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PubMed2001

Development and application of marine gamma-ray measurements: a review.

The development of instruments to measure gamma radiation in the marine environment, particularly on the sea floor, and the range of uses to which they have been put is reviewed. Since the first steps in the late 1950s, systems have been developed in at least 10 countries with the main thrust occurring in the 1970s. Development has continued up to the present, primarily in Europe and the USA. Marine gamma-ray spectrometers have been used for a range of applications including the mapping of rocks and unconsolidated sediments, mineral exploration (mainly for heavy minerals and phosphorites), sediment transport studies and investigations in relation to discharged and dumped nuclear wastes and at nuclear weapon test sites.

Europe↗
PubMed2005

Cryogenic laser induced U(VI) fluorescence studies of a U(VI) substituted natural calcite: implications to U(VI) speciation in contaminated Hanford sediments.

Time-resolved laser-induced fluorescence spectroscopy (TRLFS) and imaging spectromicroscopy (TRLFISM) were used to examine the chemical speciation of uranyl in contaminated subsurface sediments from the U.S. Department of Energy (U.S. DOE) Hanford Site, Washington. Spectroscopic measurements for contaminant U(VI) were compared to those from a natural, uranyl-bearing calcite (NUC) that had been found via X-ray absorption spectroscopy (XAS) to include uranyl in the same coordination environment as calcium. Spectral deconvolution of TRLFS measurements on the NUC revealed the unexpected presence of two distinct chemical environments consistent with published spectra of U(VI)-substituted synthetic calcite and aragonite. Apparently, some U(VI) substitution sites in calcite distorted to exhibit a local, more energetically favorable aragonite structure. TRLFS measurements of the Hanford sediments NP4-1 and NP1-6 were similar to the NUC in terms of peak positions and intensity, despite a small CaCO3 content (1.0 to 3.2 mass %). Spectral deconvolution of the sediments revealed the presence of U(VI) in calcite and aragonite structural environments. A third, unidentified U(VI) species was also present in the NP1-6 sediment. TRLFISM measurements at multiple locations in the different sediments displayed only minor variation, indicating a uniform speciation pattern. Collectively, the measurements implied that waste U(VI), long-resident beneath the sampled disposal pond (32 y), had coprecipitated within carbonates. These findings have major implications for the solubility and fate of contaminant U(VI).

Calcium Carbonate↗
PubMed1987

An improved environmental pathway model for assessing high-level waste repository risks.

An environmental pathway model useful for assessing the postclosure radiological risks from high-level waste repositories has been developed. The model describes more fully than its predecessors the long-term build-up of radionuclides in the biosphere and is consequently better suited to the analysis of the prolonged radionuclide releases potentially associated with geologic waste repositories. The effect of incorporating the additional features is to alter, in some cases substantially, the predicted population risks associated with a given long-term release of particular radionuclides. The model has been used to evaluate certain assumptions underlying the environmental standard for high-level waste repositories recently issued by the U.S. Environmental Protection Agency.

Humans↗
PubMed2001

Public and occupational risks of the Nevada (USA) Test Site.

The Nevada Test Site (NTS), north of Las Vegas, was the scene of hundreds of nuclear weapons tests over four decades, both above- and below ground. There is considerable interest, both in neighboring communities and elsewhere, in the risks it poses. Overall, the greatest risks are nonradioactive in origin, with occupational risks to employees and accident risks in transporting low-level nuclear wastes to the NTS from other Department of Energy (DOE) sites ranking highest. For radiation risks, that to workers handling radioactive materials is much higher than that to the surrounding population, either present or future. Overall, annual risks are small, with all fatalities approximately 0.008% of total Nevada deaths. At the NTS, the government spends about 5000 times more on radiation as opposed to nonradiation deaths. This suggests that at least some resources may be misallocated towards cleanup of public risks and that the occupational risk of cleanup may be much higher than the public risk. Thus risk may be multiplied by well-meaning programs.

Accidents, Occupational↗
PubMed2006

Assessing spatial, temporal, and analytical variation of groundwater chemistry in a large nuclear complex, USA.

Statistical analyses were applied at the Hanford Site, USA, to assess groundwater contamination problems that included (1) determining local backgrounds to ascertain whether a facility is affecting the groundwater quality and (2) determining a 'pre-Hanford' groundwater background to allow formulation of background-based cleanup standards. The primary purpose of this paper is to extend the random effects models for (1) assessing the spatial, temporal, and analytical variability of groundwater background measurements; (2) demonstrating that the usual variance estimate s2, which ignores the variance components, is a biased estimator; (3) providing formulas for calculating the amount of bias; and (4) recommending monitoring strategies to reduce the uncertainty in estimating the average background concentrations. A case study is provided. Results indicate that (1) without considering spatial and temporal variability, there is a high probability of false positives, resulting in unnecessary remediation and/or monitoring expenses; (2) the most effective way to reduce the uncertainty in estimating the average background, and enhance the power of the statistical tests in general, is to increase the number of background wells; and (3) background for a specific constituent should be considered as a statistical distribution, not as a single value or threshold. The methods and the related analysis of variance tables discussed in this paper can be used as diagnostic tools in documenting the extent of inherent spatial and/or temporal variation and to help select an appropriate statistical method for testing purposes.

