In standard monoenergetic ISO neutron fields, the neutron yield of neutron-producing reactions was measured in combination with the prompt photon yield, including photon energies up to 10 MeV, for the purpose of comparing the two yields. Separating the photons produced by the target (direct photons) from those generated by secondary neutron reactions was achieved using the time-of-flight method. Photon and neutron ambient dose equivalent values were calculated from measured spectral energy distributions. Quasi monoenergetic neutron fields are needed to systematically test the response of measuring instruments to neutron radiation. For this reason, ISO has defined a number of reference neutron radiation fields covering a wide energy range up to 19 MeV. Because neutron detectors may also be affected by photon radiation, the photon fluence in the ISO neutron fields has to be known. This work focuses on quasi monoenergetic accelerator-produced neutron fields in the energy range of 24 keV to 19 MeV.

As part of an evaluation of gamma -ray spectra or other spectra, the need to adapt the binning quasi -continuously may arise. Often, the re -distribution of measured events to a new energy scale may be required. The necessity to change the energy scale can have several reasons. Frequently, a drift of the detector or the amplifier leads to different energy scales of measured spectra in time. In order to calculate difference spectra or sum spectra, the energy axis and binning of all spectra has to be adapted. Moreover, before a spectrum is unfolded, its energy axis also has to be adapted to the energy scale of the response matrix. Widespread commercial software packages, which are commonly used for the analysis of spectra, do not include an algorithm which solves this task. Three algorithms are presented in this work after shedding light on the mathematical background. An analysis of the statistical uncertainty of the counts of re -binned or remapped spectra completes this paper.

In general, the energy calibration of gamma-ray detectors is carried out by using radioactive sources with well-known emission lines. The fact that the scintillator material LaBr3 includes natural radioactivity is often taken advantage of to perform an energy calibration without the need to handle an external radioactive source. For this purpose, the emission energy of photons to be detected in peaks has to be well known. Though the energies of the emission lines of the relevant isotope La-138 and further information on radioactive contaminations are published with high precision, there are inconsistencies in the literature concerning the effective energies of observed photon peaks caused by inherent radioactivity. In this article, the actual peak positions are published as a result of high-precision measurements. The potential and limitations of an energy calibration of LaBr3 3 detectors based on the inherent radioactivity are discussed, as the emission lines of 138 La are detected in clusters rather than single, clearly defined lines.

Unfolded spectra are needed for the application of some spectrum analysis methods. Frequently, iterative deconvolution methods are used, especially if the spectra have a high resolution. However, the uncertainties on the obtained results are difficult to judge. In general, the user of an unfolding code gets no information on the influence of chosen parameters, especially the choice of the first estimate of the unfolded spectrum. General studies regarding the uncertainties of unfolding algorithms are difficult to perform, if not impossible, and therefore not available. In this work, uncertainties of the results on the iterative GRAVEL algorithm, which is based on SAND II, are closely investigated by using medium resolution spectra recorded by using a CeBr 3 detector. Relevant parameters are varied systematically to gain some information on the associated uncertainties on the basis of examples. The uncertainty budget of the calculation of total fluences and doses of unfolded spectra is compared with the uncertainty budget of the results obtained by applying the conversion method. The results allow, at least, the estimation of the magnitude of typical uncertainties.

Modern gamma-ray spectrometers based on solid-state scintillators are increasingly being used in fields where previously dosemeters were applied. From the spectra, precise fluence and dose information can be derived. The most important methods of doing this are investigated in detail; the conversion method, which is based on weighing functions; and unfolding, here using the GRAVEL algorithm. Both methods can be used to process any kind of spectra, regardless of the type of spectrometer employed. The GRAVEL algorithm is described in detail. The implementation of both methods is shown and results of examples are compared. Advantages and disadvantages of both techniques are discussed. For the first time, most precise conversion data up to 20 MeV are published, even extending the quantity H*(10) to this energy. They may serve for the improvement and harmonisation of dose rate measurements using scintillation spectrometers, e.g. those used in early warning systems.

