Processing of radioactive waste

The radioactive waste generated by the operation of the research reactor should be processed in accordance with established procedures. 

Radioactive waste should be processed as early as practicable to convert it into a passively safe state and to reduce the UkeUhood of its dispersal during activities related to its storage and disposal. 

Waste packages resulting from the conditioning of radioactive waste should be in accordance with estabUshed criteria and should comply with the limits and conditions for the handUng, transport, storage and disposal of radioactive waste. 

Gaseous radioactive waste arises when air becomes contaminated or when gases that are present or used in the facility become contaminated by radioactive aerosols, vapours or gases, or when constituents of a gas become activated in passing through the reactor core or in close proximity to it. 

Certain compartments or discrete pieces of equipment in the facUity may have localized ventilation owing to the potential for leakage and the generation of airborne contamination. The air to be treated by such localized ventilation systems may also be treated by filtration and adsorption, either continuously or whenever monitoring indicates it to be necessary. 

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Metallacarboranes. These are used in homogeneous catalysis (222), including hydrogenation, hydrosilylation, isomerization, hydrosilanolysis, phase transfer, bum rate modifiers in gun and rocket propellants, neutron capture therapy (254), medical imaging (255), processing of radioactive waste (192), analytical reagents, and as ceramic precursors. 

Experimental investigations of spectroscopic and other physical-chemical properties of actinides are severely hampered by their radioactive decay and radiation which lead to chemical modifications of the systems under study. The diversity of properties of lanthanide and actinide compounds is unique due to the multitude of their valency forms (which can vary over a wide range) and because of the particular importance of relativistic effects. They are, therefore, of great interest, both for fundamental research and for the development of new technologies and materials. The most important practical problems involve storage and processing of radioactive waste and nuclear fuel, as well as pollution of the environment by radioactive waste, where most of the decayed elements are actinides. 

Solution of Zr-DBP in TBP-Isopar L was proposed earlier for the processing of radioactive wastes.47 The authors state that the advantages of this solvent were... 

Mishra, B., D.L. Olson and P.D. Ferro, 1994, Application of ceramic membranes in molten salt processing of radioactive wastes, in Proc. 123rd Ann. Meeting of Minerals, Metals, and Mater. Soc., San Francisco, USA, p. 233. 

Technical Reports Series No. 402,2001. Handling and Processing of Radioactive Waste from Nuclear Applications. International Atomic Energy Agency, Vienna. 

The design should include features for the storage and/or processing of radioactive waste generated throughout the lifetime of the facility. 

A. 1902. The aspects of the facility design that facilitate decommissioning should be discussed, such as selection of material to reduce activation and to provide for easy decontamination, detachment and handling (remotely where required) of activated components, and adequate facilities for processing of radioactive waste. 

Chemical processing or reprocessing (39) of the fuel to extract the plutonium and uranium left a residue of radioactive waste, which was stored in underground tanks. By 1945, the reactors had produced enough plutonium for two nuclear weapons. One was tested at Alamogordo, New Mexico, in July 1945 the other was dropped at Nagasaki in August 1945. 

The Natural Reactor. Some two biUion years ago, uranium had a much higher (ca 3%) fraction of U than that of modem times (0.7%). There is a difference in half-hves of the two principal uranium isotopes, U having a half-life of 7.08 x 10 yr and U 4.43 x 10 yr. A natural reactor existed, long before the dinosaurs were extinct and before humans appeared on the earth, in the African state of Gabon, near Oklo. Conditions were favorable for a neutron chain reaction involving only uranium and water. Evidence that this process continued intermittently over thousands of years is provided by concentration measurements of fission products and plutonium isotopes. Usehil information about retention or migration of radioactive wastes can be gleaned from studies of this natural reactor and its products (12). 

The main drawback to nuclear power is the production of radioactive waste. Spent fuel from a nuclear reactor is considered a high-level radioactive waste, and remains radioactive for a veiy long time. Spent fuel consists of fission products from the U-235 and Pu-239 fission process, and also from unspent U-238, Pu-240, and other heavy metals produced during the fuel cycle. That is why special programs exist for the handling and disposal of nuclear waste. 

The production of electricity fiom nuclear fission energy is accompanied by formation of radioactive waste, of which the larger hazard is the presence of long-lived transuranium isotopes. The problems associated with this waste are still debated, but if the transuranium isotopes could be removed by exhaustive reprocessing and transmuted in special nuclear devices, the hazard of the waste would be drastically reduced (Chapter 12). This may require new selective extractants and diluents as well as new process schemes. Research in this field is very active. 

In addition to the rotating columns previously described, there are a number of other designs for centrifugal extractors, many originally developed for the separation of radioactive wastes in nuclear processes (see Chapter 12). They are both of the mixer-settler type, as discussed in section 9.3.3, and of the rotating column types. 

Commonly, in vitro determination of HDAC activity is a manual assay utilizing a coupled two-step process, including enzymatic deacetylation of a substrate followed by reaction termination and readout [10]. Assays utilize nuclear extracts and substrates containing labeled (radioactive or fluorescent) acetylated histones. For the isotope-based assays, the enzymes are incubated with acetate-radiolabled histones prepared from chicken reticulocytes or chemically [ Hjacetylated peptide substrates, and the enzymatic activity is determined by liquid scintillation counting [11]. Alternatively, histones may be obtained from cells following treatment with [ H]acetyl-CoA [12]. The caveats of these approaches include the variability of prelabeled acetylated core histones within preparations, potential high costs, their labor-intensive nature and the presence of radioactive waste. 

T0040 Andco Environmental Processes, Inc., Electrochemical Iron Generation T0151 Ceramic Immobilization of Radioactive Wastes—General T0155 CFX Corporation, CFX MiniFix T0510 Metals Recovery, Inc., Metals Leaching... 

T0066 Argonne National Laboratory Transuranium Extraction (TRUEX) Process T0151 Ceramic Immobilization of Radioactive Wastes—General T0169 Clemson University, Sintered Ceramic Stabilization... 

Process economics of the GMODS are dependent on the scale of operation (D14276H, p. 5). Based on theoretical considerations (the limited number of process steps), GMODS has the potential to be a relatively low-cost process for treatment of radioactive wastes (D14276H, p. 37). In some cases, specialized equipment may be used to minimize waste volume prior to treatment, in an effort to minimize costs (D14276H, p. A-3). 

Pretreatment is required for HTV processing. Drying and size reduction of wastes are required. Additives such as glass formers may be required. Processing of nonhazardous wastes may not be economically feasible. Treatment of radioactive wastes will produce a radioactive glass that requires special handing or treatment. 

Review work for future updates of our data base should focus on iron compounds and complexes. The iron system is thought to be of crucial importance for characterizing the redox behaviour of radioactive waste repositories. Preliminary applications have indicated that the lack of data for the iron system is a source of major uncertainties associated with the definition of an oxidation potential. Hence, there is little use in developing sophisticated redox models for radionuclides as long as the dominant redox processes in a repository are poorly known. 

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