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PubMed2005

Declassification of radioactive liquid wastes generated in radio immune assay [corrected] (RIA) laboratories.

Radioactive liquid wastes of low-medium activity level are generated in radio immune assay (RIA) laboratories, which are also potentially infectious because of the pathogens from patient blood. The most common way of managing these wastes consists of a temporal storage, for partial radioactivity decay, followed by management by an authorised company. The object of this work is to study the viability of treating radioactive liquid wastes coming from RIA using membrane techniques in order to reduce their volume, which would mean an improvement from the radiological point of view and a decrease in management costs. This paper describes the results of some experiments carried out with RIA real wastes, by means of processes such as ultrafiltration and reverse osmosis. It has been proved that waste volume can be significantly reduced, obtaining a treated liquid that is free of pathogens and organic matter and with an activity level around the environmental background.

Laboratories, Hospital↗
PubMed2001

Leaching behavior and characteristics of glass components and surrogate nuclides in radioactive vitrified waste forms.

Several vitrified waste forms were fabricated and characterized, which contain simulated radioactive waste incineration ash, and a long-term leaching test was conducted by an ISO method for 820 days to assess the chemical durability of vitrified waste forms. Two semi-empirical mechanism models were applied to find out the dominant leaching mechanism of glass elements. For glass elements, dissolution associated with diffusion was the dominant leaching mechanism and leaching characteristics also depend upon solubilities of components. A type of prediction model was applied to observe the long-term leaching behavior of major glass elements and surrogates. Diffusion coefficients and dissolution rate constants, the main parameters in the long-term prediction model, were obtained for glass elements and surrogate nuclides using experimental data for short and long-term periods. The model could be used to predict long-term behavior of such elements to observe and assess the stability of vitrified waste forms.

Diffusion↗
PubMed2004

Radioactive iodine waste treatment using electrodialysis with an anion exchange paper membrane.

In order to simply and safely treat radioactive iodine waste, a study of the removal of iodide ion from radioactive waste using electrodialysis with an anion exchange paper membrane, in which trimethylhydroxylpropylammonium groups were homogeneously dispersed with high density. In Na125I and Na36Cl concentration-cell system, electric ion and water conductances, phenomenological coefficients, have been experimentally determined on basis of nonequilibrium thermodynamics. Prepared paper membrane had higher permselectivity of 125I ion than 36Cl ions by approximately 21%. On the other hand, water flux that was accompanied by an ionic transference in prepared paper membrane was greatly larger than that in typical synthesized membrane. It is suggested that a depression of water mobility is important to practice an ideal radioactive iodide waste electrodialysis system with a novel anion exchange paper membrane.

Anions↗
PubMed1998

National waste management infrastructure in Ghana.

Radioactive materials have been used in Ghana for more than four decades. Radioactive waste generated from their applications in various fields has been managed without adequate infrastructure and any legal framework to control and regulate them. The expanded use of nuclear facilities and radiation sources in Ghana with the concomitant exposure to human population necessitates effective infrastructure to deal with the increasing problems of waste. The Ghana Atomic Energy Act 204 (1963) and the Radiation Protection Instrument LI 1559 (1993) made inadequate provision for the management of waste. With the amendment of the Atomic Energy Act, PNDCL 308, a radioactive waste management centre has been established to take care of all waste in the country. To achieve the set objectives for an effective waste management regime, a waste management regulation has been drafted and relevant codes of practice are being developed to guide generators of waste, operators of waste management facilities and the regulatory authority.

Ghana↗
PubMed2001

Radiological impact on the workers, members of the public, and environment from the partial decommissioning of Pakistan Research Reactor-I and its associated radioactive residues.

