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Regulatory development of the interim and revised regulations for radioactivity in drinking water--past and present issues and problems.

Developing the Revised Regulations for Radioactivity in Drinking Water under the Safe Drinking Water Act requires information from all related areas and disciplines. As one step in the regulatory process, the background and history of that process as it applies to radioactivity in drinking water is described. The issues involved in developing the revised regulations are as follows: monitoring and sources of exposure, dose evaluation, health effects, engineering, economics and general policy development.

Animals↗

Contamination of firn layers by radioactive fission products from atmospheric fallout.

Measurements of gross beta activity and 3H concentration of firn samples from different regions can be used to determine environmental contamination by radioactive fallout from nuclear weapons tests in the atmosphere since 1952. The exposure dose to the population due to radioactive fission products in the drinking water supply from glacierized areas is compared to maximum acceptable concentrations derived from ICRP annual limits of intake (ALI). It is shown that even from heavily contaminated layers the risk to the population is acceptable.

Arctic Regions↗

Radioactive contamination of manufactured products.

Cases of inadvertent radioactive contamination of manufactured articles have occurred sporadically in the past and bore little relationship to each other. Since 1983, however, seven instances have occurred of accidental radioactive contamination of steel either manufactured in or imported into the United States. Five of the contamination events went unrecognized by the mill operators and were discovered by others through radiation monitoring conducted for other unrelated purposes. Impacts have included costs to mill operators in the United States for decontaminating their steel plants which have ranged from $50,000 to more than $2,200,000. The states, the U.S. Nuclear Regulatory Commission and the private sector have taken steps to further assess the scope of the problem and to improve responses when such incidents occur.

Brazil↗

Measurements of radioactive gaseous releases to air from target halls at a high-energy proton accelerator.

Measurements of induced radioactivity concentration in air were made at five target halls associated with the Fermilab high-energy proton synchrotron. A gas flow-through ionization chamber was used to continuously sample air released from an exhaust stack at each location. The radioactive decay of a grab sample of air from each target hall was recorded, and a best-fit of each decay curve was made via iterative steps to determine the mixture of radionuclides present. The radionuclides 11C, 13N, 15O, 38Cl, 39Cl, and 41Ar were identified. Two distinct radionuclide mixtures or "signatures" were found and were correlated to the geometry of the proton loss point. The normalized activity release rates for the five target areas agree within a factor of two of the average value of 2.7 muBq per proton for 800 GeV protons.

Air Pollutants, Radioactive↗

Electrical charge characteristics of long-lived radioactive dust.

Respirable long-lived radioactive dust (LLRD), i.e., dust containing long-lived radionuclides such as 238U, 232Th, 226Ra, 224Ra and 228Th, interacts with unipolar and bipolar atmospheres through diffusion charging, electrical charge neutralization, and electrical self-charging mechanisms. Because of these interactions, and depending on the type of dust as well as its method of production, LLRD is found in electrically charged and neutral states. Electrical charge is important because it influences the deposition of particles in the human respiratory system. Particle size, electrical charge, and radioactive particle size distributions were measured in an area of an underground U mine where U ore crushing and transportation operations were conducted. In addition, concurrent measurements of 222Rn progeny and 220Rn progeny were made. A variety of instrumentation was used, such as particle counters. The electrical charge associated with dust generated in the primary crushing operation was substantially higher (3e- at 1 microns and approximately 500e- at 3 microns) than for the conveyor belt (2e- at 1 microns and approximately 50e- at 8 microns). In both cases the charge distribution was significantly higher than that predicted by Boltzmann's distribution.

Air Pollutants↗

Radioactivity in zirconium oxide powders used in industrial applications.

Recent work involving the decommissioning of a former ceramic manufacturing facility licensed by the Nuclear Regulatory Commission for activities involving depleted uranium oxide has uncovered the presence of unexpected high levels of natural radioactivity in non-licensed zirconium oxide powders also used in the same facility. A comparison between the levels of source material found in samples of this material and the current regulatory guidance for licensed activities and decommissioning has been conducted. It has been determined that the radioactivity in the zirconium oxide is of a high enough magnitude to raise health physics concerns in the areas of licensing and regulatory compliance, decontamination criteria, and worker health and safety. An examination of these areas has been conducted and the implications associated with our findings are presented.

Powders↗

Characterization of low-level radioactive waste generated by a large university/hospital complex.

Descriptions of the physical characteristics and radioactive contents of waste generated by a large university/hospital complex were recorded in a computerized data base for 1 y. The data were summarized to create a waste stream profile so that major waste sources could be identified and minimization efforts quantified. The resultant profile provides a comprehensive description of the low-level radioactive waste produced by a large biomedical research and patient care facility, and projects the methods that will be used to process and ultimately dispose of the material.