In cases of nuclear or other radiologically relevant incidents or accidents (“radiological event”), including terrorist attacks, appropriate protection of the public against ionising radiation and radioactive contamination is of major importance. In such scenarios, radiation protection authorities and other decision-makers quickly need reliable information based on sound radiological data in order to determine and optimize countermeasures. The nuclear accidents in Chernobyl (1986) and Fukushima (2011) are major examples where radiation protection measures were crucial for preserving a tremendous number of human lives. However, certain smaller events have also caused severe problems, e.g., the Tokaimura nuclear criticality accident (1999). According to the IAEA Safety Standard No. GSR Part 7, “Preparedness and Response for a Nuclear or Radiological Emergency” (1), safety and security measures have the shared aim of protecting human life and health as well as protecting the environment. This document also emphasises the importance of adequate protective measures following nuclear and radiological emergencies. Reliable radiological data, available at the earliest possible stage, are a prerequisite for effectively protecting people from such unexpected but potentially highly dangerous events. Therefore, the European joint research project 16ENV04 named “Preparedness”, funded by the European Metrology Programme for Innovation and Research (EMPIR), is meant to develop reliable instrumentation and methods needed in the field of radiation protection in the aftermath of a nuclear or radiological emergency. The goal is to quickly gather quantitative data on the activity concentrations of contaminated areas and dose rate levels by aerial measurements, and analyse these air contaminations by flexible and transportable air sampling systems. For large-area ground contaminations, surveillance by unmanned airborne monitoring systems (UAMSs), specifically unmanned aerial vehicles (UAVs) equipped with spectrometric detectors, is the best solution to protect first responders and other task forces against contaminations and hazards due to ionising radiation. However, advanced calibration procedures based on reference materials and standard radionuclide sources must be elaborated for these systems and verified by Monte Carlo simulations. For airborne radioactivity monitoring, transportable air sampling field stations equipped with high-resolution spectrometric detectors and appropriate shielding is needed to allow the measurement of radioactivity concentration levels in the air of affected areas. After the release of a radioactive plume to the atmosphere, the levels of the ambient dose equivalent rate and activity concentrations in air provide essential information about the progression of the radioactive cloud. This information is important for decision-makers to be able to take timely and adequate countermeasures to protect the members of the public against the dangers of ionising radiation. After a major release of radionuclides, short-term decontamination may not always be possible. Hence, concepts for long-term measurements have to be developed. Metrologically sound data is needed in this field as well, because decisions on e.g. decontamination measures or release of restricted areas are of vital importance. Passive dosimeters must therefore be studied with regard to their applicability for this purpose. Furthermore, the “Preparedness” project addresses the question whether non‐governmental networks could support official dose rate data or undermine them because of insufficient quality.

This intercomparison serves to investigate the long-term behaviour of passive H*(10) dosemeters which may be used in the aftermath of a radiological or nuclear event. In routine operation, such dosemeters are generally used to monitor installations like nuclear power plants and accelerators. Such dosemeters are used in the radiation field of the natural ambient radiation, including terrestrial and secondary cosmic radiation. From October 2017 to April 2018, photon dosemeters of 38 dosimetry systems were exposed to ionising radiation at three dosimetric reference sites which are operated by the Physikalisch-Technische Bundesanstalt (PTB). In addition to measurements which were carried out under natural conditions, a number of dosemeters was also irradiated artificially under two angles in PTB's photon fields. 34 measuring bodies and institutions which are mainly involved in ambient radiation monitoring in Europe took part in this intercomparison in which the response of the dosemeters to terrestrial and also to secondary cosmic radiation was determined. As a result of this intercomparison, some sources of uncertainty and some errors were found. The intercomparison revealed the typical precision that has to be expected when long-term dose measurements are carried out in the natural environment. The successful participation in this intercomparison was documented by certificates that were issued to the participants. The short designation of this intercomparison is "IC2017prep".

The typical uncertainty of a low-dose rate calibration of a detector, which is calibrated in a dedicated secondary national calibration laboratory, is investigated, including measurements in the photon field of metrology institutes. Calibrations at low ambient dose equivalent rates (at the level of the natural ambient radiation) are needed when environmental radiation monitors are to be characterised. The uncertainties of calibration measurements in conventional irradiation facilities above ground are compared with those obtained in a low-dose rate irradiation facility located deep underground. Four laboratories quantitatively evaluated the uncertainties of their calibration facilities, in particular for calibrations at low dose rates (250 nSv/h and 1 μSv/h). For the first time, typical uncertainties of European calibration facilities are documented in a comparison and the main sources of uncertainty are revealed. All sources of uncertainties are analysed, including the irradiation geometry, scattering, deviations of real spectra from standardised spectra, etc. As a fundamental metrological consequence, no instrument calibrated in such a facility can have a lower total uncertainty in subsequent measurements. For the first time, the need to perform calibrations at very low dose rates (< 100 nSv/h) deep underground is underpinned on the basis of quantitative data.

A new generation of dosemeters, based on the scintillators LaBr3, CeBr3 and SrI2, read out with conventional photomultipliers, to be used in the field of environmental gamma-radiation monitoring, was investigated. The main features of these new instruments and especially their outdoor performance, studied by long-term investigations under real weather conditions, are presented. The systems were tested at the reference sites for environmental radiation of the Physikalisch-Technische Bundesanstalt. The measurements are compared with that of well characterized classical dose rate reference instruments to demonstrate the suitability of new spectrometers for environmental dose rate monitoring even in adverse weather conditions. Their potential to replace the (mainly Geiger Müller based) dose rate meters operated in about 5000 European early waning network stations as well as in environmental radiation monitoring in general is shown.

