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PubMed2006

Low-activity radioactive materials management at the U.S. Department of Energy.

The U.S. Department of Energy (U.S. DOE) is making significant progress with the cleanup of its legacy radioactively-contaminated facilities and sites left from research and development and production of nuclear materials and weapons. Sites like Rocky Flats, Battelle Columbus Laboratories, Fernald, Mound, Brookhaven National Laboratory, Hanford, and Oak Ridge are faced daily with decisions related to disposition of waste and radioactive material. One key to this success is the disposition of waste arising from cleanup. Most of the generated waste volume has very low levels of radioactive contamination. The waste includes contaminated soil, debris from demolition, or scrap metal and equipment. The cost of disposing of large volumes of waste can be prohibitive, so there is incentive to find innovative ways to disposition wastes. This paper describes the current status of policy development in this area, such as development of a draft programmatic environmental impact statement and monitoring of related rulemaking at the U.S. Nuclear Regulatory Commission. The paper also provides an overview of draft U.S. DOE guidance on control and release of property with residual radioactive material, and site-specific applications of DOE guidance.

Decision Making↗
PubMed2006

Measurement of helium isotopes in soil gas as an indicator of tritium groundwater contamination.

The focus of this study was to define the shape and extent of tritium groundwater contamination emanating from a legacy burial ground and to identify vadose zone sources of tritium using helium isotopes (3He and 4He) in soil gas. Helium isotopes were measured in soil-gas samples collected from 70 sampling points around the perimeter and downgradient of a burial ground that contains buried radioactive solid waste. The soil-gas samples were analyzed for helium isotopes using rare gas mass spectrometry. 3He/4He ratios, reported as normalized to the air ratio (RA), were used to locate the tritium groundwater plume emanating from the burial ground. The 3He (excess) suggested that the general location of the tritium source is within the burial ground. This study clearly demonstrated the efficacy of the 3He method for application to similar sites elsewhere within the DOE weapons complex.

Environment↗
PubMed2003

Hanford single-pass reactor fuel storage basin demolition.

The Environmental Restoration Contractor at the Hanford Site is tasked with removing auxiliary reactor structures and leaving the remaining concrete structure surrounding each reactor core. This is referred to as Interim Safe Storage. Part of placing the F Reactor into Interim Safe Storage is the demolition of the fuel storage basin, which was deactivated in 1970 by placing debris material into the basin prior to back filling with soil. Besides the debris material (wooden floor decking, handrails, and monorail pieces), the fuel storage basin contents included the possibility of spent nuclear fuel, fuel buckets, fuel spacers, process tubes, and tongs. Demolition of the fuel storage basin offered many unique radiological control challenges and innovative approaches to demolition. This paper describes how the total effective dose equivalent and contamination were controlled, how the use of a remote operated excavator was employed to remove high-dose-rate material, and how wireless technology was used to monitor changing radiological conditions.

Decontamination↗
PubMed1998

Cancer mortality in the commune of Pargny sur Saulx in France.

Radioactive thorium wastes were found in April 1997 at the former industrial site of 'Orflam-Plast' in the commune of Pargny sur Saulx in the Northeast of France, where industrial activity began in 1934. On this site, between 1934 and 1970, cerium for lighter stones and thorium nitrate were extracted from imported monazite sand, a mineral containing elevated levels of natural radioactivity. We decided to study cancer mortality in the surrounding population. We found an excess of mortality due to lung and bladder cancer in the commune of Pargny sur Saulx and its neighbours, between 1968 and 1994. This excess did not seem to be linked to the river of Saulx which was a possible source of contamination. We conclude that a cancer incidence study of the former workers of this industrial site is necessary in order to investigate the role of natural radioactivity from monazite processing in the risk of cancer mortality among this workforce.

Adult↗
PubMed1985

Natural radioactivity of Australian building materials, industrial wastes and by-products.

