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At least 19 recordsLinked to original sources
PubMed2001

Foaming in simulated radioactive waste.

Radioactive waste treatment process usually involves concentration of radionuclides before waste can be immobilized by storing it in stable solid form. Foaming is observed at various stages of waste processing like SRAT (sludge receipt and adjustment tank) and melter operations. This kind of foaming greatly limits the process efficiency. The foam encountered can be characterized as a three-phase foam that incorporates finely divided solids (colloidal particles). The solid particles stabilize foaminess in two ways: by adsorption of biphilic particles at the surfaces of foam lamella and by layering of particles trapped inside the foam lamella. During bubble generation and rise, solid particles organize themselves into a layered structure due to confinement inside the foam lamella, and this structure provides a barrier against the coalescence of the bubbles, thereby causing foaming. Our novel capillary force balance apparatus was used to examine the particle-particle interactions, which affect particle layer formation in the foam lamella. Moreover, foaminess shows a maximum with increasing solid particle concentration. To explain the maximum in foaminess, a study was carried out on the simulated sludge, a non-radioactive simulant of the radioactive waste sludge at SRS, to identify the parameters that affect the foaming in a system characterized by the absence of surface-active agents. This three-phase foam does not show any foam stability unlike surfactant-stabilized foam. The parameters investigated were solid particle concentration, heating flux, and electrolyte concentration. The maximum in foaminess was found to be a net result of two countereffects that arise due to particle-particle interactions: structural stabilization and depletion destabilization. It was found that higher electrolyte concentration causes a reduction in foaminess and leads to a smaller bubble size. Higher heating fluxes lead to greater foaminess due to an increased rate of foam lamella generation in the sludge system.

Chemical Phenomena↗
PubMed1995

A methodology for evaluating the toxicity of radioactive waste and its application to the radioactive waste generated in Pennsylvania.

Communicating with the public on the risks of low-level radioactive waste disposal is difficult due to the lack of comparisons that are understandable to the public. This paper presents a methodology for analyzing the intrinsic toxicity of radionuclides in waste and comparing it to that for soil or other wastes that may contain naturally-occurring radionuclides. The intrinsic toxicity of each radionuclide is normalized by dividing its specific activity in the waste by an appropriate ingestion risk standard, such as the U.S. EPA proposed drinking water limits. To illustrate the usefulness of this method, it was used to analyze Pennsylvania's commercial low-level radioactive waste inventory. The results are presented along with an indication of the usefulness of this method for screening purposes to analyze and identify problematic constituents in various waste streams.

Evaluation Studies as Topic↗
PubMed1995

[Management and storage of radioactive waste].

Management of radioactive waste is a matter of public concern. Such management, however, is today handled industrially in France, and when these techniques are well applied, it is possible to create storage centres. Waste having a short half-life is now stored in the Centre de l'Aube, which replaces the one begun in 1969 in the Department de la Manche. For waste with a long half-life, following the law passed in 1991, ANDRA is pursuing its programme of site prospection to establish two underground laboratories for studying geological storage.

Drug Storage↗
PubMed1978

[Draining of radioactive waste water from departments working with radioactive material after introduction of the law for radiation protection (author's transl)].

In order to establish the drainage of radioactive waste water 1976 in the Federal Republic of Germany a new law for radiation protection was introduced. In this paper a concept is introduced how to determine specifications for constructing a decay plant using the given data of a department for nuclear medicine. The given boundary conditions were to secure a low concentration of radioactive material in order to establish the drainage of extreme low activities without diluting it.

Berlin↗
PubMed1986

Disposal of low-level radioactive wastes.

The generation of low-level radioactive waste is a natural consequence of the societal uses of radioactive materials. These uses include the application of radioactive materials to the diagnosis and treatment of human disease and to research into the causes of human disease and their prevention. Currently, low level radioactive wastes are disposed of in one of three shallow land-burial disposal sites located in Washington, Nevada, and South Carolina. With the passage in December 1980 of Public Law 96-573, "The Low-Level Radioactive Waste Policy Act," the disposal of low-level wastes generated in each state was identified as a responsibility of the state. To fulfill this responsibility, states were encouraged to form interstate compacts for radioactive waste disposal. At the present time, only 37 states have entered into compact agreements, in spite of the clause in Public Law 96-573 that established January 1, 1986, as a target date for implementation of state responsibility for radioactive wastes. Recent action by Congress has resulted in postponement of the implementation date to January 1, 1993.

