Radon Flux Measurement System.

ABSTRACT: Disposal of naturally occurring radioactive material (NORM) and technologically enhanced naturally occurring radioactive material (TENORM) waste in the State of Oregon is prohibited unless it can be demonstrated that the material is nonradioactive as defined by its radionuclide content and potential for emission into the environment. It was determined that a radon flux on the surface of the waste no greater than 0.37 Bq m -2 s -1 would meet this requirement. This article provides a method to estimate the radon flux through indirect measurement of the radon mass exhalation rate. It describes a device that consists of a radon accumulation chamber coupled with a continuous radon monitor and software to process the results and calculate the radon mass exhalation rate and radon flux for an unknown sample of approximately 500 g. The chamber system was tested with a uranium ore sample.

Potential Airborne Releases and Deposition of Radionuclides from the Santa Susana Field Laboratory during the Woolsey Fire.

ABSTRACT: The Santa Susana Field Laboratory (SSFL), located in southern California, is a former research facility, and past activities have resulted in residual radioactive contamination in Area IV of the Site. The Woolsey Fire burned across the site, including some of the contaminated areas, on 8-11 November 2018. Atmospheric transport modeling was performed to determine where the smoke plume went while the fire burned across the SSFL and the deposition footprint of particulates in downwind communities. Any radionuclides on vegetation and in surface soil released by the fire were assumed to follow particulate matter transport path and deposition. The predicted deposition footprint was used to guide confirmatory soil sampling at 16 locations including background. Highest offsite deposition was determined to be northeast of the Oak Park community, which is located about 6 km southwest of SSFL. Depth-profile sampling was used to evaluate whether radionuclides of SSFL origin were potentially emitted and deposited during the Woolsey Fire. If radionuclides had been deposited from the Woolsey Fire at sufficient concentrations, then they would be detected in the surface layer and would be expected to be higher within the plume footprint than outside it. An upper bound estimate of the hypothetical effective dose to a person in Oak Park based on measured radionuclide concentrations in soil and vegetation on the SSFL was less than 0.0002 mSv. The occurrence of naturally occurring radionuclides at concentrations above the established background for the SSFL was attributed to natural variability in geologic formations and not SSFL. No anthropogenic radionuclides were measured at levels above those expected from global fallout. The soil sampling confirmed that no detectable levels of SSFL-derived radionuclides migrated from SSFL at the locations sampled because of the Woolsey Fire or from past operations of the SSFL.

Comparison of Doses from Disposals of Technologically Enhanced Naturally Occurring Radioactive Materials in Kentucky and Oregon.

ABSTRACT: Oil and natural gas fracking waste contains technologically enhanced naturally occurring radioactive material (TENORM) and has increasingly been disposed of in unpermitted landfills, causing concern among regulators and the public about potential exposures. There are numerous issues with TENORM waste, including the lack of Federal regulations on its disposal and the lack of permitted landfills capable of accepting these waste streams. This paper examines two situations in which TENORM was placed in unpermitted landfills, one in Kentucky and one in Oregon. The same modeling and dose calculation methods were used in both cases, allowing for a comparison between the two sites. Site-specific differences, source terms, and doses from the disposals and potential remediation options are discussed and compared. Predicted groundwater concentrations are shown and compared against the relevant regulations for each site. Despite the differences in site and TENORM waste characteristics, it was more protective of the community and the environment to leave the waste in place at both sites. Radiation doses to landfill workers on site and to members of the public were low, both during the original disposal and for the remediation alternatives evaluated. Removal of the TENORM material in either case presents significant non-radiological risks that outweigh any benefit from the long-term dose reduction.

A million persons, a million dreams: a vision for a national center of radiation epidemiology and biology.

