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PubMedDate not supplied

Estimation of past seepage volumes from calcite distribution in the Topopah Spring Tuff, Yucca Mountain, Nevada.

Low-temperature calcite and opal record the past seepage of water into open fractures and lithophysal cavities in the unsaturated zone at Yucca Mountain, Nevada, site of a proposed high-level radioactive waste repository. Systematic measurements of calcite and opal coatings in the Exploratory Studies Facility (ESF) tunnel at the proposed repository horizon are used to estimate the volume of calcite at each site of calcite and/or opal deposition. By estimating the volume of water required to precipitate the measured volumes of calcite in the unsaturated zone, seepage rates of 0.005 to 5 liters/year (l/year) are calculated at the median and 95th percentile of the measured volumes, respectively. These seepage rates are at the low end of the range of seepage rates from recent performance assessment (PA) calculations, confirming the conservative nature of the performance assessment. However, the distribution of the calcite and opal coatings indicate that a much larger fraction of the potential waste packages would be contacted by this seepage than is calculated in the performance assessment.

Calcium Carbonate↗

PubMedDate not supplied

Visualization experiment to investigate capillary barrier performance in the context of a Yucca Mountain emplacement drift.

The use of capillary barriers as engineered backfill systems to divert water away from radioactive waste potentially stored in a Yucca Mountain emplacement drift is investigated. We designed and conducted a flow visualization experiment to investigate capillary barrier performance in this context. A two-dimensional, thin slab, test system replicated the physical emplacement drift to one-quarter scale (1.4-m diameter) and included the simulated drift wall, waste canister, pedestal, capillary barrier backfill, and host-rock fracture system. Water was supplied at the top of the simulated drift and allowed to discharge by way of wicks located along the left wall of the cell (simulated fractures) or by a gravity drain at the bottom of the right side (simulated impermeable rock with floor drain). Photographs captured the migration of water and a blue dye tracer within the system, analytical balances measured the mass balance of water, while tensiometers measured the capillary pressure at numerous locations. Of particular concern to this test was the drainage of the capillary barrier, which terminates against the drift wall. We found that while the simulated fractures (left side) and drain (right side) each influenced the performance of the capillary barrier at early time, they had little differential affect at later times. Also of concern was the small disparity in capillary properties between the fine and coarse layer (limited by the need of a fine-grained material that would not filter into the coarse layer under dry conditions). While the capillary barrier was able to divert the majority of flow toward the edges of the system and away from the simulated waste canister, the barrier did not preclude flow in the coarse layer, which was noted to be visually wet next to the waste canister on day 92 and was continuing to take on water at termination on day 112.

Engineering↗

PubMed2005

Modelling of activation processes for GR-280 graphite at Ignalina NPP.

Ignalina Nuclear Power Plant (INPP) operates two RBMK-1500 water-cooled graphite-moderated channel-type power reactors. The total mass of graphite in the cores of both units at INPP is about 3600 tons. Modelling of activation processes in the reactor's structural materials is necessary for decommissioning planning, because large amounts of activated structural materials (graphite, stainless steel, concrete, etc.) should be managed as radioactive waste. Knowledge of radiological characteristics and a radioactive inventory of irradiated materials are essential in planning of the decommissioning processes. The purpose of this work was to perform conservative neutron activation analysis for decommissioning purposes of INPP. ORIGEN computer code was used for the calculations. Activity levels were calculated for different nuclides present in the graphite and estimates were made how these activity levels depend on irradiation time, neutron flux value and other parameters. Obtained results were compared with the data available from other investigations for GR-280 graphite.

Computer Simulation↗

PubMed2006

Residual waste from Hanford tanks 241-C-203 and 241-C-204. 1. Solids characterization.