The natural radioactivity due to the presence of 226Ra, 232Th and 40K in conventional raw materials and some solid industrial wastes and by-products which are being used or have a potential for use in the building and ceramic industries in Australia has been measured by gamma-ray spectrometry. The majority of materials examined in this work showed fairly low levels of radioactivity. Some samples of red mud, phosphogypsum, zircon products and fly ash did show higher levels of radioactivity than would be acceptable on the basis of a criterion formula for gamma-ray activity suggested for use in some OECD countries. But this higher level of radioactivity should not pose an environmental health problem when these materials constitute a relatively small portion of the materials used in a normal building. The present work has also shown that the radioactivity levels of some of the materials can be reduced through the removal of fines by sieving, as the fines seem to contain a higher concentration of radioactive nuclides.

Australia↗
PubMed2006

The contemporary materials cycle for radioactive 137Cs in the United States.

The materials cycle for (137)Cs, a low-level radioactive material of interest from a security perspective (as a possible source for "dirty bombs") as well as for its extensive industrial and medical uses, has been characterized for the United States for the year 2000. The focus is on products utilizing the isotope rather than on isotope production and subsequent disposal as a result of nuclear power generation. The results indicate that, during 2000, of the 1.5 PBq of (137)Cs that entered use, 94% was contained in sources in imported devices; the amounts in domestic source material recycling (4%) or as imported source materials (2%) were trivial by comparison. Losses from use were about 0.5 PBq; of this amount 86% was by radioactive decay, 11% was active source material that was recovered and recycled, and 3% was source material sent to low-level disposal sites. The current stock of (137)Cs in use is about 20 PBq; this stock is currently growing by more than 1 PBq per year (the difference between inputs to and losses from use). As a result, the security challenge related to monitoring stock in use is increasing by around 5% per year.

Cesium Radioisotopes↗
PubMed2003

Advanced characterization system deployments at the hanford site.

The Advanced Characterization System (ACS) uses readily available commercial radiation Environmental Restoration Contractor (ERC) detection and measurement equipment in a complementary staged system to locate and identity contamination in structures, systems and land area at Hanford's Environmental Restoration Contractor work sites. Large structures, such as former plutonium production reactors and separations facilities, are thoroughly and comprehensively characterized, not only for decontamination and decommissioning (D&D), but also for disposal and/or release. The ACS uses gamma-ray imaging instruments, in situ gamma spectrometry and large-area data-logging contamination survey meters to generate sufficient quality data to make operational and release decisions. The system is also used to safely characterize in-place systems without violating any containment and to localize activity in unusual situations.

Decontamination↗
PubMed2004

Colloid formation at waste plume fronts.

Highly saline and caustic tank waste solutions containing radionuclides and toxic metals have leaked into sediments at U.S. Department of Energy (DOE) facilities such as the Hanford Site (Washington state). Colloid transport is frequently invoked to explain migration of radionuclides and metals in the subsurface. To understand colloid formation during interactions between highly reactive fluids and sediments and its impact on contaminant transport, we simulated tank waste solution (TWS) leakage processes in laboratory columns at ambient and elevated (70 degrees C) temperatures. We found that maximum formation of mobile colloids occurred at the plume fronts (hundreds to thousands times higher than within the plume bodies or during later leaching). Concentrations of suspended solids were as high as 3 mass %, and their particle sizes ranged from tens of nanometers to a few micrometers. Calcium carbonate is always one of the dominant phases of the plume front colloids, while the other phases varied with solution pH and temperature. During infiltration of the leaked high-Na+ waste solution, rapid and completed Na+ replacement of exchangeable Ca2+ and Mg2+ from the sediment caused accumulation of these divalent cations at the moving plume front. Precipitation of supersaturated Ca2+/Mg2+-bearing minerals caused dramatic pH reduction atthe plume front. In turn, the reduced pH caused precipitation of other minerals. This understanding can help predict the behavior of contaminant trace elements carried by the tank waste solutions and could not have been obtained through conventional batch studies.

Adsorption↗