The Pakistan Research Reactor-I (PARR-I) is a swimming pool type research reactor originally designed and built for a thermal power of 5 MW using High Enriched Uranium (HEU) fuel. In 1990-1991 the reactor was redesigned, partially decommissioned and recommissioned to operate with Low Enriched Uranium (LEU) fuel at a thermal power of 10 MW. An essential requirement, construction and commissioning of a wet spent fuel storage bay and fabrication of an irradiated fuel transfer cask were completed before actual dismantling of the reactor core. During the partial decommissioning operations, radioactive waste generated included 600 m3 low-level liquid radioactive waste and 14 m3 of solid radioactive waste with an average specific activity of 4.52 Bq ml(-1) and 2.22 kBq g(-1), respectively. External radiation doses of the workers were determined using TLD (NG 6,7) and direct reading dosimeters. The maximum individual external radiation dose received by any worker during this practice was 5 mSv, which was 25% of the annual dose limit of 20 mSv. Detection and measurement of internal contamination was carried out using bioassay techniques. During the whole operation, not a single case of internal contamination was detected. The ambient radiation levels around waste seepage pits are periodically monitored using TLD (G-2 cards) and G. M. radiation survey meters. Underground migration of radioactivity is checked by analyzing seepage water samples taken from boreholes that have been dug at different locations in the vicinity of the radioactive residues. The monitoring around disposal sites containing radioactive residues has been continued during the last 9 y and will be continued in the future. So far, no rise in the environmental gamma radiation dose level and migration of underground radionuclides has been found in the vicinity of these disposal sites. Working personal during the decommissioning of PARR-I have been found to be radiologically safe. Adherence to the ALARA principle, sound decommissioning and proper radioactive waste disposal procedures helped to protect the working personnel, members of the public, and the environment from the harmful effects of the ionizing radiations present due to the partial decommissioning of the research reactor and its radioactive residues. Experience gained during this work, along with the current international procedures, will be helpful for full restoration of the environment from radioactive residues likely to be generated in the future from any other practices in Pakistan.

Body Burden↗
PubMed1997

Analysis of long-lived radionuclidic impurities in short-lived radiopharmaceutical waste using gamma spectrometry.

Large hospitals and biomedical research centers utilize decay-in-storage programs to minimize the volume of their low level radioactive waste. However, some medically useful radionuclides often contain small amounts of long-lived radionuclidic impurities which may complicate simple waste management procedures. We have evaluated the extent of this problem in low level radioactive waste involving 67Cu and (111)In over a 6-mo cycle of decay-in-storage by identifying the residual radionuclides in our dry waste using a multichannel analyzer. The multichannel analyzer was also used to quantify the radionuclide constituents of our liquid waste at the beginning of a decay-in-storage cycle. Radionuclides were identified by the presence of characteristic photopeaks of each isotope in the gamma spectrum and quantified by region of interest analysis. After a decay-in-storage cycle, long-lived 58Co, 57Co, and 56Co isotopes were observed in dry 67Cu waste and (114m)In identified in dry (111)In waste. The (114m)In was detected in dry (111)In waste containing initial (114m)In activity of 740 kBq (20 microCi), while the cobalt radionuclides were detected in dry 67Cu waste containing initial 58Co, 57Co, and 56Co activities of 444, 148, and 148 kBq (12, 4, and 4 microCi), respectively. Such dry low level radioactive waste was thus disqualified from short-term radioactive waste storage programs. The radionuclide constituents in the liquid waste were quantified in microCi mL(-1) and confirmed to be within the Nuclear Regulatory Commission set limits of 2 x 10(-4), 6 x 10(-4) and 6 x 10(-5) microCi mL(-1) for 58Co, 57Co, and 56Co, respectively, before disposal. The highest levels of long-lived isotopes that have been found in our liquid low level radioactive waste at the beginning of decay-in-storage were 5.5 x 10(-4), 4.8 x 10(-4), and 1.4 x 10(-4) microCi mL(-1) for 58Co, 57Co, and 56Co, respectively. Gamma spectrometry can be used to aid waste segregation and final management decisions on low level radioactive waste.

Copper Radioisotopes↗
PubMed2000

Removal of 125I from radioactive experimental waste with an anion exchange paper membrane.

The behavior of radioactive iodide and chloride ions through an anion exchange paper membrane to remove 125I from radioactive experimental waste has been studied with nonequilibrium thermodynamic analyses. Anion exchange paper membrane was found to be electroconductively more permeable to iodide ion than to chloride ion. The iodide ion bound more strongly to the anion exchange site within a membrane phase than the chloride ion by more than twice. The results suggested that an anion exchange paper membrane was appropriate for the filtration removal system.

Filtration↗
PubMed1998

Engineering a recombinant Deinococcus radiodurans for organopollutant degradation in radioactive mixed waste environments.