Bulk X-ray diffraction (XRD), synchrotron X-ray microdiffraction (microXRD), and scanning electron microscopy/ energy-dispersive X-ray spectroscopy (SEM/EDS) were used to characterize solids in residual sludge from single-shell underground waste tanks C-203 and C-204 at the U.S. Department of Energy's Hanford Site in southeastern Washington state. Cejkaite [Na4(UO2)(CO3)3] was the dominant crystalline phase in the C-203 and C-204 sludges. This is one of the few occurrences of cejkaite reported in the literature and may be the first documented occurrence of this phase in radioactive wastes from DOE sites. Characterization of residual solids from water leach and selective extraction tests indicates that cejkaite has a high solubility and a rapid rate of dissolution in water at ambient temperature and that these sludges may also contain poorly crystalline Na2U207 [or clarkeite Na[(UO2)O(OH)](H2O)0-1] as well as nitratine (soda niter, NaNO3), goethite [alpha-FeO(OH)], and maghemite (gamma-Fe2O3). Results of the SEM/EDS analyses indicate that the C-204 sludge also contains a solid that lacks crystalline form and is composed of Na, Al, P, O, and possibly C. Other identified solids include Fe oxides that often also contain Cr and Ni and occur as individual particles, coatings on particles, and botryoidal aggregates; a porous-looking material (or an aggregate of submicrometer particles) that typically contain Al, Cr, Fe, Na, Ni, Si, U, P, O, and C; Si oxide (probably quartz); and Na-Al silicate(s). The latter two solids probably represent minerals from the Hanford sediment, which were introduced into the tank during prior sampling campaigns or other tank operation activities. The surfaces of some Fe-oxide particles in residual solids from the water leach and selective extraction tests appear to have preferential dissolution cavities. If these Fe oxides contain contaminants of concern, then the release of these contaminants into infiltrating water would be limited by the dissolution rates of these Fe oxides, which in general have lowto very low solubilities and slow dissolution rates at near neutral to basic pH values under oxic conditions.

Microscopy, Electron, Scanning↗

PubMed2003

Spent ion exchange resin-its treatment from the point of view of safe disposal.

Ion exchange process is one of the treatment methods for radioactive waste. The resin becomes no longer useful after number of cycles of usage. At the same time the regenerated resin cannot be considered as non active waste for disposal. Hence it is felt necessary that the regenerated resin is treated in a fashion so as to result in a form which can be considered as inactive material. It is possible to convert this spent resin into multivalent ionic form which are generally non leachable, thus providing the necessary properties for meeting the disposal criteria. Studies were carried out for the exchange of radioactive ions on these resins with ions like Al3+, Sn4+, Pb2+ and Fe3+ etc. The studies included leachability aspects, exchange with other active ions, thermal characteristics, compressive strength of the cement blocks loaded with the resin etc. Our studies indicated that the order of the stability of the resin with respect to properties like leachability, exchange properties etc. follow the trend as follows: Sn4+ > Pb2+ > Al3+ > Fe3+.

Compressive Strength↗

PubMed1962

Sanitary engineering aspects of nuclear energy developments.

So many developments have taken place in the field of nuclear energy since 1956, when the author's previous paper on radioactive waste disposal was published in the Bulletin of the World Health Organization, that a fresh review of the subject is now appropriate.The present paper deals with those aspects of the problem which are of most interest to the sanitary engineer. It considers specific points in the latest recommendations of the International Commission on Radiological Protection in relation to public drinking-water supplies, and examines the problem of fall-out, with special reference to the presence and significance of strontium-90 in drinking-water. A general survey of the various uses of radioactive materials is followed by a discussion of the legislative and control measures necessary to ensure safe disposal of wastes. The methods of waste disposal adopted in a number of nuclear energy establishments are described in detail. The paper concludes with some remarks on solid waste disposal, siting of nuclear energy industries and area monitoring.

Humans↗

PubMed2006

Role of state regulatory agencies in the disposition of low-activity radioactive materials.

Since the opening of the first disposal site for commercially generated low-level radioactive waste at Beatty, Nevada, in September 1962, the states have been explicitly involved in the process. The states have been involved as landowners, regulators, environmental monitors, and sometimes promoters of the sites and/or the businesses operating the sites.

Decision Making↗

PubMed2000

Engineering radiation-resistant bacteria for environmental biotechnology.

Seventy million cubic meters of ground and three trillion liters of groundwater have been contaminated by leaking radioactive waste generated in the United States during the Cold War. A cleanup technology is being developed based on the radiation-resistant bacterium Deinococcus radiodurans, which is being engineered to express bioremediating functions.

Bacteria↗

PubMedDate not supplied

[Mechanism of induction of cytogenetic damage in plant meristematic cells caused by combined effect of heavy natural radionuclides and heavy and alkaline metals].