BACKGROUND: Epidemiologic studies of radiation-exposed populations form the basis for human safety standards. They also help shape public health policy and evidence-based health practices by identifying and quantifying health risks of exposure in defined populations. For more than a century, epidemiologists have studied the consequences of radiation exposures, yet the health effects of low levels delivered at a low-dose rate remain equivocal. MATERIALS AND METHODS: The Million Person Study (MPS) of U.S. Radiation Workers and Veterans was designed to examine health effects following chronic exposures in contrast with brief exposures as experienced by the Japanese atomic bomb survivors. Radiation associations for rare cancers, intakes of radionuclides, and differences between men and women are being evaluated, as well as noncancers such as cardiovascular disease and conditions such as dementia and cognitive function. The first international symposium, held November 6, 2020, provided a broad overview of the MPS. Representatives from four U.S. government agencies addressed the importance of this research for their respective missions: U.S. Department of Energy (DOE), the Centers for Disease Control and Prevention (CDC), the U.S. Department of Defense (DOD), and the National Aeronautics and Space Administration (NASA). The major components of the MPS were discussed and recent findings summarized. The importance of radiation dosimetry, an essential feature of each MPS investigation, was emphasized. RESULTS: The seven components of the MPS are DOE workers, nuclear weapons test participants, nuclear power plant workers, industrial radiographers, medical radiation workers, nuclear submariners, other U.S. Navy personnel, and radium dial painters. The MPS cohorts include tens of thousands of workers with elevated intakes of alpha particle emitters for which organ-specific doses are determined. Findings to date for chronic radiation exposure suggest that leukemia risk is lower than after acute exposure; lung cancer risk is much lower and there is little difference in risks between men and women; an increase in ischemic heart disease is yet to be seen; esophageal cancer is frequently elevated but not myelodysplastic syndrome; and Parkinson's disease may be associated with radiation exposure. CONCLUSIONS: The MPS has provided provocative insights into the possible range of health effects following low-level chronic radiation exposure. When the 34 MPS cohorts are completed and combined, a powerful evaluation of radiation-effects will be possible. This final article in the MPS special issue summarizes the findings to date and the possibilities for the future. A National Center for Radiation Epidemiology and Biology is envisioned.

Dose Assessment for Technologically Enhanced Naturally Occurring Radioactive Materials Disposal in Landfills.

ABSTRACT: Technologically enhanced naturally occurring radioactive material (TENORM) is gaining notoriety in the public sector, as the oil and gas industry looks for disposal locations for its slightly radioactive waste streams. Due in part to both the lack of federal regulations on the disposal of TENORM and the lack of permitted landfills that are designated for TENORM waste, occasionally it ends up being unknowingly placed in municipal landfills. It was alleged that a municipal landfill in Kentucky accepted 1.05 × 106 kg of TENORM over approximately 8 mo starting in July 2015. This matter is still in litigation, and many facts, including whether the material in question actually constituted TENORM, are still in dispute. The authors had no means available to independently verify the actual composition of the material. Therefore, for purposes of this article only, we assume that the material in question did constitute TENORM. This qualification allows us to evaluate potential doses while respecting the litigation process. Doses from the disposals and for two remediation alternatives, (1) closure-in-place and monitoring and (2) excavation and redisposition of waste, were evaluated, taking into consideration the landfill construction, local geology and hydrology, meteorology, background radiation, population distribution, and current and future land uses. This study outlines appropriate methods for calculating doses to potential receptors for a variety of exposure pathways that are broadly applicable to municipal or chemical/hazardous waste landfills. As this study demonstrates, doses to landfill workers and members of the public are low, both during the disposal and for the remediation alternatives evaluated, and well below regulatory limits. Removal of the materials does not reduce present day doses, and it presents other risks that outweigh any benefit from the long-term dose reduction.

Analysis of Environmental Data to Support Quantification of Historical Releases from a Former Uranium Processing Facility in Apollo, Pennsylvania.

ABSTRACT: This paper describes how environmental measurement data were used to help quantify the spatial impact and behavior of uranium released to the environment from a uranium manufacturing facility in Apollo, PA. The Apollo facility released enriched uranium to the environment while it operated between 1957 and 1983. Historical monitoring data generated by the site, along with other independent data sources, provided a long-term record documenting the presence and behavior of uranium in the local environment. This record of evidence, together with reconstructed estimates of facility releases, has been used to estimate environmental concentrations during facility operations and potential exposures to members of the public. Historical environmental measurement data were also used to confirm predictions of deposition and concentrations in air. The data are used here to derive atmospheric deposition velocities for the uranium emissions. Based on the spatial pattern of measurements and calculated deposition velocities around the facility, the released material contained larger particles that deposited close to the facility, and the released material remains largely in the surface layers of the soil, indicating limited downward mobility. Evidence of measurable impacts was determined to extend a relatively short distance (<500 m) from the facility. The soil data collected around Apollo are also compared to findings related to uranium mobility at another facility where uranium was released to the environment, and similar behavior was observed at both sites.