Radioactive Waste↗
PubMed1982

Radionuclide export and elimination by coyotes at two radioactive waste disposal areas in southeastern Idaho.

Coyote fecal samples were collected near a radioactive waste leaching pond and a solid radioactive waste disposal facility and analyzed for radioactivity. Elevated concentrations of 137Cs, 90Sr and 238Pu in the samples from the liquid radioactive waste leaching area were attributed to coyotes ingesting contaminated pond water and/or small mammals. Elevated 241Am concentrations in coyote fecal samples collected around the solid radioactive waste disposal facility were due to ingestion of contaminated small mammals. Assumptions relative to the coyote use of these areas permitted an estimate of the maximum quantity of radioactivity exported and eliminated around the facilities. An annual total of 7.2, 31.4 and 1.8 microCi (90Sr, 137Cs, 238Pu, 239,240Pu, 241Am, 242Cm and 244Cm) was eliminated by coyotes within a 6.3 km radius of the solid radioactive waste disposal facility, liquid waste leaching pond, and control area, respectively. These quantities of radioactivity eliminated by coyotes were similar or less than quantities transported by other mechanisms such as waterfowl and vegetative uptake of radioactivity. Coyotes are a mode of radionuclide transport from the two radioactive waste disposal areas; however, due to the low radionuclide concentrations and low yearly radionuclide inventories in coyote fecal samples, it is doubtful that any significant environmental consequences occur as a result of this transport mechanism.

Animals↗
PubMed2002

Microbially mediated redox processes in natural analogues for radioactive waste.

Natural analogues allow scientists to investigate biogeochemical processes relevant to radioactive waste disposal that occur on time scales longer than those that may be studied by time-limited laboratory experiments. The Palmottu U-Th deposit in Finland and the Bangombé natural nuclear reactor in Gabon involve the study of natural uranium, and are both considered natural analogues for subsurface radioactive waste disposal. The microbial population naturally present in groundwater may affect the redox conditions, and hence, the radionuclide solubility and migration. Therefore, groundwater samples from the two sites were investigated for microbial populations. The total numbers of cells ranged from 10(4) to 10(6) cells ml(-1). Iron-reducing bacteria (IRB) were the largest culturable microbial population in the Palmottu groundwater and were present at up to 1.3 x 10(5) cells ml(-1). Sulfate-reducing bacteria (SRB) and acetogens could also be cultured from the Palmottu groundwater. The numbers of IRB and SRB were largest in groundwater with the lowest uranium concentrations. Removal of dissolved U(VI) from solution was concomitant with the growth of IRB enrichment cultures and the reduction of iron. The redox buffer in the Palmottu groundwater consists of iron and uranium species, both of which are affected by IRB. IRB and aerobic heterotrophs were cultured from the Bangombé groundwater, where redox potentials are buffered by iron and organic carbon species. Microbial populations similar to those found at Palmottu and Bangombé are found throughout the Fennoscandian Shield, a potential host rock for subsurface radioactive waste disposal. These results confirm that microorganisms can be expected to play a role in stabilizing radioactive waste disposed of in the subsurface by lowering redox potential and immobilizing radionuclides.

Bacteria↗
PubMed1993

Radioactive waste management at a large university and medical research complex.

A radioactive waste management program was developed for a large university and medical research complex to contain costs and to reduce the impact of the Low-Level Radioactive Waste Policy Act. The program takes advantage of decay-in-storage, incineration, special packaging techniques, and increased training and awareness. A series of metrics are presented to evaluate the effectiveness of the radioactive waste management program. Through the use of this program the amount of waste disposed of at commercial burial sites decreased from 98% to 1.61% of the waste generated. At the same time the volume of waste generated per laboratory declined by almost 45%, from 0.35 m3 (12.31 ft3) to 0.19 m3 (6.80 ft3).

Academic Medical Centers↗
PubMed2003

Review of the radioactive waste management system in Nigeria.

The management of radioactive waste in Nigeria from early 1960 to date is reviewed. As in many developing countries, waste management in Nigeria has been shown to be ineffective. The factors that are responsible for this ineffectiveness are identified and discussed. The steps being taken by and the opportunities available to the newly established Nigerian Nuclear Regulatory Authority towards addressing this problem of ineffectiveness are discussed. The efforts of this newly set up body towards managing the resultant radioactive wastes that will be generated during the use of a reactor and an accelerator that will soon be commissioned in Nigeria are also mentioned. Likely ways of further addressing the problems militating against waste management in developing countries are suggested.

Developing Countries↗