A bounding estimate of neutron dose based on measured photon dose around single pass reactors at the Hanford site.

Neutron and photon radiation survey records have been used to evaluate and develop a neutron to photon (NP) ratio to reconstruct neutron doses to workers around Hanford's single pass reactors that operated from 1945 to 1972. A total of 5,773 paired neutron and photon measurements extracted from 57 boxes of survey records were used in the development of the NP ratio. The development of the NP ratio enables the use of the recorded dose from an individual's photon dosimeter badge to be used to estimate the unmonitored neutron dose. The Pearson rank correlation between the neutron and photon measurements was 0.71. The NP ratio best fit a lognormal distribution with a geometric mean (GM) of 0.8, a geometric standard deviation (GSD) of 2.95, and the upper 95 th % of this distribution was 4.75. An estimate of the neutron dose based on this NP ratio is considered bounding due to evidence that up to 70% of the total photon exposure received by workers around the single pass reactors occurs during shutdown maintenance and refueling activities when there is no significant neutron exposure. Thus when this NP ratio is applied to the total measured photon dose from an individual film badge dosimeter, the resulting neutron dose is considered bounded.

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.

Analysis of the mortality experience amongst U.S. nuclear power industry workers after chronic low-dose exposure to ionizing radiation.

Workers employed in 15 utilities that generate nuclear power in the United States have been followed for up to 18 years between 1979 and 1997. Their cumulative dose from whole body ionizing radiation has been determined from the dose records maintained by the facilities themselves and the REIRS and REMS systems maintained by the Nuclear Regulatory Commission and the Department of Energy, respectively. Mortality in the cohort from a number of causes has been analyzed with respect to individual radiation doses. The cohort displays a very substantial healthy worker effect, i.e. considerably lower cancer and noncancer mortality than the general population. Based on 26 and 368 deaths, respectively, positive though statistically nonsignificant associations were seen for mortality from leukemia (excluding chronic lymphocytic leukemia) and all solid cancers combined, with excess relative risks per sievert of 5.67 [95% confidence interval (CI) -2.56, 30.4] and 0.506 (95% CI -2.01, 4.64), respectively. These estimates are very similar to those from the atomic bomb survivors study, though the wide confidence intervals are also consistent with lower or higher risk estimates. A strong positive and statistically significant association between radiation dose and deaths from arteriosclerotic heart disease including coronary heart disease was also observed in the cohort, with an ERR of 8.78 (95% CI 2.10, 20.0). While associations with heart disease have been reported in some other occupational studies, the magnitude of the present association is not consistent with them and therefore needs cautious interpretation and merits further attention. At present, the relatively small number of deaths and the young age of the cohort (mean age at end of follow-up is 45 years) limit the power of the study, but further follow-up and the inclusion of the present data in an ongoing IARC combined analysis of nuclear workers from 15 countries will have greater power for testing the main hypotheses of interest.