Uncertainty due to primary sampling of 222Rn in analyses of water.

Measurement uncertainty is an important variable, to be accounted for when decisions have to be made based on measurement results. Measurement uncertainty is composed of two main components; one is related to the primary sampling, the other to the sample preparation and the subsequent analysis of the sample. The component related to the sample preparation and the analysis is commonly well evaluated in proficiency testing while there is generally no straightforward similar approach to evaluate sampling uncertainty. ISO 17025:2017 explicitly requires that testing laboratories performing sampling and analyses determine the uncertainty related to the primary sampling. In order to determine uncertainty arising in the primary sampling of 222Rn in water destined for human consumption, three laboratories IRE (BE), DiSa (LU) and SCK CEN (BE) initiated a joined sampling and measurement campaign. The dual split sample method in combination with ANOVA was used to evaluate the primary sampling uncertainty (precision) of the different methods. The tests showed that sampling bias is very probably, but that with good laboratory practice the sampling uncertainty precision and respectively bias can be kept below 5%.

Experimental determination of soil sampling uncertainty in the context of environmental radiological monitoring.

Uncertainty associated with nuclear counting analyses are attributed to two main components of uncertainty; one is related to sampling, the other to sample preparation and the subsequent nuclear counting. The ISO/IEC 17025 standard of 2017 require accredited laboratories carrying out their own sampling to estimate the uncertainty associated with sampling in the field. This study presents the results of a sampling campaign and analysis by gamma spectrometry to determine the sampling uncertainty related to the measurement of radionuclides in soil.

Comparison of different approaches of soil sampling uncertainty determination.

The ISO/IEC 17025 standard requires that all significant contributions have to be propagated to the measurement uncertainty, including also sampling uncertainties. We evaluated soil sampling uncertainties for gamma-ray spectrometry by using in-house and split-sample methods. By in-house method, the sampling uncertainty was determined by comparing standard deviations of measurement results and average analytical uncertainty. With split-sample method, it was calculated using between-sample and between-analysis variances. If analytical uncertainty is reliably determined, the in-house method is recommended because fewer measurements are needed.

The assessment of the April 2020 chernobyl wildfires and their impact on Cs-137 levels in Belgium and The Netherlands.

In April 2020, several wildfires took place in and around the Chernobyl exclusion zone. These fires reintroduced radioactive particles deposited during the 1986 Chernobyl disaster into the atmosphere, causing concern about a possible radiation hazard. Several countries and several stations of the International Monitoring System measured increased Cs137 levels. This study presents the analyses made by RIVM and SCK CEN/RMI during the April 2020 wildfires. Furthermore, more in-depth research was performed after the wildfires. A statistical analysis of Cs137 detections is presented, comparing the April 2020 detections with historical detections. Inverse atmospheric transport modelling is applied to infer the total released Cs137 during the wildfires. Finally, it is assessed whether the Cs137 detections in Belgium and the Netherlands can be attributed to the wildfires.

Development of 'on-site' measurement methods for assay of plutonium isotopes.

Over the past decades, radioanalytical methods for environmental monitoring of plutonium (Pu) isotopes from contaminated soils were developed to respond in case of a nuclear accident but also for routine analyses. In this paper we prove the possibility of on-site analysis of plutonium using alpha particle spectrometry. Tests are performed with two types of soils: a "brown" soil and a "sandy" soil, both spiked with 242Pu. The proposed method starts with leaching the soil, then separating the radionuclides of interest through a TEVA column and finally preparing counting planchets for alpha-spectrometry analyses. The aim of this work was to obtain a fast and reliable procedure, from the sample preparation to the analysis, applicable directly in the field and lasting no longer than a working day. The testing involved several parameters, such as the soil-to-liquid ratio, the acid molarity, the influence of a purification step, the source preparation. For each procedure defined, the time and the recovery rates of 242Pu were recorded and compared. Results have proven that the recovery rates increase with the solid-to-liquid ratio, with the acid molarity, with the purification step but decrease with the mixing time. The two methods used for source preparation showed similar results and the sources were measured by alpha spectrometry, using two different counting devices. The final selected sample preparation procedure has a throughput of 3 h, with recovery rates of 33.8 ± 3.1% for the "brown" soil and 77.3 ± 9.2% for the "sandy" soil and is suitable for a field application.

Guidelines for first responders based on results from deploying a mockup radiological dispersal device.

During the past 7th Security Framework Program the European Commission funded a research project called CATO (CBRN Crisis management, Architectures, Technologies and Operational procedures) to develop a prototype decision support system for crisis management in addition to providing a suite of guidelines for first responders and incident commanders when dealing with chemical, biological, radiological or nuclear incidents. In order to derive these guidelines a proof-of-concept experiment was setup during which several passive agent (Stable CsCl) dispersions with improvised explosive devices and vehicle-borne improvised explosive devices were carried out. Each dispersion was thoroughly characterised by a number of monitoring devices, including high-volume air samplers and size-segregated air samplers. All environmental and forensic samples were collected by the UK counter terrorism police, following strict labelling and chain-of-custody protocols. The samples were analysed at the Belgian Nuclear Research Center suing the k0 method for instrumental neutron activation technique. A full consequence assessment analysis was carried out assuming that the observed concentration of Cs-133 in samples was Cs-137 instead and use was made of the specific activity of Cs-137. Due to the sensitivity of the information the European Commission classified this research. The resulted reported on in this work have been unclassified and are released to assist emergency planners and first responders to take the necessary precautions. The results indicate that, up to distances of 50 m from ground zero radiation levels will be considerable and therefore live-saving actions must be performed by fire/rescue wearing full protective gear. In addition, low-wind conditions will favor a long airborne residence time and therefore the use of full-face protective gear is a must. In order to protect first responders, a radiation protection specialist is to determine how long people can enter and remain in the contaminated area. The recovery of evidence in the case of a car-bomb will be hard or even impossible due to the high level of radioactive material remaining inside the vehicle.

Determination of homogeneity of the top surface deadlayer in an old HPGe detector.

A collimated source of 241Am was scanned over the endcap of a 21 year old coaxial HPGe-detector that had spent about 75% of its life at room temperature (and the remaining time at 77 K). The detector response was recorded and used as a measure of the relative thickness of the top deadlayer. This thickness was not homogeneous and was thicker near to the outer surface of the crystal compared to the centre, which could be a result of increased diffusion of Li atoms during times the detector was kept at room temperature. The results were compared with two newer HPGe-detectors that proved to have homogeneous top deadlayers.