Reconstruction of Enriched Uranium Released to Air from the Former Apollo Facility, Apollo, Pennsylvania.

ABSTRACT: The former Apollo facility converted enriched uranium hexafluoride into uranium oxide for shipment to nuclear fuel fabrication plants from 1957 to 1983. This paper describes quantification of the source term from the Apollo facility in terms of quantities of uranium released, particle size, and solubility characteristics. Releases occurred through stacks, rooftop vents, and an incinerator that operated from 1964 to 1969. Incidental and accidental releases are addressed as part of this analysis. Atmospheric releases of uranium from plant operations were estimated from stack sampling and production records. Roof vents, both filtered and unfiltered, were the major emission points from the plant. The total estimated release of uranium activity (including 234U, 235U, and 238U) to the air was 28 GBq. Measurements by others found that the releases were primarily associated with large particles and that their solubility was variable but generally low (Class Y). The release estimates presented here and those findings were incorporated into a sophisticated atmospheric transport model to estimate atmospheric concentrations and soil contamination levels due to the releases and to reconstruct historical doses to individuals that lived in the vicinity of the former Apollo facility.

Use of Routine Environmental Monitoring Data to Establish a Dose-based Compliance System for a Low-level Radioactive Waste Disposal Site.

A dose-based compliance methodology was developed for Waste Control Specialists, LLC, low-level radioactive waste facility in Andrews, Texas, that allows routine environmental measurement data to be evaluated not only at the end of a year to determine regulatory compliance, but also throughout the year as new data become available, providing a continuous assessment of the facility. The first step in the methodology is a screening step to determine the potential presence of site emissions in the environment, and screening levels are established for each environmental media sampled. The screening accounts for spatial variations observed in background for soil and temporal fluctuations observed in background for air. For groundwater, the natural activity concentrations in groundwater wells at the facility are highly variable, and therefore the methodology uses ratios for screening levels. The methodology compares the ratio of gross alpha to U + U to identify potentially abnormal alpha activity and the ratio of U to U to identify the potential presence of depleted uranium. Compliance evaluation is conducted for any samples that fail the screening step. Compliance evaluation uses the radionuclide-specific measurements to first determine (1) if the dose exceeds the background dose and if so, (2) the dose consequences, so that the appropriate investigation or action occurs. The compliance evaluation is applied to all environmental samples throughout the year and on an annual basis to determine regulatory compliance. The methodology is implemented in a cloud-based software application that is also made accessible to the regulator. The benefits of the methodology over the existing system are presented.

Recent Epidemiologic Studies and the Linear No-Threshold Model For Radiation Protection-Considerations Regarding NCRP Commentary 27.

National Council on Radiation Protection and Measurements Commentary 27 examines recent epidemiologic data primarily from low-dose or low dose-rate studies of low linear-energy-transfer radiation and cancer to assess whether they support the linear no-threshold model as used in radiation protection. The commentary provides a critical review of low-dose or low dose-rate studies, most published within the last 10 y, that are applicable to current occupational, environmental, and medical radiation exposures. The strengths and weaknesses of the epidemiologic methods, dosimetry assessments, and statistical modeling of 29 epidemiologic studies of total solid cancer, leukemia, breast cancer, and thyroid cancer, as well as heritable effects and a few nonmalignant conditions, were evaluated. An appraisal of the degree to which the low-dose or low dose-rate studies supported a linear no-threshold model for radiation protection or on the contrary, demonstrated sufficient evidence that the linear no-threshold model is inappropriate for the purposes of radiation protection was also included. The review found that many, though not all, studies of solid cancer supported the continued use of the linear no-threshold model in radiation protection. Evaluations of the principal studies of leukemia and low-dose or low dose-rate radiation exposure also lent support for the linear no-threshold model as used in protection. Ischemic heart disease, a major type of cardiovascular disease, was examined briefly, but the results of recent studies were considered too weak or inconsistent to allow firm conclusions regarding support of the linear no-threshold model. It is acknowledged that the possible risks from very low doses of low linear-energy-transfer radiation are small and uncertain and that it may never be possible to prove or disprove the validity of the linear no-threshold assumption by epidemiologic means. Nonetheless, the preponderance of recent epidemiologic data on solid cancer is supportive of the continued use of the linear no-threshold model for the purposes of radiation protection. This conclusion is in accord with judgments by other national and international scientific committees, based on somewhat older data. Currently, no alternative dose-response relationship appears more pragmatic or prudent for radiation protection purposes than the linear no-threshold model.

