioactive. The acidic wash and rinse solutions contain radionuclides and lead and must be handled accordingly. However, decontaminating the lead results in a smaller mass of mixed waste and allows the decontaminated lead to be reused or recycled. Commercial rinse products are also available for this purpose. 

Contaminated wastes derive from the fabrication of weapon components and related activities also. Further, the end of Cold War resulted in closing weapons production facilities and the creation of decontamination products, surplus plutonium, and other radioactive materials. These materials have to be safely disposed so that they do not cause any harm to public health or the environment. Moreover, they have to be secured so that they carmot be easily recovered and reused. 

During any release of radioactive materials, surfaces of objects or equipment may become contaminated. The objective of these measurements is to identify those objects that should be decontaminated, disposed of as waste, or treated in some other controlled fashion. The physical quantity that is generally measured is surface activity. Measurements may be radionuclide-specific or can also be assessed based on dose-rate measurements. The results are generally expressed in Bq/m or Sv/h or equivalent, respectively. 

Besides the metallic structures of the circuits and components, nuclear power plants contain huge masses of concrete, a small fraction of which is activated and/ or contaminated. In order to keep the resulting waste volumes as small as possible, the fraction which contains radionuclides has to be separated during dismantling from the non-radioactive bulk of the material the techniques used for this will not be discussed in what follows. Likewise, decontamination of building walls and surfaces will not be treated here. 

The radioactive effluent piped from the 116-N-2 storage tank was internal decontamination solution from cleaning the primary coolant loop in N Reactor and various waste decontamination solutions from small decontamination Jobs. The primary loop was decontaminated every 3 to 5 years. The radioactive wastewater resulting from this procedure contained phosphoric acid and diethyl thiourea. The wastewater was neutralized in the 116-N-2 facility. 

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