Analysis of Variance↗
PubMedDate not supplied

Laser resonance ionization mass spectrometry measurements of cesium in nuclear burn-up and sediment samples.

Isotopic ratio measurements of 135Cs to 137Cs were performed using both resonance ionization mass spectrometry (RIMS) and thermal ionization mass spectrometry (TIMS) to determine the chronological age of nuclear fuel burn-up samples. Initial measurements on a lake sediment sample are being performed at NIST for determination of cesium content in the sample. Atomization behavior of the graphite furnace source, the overall efficiency and selectivity were measured for different sample preparations. Single-resonance excitation 6s 2S1/2 (F=4) --> 6p 2P3/2 (F' = 5) with an extended cavity diode laser followed by photoionization with the 488nm line of an argon ion laser yielded optical selectivity for 135Cs and 137Cs of more than two orders of magnitude against stable 133Cs and overall selectivity of 10(8). An overall efficiency of 5 x 10(-7) was measured for standard 133Cs solutions and for the nuclear fuel burn-up samples.

Cesium Radioisotopes↗
PubMed2003

Assessment of doses to the offspring of the Techa River cohort due to intakes of radionuclides by the mother.

The Techa River was contaminated as a result of radioactive releases by the Mayak plutonium production facility in 1949-1956. The residents of riverside communities were exposed to internal irradiation from radionuclides ingested mainly with river water, and also to external gamma irradiation resulting from shoreline and flood-plain contamination. The most important role in population exposure was played by (89,90)Sr and 137Cs. The persons born after the onset of the contamination have been identified as the 'Techa River Offspring Cohort' (TROC). The TROC has the potential to provide direct data on health effects in progeny that resulted from exposure of a general population to chronic radiation. This report describes the results of the calculation of fetal doses due to intakes of radionuclides by their mothers. Particular attention has been given to fetal dose from 90Sr because this nuclide is the most significant in terms of population dose for the Techa River. The comparison of the fetal bone marrow doses evaluated using different approaches proposed in the literature has shown a large dispersal in dose values. The main cause of this is the difference in model assumptions simplifying some developmental aspects of fetal haematopoiesis and bone formation. This paper presents an analysis of these basic assumptions that could be useful for further improvements in fetal dosimetry.

Body Burden↗
PubMed1998

Comprehensive quality assurance in medical use and a standard of care--NRC. Advance notice of proposed rulemaking: withdrawal.

The Nuclear Regulatory Commission (NRC) is withdrawing an advance notice of proposed rulemaking (ANPRM) that requested public comments on questions related to comprehensive quality assurance and a standard of care in medical uses of byproduct material. The Commission has decided to withdraw this ANPRM because of the effective implementation of the "Quality Management Program and Misadministrations" rule and the NRC's current efforts in revising the existing regulation for medical uses of byproduct material into a more risk-informed and performance-based regulation.

Government Agencies↗
PubMed1998

Comprehensive quality assurance in medical use and a standard of care; correction--NRC. Advance notice of proposed rulemaking: withdrawal; correction.

This document corrects a notice appearing in the Federal Register on December 2, 1998 (63 FR 66496), that withdraws an advance notice of proposed rulemaking that requested public comments on questions related to comprehensive quality assurance and a standard of care in medical uses of byproduct material. This action is necessary to correct an erroneous telephone number.

Government Agencies↗
PubMed2003

Separation and recovery of radioactive and non-radioactive toxic trace elements from aqueous industrial effluents.

An update is presented on liquid membrane-based processes as viable and relevant alternatives to conventional approaches such as precipitation, solvent extraction, ion exchange processes and electrochemical techniques for the removal and recovery of some toxic and/or valuable trace metal ions including some actinides and fission products e.g. U, Am, Y etc and As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Zn etc from radioactive as well as non-radioactive aqueous waste solutions respectively. In particular, results of experiments aimed at developing supported liquid membrane(SLM)-based process using commercially available porous membranes and indigenously prepared track--etch membranes (TEMs) have been critically examined in laboratory studies to generate basic data needed to evaluate their utility for continuous operation without regeneration. These include effect of pore size, porosity, optimum pore size and their reusability. It is clearly demonstrated that indigenously prepared 10 microm thick TEMs with a porosity in the range of 2-5% give comparable transport rates for metal ions-matching with that of commercial membranes of much higher thickness (160 microm) and higher porosity of 60-85%. The smaller thickness of TEMs more than compensates for their lower porosity. It is shown that because of their well defined pore characteristics TEMs could serve as model supports in SLM studies. By comparing the values of permeability coefficient (P) for TEM and polytetraflouroethylene (PTFE) supports for the transport of Pb2+ chosen as a typical divalent metal ion, and using di-2 ethyl hexyl phosphoric acid (D2EHPA) as the carrier, it is unambiguously proved that diffusion of the metal complex across the membrane is the rate controlling step in metal ion transport in SLM-based processes. An overview of the experimental findings along with future outlook and suggestions for further work are presented in this paper.

Actinoid Series Elements↗