Hospitals↗

Determining the probability of radioactive materials on properties in Monticello, Utah.

The former uranium mill site at Monticello, UT, is a surplus facility subject to cleanup under the Surplus Facilities Management Program. Surrounding properties contaminated with mill site material are also subject to cleanup and are referred to as Monticello Vicinity Properties. The objective of this study was to determine the probability that a vicinity property not addressed under the Monticello Vicinity Properties project could contain Monticello mill-related residual radioactive material in excess of Department of Energy guidelines. The study was conducted in a short time frame to protect public health. Statistical methods were used to select 48 random properties for radiological screening surveys. Results of this study may be used to predict the potential number of unassessed properties (results suggest approximately 20%) that contain radioactive contamination that exceeds Department of Energy guidelines and will require remedial action.

Environmental Exposure↗

Determining the collection efficiency of gummed paper for the deposition of radioactive contaminants in simulated rain.

An extensive network of gummed paper collectors was used during the 1950s for routine monitoring of radioactive fallout from weapons testing. The experiments reported in this paper were designed to examine the collection efficiency of gummed paper for wet deposition of several types of soluble and insoluble radioactive contaminants under conditions similar to those found during natural rainstorms. The collection efficiencies for each substance were determined over a range of rainfall amounts and at two separate rainfall intensities. The collection efficiency of the gummed paper is highest for large insoluble particles and lowest for soluble ionic substances. The values for 7Be and 131I ranged from about 0.30 (30%) at 2.5 mm of rain to 0.04-0.06 (4%-6%) at 20 mm of rain. These values were negatively correlated with the amount of rain and were unaffected by rain intensity. This suggests that the collection efficiency of either ion is simply a matter of rapid saturation and runoff. Neither rain amount nor rain intensity has much effect on the collection efficiency of large insoluble particles. These particles seem to settle readily onto the surface of the gummed paper from which they are not easily removed by additional rain. Analysis of the collection efficiencies of the gummed paper included the activity of both the gummed paper and the standing water on the paper. A large portion of the activity for the ionic substances was found in the standing water. There was less activity by insoluble particles in standing water. This indicates that for estimates of deposition of soluble substances, considerable bias could be introduced into the results if the standing water is discarded prior to analysis.

Adhesives↗

Radioactive contamination in hospitals from nuclear medicine patients.

Comparatively little research has been published on radioactive contamination from nuclear medicine patients using hospital toilet facilities. The present study was undertaken to obtain an estimate of the amount of restroom contamination found in a typical 700-bed community hospital as a result of nuclear medicine procedures. Wipe tests were performed on designated areas for two 1-wk periods approximately 6 mo apart. For a typical workload of approximately 25-30 procedures per day, it was found that radioactive contamination ranged from approximately 10(3) Bq 100 cm-2 99mTc for the nuclear medicine restrooms to approximately 10(4) Bq 100 cm-2 for men's toilet facilities. The major component of the activity was found in the vicinity of the toilet. Although this contamination is minimal, it is recommended that nuclear medicine patients be directed to designated restroom facilities while awaiting examinations.

Female↗

Computer-assisted management of liquid radioactive waste at the University of California, San Diego.

Commercially available software has been obtained and internal software applications have been developed to implement a tracking system for liquid radioactive wastes. This system utilizes a number of data bases that maintain sampling, waste pickup and disposition information based on various parameters. Computerization has allowed access to summary information and inventory totals that are necessary for radioactive materials license compliance. Comparative reports, which are used to show trends and track historical information, can also be generated.

California↗

A factorization procedure for calculations of gamma exposure from radioactive clouds.

A procedure is proposed to factor the integrand in the expression for dose characteristics of gamma emission of radioactive clouds. This method permits a reduction of the multiplicity of the integration for conventional models with an arbitrary collocation of a source and a receptor. This can result in more economic numerical schemes for analyzing the consequences of radioactive releases into the atmosphere.

Air Pollutants, Radioactive↗

Sites in the United States contaminated with radioactivity.

Over the century that radioactive materials have been mined, processed, produced, and utilized, many sites across the United States have become contaminated. Such sites include bases and installations of the Department of Defense, weapons production and research facilities of the Department of Energy, properties under the authority of other Federal agencies, privately-owned and governmental facilities that are licensed by the Nuclear Regulatory Commission and its Agreement States, and sites licensed by or the responsibility of states. This review reports on aspects of work by the Environmental Protection Agency, the Department of Defense, the Department of Energy, the Nuclear Regulatory Commission, and others to identify sites contaminated with radioactive materials. It also describes the principal programs that have been instituted to deal with them.

