Overview of the Full-scale Radiological Dispersal Device Field Trials.

In 2012, Defence Research and Development Canada, in partnership with a number of other Canadian and International organizations, led a series of three field trials designed to simulate a Radiological Dispersal Device (RDD). These trials, known as the Full-Scale RDD (FSRDD) Field Trials, involved the explosive dispersal of a short-lived radioactive tracer ((140)La, t1/2 = 40.293 h). The FSRDD Field Trials required a significant effort in their planning, preparation, and execution to ensure that they were carried out in a safe, efficient manner and that the scientific goals of the trials were met. The discussion presented here details the planning and execution of the trials, outlines the relevant radiation safety aspects, provides a summary of the source term and atmospheric conditions for the three dispersal events, and provides an overview of the measurements that were made to track the plumes and deposition patterns.

Real Time in Situ Gamma Radiation Measurements of the Plume Evolution from the Full-Scale Radiological Dispersal Device Field Trials.

During the Full-Scale Radiological Dispersal Device Field Trials carried out in Suffield in 2012, several suites of detection and sampling equipment were used to measure and characterize the explosive dispersal of the short half-life radioactive tracer Lanthanum-140 ((140)La). The equipment deployed included networks of in situ real-time radiation monitoring detectors providing measurements of different sensitivities and characteristics. A dense array of lower sensitivity detectors was established near field, ranging from 10 to 450 m from the detonation location. A sparser array of more sensitive detectors was established in the far field (150 m to 3.5 km from the detonation location). Each was used to collect and report the dose rate data from the radioactive plume passage with a sample time resolution of 1 s. The two systems went through independent calibrations and were compared and shown to be consistent with each other. The in situ gamma radiation measurements have allowed the movement and evolution of the plume to be described and to identify deposition rates and non-uniformities in the temporal shape of the plume. This knowledge could be applied for emergency planning guidance for the case of release of radioactive material by a radiological dispersive device.

Deposition Measurements From the Full-Scale Radiological Dispersal Device Field Trials.

In 2012, Defence Research and Development Canada led a series of experiments, titled the Full-Scale Radiological Dispersal Device Field Trials, in which short-lived radioactive material was explosively dispersed and the resulting plume and deposition were characterized through a variety of methods. Presented here are the results of a number of measurements that were taken to characterize the radioactive ground deposition. These included in situ gamma measurements, deposition filter samples, and witness plate measurements that were taken in situ with handheld beta survey meters. The results from the different measurement techniques are compared to each other and to a simple deposition model. Results showed that approximately 3% of the original source activity was deposited in the immediate vicinity of ground zero, and an additional 15-30% of the original activity was deposited within 450 m of ground zero. Implications of these results for emergency response are discussed.

The Sensitivity of Atmospheric Dispersion Calculations in Near-field Applications: Modeling of the Full Scale RDD Experiments with Operational Models in Canada, Part I.

Three radiological dispersal devices were detonated in 2012 under controlled conditions at Defence Research and Development Canada's Experimental Proving Grounds in Suffield, Alberta. Each device comprised a 35-GBq source of (140)La. The dataset obtained is used in this study to assess the MLCD, ADDAM, and RIMPUFF atmospheric dispersion models. As part one of a two-part study, this paper focuses on examining the capabilities of the above three models and evaluating how well their predictions of air concentration and ground deposition match observations from the full-scale RDD experiments.

Radiation Modeling and Finite Cloud Effects for Atmospheric Dispersion Calculations in Near-field Applications: Modeling of the Full Scale RDD Experiments with Operational Models in Canada, Part II.

Three radiological dispersal devices were detonated in 2012 under controlled conditions at Defence Research and Development Canada's Experimental Proving Grounds in Suffield, Alberta. Each device comprised a 35-GBq source of (140)La. The dataset obtained is used in this study to assess the MLCD, ADDAM, and RIMPUFF atmospheric dispersion models. As a continuation of Lebel et al. (2016), this paper examines different methodologies for making dose estimates with atmospheric dispersion models.

Radiological hazard estimates from contaminated C7 canisters on the C4 protective mask.

This study compares the external hazard posed by radioactive material trapped in the C7 filter canister of the Canadian C4 full-face mask to the internal hazard from the portion of the material that bypasses the mask and is inhaled. Published measured protection factors (PFs) are used to define the ratio of radioisotope concentration outside of the mask to that inside the mask. The hazards for a variety of radioisotopes are quantified using a Monte Carlo model for the external hazard from the contaminated canister and International Commission on Radiological Protection Publication 68 internal dose coefficients for 1 micron internalized particulate material. In general, the external hazard from a contaminated canister exceeds the internal hazard from material that bypasses the filters for only the most highly protective negative-pressure masks and then only for gamma emitting materials. Our model shows that it is highly unlikely that a canister can become contaminated with enough radioactive material to pose an immediate threat to the wearer, even for pessimistic radiological dispersal device scenarios, when the mask is being worn properly. The "as low as reasonably achievable" (ALARA) principle, however, suggests that filters should be changed as frequently as practical, and the dose measured in the filter may be useful for determining dose of record and for forensic investigations.

Validation of an inductively coupled plasma mass spectrometry (ICP-MS) method for the determination of cerium, strontium, and titanium in ceramic materials used in radiological dispersal devices (RDDs).

In radiological dispersal device (RDD) studies, sintered ceramics made of CeO2 and SrTiO3 were used to simulate actinide oxides and (90)SrTiO3, respectively. Instrumental neutron activation analysis (INAA), inductively coupled plasma optical emission spectroscopy (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS) were investigated as possible analytical techniques for the measurement of SrTiO3 and CeO2 constituents in powder forms, sintered ceramics, and air particulates collected following a detonation. For ICP-OES and ICP-MS analysis, new digestion procedures were developed using a closed-vessel microwave apparatus. Acid mixtures (HNO3:H2O2:HF (16:2:1) and HNO3:H2O2 (1:4)) were found to be effective for the digestion of SrTiO3 and CeO2, respectively. The intercomparison study confirmed that the results obtained by ICP-OES/MS are in good agreement with INAA results. This also confirms the efficiency of the digestion procedures for these refractory materials and the inter-exchangeability of the instrumentation tested. Comparison between the ICP-OES and the ICP-MS instrumentation for the determination of air particulates shows, that although the two methods are equivalent, ICP-MS provides better detection limits (0.11, 0.02, and 0.04 microg per filter for Ti, Sr, and Ce, respectively) and the possibility to determine isotopic fractionation as the result of an explosion.