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.

Estimation of absorbed radiation doses to skin and S-values for organs at risk due to nasal administration of PET agents using Monte Carlo simulations.

PURPOSE: The intranasal (IN) administration of radiopharmaceuticals is of interest in being a viable route for the delivery of radiopharmaceuticals that do not ordinarily cross the blood-brain barrier (BBB). However, to be viable in a patient population, good image quality as well as safety of the administration should be demonstrated. This work provides radiation dosimetry calculations and simulations related to the radiation safety of performing such experiments in a human cohort. METHODS: We performed Monte Carlo (MC) simulations to estimate radiation dose to the skin inside a cylindrical model of the nasal cavity assuming a homogenous distribution layer of 11 C and 18 F and calculated a geometry conversion factor (FP-C ) which can be used to convert from a planar geometry to a cylindrical geometry using more widely available software tools. We compared radiation doses from our simulated cylindrical geometry with the planar dose estimates employing our geometry conversion factor from VARSKIN 6.1 software and also from an analytical equation. Furthermore, in order to estimate radiation dosimetry to surrounding organs of interest, we performed a voxelized MC simulation of a fixed radioactivity inside the nasal cavity and calculated S-values to organs such as the eyes, thyroid, and brain. RESULTS: MC simulations of contamination scenarios using planar absorbed doses of 15.50 and 8.60 mGy/MBq for 18 F and 11 C, respectively, and 35.70 and 19.80 mGy/MBq per hour for cylindrical geometries, leading to determination of an FP-C of 2.3. Planar absorbed doses (also in units of mGy/MBq) determined by the analytical equation were 16.96 and 8.68 (18 F and 11 C) and using VARSKIN were 16.60 and 9.26 (18 F and 11 C), respectively. Application of FP-C to these results demonstrates values with a maximum difference of 9.41% from the cylindrical geometry MC calculation, demonstrating that when accounting for geometry, more simplistic techniques can be utilized to estimate IN dosimetry. Voxelized MC simulations of radiation dosimetry from a fixed source of 1 MBq of activity confined to the nasal cavity resulted in S-values to the thyroid, eyes, and brain of 1.72 x 10-6 , 1.93 x 10-5 , and 3.51 x 10-6  mGy/MBq·s, respectively, for 18 F and 1.80 × 10-6 , 1.95 × 10-5 , and 3.54 × 10-6  mGy/MBq·s for 11 C. CONCLUSION: Dosimetry concerns about IN administrations of PET radiotracers should be considered before clinical use. Values presented in the simulations such as the S-values can be further used for assessment of absorbed doses in cases of IN administration, and can be used to develop and adapt specific study protocols. All three presented methods provided similar results when considering the use of a geometry conversion factor for planar to cylindrical geometry, demonstrating that standard tools rather than dedicate MC simulations may be used to perform dose calculations in nasal administrations.

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.

SCALING PARAMETERS FOR HOT-PARTICLE BETA DOSIMETRY.

Scaling of dose-point kernel (DPK) values for beta particles transmitted by high-Z sources will overestimate dose at shallow depths while underestimating dose at greater depths due to spectral hardening. A new model has been developed based on a determination of the amount of monoenergetic electron absorption that occurs in a given source thickness through the use of EGSnrc (Electron Gamma Shower) Monte Carlo simulations. Integration over a particular beta spectrum provides the beta-particle DPK following self-absorption as a function of source thickness and radial depth in water, thereby accounting for spectral hardening that may occur in higher-Z materials. Beta spectra of varying spectral shapes and endpoint energies were used to test the model for select source materials with 7.42 ≤ Z ≤ 94. The results demonstrate that significant improvements can be made to DPK-based dosimetry models when dealing with high-Z volumetric sources. This new scaling model is currently being used to improve the accuracy of the beta-dosimetry calculations in VARSKIN 5.