Government Agencies↗

The use of delay tanks in the management of radioactive waste from thyroid therapy.

An underground system of tanks was installed to delay the discharge of 131I waste from the thyroid therapy unit to the on-site sewage treatment plant. As a consequence, the level of radioactivity discharged to sewage has fallen by a factor of 530, reducing the radiation dose to hospital and auxiliary service staff. Cancer patients are no longer required to collect their urine, hence increasing the hygiene for all concerned. A model was developed of iodine waste which estimates the dose rate above the delay tanks and the activity of iodine discharged. The maximum effective dose to a member of the public due to the holding tanks is 40 microSv.year-1. There is now better management of the radioactive waste from the iodine therapy ward.

Humans↗

Understanding the toxicity of buried radioactive waste and its impacts.

The oral ingestion toxicities of buried high level radioactive waste from nuclear power plants and of the natural radioactivity in the ground are calculated and expressed as cancer doses, the number of fatal cancers predicted by the linear no-threshold theory if all of the material were fed to people. Unless the size of the U.S. nuclear power industry is greatly expanded, there will probably never be more than 2 trillion cancer doses (CD) in U.S. repositories, as compared with 31 trillion CD in the ground above them. Measurements of the uranium, thorium, and radium in human bodies indicate that the latter cause 500 deaths per year in U.S. The great majority of this material is derived from the top few meters of soil that are penetrated by plant roots. It is concluded that the annual number of U.S. deaths from buried nuclear wastes will be about 1.0 (or less), orders of magnitude less than the number from coal burning electricity generation, the principal competitor of nuclear power.

Algorithms↗

Radioactive materials in biosolids: dose modeling.

The Interagency Steering Committee on Radiation Standards (ISCORS) has recently completed a study of the occurrence within the United States of radioactive materials in sewage sludge and sewage incineration ash. One component of that effort was an examination of the possible transport of radioactivity from sludge into the local environment and the subsequent exposure of humans. A stochastic environmental pathway model was applied separately to seven hypothetical, generic sludge-release scenarios, leading to the creation of seven tables of Dose-to-Source Ratios (DSR), which can be used in translating from specific activity in sludge into dose to an individual. These DSR values were then combined with the results of an ISCORS survey of sludge and ash at more than 300 publicly owned treatment works, to explore the potential for radiation exposure of sludge workers and members of the public. This paper provides a brief overview of the pathway modeling methodology employed in the exposure and dose assessments and discusses technical aspects of the results obtained.

Environmental Monitoring↗

ISCORS Catalog of References to Parameter Values and Distributions Used in Environmental Pathway Modeling for Cleanup of Sites Contaminated with Radioactivity.

Federal and state regulatory agencies that are concerned with issues of environmental management have adopted approaches toward policy-making that are dose- and risk-informed. To that end they (and others) have developed environmental models and computer codes to mimic the transport of contaminants along air, water, food-chain, and related pathways for estimating potential exposures, doses, and risks to individuals, populations, and ecosystems. Their calculations commonly find application in the planning of remediation, and thereafter in the demonstration of compliance with federal and state cleanup standards. As the models and codes have become more sophisticated, so also have requirements on the accuracy and level of detail of the numerical point values and probability distributions of environmental transfer factors and other parameters that serve as input parameters to them. In response to this growing need, the federal Interagency Steering Committee On Radiation Standards (ISCORS) and the Argonne National Laboratory have developed an on-line, national repository of information on parameter values and distributions of known provenance and demonstrated utility. The ISCORS Catalog of References to Parameter Values and Distributions Used in Environmental Pathway Modeling for Cleanup of Sites Contaminated with Radioactivity is a web-based, indexed compilation of references, compendia, databases, and other sources of peer-reviewed information on parameters. It does not itself contain numerical point values or distributions for any particular parameter, but rather it provides links or directions to sites or other published materials where such information can be obtained. Designed to be user-friendly, easily searchable, and readily up-dateable, the Catalog is being filled, after some initial priming, mainly through on-line submissions of proposed references by the Catalog users themselves. The relevant information on a proposed reference is submitted to ISCORS in a simple, standardized format; it is vetted (with acceptance criteria such as publication in a peer-reviewed technical journal, or appearance in a formally-issued federal agency report) and then added semi-automatically to the Catalog. Built around a relational database, the system offers subject- and text-search capabilities, provides information on parameter definitions and methods of measurement, on transport/exposure pathways, and on standard models and codes. The Catalog is intended for use by (and being populated by) the professionals, managers, and others involved or interested in the application of pathway modeling to estimate doses and risks associated with sites contaminated with radioactive or other hazardous materials.

Databases as Topic↗

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↗