A Method to Assess Predominant Energies of Exposure in a Nuclear Research Centre - Saclay (France)

Abstract

A study of dosimetric errors is under way within an international collaborative study of cancer risk among workers in the nuclear industry. The objective is to quantify errors in the estimated photon doses to individual organs used for cancer risk estimation. One source of errors is the response of old dosemeters in workplace exposure conditions. As these conditions are not well known, the International Study must rely on expert estimations. This paper describes a method to assess the proportion of the dose from photons in three energy ranges (< 100, 100-300, > or = 300 keV) using the responses under filters of a multi-element dosemeter. The method was tested on experimental and simulated data and provides a good estimate of the proportion of dose from photons below 100 keV, the most critical for dosemeter response. It was applied to personnel readings in one facility, confirming the experts' estimation. Beyond the International Study, the method has implication for the monitoring and protection of workers.

External radiation exposure and mortality in a cohort of French nuclear workers

“…Exposure characteristics, such as the type of radiation, its energy and the geometry of exposure, may have also resulted in uncertainties in the recorded doses. Those uncertainties were quantified by the IARC for a sample of dosimeters including types used at CEA and Cogema 11 12…”

Dose Estimation for a Study of Nuclear Workers in France, the United Kingdom and the United States of America: Methods for the International Nuclear Workers Study (INWORKS)

“…We had no indication of major changes in the exposure conditions of the facilities and therefore, our assessment of exposure conditions remained unchanged (12). It should be emphasized that our initial assessment already accounted for large variations in exposure conditions (7).…”

“…Controlled experiments were conducted on phantoms to determine their response to different geometries and energies of exposure found in the facilities participating in the study. Next, panels of experts were convened to characterize typical exposures of workers at nuclear facilities in terms of photon energies and geometries (12). A database of correction factors was created to convert historical recorded dose values to estimates of organ doses for workers in each facility, adjusting for variations in dosimeter response to predominant energy and geometry of exposure (conditions of exposure), as well as yielding estimates of uncertainty (6, 7).…”

Risk of cancer after low doses of ionising radiation: retrospective cohort study in 15 countries

“…Errors from these sources were quantified and bias factors specific to the doses to each organ of interest calculated for each model of dosimeter used and by type of facility (nuclear power plants and mixed activities facilities) 11 12. Organ doses were derived by dividing recorded doses by the appropriate organ dose bias factor.…”