The analysis of experimental data on the combined effect of 232Th and water from melted snow containing metal ions from industrally loaded territories on Tradescantia (clone 02) and on Allium shoenoprasum meristematic root tip cells treated with heavy natural radionuclides from natural water sources in the area of radioactive wastes storehouse is presented. It was demonstrated that plant meristematic cells response to heavy metals and heavy natural radionuclides, both from two-component model system and from natural water sources, have commom features.

Allium↗

PubMed1992

Historical perspective: a forward look, a backward look.

This paper summarizes how the problems of fallout, genetics, radioactive waste, and regulatory control of radiation were perceived by Dunning, Straub, Taylor, and others in 1955 at the inaugural meeting of the Health Physics Society. It was stated that health physicists had a great opportunity to resolve these problems and to avoid past mistakes. Throughout the 1950s, health physicists made major contributions to elucidating the fallout problem and contributed to its resolution, and it can be considered a success story. Waste disposal is not considered to be a success to date. A major difference has been the lack of political will to grapple with a perceived "no win" situation. The evolution of radiation limits is briefly traced over the past 37 y from voluntary standards to rigorously enforced regulations demanded by society. This paper speculates that the changing international scene makes the United States the pre-eminent nuclear power which will challenge future health physicists to maintain a balance between the control of radioactive material and its peaceful applications.

Health Physics↗

PubMed2005

Radiobiological monitoring of striped field mouse populations in the Moscow recreation forest "Kuzminki".

The results of radiometric and haematological studies of striped field mice (Apodemus agrarius) sampled over the years 1995-2003 from the territory of the preserved radioactive waste burial (RWB), which is located in the Moscow recreation forest "Kuzminki", are presented and discussed in the paper. It was shown that the level of 90Sr-90Y content in mice sampled from the RWB area varies within the range of 0-1200 Bq/kg with an average of 98.7+/-21.5 Bq/kg. The content of 90Sr-90Y in the body of 80% of the mice sampled from the RWB area was below 100 Bq/kg. Only in 4% of the sampled mice, the 90Sr-90Y specific radioactivity was above 300 Bq/kg. Haematological indications of the animals sampled from the RWB area were within the range of normal physiological fluctuations. Nevertheless, a slight but statistically significant increase in the average amount of erythrocytes and the average percentage of banded neutrophils was registered in peripheral blood of the mice.

Animals↗

PubMed2005

Large-scale modeling of reactive solute transport in fracture zones of granitic bedrocks.

Final disposal of high-level radioactive waste in deep repositories located in fractured granite formations is being considered by several countries. The assessment of the safety of such repositories requires using numerical models of groundwater flow, solute transport and chemical processes. These models are being developed from data and knowledge gained from in situ experiments such as the Redox Zone Experiment carried out at the underground laboratory of Aspö in Sweden. This experiment aimed at evaluating the effects of the construction of the access tunnel on the hydrogeological and hydrochemical conditions of a fracture zone intersected by the tunnel. Most chemical species showed dilution trends except for bicarbonate and sulphate which unexpectedly increased with time. Molinero and Samper [Molinero, J. and Samper, J. Groundwater flow and solute transport in fracture zones: an improved model for a large-scale field experiment at Aspö (Sweden). J. Hydraul. Res., 42, Extra Issue, 157-172] presented a two-dimensional water flow and solute transport finite element model which reproduced measured drawdowns and dilution curves of conservative species. Here we extend their model by using a reactive transport which accounts for aqueous complexation, acid-base, redox processes, dissolution-precipitation of calcite, quartz, hematite and pyrite, and cation exchange between Na+ and Ca2+. The model provides field-scale estimates of cation exchange capacity of the fracture zone and redox potential of groundwater recharge. It serves also to identify the mineral phases controlling the solubility of iron. In addition, the model is useful to test the relevance of several geochemical processes. Model results rule out calcite dissolution as the process causing the increase in bicarbonate concentration and reject the following possible sources of sulphate: (1) pyrite dissolution, (2) leaching of alkaline sulphate-rich waters from a nearby rock landfill and (3) dissolution of iron monosulphides contained in Baltic seafloor sediments. Based on these results, microbially mediated processes are postulated as the most likely hypothesis to explain the measured increase of dissolved bicarbonates and sulphates after tunnel construction.

