Hand calculations for transport of radioactive aerosols through sampling systems.

Workplace air monitoring programs for sampling radioactive aerosols in nuclear facilities sometimes must rely on sampling systems to move the air to a sample filter in a safe and convenient location. These systems may consist of probes, straight tubing, bends, contractions and other components. Evaluation of these systems for potential loss of radioactive aerosols is important because significant losses can occur. However, it can be very difficult to find fully described equations to model a system manually for a single particle size and even more difficult to evaluate total system efficiency for a polydispersed particle distribution. Some software methods are available, but they may not be directly applicable to the components being evaluated and they may not be completely documented or validated per current software quality assurance requirements. This paper offers a method to model radioactive aerosol transport in sampling systems that is transparent and easily updated with the most applicable models. Calculations are shown with the R Programming Language, but the method is adaptable to other scripting languages. The method has the advantage of transparency and easy verifiability. This paper shows how a set of equations from published aerosol science models may be applied to aspiration and transport efficiency of aerosols in common air sampling system components. An example application using R calculation scripts is demonstrated. The R scripts are provided as electronic attachments.

Monte Carlo model of HPGe detectors used in routine lung counting.

An MCNP model of a pair of planar HPGe detectors (designated as: detector 3 and detector 4), that are used for routine lung counting at AECL, was developed. The model was benchmarked against experimental results, where a multi-line (152)Eu source was counted in several different geometrical arrangements. The best agreement for both detectors was achieved when side and back dead layers (of both detectors) were quadrupled, with respect to the ones quoted by their manufacturer (Canberra). In the case of detector 4, the agreement between simulated and measured spectra was within 4%, throughout the whole γ-spectrum, spanning 70-1600 keV. The same was true for detector 3 at the lower end of the γ-spectrum. However, at the high end of the γ-spectrum, the agreement was within 7% and 12% for (152)Eu γ-lines at 778.9 and 1408.01 keV.

Parallels of radiation and financial risk management: impacts on public acceptance.

The financial collapse of 2007 provides an opportunity for a cross-discipline comparison of risk assessments. Flaws in financial risk assessments bear part of the blame for the financial collapse. There may be a potential for similar flaws to be made in radiological risk assessments. Risk assessments in finance and health physics are discussed in the context of a broader view of the risk management environment. Flawed risk assessments can adversely influence public acceptance of radiological technologies, so the importance of quality is magnified.

Field comparison of the sampling efficacy of two smear media: cotton fiber and kraft paper.

Two materials were compared in field tests at the Defense Waste Processing Facility: kraft paper (a strong, brown paper made from wood pulp prepared with a sodium sulfate solution) and cotton fiber. Based on a sampling of 46 pairs of smears, the cotton fiber smears provide a greater sensitivity. The cotton fiber smears collected an average of 44% more beta activity than the kraft paper smears and 29% more alpha actvity. Results show a greater sensitivity with cotton fiber over kraft paper at the 95% confidence level. Regulatory requirements for smear materials are vague. The data demonstrate that the difference in sensitivity of smear materials could lead to a large difference in reported results that are subsequently used for meeting shipping regulations or evaluating workplace contamination levels.