Low-activity waste

Uranium oxide [1344-57-6] from mills is converted into uranium hexafluoride [7783-81-5] FJF, for use in gaseous diffusion isotope separation plants (see Diffusion separation methods). The wastes from these operations are only slightly radioactive. Both uranium-235 and uranium-238 have long half-Hves, 7.08 x 10 and 4.46 x 10 yr, respectively. Uranium enriched to around 3 wt % is shipped to a reactor fuel fabrication plant (see Nuclear REACTORS, NUCLEAR FUEL reserves). There conversion to uranium dioxide is foUowed by peUet formation, sintering, and placement in tubes to form fuel rods. The rods are put in bundles to form fuel assembHes. Despite active recycling (qv), some low activity wastes are produced. 

Fig. 12.5 Schematic representation of the reprocessing of Ught-water reactor spent fuels. The solvent extraction steps are shown in the dotted frames (HA, MA, LA, for high, medium, and low activity wastes, respectively). 

Sodium-rich glass compositions tested in single-pass flow-through (SPFT) apparatus at Pacific Northwest National Laboratory support the low-activity waste (LAW) glass disposal... 

McGrail, B. P., Icenhower, J. P., Martin, P. F., Schaef, H. T., O Hara, M. J., Rodriguez, E. A. Steele, J. L. 2001 i). Waste Form Release Data Package for the 2001 Immobilized Low-Activity Waste Performance Assessment. Pacific Northwest National Laboratory, PNNL-13043, Rev. 2, Richland, WA. 

LDH LEU LIBD LAW LET LILW LIP LLNL LLW LMA LMFBR LOI LREE L/S LTA LWR Layered double hydroxide Low enriched uranium Laser-induced breakdown detection Low-activity waste Linear energy transfer Low- and intermediate-level nuclear waste Lead-iron phosphate Lawrence Livermore National Laboratory Low-level nuclear waste Law of mass action Liquid-metal-cooled fast-breeder reactor Loss on ignition Light rare earth elements (La-Sm) Liquid-to-solid ratio (leachates) Low-temperature ashing Light water reactor... 

The flowsheet has three aqueous effluents. The first is the decontaminated aqueous raffinate stream. For economic reasons, entrained solvent in the raffinate must be recovered test results show that coalescers are practical and effective [89], In the baseline SWPF, the raffinate stream will be transferred to the Saltstone Facility, where it will be disposed of in a cementitious low-activity waste form called saltstone. The... 

The aqueous waste stream (2AW) containing the 241 was concentrated and stripped of acid using two batch evaporators in the Low Activity Waste (LAW) system. The first concentration step was performed in the LAW batch evaporator. Acid stripping with water and additional evaporation was performed in the second LAW batch evaporator. The average concentration of the Am entering this two-step evaporation process was 3.4 x 10 g/L after the first step, the Am concentration was 0.08 to 0.15 g/L after the second step, the Am concentration was 0.2 to 0.3 g/L, and the nitric acid concentration was 2.0 to 2.5M. 

The additional module is designed for low-activity waste storage, which is produced in the course of the storage facility operation. It is a chamber working of 83 m in cross- section. Waste in received for the storage in metallic drums of 0.6 or 1.6 m in diameter. 

The low activity waste water is generally processed by distillation, whereupon a decontaminated distillate is obtained, which can be fed back into the process or discharged from the plant, and a residue in which radioactive nuclides are present in concentrated form. This residue can be bituminized or encased in concrete. 

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. 

Ferrous sulfamate has been the reductant for plutonium during partitioning of uranium and plutonium in the Purex process at SRP since startup. In recent years, a desire to reduce waste volumes has led to studies of alternative reductants or combinations of FeSA with other reductants. The FeSA in the Pu strip solution produces Fe(OH) 3 and Na2S0i in neutralized waste these compounds account for a large percentage of the solid material in Purex low activity waste. In an effort to reduce these wastes, we investigated HAN as a substitute for part or all of the FeSA in the Purex first cycle. 

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. 

Curmning, l.W. et al.. Development of combined precipitation and nltrafiltration process and its application to the treatment of low active wastes, IAEA-SM-303-21P, IAEA, Vienna, Anstria, 1992, p. 26. 

Since 2003, RO-based unit operation to remove the radionuclides C Cs, ° Ru, U, Pu) from delay tank is continued, and the performance of the system was found to be promising [49-51]. The final discharge of low-level active waste (i.e., a mixture of evaporator condensate, ADU filtrate, and waste generated from personnel contamination [like hand washing to remove contamination from hand]) is carried out from the delay tank, which temporarily holds low-active waste. We thus evaluated RO for the removal of alpha activity, beta activity, nitrates, and total dissolved salts (TDSs) from delay tank water at the pilot plant. The delay tank water composition is given in Table 26.4. The specification of the membrane module, which was supplied by the Desalination Division of the BARC (Mumbai), is listed in Table 26.5. The module was... 

In the United States the chemical processing of low activity waste (LAW)... 

Cement and cement composites in view of their low costs and amenability to simple processing techniques have to date met the acceptance criteria for immobilisation of relatively low active waste concentrates. 

Low activity waste consisting of technological residues such as vinyl sheets, gloves, boots, cotton, etc. .. or thermal insulating materials was incinerated or compacted before being... 

Let us consider removal of radioactive Cs ions (e.g. Cs) from a waste solution containing sodium salts. As an example, the chemical concentration of Cs in solution corresponding to an activity concentration of 1 pCi dm (which is typical in low-active waste) is 8 x 10 i mol dm . Selectivity coefficients kaiua are typically in the order of 10 -100 in zeoHtes. Thus, unless the Na concentration in solution is very low ([Na] 10" mol dm" ), the K, (and volumetric... 

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