Bicarbonates↗

PubMedDate not supplied

[Radionuclide accumulation by a microbial sorbent].

Accumulation of a wide range of radionuclides by the microbial sorbent has been studied. The microbial sorbent represents granules stable in water solutions for a long period of time. The sorbent includes: concentrated biomass of metabolically active microorganisms, sources of carbon and energy, phosphorus, nitrogen, etc. Availability of nutrition sources in the sorbent provides for metabolic activity of microorganisms immobilized in granules. Metabolic activity of the sorbent was characterized. Physico-chemical sorption and metabolic activity of microorganisms lead to the extraction of a wide spectrum of radionuclides (51Cr, 54Mn, 60Co, 90Sr, 134Cs, 137Cs, 140La, 144Ce, 226Ra, 83Rb) from liquid radioactive waste. The extraction factor for some radionuclides was 10(5)-10(6). The waste sorbent may be utilized. Absence of water phase in the ash concentrate permits the radionuclides to be buried in borosilicate or volcanic glass (accepted time of existence 10(5)-10(7) years). The sorbent may be used to create new biotechnologies of radionuclide accumulation from water solutions.

Absorption↗

PubMed2002

An initial radiation safety needs assessment of Costa Rica: the South Texas Chapter of the Health Physics Society's strategic planning appraisal for participation in the "Radiation Safety Without Borders" initiative.

In response to the Health Physics Society's recent 'radiation safety without borders" initiative, the South Texas Chapter of the Health Physics Society selected Costa Rica as its partner country of choice. To develop an understanding of the radiation safety needs of this country, the fall 2001 University of Texas Health Science Center at Houston School of Public Health Environmental Radiation and Radioactivity class was tasked with the assignment of assessing the possible radiation safety needs and concerns for this country. The assignment culminated in a class presentation to the membership of the South Texas Chapter during its annual fall meeting. Using library and web based resources, tile students reviewed a number of public health and radiation-related topics. Life expectancies were found to be equivalent to the United States, even though significant differences in per capita health expenditures were noted. Costa Rica exhibited lower population mortality rates from major causes such as cardiovascular diseases, neoplasms, and external sources. Maternal and infant mortality rates were found to be much higher in Costa Rica than in the United States. Naturally occurring radiation sources such as uranium deposits were not identified as apparent major radiation issues of concern, although ultraviolet radiation exposures are consistently high. Several recent events in the country and the region involving patient overexposures suggest that concerns are likely focused on ensuring the proper use and maintenance of healing arts radiation equipment. The lack of available information on radioactive waste disposal suggests that waste handling also may be an issue warranting attention. The exercise proved to be very educational for the students, and the information gathered will serve to focus the Chapter's efforts when technical exchanges are initiated. The importance of linking this initiative to other existing programs within the country is also discussed.

Costa Rica↗

PubMed2001

Solute transport properties of compacted Ca-bentonite used in FEBEX project.

The present Spanish concept of a deep geological high level waste repository includes an engineered clay barrier around the canister. The clay presents a very high sorption capability for radionuclides and a very small hydraulic conductivity, so that the migration process of solutes is limited by sorption and diffusion processes. Therefore, diffusion and distribution coefficients in compacted bentonite (i.e. in "realistic" liquid to solid ratio conditions) are the main parameters that have to be obtained in order to characterise solute transport that could be produced after the canister breakdown. Through-Diffusion (TD) and In-Diffusion (ID) experiments with HTO, Sr, Cs and Se were carried out using compacted FEBEX bentonite, which is the reference material for the Spanish concept of radioactive waste disposal. Experiments were interpreted by means of available analytical solutions that allow the estimation of diffusion coefficients and, in some cases, distribution coefficients. Analytical solutions are simple to use, but rely on hypotheses that do not hold in all the experiments. These experiments were interpreted also using an automatic parameter estimation code that overcomes the limitations of analytical solutions. Numerical interpretation allows the simultaneous estimation of porosity, diffusion and distribution coefficients, accounts for the role of porous sinters and time-varying boundary concentrations, and can use different types of raw concentration data.

Adsorption↗

PubMed2006

Practical aspects of peptide receptor radionuclide therapy with [177Lu][DOTA0, Tyr3]octreotate.

