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PubMed1989

Low-level radioactive wastes. Council on Scientific Affairs.

Under a federal law, each state by January 1, 1993, must provide for safe disposal of its low-level radioactive wastes. Most of the wastes are from using nuclear power to produce electricity, but 25% to 30% are from medical diagnosis, therapy, and research. Exposures to radioactivity from the wastes are much smaller than those from natural sources, and federal standards limit public exposure. Currently operating disposal facilities are in Beatty, Nev, Barnwell, SC, and Richland, Wash. National policy encourages the development of regional facilities. Planning a regional facility, selecting a site, and building, monitoring, and closing the facility will be a complex project lasting decades that involves legislation, public participation, local and state governments, financing, quality control, and surveillance. The facilities will utilize geological factors, structural designs, packaging, and other approaches to isolate the wastes. Those providing medical care can reduce wastes by storing them until they are less radioactive, substituting nonradioactive compounds, reducing volumes, and incinerating. Physicians have an important role in informing and advising the public and public officials about risks involved with the wastes and about effective methods of dealing with them.

Environmental Monitoring↗
PubMed1987

Trees as indicators of subterranean water flow from a retired radioactive waste disposal site.

Tree sampling helped locate a subterranean flow of tritiated water from a low-level radioactive waste disposal site that had not been detected by well water monitoring alone. Deciduous trees growing in a natural forest on the hillsides downslope from the site were sampled for the presence of tritiated water in sap of maple trees and in leaf water extracted from oak and hickory trees. Elevated concentrations of 3H were detected in the leaf water extracted from several trees located 50 m downslope from the western boundary of the fenced exclusion zone. A 3-m-deep well drilled near these trees indicated that the source of tritiated water was a narrow zone of subterranean flow.

Radioactive Waste↗
PubMed2003

Engineering Deinococcus geothermalis for bioremediation of high-temperature radioactive waste environments.

Deinococcus geothermalis is an extremely radiation-resistant thermophilic bacterium closely related to the mesophile Deinococcus radiodurans, which is being engineered for in situ bioremediation of radioactive wastes. We report that D. geothermalis is transformable with plasmids designed for D. radiodurans and have generated a Hg(II)-resistant D. geothermalis strain capable of reducing Hg(II) at elevated temperatures and in the presence of 50 Gy/h. Additionally, D. geothermalis is capable of reducing Fe(III)-nitrilotriacetic acid, U(VI), and Cr(VI). These characteristics support the prospective development of this thermophilic radiophile for bioremediation of radioactive mixed waste environments with temperatures as high as 55 degrees C.

Biodegradation, Environmental↗
PubMed1990

Low-level radioactive wastes. AMA Council on Scientific Affairs.

Under a federal law, each state by January 1, 1993, must provide for safe disposal of its low-level radioactive wastes. Most of the wastes are from using nuclear power to produce electricity, but 25% to 30% are from medical diagnosis, therapy, and research. Exposures to radioactivity from the wastes are much smaller than those from natural sources, and federal standards limit public exposure. Currently operating disposal facilities are in Beatty, Nev, Barnwell, SC, and Richland, Wash. National policy encourages the development of regional facilities. Planning a regional facility, selecting a site, and building, monitoring, and closing the facility will be a complex project lasting decades that involves legislation, public participation, local and state governments, financing, quality control, and surveillance. The facilities will utilize geological factors, structural designs, packaging, and other approaches to isolate the wastes. Those providing medical care can reduce wastes by storing them until they are less radioactive, substituting nonradioactive compounds, reducing volumes, and incinerating. Physicians have an important role in informing and advising the public and public officials about risks involved with the wastes and about effective methods of dealing with them.

Physician's Role↗
PubMed2005

Calculation of absorbed dose around a facility for disposing of low activity natural radioactive waste (C3-dump).

A C3-dump is a facility for disposing of low activity natural radioactive waste containing the uranium series 238U, the thorium series 232Th and 40K. Only the external radiation owing to gamma rays, X-rays and annihilation photons is considered in this study. For two situations--the semi-infinite slab and the tourist geometry--the conversion coefficients from specific activity to air kerma rate at 1 m above the relevant level are calculated. In the first situation the waste material is in contact with the air but in the tourist geometry it is covered with a 1.35 m thick layer. For the calculations, the Monte Carlo radiation transport code MCNP is used. The yield and photon energy for each radionuclide are according to the database of Oak Ridge National Laboratory. For the tourist situation, the depth-dose distribution through the covering layer is calculated and extrapolated to determine the exit dose.

Computer Simulation↗
PubMed2000

Mixing and sulphate-reducing activity of bacteria in swelling, compacted bentonite clay under high-level radioactive waste repository conditions.

