Development of rapid methods for assessing doses from internally deposited radionuclides

Internal dose reconstruction under Part B of the energy employees compensation act

The reconstruction of internal doses under Part B of the Energy Employees Occupational Illness Compensation Program Act differs in multiple ways from that used in a typical operational setting. There are, for example, no limits at or above which doses must be assessed; all doses, including unmonitored or potentially undetected doses, must be reconstructed. In addition, the primary dose of concern is that delivered to the organ in which the cancer originated, and only the dose delivered to that organ prior to the time the cancer was diagnosed is relevant. Additional challenges are presented in the requirement to partition dose by radiation type and energy rather than by radionuclide, the need to include any potential dose that could have been received but was unmonitored or undetected, the inability to collect follow-up samples, and, in many cases, a general lack of information regarding the employee's work history, such as specific duties or location within a site. To overcome these challenges, the NIOSH dose reconstruction program has adopted a set of default values that include assumptions that are favorable to the claimant when there is more than one plausible choice. Due to the large number of claims that must be reconstructed, efforts are continuously underway to expedite the rate at which they can be processed. This is being achieved by taking advantage of situations in which it can be documented that more detailed evaluations would not change the outcome of the adjudication of the claim.

Establishing bounding internal dose estimates for thorium activities at Rocky Flats

As part of an evaluation of a Special Exposure Cohort petition filed on behalf of workers at the Rocky Flats Plant, the National Institute for Occupational Safety and Health (NIOSH) was required to demonstrate that bounding values could be established for radiation doses due to the potential intake of all radionuclides present at the facility. The main radioactive elements of interest at Rocky Flats were plutonium and uranium, but much smaller quantities of several other elements, including thorium, were occasionally handled at the site. Bounding potential doses from thorium has proven challenging at other sites due to the early historical difficulty in detecting this element through urinalysis methods and the relatively high internal dose delivered per unit intake. This paper reports the results of NIOSH's investigation of the uses of thorium at Rocky Flats and provides bounding dose reconstructions for these operations. During this investigation, NIOSH reviewed unclassified reports, unclassified extracts of classified materials, material balance and inventory ledgers, monthly progress reports from various groups, and health physics field logbooks, and conducted interviews with former Rocky Flats workers. Thorium operations included: (1) an experimental metal forming project with 240 kg of thorium in 1960; (2) the use of pre-formed parts in weapons mockups; (3) the removal of Th from U; (4) numerous analytical procedures involving trace quantities of thorium; and (5) the possible experimental use of thorium as a mold coating compound. The thorium handling operations at Rocky Flats were limited in scope, well-monitored and documented, and potential doses can be bounded.

The NIOSH Radiation Dose Reconstruction Project: managing technical challenges

Approximately two years after promulgation of the Energy Employees Occupational Illness Compensation Program Act, the National Institute for Occupational Safety and Health Office of Compensation and Analysis Support selected a contractor team to perform many aspects of the radiation dose reconstruction process. The project scope and schedule necessitated the development of an organization involving a comparatively large number of health physicists. From the initial stages, there were many technical and managerial challenges that required continuous planning, integration, and conflict resolution. This paper identifies those challenges and describes the resolutions and lessons learned. These insights are hopefully useful to managers of similar scientific projects, especially those requiring significant data, technical methods, and calculations. The most complex challenge has been to complete defensible, individualized dose reconstructions that support timely compensation decisions at an acceptable production level. Adherence to applying claimant-favorable and transparent science consistent with the requirements of the Act has been the key to establishing credibility, which is essential to this large and complex project involving tens of thousands of individual stakeholders. The initial challenges included garnering sufficient and capable scientific staff, developing an effective infrastructure, establishing necessary methods and procedures, and integrating activities to ensure consistent, quality products. The continuing challenges include maintaining the project focus on recommending a compensation determination (rather than generating an accurate dose reconstruction), managing the associated very large data and information management challenges, and ensuring quality control and assurance in the presence of an evolving infrastructure. The lessons learned concern project credibility, claimant favorability, project priorities, quality and consistency, and critical path project activities.

Data collection, processing, validation, and verification

The collection, processing, validation, verification, formatting, filing, and storage of the required input data are some of the most important components in the National Institute for Occupational Safety and Health (NIOSH) Radiation Dose Reconstruction Program. Without question, the quality and scientific validity of the reconstructed dose estimates are totally dependent on these aspects of the program. Of equal importance is that the data be filed not only in a readily accessible format, but also in one that facilitates error-free retrievability. One often unrecognized key factor is that each and every item of data must be collected with careful consideration of the use to which it is to be applied. Two important databases have been established in support of the dose reconstruction operations. They are the NIOSH Office of Compensation Analysis and Support Claims Tracking System and the Site Research Database. The former contains information directly relating to individual workers. When such information is not available, surrogate sources (i.e., area monitoring data) are used to establish the "radiation environment" in which the worker was employed. This information is uploaded into the Site Research Database. Procedures for these systems entail identifying, collecting, and processing information from more than 300 Department of Energy and Atomic Weapons Employer related facilities. To date, more than one million worker-related employment and dosimetry records and more than 33,000 research documents have been uploaded into the associated computer systems.