An overview of EPA regulation of the safe disposal of transuranic waste at the Waste Isolation Pilot Plant.

In March of 1999, the Waste Isolation Pilot Plant (WIPP) in southeast New Mexico, the world's first deep geological repository for radioactive materials, began receiving defense-related transuranic waste. The WIPP was designed and constructed by the U.S. Department of Energy, but critical to its opening was certification by the U.S. Environmental Protection Agency that the repository complies with the radioactive waste disposal regulations set forth as environmental radiation protection standards (40 CFR Part 191) and compliance criteria (40 CFR Part 194). This paper provides a summary of the regulatory process, including the Environmental Protection Agency's waste containment, groundwater protection, and individual dose regulations for the WIPP; the Department of Energy's performance assessment and the other parts of its compliance certification application; and the Environmental Protection Agency's review and analysis of the compliance certification application and related documentation.

National and regional distributions of airborne radon concentrations in U.S. homes.

The National Residential Radon Survey was conducted during 1989 and 1990 to provide data on the frequency distribution of annual average radon concentrations in U.S. residences nationwide, in U.S. Environmental Protection Agency defined Regions, and in subgroups of the housing stock. The National Residential Radon Survey also provided housing and demographic data and a preliminary assessment of the relationship of housing and geographical characteristics to residential radon concentrations. This paper focuses solely on the national and regional estimates of annual average radon concentrations. A stratified, three-stage sampling procedure was used to select housing units for the survey. Data were collected through personal interviews with residents and placement of alpha track detectors in each level of the residences for 12 mo. The survey found an arithmetic annual average radon concentration in U.S. homes of 46.3 +/- 4.4 Bq m-3 (1.25 +/- 0.12 pCi L-1). About 6.0 +/- 1.4% of homes (5.8 million) had radon levels greater than the U.S. Environmental Protection Agency's action level for mitigation of 148 Bq m-3 (4 pCi L-1). Concentrations varied significantly across Environmental Protection Agency Regions. A lognormal distribution was found to closely approximate the major distributions of radon concentrations.

Reducing the risks from radon.

The U.S. Environmental Protection Agency estimates that residential radon levels in the United States lead to approximately 13,600 lung cancer deaths per year. To address this problem, the Agency has identified three program initiatives that can provide substantial reductions in the public's risks: (1) public information activities that urge the public to test for radon and reduce elevated concentrations in existing homes, (2) new construction standards to reduce radon entry, and (3) radon testing and mitigation during real estate transactions. This paper analyzes the costs and risk reductions that could result from the implementation of these major initiatives, showing how all three elements cost-effectively protect the public's health.

Microradiography: a theoretical basis and practical applications.

If low magnification (less than 40x) is required of either thick soft tissue specimens (greater than 20 mm) containing contrast media filled structures or dense tissue, such as bone (greater than 5 mm), a diagnostic, radiographic tube and a 50 kVp setting would prove satisfactory. In this situation Kodak Type R film would provide the required resolution. When the same image enlargement is desired but the soft tissue (greater than 20 mm) does not contain contrast media or the dense tissue is thinner (0.5-5 mm), a specialized radiographic tube is necessary. The unit must be capable of generating a range of 30-40 kVp. Most mammography equipment will produce the necessary kilovoltage if neither a Faxitron nor the resources to build a unit are available. Once again the Kodak Type R or a similar industrial radiographic film would be the film of choice. When high magnification (greater than 40x) is required, indicating thin low density (10-20 mm) or high density (less than 0.5 mm) tissues are being examined, a specialized tube capable of producing 20 kVp is necessary. Kodak High Resolution glass plates or polyester-based film must be used to record the image. Due to grain size visible at high magnifications, both the Kodak Type R radiographic films and the Agfa photographic films proved unsuitable.