Lutetium-177 is increasingly used in patients for receptor-targeted radionuclide therapy with peptides such as [DOTA0,Tyr3]octreotate. In our therapy facility, we are performing yearly 400 treatments with each 7.4 GBq [177Lu][DOTA0,Tyr3]octreotate. Finger dosimetry data during radiolabeling reveal higher doses on the right hands of right-handed workers with the highest equivalent dose for the middle finger (53+/-12 microSv/GBq). Extrapolating dosimetry data, assuming 400 doses of 7.4 GBq per year performed by 4 workers, result in a mean equivalent dose of 23+/-11 mSv and 14+/-6 mSv for finger top and ring dose, respectively. Preparation of 400 doses will result in an effective dose of 0.5-1.5 mSv per year for these 4 workers. The extra radiation dose for workers during the radiolabeling of these doses thus remains below 10% of the legal annual limits, which is in accordance with the ALARA optimization principle. Based on measurements of the maximal radiation level at 1 m distance (7.5+/-3.6 microSv/h), patients treated with 7.4 GBq [177Lu][DOTA0,Tyr3]octreotate can already leave the therapy facility the next day. As radioactive waste streams are based on the half-lives of the used radionuclides, 177Lu-waste (t1/2=6.7 d) was initially collected along with the 131I-waste (t1/2=8 d). According to both manufacturers' specifications, 177Lu contains less than 0.4 kBq 177mLu/MBq 177Lu (at the end of neutron irradiation), when produced by the [176Lu n, gamma 177Lu] reaction via thermal neutron bombardment of enriched lutetium oxide. Unfortunately, because of the huge amounts of 177Lu used, contaminating 177mLu turned out to prevent the quick discharge of this waste, for some containers even after some years of storage. Therefore, a technique for calibrating 177mLu was developed, simultaneously confirming the manufacturer's specifications on the presence of 177mLu in 177Lu. Subsequently a reliable technique was developed to measure 177mLu in waste containers using a beta/gamma-contamination monitor. It is advised to collect 177mLu/177Lu-waste and certainly high-activity lutetium waste separated from 131I according the regulations in the country of use. Apart from the mentioned waste, excreta from patients are collected in decay tanks, where they are stored for 1-2 months before they are discarded into the general sewer within the overall tolerated discharge limit (150 radiotoxicity equivalents/year for our department).

Body Burden↗

PubMed1999

Medical effects of internal contamination with uranium.

The purpose of this work is to present an outline of the metabolic pathways of uranium isotopes and compounds, medical consequences of uranium poisoning, and an evaluation of the therapeutic alternatives in uranium internal contamination. The chemical toxicity of uranium has been recognized for more than two centuries. Animal experiments and human studies are conclusive about metabolic adverse affects and nephro- toxicity of uranium compounds. Radiation toxicity of uranium isotopes has been recognized since the beginning of the nuclear era, with well documented evidence of reproductive and developmental toxicity, as well as mutagenic and carcinogenic consequences of uranium internal contamination. Natural uranium (238U), an alpha emitter with a half-life of 4.5x10(9) years, is one of the primordial substances of the universe. It is found in the earth's crust, combined with 235U and 234U, alpha, beta, and gamma emitters with respective half-lives of 7.1x10(8) and 2.5x10(5) years. A special emphasis of this paper concerns depleted uranium. The legacy of radioactive waste, environmental and health hazards in the nuclear industry, and, more recently, the military use of depleted uranium in the tactical battlefield necessitates further insight into the toxicology of depleted uranium. The present controversy over the radiological and chemical toxicity of depleted uranium used in the Gulf War warrants further experimental and clinical investigations of its effects on the biosphere and human organisms.

Animals↗

PubMed1987

A case-control study of lung cancer relative to domestic radon exposure.

Public concern was expressed regarding the possibility of adverse health effects with the disposal of radioactive waste in Port Hope, Ontario. A case-control study was carried out to estimate the relative importance of domestic radon gas exposure in the causation of lung cancer in the town over a ten-year period. Twenty-seven cases met the entry criteria. Statistical analyses of results did not provide conclusive results that linked an increased risk of lung cancer and elevated domestic alpha radiation levels, when all factors were considered. However, a very strong association was demonstrated between cigarette smoking and lung cancer.

Humans↗