True and spurious anomalies in ambient dose rate monitoring

Ambient dose rate surveys reveal zones of an elevated dose rate. As the observation results from two physical processes-the 'true' process in nature that one wants to assess and the observation process that consists of measuring under certain conditions-an observed anomaly can have its cause in either process. Anomalous effects rooted in the observation process are called spurious. Distinction between true and spurious anomalies may not be straightforward in many cases. As an example, dose rate surveying using a specific instrument is discussed, whose analysis shows the presence of both types of anomalies. Examples of both types are shown. The physical cause of a true anomaly can often be identified by inspecting the environment or by more sophisticated investigation, e.g. by gamma spectrometry. Identification of spurious anomalies is more difficult and requires investigation of count time series.

Citizen monitoring of ambient dose rate: the SAFECAST project

Citizen Science (CS) is research performed by citizens who are not professional scientists in general. SAFECAST was founded in Japan after the Fukushima accident 2011, motivated by distrust in the perceived biassed information by authorities about radiation situation. Measurements of ambient dose rate (ADR) performed by citizens were intended to verify and complement official data using bGeigieNano designed for purpose, recording ADR, GPS coordinates and date/time allowing projection on digital maps. The project expanded internationally, by mid-2022 containing ⁓180 million measurements. CS generates large amount of data as valuable source for science; it has educational value and serves communication between citizens and professionals. Problems consist in quality assurance (QA): citizens who are no trained metrologists are usually little familiar with notions of representativeness, measurement protocols and uncertainty that are the central QA topics. We discuss variability of response of instruments of the same kind under same ambient conditions and isotropy of response under field conditions.

RESPONSE OF CURRENT AREA DOSEMETERS TO NEW OPERATIONAL QUANTITIES

New operational quantities for external radiation exposure presented by the ICRU brought changes, which can affect the use of current dosemeters. Dosemeters calibrated in the old quantities should be tested, and the results obtained should be analyzed with respect to the new quantities. The difference between the old and new quantities depends primarily on photon energy. This work concerns instruments for area monitoring, which were exposed to reference photon and neutron spectra of mean energies from 65 to 1250 keV and from 0.02 to 10 MeV, respectively. As expected, it was revealed that the current photon dosemeters overestimate the new quantity ambient dose. For the measurements within the energy interval chosen, it seems to be acceptable to implement a correction factor to optimize the response. For the purposes of measurements of photons of lower energies, further research would be needed. To adapt the response of the neutron dosemeter tested, recalibration or redesign can be considered, but no fundamental changes seem to be necessary for the investigated spectra.

Modelling the atmospheric dispersion of radiotracers in small-scale, controlled detonations: validation of dispersion models using field test data

A series of modelling exercises, based on field tests conducted in the Czech Republic, were carried out by the 'Urban' Working Groups as part of the International Atomic Energy Agency's Environmental Modelling for Radiation Safety II, Modelling and Data for Radiological Impact Assessment (MODARIA) I and MODARIA II international data compilation and model validation programmes. In the first two of these programmes, data from a series of field tests involving dispersion of a radiotracer,^99mTc, from small-scale, controlled detonations were used in a comparison of model predictions with field measurements of deposition. In the third programme, data from a similar field test, involving dispersion of¹⁴⁰La instead of^99mTc, were used. Use of longer-lived¹⁴⁰La as a radiotracer allowed a greater number of measurements to be made over a greater distance from the dispersion point and in more directions than was possible for the earlier tests involving shorter-lived^99mTc. The modelling exercises included both intercomparison of model predictions from several participants and comparison of model predictions with the measured data. Several models (HotSpot, LASAIR, ADDAM/CSA-ERM, plus some research models) were used in the comparisons, which demonstrated the challenges of modelling dispersion of radionuclides from detonations and the need for appropriate meteorological measurements.

