Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Radiation dose estimation by completely automated interpretation of the dicentric chromosome assay

Abstract: Accuracy of the automated dicentric chromosome (DC) assay relies on metaphase image selection. This study validates a software framework to find the best image selection models that mitigate inter-sample variability. Evaluation methods to determine model quality include the Poisson goodness-of-fit of DC distributions for each sample, residuals after calibration curve fitting and leave-one-out dose estimation errors. The process iteratively searches a pool of selection model candidates by modifying statistical and filter cut-offs to rank the best candidates according to their respective evaluation scores. Evaluation scores minimize the sum of squared errors relative to the actual radiation dose of the calibration samples. For one laboratory, the minimum score for the curve fit residual method was 0.0475 Gy2, compared to 1.1975 Gy2 without image selection. Application of optimal selection models using samples of unknown exposure produced estimated doses within 0.5 Gy of physical dose. Model optimization standardizes image selection among samples and provides relief from manual DC scoring, improving accuracy and consistency of dose estimation.

Dosimetric implications of atmospheric dispersal of tritium near a heavy-water research reactor facility.

Abstract: An estimate of the tritium dose to the public in the vicinity of the heavy water research reactor facility at AECL-Chalk River Laboratories, Ontario, Canada, has largely been accomplished from analyses on regularly-collected samples of air, precipitation, drinking water and foodstuffs (pasture, fruit, vegetables and milk) and environmental dose models. To increase the confidence with which public doses are calculated, tritium doses were estimated directly from the ratio of tritiated species in urine samples from members of the general public. Single cumulative 24 h urine samples from a few adults living in the vicinity of the heavy-water research reactor facility at Chalk River Laboratories, Canada were collected and analysed for tritiated water and organically bound tritium. The participants were from Ottawa (200 km east), Deep River (10 km west) and Chalk River Laboratories. Tritiated water concentrations in urine ranged from 6.5 Bq.l -1 for the Ottawa resident to 15.9 Bq.l -1 for the Deep River resident, and were comparable to the ambient levels of tritium-in-precipitation at their locations. The ultra-low levels of organically bound tritium in urine from these same individuals were measured by 3 He-ingrowth mass spectrometry and were 0.06 Bq.l -1 (Ottawa) and 0.29 Bq.l -1 (Deep River). For Chalk River Laboratories workers, tritiated water concentrations in urine ranged from 32 Bq.l -1 to 9.2 × 10 4 Bq.l -1 1 , depending on the ambient levels of tritium in their workplace. The organically bound tritium concentrations in urine from the same workers were between 0.08 Bq.l -1 and 350 Bq.l -1 . With a model based on the ratio of tritiated water to organically bound tritium in urine, the estimated dose arising from organically bound tritium in the body for the Ottawa and Deep River residents was about 26% and 50%, respectively, ol the body water tritium dose. The workers in a reactor building at Chalk River Laboratories had less than 10% dose contribution from organically hound tritium, but had higher overall tritium dose due to frequent intakes of tritiated water vapour in the workplace. The results of this study suggest that most of the tritium dose to workers at Chalk River and general population near Chalk River is the result of tritiated water intakes and not due to dietary intake of organically bound tritium.