Implementation of ICRP 116 Dose Conversion Coefficients for Reconstructing Organ Dose in a Radiation Compensation Program.

Since 2000, National Institute for Occupational Safety and Health (NIOSH) has used dose conversion coefficients published by the International Commission on Radiation Protection in report 74 (ICRP 74) to determine organ dose from external radiation sources. In 2010, the ICRP issued publication 116 using more realistic phantoms than ICRP 74. NIOSH has developed a Monte Carlo method to sample the energy-organ-specific distribution of the ICRP 116 conversion coefficients to determine the organ dose and the associated uncertainty. Using Monte Carlo methods, irradiation geometry factors (IGFs) were developed to convert the measured dosemeter dose on the front of the body to values that are compatible with ICRP 116 organ dose conversion coefficients. Specific IGFs were developed for (1) both neutrons and photon exposures, (2) to male and female workers and (3) for rotational and isotropic exposure geometries. The computed mean organ dose and the associated uncertainty are used in the probability of causation calculation for compensation.

Development of rapid methods for assessing doses from internally deposited radionuclides.

During the initial phases of the National Institute for Occupational Safety and Health Radiation Dose Reconstruction Program, all calculations of organ doses due to internally deposited radionuclides were performed using the Integrated Modules for Bioassay Analysis program. However, limitations associated with this program, including the need to calculate separate internal dose assessments for each radionuclide, created inefficiencies in the processing of claims. As a result, the National Institute for Occupational Safety and Health developed and introduced a suite of tools to expedite the process. The first of these was the Chronic Annual Dose Workbook program. This innovative tool permits a dose reconstructor to calculate, in a single step, an organ dose that involves up to 255 separate intakes in any combination of radionuclides, intake modes, and absorption types. In addition, the program enables dose reconstructors to determine the specific radionuclide characteristics that will deliver the highest organ dose for a specific intake. Furthermore, the results are displayed in a format that is compatible with the Interactive RadioEpidemiological Program, which is used by the U.S. Department of Labor in establishing the probability of causation. The value of the probability of causation, in combination with other information, subsequently enables the U.S. Department of Labor to render a decision on compensability. These developments have played a major role in enabling the dose reconstruction teams to meet the claim processing goals with increased efficiency and accuracy.

External dose reconstruction under Part B of the energy employees compensation act.

External doses reconstructed under Part B of the Energy Employees Occupational Illness Compensation Program Act include not only those that were recorded by personal dosimeters, but also those that were not recorded. Recorded doses may require corrections to account for measurement bias or limitations in the dosimeters' capabilities. Unrecorded doses that have been reconstructed include (1) those missed due to limits of detection associated with personal dosimeters, (2) external ambient doses that may have been inadvertently omitted from the monitoring results (or were not monitored altogether in the case of nonradiation workers), and (3) doses incurred as a result of medical x-ray examinations required by employers. Additionally, some workers were not monitored (or their dosimetry data are not available) even though there was a potential for exposure; doses to such workers are typically assigned based on the records of coworkers who performed the same, or similar, tasks. Additional issues that complicate the dose reconstruction process include the requirements that (1) all external doses must be partitioned according to radiation type and energy, and (2) the accompanying doses to specific body organs must be estimated. Since the external dose reconstruction process typically incorporates many claimant-favorable methodologies, parameters, and assumptions, the doses assigned do not necessarily reflect either realistic or actual estimates of the doses received, and external doses assigned to workers under the Act often are substantially higher than those contained in the dosimetry records.