Urban working groups in the IAEA's model testing programmes: overview from the MODARIA I and MODARIA II programmes

The IAEA's model testing programmes have included a series of Working Groups concerned with modelling radioactive contamination in urban environments. These have included the Urban Working Group of Validation of Environmental Model Predictions (1988-1994), the Urban Remediation Working Group of Environmental Modelling for Radiation Safety (EMRAS) (2003-2007), the Urban Areas Working Group of EMRAS II (2009-2011), the Urban Environments Working Group of (Modelling and Data for Radiological Impact Assessments) MODARIA I (2013-2015), and most recently, the Urban Exposures Working Group of MODARIA II (2016-2019). The overarching objective of these Working Groups has been to test and improve the capabilities of computer models used to assess radioactive contamination in urban environments, including dispersion and deposition processes, short-term and long-term redistribution of contaminants following deposition events, and the effectiveness of various countermeasures and other protective actions, including remedial actions, in reducing contamination levels, human exposures, and doses to humans. This paper describes the exercises conducted during the MODARIA I and MODARIA II programmes. These exercises have included short-range and mid-range atmospheric dispersion exercises based on data from field tests or tracer studies, hypothetical urban dispersion exercises, and an exercise based on data collected after the Fukushima Daiichi accident. Improvement of model capabilities will lead to improvements in assessing various contamination scenarios (real or hypothetical), and in turn, to improved decision-making and communication with the public following a nuclear or radiological emergency.

Mean ambient dose rate in various cities, inferred from Safecast data

Safecast is a citizen science project, aimed to environmental monitoring. Its main activity is measuring ambient dose rate all over the world. The freely accessible data, currently (January 2020) more than 120 million observations, were used to calculate mean values of dose equivalent rate in various cities where sufficient data is available. The results mainly reflect dose rate from terrestrial radiation, whose variability is controlled by the one of geochemistry, namely the concentrations of uranium, thorium and potassium. Further influence comes from cosmic radiation and in a few cases, from anthropogenic radiation caused by nuclear fallout. Mean dose rate has been calculated for 330 cities and towns worldwide. Results are shown in tables, graphs and as maps.

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.

SUPPORT TO CITIZEN RADIATION MONITORING OF RADIOACTIVITY IN THE CZECH REPUBLIC-PROJECT RAMESIS

Project 'RAMESIS', solved by SURO+UTEF+NUVIA, is aimed at the improvement of population safety through supporting Citizen Monitoring in Czechia. Radiation monitoring system at the level of institutions, schools and citizens will be developed and implemented, covering equipment for both fixed-site and mobile monitoring using simple-designed and easy-to-operate detectors, enabling their usage by public and mass-production at acceptable price. The instrumentation includes central application for reception, storage, administration and publication of monitoring results analyzed and presented on web-portal, tools for user's local online and offline data visualization on a map background, and web portal providing training and informational materials for understanding radiation problems. The system will be implemented in selected institutions and schools, initial sets of detectors are distributed free of charge among schools, institutions and the public. This article describes the technical part of the project, solved in the framework of Ministry of Interior-founded security research ID VI20152019028.

RAMESIS PROJECT: COLLABORATION WITH SCHOOLS AND INSTITUTIONS ON THE BUILDING OF A CITIZEN MONITORING NETWORK

In a radiation emergency situation, including its post-emergency recovery phase, substantial needs for radiation measurements can be expected. In such situations, responsible authorities might not be able to satisfy all requirements for measurement. Therefore, involvement of local communities is desirable. Citizen radiation monitoring networks, established in advance as citizen science structures, can serve as a knowledge basis for later participation in self-help protective actions. The article describes the progress of citizen radiation monitoring networks being established in the Czech Republic in the frame of Radiation Monitoring Network for Institutions and Schools project. During the project launch, it has been shown that conducting radiation measurements and results processing have educational effect on students and enhance awareness among interested groups in the field of radiation protection and radiation in general. This article describes the socially oriented part of the project.

RESPONSE OF THE CZECH RMN NETWORK TO THUNDERSTORM ACTIVITY

Thunderstorm ground enhancement (TGE) is a phenomenon that enhances radiation background on the ground related to thunderstorm activity and charge structure of the thundercloud. On the other hand, the rise of gamma background is connected with precipitation by the washout of radon progeny from the atmosphere. In our analysis, we examined known enhancements of gamma background, previously attributed solely to radon progeny, using data from the Czech Radiation Monitoring Network (RMN) to investigate the enhancements with respect to thunderstorms and TGE phenomena. We also used radar precipitation data and data from the lightning location network to analyze their influences on the radiation background enhancement during three thunderstorm events that occurred in summer 2016 over the Czech Republic (Central Europe). We state that the RMN might have detected TGE over the Czech Republic.