A review of dosimetry used in epidemiological studies considered to evaluate the linear no-threshold (LNT) dose-response model for radiation protection.

BACKGROUND: Accurate dosimetry is key to deriving the dose response from radiation exposure in an epidemiological study. It becomes increasingly important to estimate dose as accurately as possible when evaluating low dose and low dose rate as the calculation of excess relative risk per Gray (ERR/Gy) is very sensitive to the number of excess cancers observed, and this can lead to significant errors if the dosimetry is of poor quality. By including an analysis of the dosimetry, we gain a far better appreciation of the robustness of the work from the standpoint of its value in supporting the shape of the dose response curve at low doses and low dose rates. This article summarizes a review of dosimetry supporting epidemiological studies currently being considered for a re-evaluation of the linear no-threshold assumption as a basis for radiation protection. The dosimetry for each study was evaluated based on important attributes from a dosimetry perspective. Our dosimetry review consisted of dosimetry supporting epidemiological studies published in the literature during the past 15 years. Based on our review, it is clear there is wide variation in the quality of the dosimetry underlying each study. Every study has strengths and weaknesses. The article describes the results of our review, explaining which studies clearly stand out for their strengths as well as common weaknesses among all investigations. PURPOSE: To summarize a review of dosimetry used in epidemiological studies being considered by the National Council on Radiation Protection and Measurements (NCRP) in an evaluation of the linear no-threshold dose-response model that underpins the current framework of radiation protection. MATERIALS AND METHODS: The authors evaluated each study using criteria considered important from a dosimetry perspective. The dosimetry analysis was divided into the following categories: (1) general study characteristics, (2) dose assignment, (3) uncertainty, (4) dose confounders (5) dose validation, and (6) strengths and weaknesses of the dosimetry. Our review focused on approximately 20 studies published in the literature primarily during the past 15 years. RESULTS: Based on the review, it is clear there is wide variation in the quality of the dosimetry underlying each study. Every study has strengths and weaknesses. This paper describes the results of our review, identifies common weaknesses among all investigations, and recognizes studies that clearly stand out for their overall strengths. CONCLUSIONS: The paper concludes by offering recommendations to investigators on possible ways in which dosimetry could be improved in future epidemiological studies.

Organ Dose-Rate Calculations for Small Mammals at Maralinga, the Nevada Test Site, Hanford and Fukushima: A Comparison of Ellipsoidal and Voxelized Dosimetric Methodologies.

Radiological dosimetry for nonhuman biota typically relies on calculations that utilize the Monte Carlo simulations of simple, ellipsoidal geometries with internal radioactivity distributed homogeneously throughout. In this manner it is quick and easy to estimate whole-body dose rates to biota. Voxel models are detailed anatomical phantoms that were first used for calculating radiation dose to humans, which are now being extended to nonhuman biota dose calculations. However, if simple ellipsoidal models provide conservative dose-rate estimates, then the additional labor involved in creating voxel models may be unnecessary for most scenarios. Here we show that the ellipsoidal method provides conservative estimates of organ dose rates to small mammals. Organ dose rates were calculated for environmental source terms from Maralinga, the Nevada Test Site, Hanford and Fukushima using both the ellipsoidal and voxel techniques, and in all cases the ellipsoidal method yielded more conservative dose rates by factors of 1.2-1.4 for photons and 5.3 for beta particles. Dose rates for alpha-emitting radionuclides are identical for each method as full energy absorption in source tissue is assumed. The voxel procedure includes contributions to dose from organ-to-organ irradiation (shown here to comprise 2-50% of total dose from photons and 0-93% of total dose from beta particles) that is not specifically quantified in the ellipsoidal approach. Overall, the voxel models provide robust dosimetry for the nonhuman mammals considered in this study, and though the level of detail is likely extraneous to demonstrating regulatory compliance today, voxel models may nevertheless be advantageous in resolving ongoing questions regarding the effects of ionizing radiation on wildlife.