AIM: The fate of micro-organisms in the bentonite clay surrounding high-level radioactive waste (HLW)-containing copper canisters in a future Swedish underground (500 m) repository were investigated. METHODS AND RESULTS: Laboratory experiments were designed in which the mixing of various bacterial species with swelling bentonite was studied. A clear trend of fewer cultivable bacteria at depth was seen in the clay. This trend was consistent as the incubation time was increased from 8 h to 28 weeks. Sulphate-reducing bacteria were found to be active, reducing sulphate at the lowest density studied, 1.5 g cm-3, but sulphate reduction activity ceased at higher densities. CONCLUSIONS: The number of viable micro-organisms in an HLW repository bentonite clay buffer will decrease rapidly during swelling and very few viable cells will be present at full compaction. SIGNIFICANCE AND IMPACT OF THE STUDY: Sulphate-reducing bacteria will most probably not be able to induce corrosion of HLW-containing copper canisters.

Bacteria↗
PubMedDate not supplied

Radioactive waste disposal in seas adjacent to the territory of the Russian Federation.

The former USSR illegally dumped into the ocean liquid and solid radioactive wastes (RW) originating from nuclear-powered vessels and ships. The Russian President created a special Commission to analyse both the scale and consequences of this activity. According to documentary data and expert estimates at the Commission's disposal, the maximum activity of RW that entered the seas adjacent to Russian territory could have been as much as 2,500 kCi at the time of disposal. The greatest radio-ecological hazard comes from reactors from nuclear submarines and core plates of the nuclear icebreaker 'Lenin', which had spent nuclear fuel in place and which were dumped in shallow water in the Kara Sea near Novaya Zemlya. Editor's note: This article extracts material from a Commission which published a report produced in Russia in 1993. Numerous sources in many Ministries and other government agencies, noted in the text, formed the basis for the final draft. The authors of the draft report were A. Yablokov, V. Karasev, V. Rumyantsev, M. Kokeev, O. Petrov, V. Lystsov, A. Yemelyanenkov and P. Rubtsov. After approving the draft report, the Commission submitted the report to the President of the Russian Federation in February 1993. By Presidential decision, this report (after several technical corrections) was open to the public: it is known variously as 'the Yablokov Commission report, or more simply the 'Yablokov Report', the 'White Book' or 'Yablokov White Paper'. During April-May 1993, 500 copies were distributed among governmental agencies inside Russia, and abroad through a net of Russian Embassies. This article was later sent to Dr Mike Champ as part of the ongoing collections of papers on the Arctic published in this journal (edited by Champ et al.: 1997 'Contaminants in the Arctic', Marine Pollution Bulletin 35, pp. 203-385 and in Marine Pollution Bulletin 2000, vol. 40, pp. 801-868, and continued with the present collection).

Accidents↗
PubMed1997

Radiation doses to critical groups since the early 1950s due to discharges of liquid radioactive waste from Sellafield.

First, some of the early work is reviewed on exposure pathways in connection with proposed and early liquid radioactive waste discharges from Sellafield. The main historical features of these discharges, affected by relevant plant operations, are then briefly described. The important radiological exposure pathways resulting from the discharges and people's consumption and occupancy habits are considered. To place the changing scenario onto a consistent basis using present-day methodology, a reconstruction of exposures has been carried out using environmental monitoring data and models. The three major pathways are examined of Porphyra/laverbread consumption in South Wales, fish and shellfish consumption near Sellafield, and external exposure over local and more distant sediments. The results show that over the period 1952 to about 1970 the laverbread pathway was probably critical, taking a cautious approach. Effective dose rates fluctuated at around 1 mSv y(-1) from about 1956 to 1971. From about 1970 to 1985, the fish and shellfish pathway was likely to have been critical, with effective dose rates peaking at about 2 mSv y(-1) in 1975-1976. External exposure was likely to have been of lesser importance than the other two pathways until about 1985, when with the retention of previously-released radiocesium on sediments it has become dominant. This phenomenon applies particularly further afield where radiocesium concentrations have been slower to decline; in the Ribble estuary, houseboat dwellers have been the critical group from about 1985. Effective doses have been at about 0.3 mSv y(-1) and declining; they are due to the effects of radiocesium discharges in earlier years. Dose rates have remained within contemporary ICRP dose limits.

Actinoid Series Elements↗
PubMed1987

Measurement of 99Tc in low-level radioactive waste from reactors using 99mTc as a tracer.

A radiochemical procedure has been developed for measuring 99Tc in major low-level radioactive waste streams from commercial nuclear power facilities which contain numerous potential contaminants. Separation was by alkaline precipitation and anion exchange chromatography; trace amounts of 60Co and other radioactive contaminants were removed by solvent separation. Pure separations were obtained with average radiochemical yield of 47.3 +/- 4.3% determined by a 99mTc tracer. The lower limit of detection for 99Tc was found to be 0.16 pCi/g based on 10-g sample and a 100-min counting time.

Alkalies↗
PubMed2000

Cleaning of liquid radioactive wastes using natural zeolites.

Natural zeolite, clinoptilolite, was used to eliminate liquid radioactive wastes (LRW) 137Cs and 90Sr. The influence of several factors (pH of solution, grain size of the zeolite, etc.) on the process effectivity was studied. It was shown that clinoptilolite is an effective filter of the nuclides above.

Journal Article↗