Thousands of waste sites around the world contain mixtures of toxic chlorinated solvents, hydrocarbon solvents, and radionuclides. Because of the inherent danger and expense of cleaning up such wastes by physicochemical methods, other methods are being pursued for cleanup of those sites. One alternative is to engineer radiation-resistant microbes that degrade or transform such wastes to less hazardous mixtures. We describe the construction and characterization of recombinant Deinococcus radiodurans, the most radiation-resistant organism known, expressing toluene dioxygenase (TDO). Cloning of the tod genes (which encode the multicomponent TDO) into the chromosome of this bacterium imparted to the strain the ability to oxidize toluene, chlorobenzene, 3,4-dichloro-1-butene, and indole. The recombinant strain was capable of growth and functional synthesis of TDO in the highly irradiating environment (60 Gy/h) of a 137Cs irradiator, where 5x10(8)cells/ml degraded 125 nmol/ml of chlorobenzene in 150 min. D. radiodurans strains were also tolerant to the solvent effects of toluene and trichloroethylene at levels exceeding those of many radioactive waste sites. These data support the prospective use of engineered D. radiodurans for bioremediation of mixed wastes containing both radionuclides and organic solvents.

Chromosome Mapping↗
PubMed2006

A radioactive metal processing industry perspective source.

The current U.S. economic environment for the disposition of radioactive waste, including very-low-activity metals, is currently experiencing relatively low radioactive disposal costs and readily available disposal space. Despite the recent market increase in demand for recycled scrap metal commodities, there is still little change in the behavior of the nuclear industry (including radioactive waste processors and radioactive scrap metal recyclers) to pursue the recycling of potentially contaminated scrap metal. The relatively low cost of traditional radioactive waste disposal combined with the perceived risks associated with recycling of previously contaminated metals means that most U.S. radioactive facility managers and stakeholders will elect not to recycle. Current technology exists and precedence has been set for prescreening (by means of bulk radioactive assay techniques) scrap metal that is not contaminated and diverting it to industrial landfills for disposal. Other processes also allow some radiologically contaminated metals to be melted and recast into products with low, but acceptable, activity levels for restricted use in the nuclear industry. A new concept is being considered that would create a centralized licensed facility for the process and disposition of "very-low-activity" metals for "directed first use." The advantages to this type of approach would include a standardized method for licensing the clearance process.

Decision Making↗
PubMed2001

Ferrate treatment for removing chromium from high-level radioactive tank waste.

A method has been developed for removing chromium from alkaline high-level radioactive tank waste. Removing chromium from these wastes is critical in reducing the volume of waste requiring expensive immobilization and deep geologic disposition. The method developed is based on the oxidation of insoluble chromium(III) compounds to soluble chromate using ferrate. This method could be generally applicable to removing chromium from chromium-contaminated solids, when coupled with a subsequent reduction of the separated chromate back to chromium(III). The tests conducted with a simulated Hanford tank sludge indicate that the chromium removal with ferrate is more efficient at 5 M NaOH than at 3 M NaOH. Chromium removal increases with increasing Fe(VI)/Cr(II) molar ratio, but the chromium removal tends to level out for Fe(VI)/ Cr(III) greaterthan 10. Increasingtemperature leadsto better chromium removal, but higher temperatures also led to more rapid ferrate decomposition. Tests with radioactive Hanford tank waste generally confirmed the simulant results. In all cases examined, ferrate enhanced the chromium removal, with a typical removal of around 60-70% of the total chromium present in the washed sludge solids. The ferrate leachate solutions did not contain significant concentrations of transuranic elements, so these solutions could be disposed as low-activity waste.

Chromium↗
PubMed1993

Managing radioactively contaminated infectious waste at a large biomedical facility.

Proper management of infectious waste containing radioactive material depends on three program elements. First, screening methods are required to identify medical waste containing radioactive material. Second, a means of managing the volume of waste identified has to be developed. Management includes identifying the radioisotopes, dealing with the physical requirements of the waste (e.g., the need for cold storage), and treating the material as a mixed waste. Finally, methods to limit production of waste at its source must be implemented. This includes educating the radioactive material users, enabling them with the means of reducing waste volume, and giving them feedback on how well they are implementing the waste reduction practices.

Academic Medical Centers↗