Environmental radiation monitoring networks have been established in Europe and world-wide for the purpose of protecting population and environment against ionizing radiation. Some of these networks had been established during the cold war period and were improved after the Chernobyl accident in 1986. Today, the German Federal Office for Radiation Protection (BfS) operates an early warning network with roughly 1800 ambient dose equivalent rate (ADER) stations equally distributed over the German territory. The hardware and software of all network components are developed in-house allowing the continuous optimization of all relevant components. A probe characterization and quality assurance and control program are in place. Operational and technical aspects of the network and data harmonization techniques are described. The latter allows for calculating of the terrestrial and net ADER combined with uncertainties mainly from site specific effects. Harmonized data are finally used as input to the German emergency management system and the European radiological data exchange platform.

In radiation protection, the quantity ambient dose equivalent, in short H*(10), is very important in the field of area dosimetry, because this quantity is used to estimate the effective dose to human beings, whose permissible limits are restricted by law. The conversion coefficient from air kerma to H*(10), valid for a 137Cs photon field, is essential as it enters the realization of the quantity H*(10) as well as every (directly or indirectly) related calibration. The basic calibration factor of any dose rate instrument is usually related to a calibration in a 137Cs photon field, which underlines the importance of the conversion coefficient discussed in this article. Because different values of this coefficient are used in different calibration facilities, a harmonized best value will be proposed based on detailed investigations on the origin of the values recommended in the past. The newly recommended value differs by almost 1% from the value used by most institutes, at the moment, which is large in comparison with the typical uncertainties in primary fields. The goal of this article is to interpret known ICRU/ICRP data adequately, not to calculate new data.

EURADOS Working Group 3 (WG3) aims at providing information about the correct measurement of the ambient dose equivalent (rate) in the environment and has a specific subgroup (WG3-SG2) that focuses on passive environmental dosimetry. One of the initial tasks of the subgroup was to gain an overview of passive dosimetry practices in Europe. On the basis of a survey carried out by this subgroup in 2013/2014, information on the state-of-the-art was gained, several conclusions were drawn and some open questions have been identified, e.g. the harmonization in the terminology, uncertainty assessment procedures and corrections of measured values by passive dosemeters due to transport and climate.

The responses of electronic dose rate meters were investigated in a large volume radon chamber at PTB in a wide range of radon activity concentrations. The measurements were conducted under controlled laboratory conditions and measured dose rate data are compared with Monte-Carlo simulations. Consequences concerning environmental monitoring are described. A further result is that the direct measurement of the dose rates produced by radon progeny in air is hardly possible in radon atmospheres with high activity concentrations, because the major contribution of measured dose rates is produced by radon progeny on the housing of the dose rate instruments. The latter effect largely depends on the ability of surfaces to absorb radon progeny. The Monte-Carlo simulations revealed quantitative results on the height of the single contributions to the total dose rate measured in the radon chamber. When environmental dose rate measurements are performed, the plate-out on detectors can be neglected.

After the Chernobyl nuclear power plant accident in 1986, followed by the Fukushima Nuclear power plant accident 25 years later, it became obvious that real-time information is required to quickly gain radiological information. As a consequence, the European countries established early warning network systems with the aim to provide an immediate warning in case of a major radiological emergency, to supply reliable information on area dose rates, contamination levels, radioactivity concentrations in air and finally to assess public exposure. This is relevant for governmental decisions on intervention measures in an emergency situation. Since different methods are used by national environmental monitoring systems to measure area dose rate values and activity concentrations, there are significant differences in the results provided by different countries. Because European and neighboring countries report area dose rate data to a central data base operated on behalf of the European Commission, the comparability of the data is crucial for its meaningful interpretation, especially in the case of a nuclear accident with transboundary implications. Only by harmonizing measuring methods and data evaluation, is the comparability of the dose rate data ensured. This publication concentrates on technical requirements and methods with the goal to effectively harmonize area dose rate monitoring data provided by automatic early warning network systems. The requirements and procedures laid down in this publication are based on studies within the MetroERM project, taking into account realistic technical approaches and tested procedures.

Short-term pronounced increases of the ambient dose equivalent rate, due to rainfall are a well-known phenomenon. Increases in the same order of magnitude or even below may also be caused by a nuclear or radiological event, i.e. by artificial radiation. Hence, it is important to be able to identify natural rain events in dosimetric early warning networks and to distinguish them from radiological events. Novel spectrometric systems based on scintillators may be used to differentiate between the two scenarios, because the measured gamma spectra provide significant nuclide-specific information. This paper describes three simple, automatic methods to check whether an Ḣ*(10) increase is caused by a rain event or by artificial radiation. These methods were applied to measurements of three spectrometric systems based on CeBr3, LaBr3 and SrI2 scintillation crystals, investigated and tested for their practicability at a free-field reference site of PTB.

Under the umbrella of the European Radiation Dosimetry Group (EURADOS), different working groups have responded to the requests of monitoring services in Europe for independent tests of dosimetry systems for harmonization and quality assurance. After having performed regular intercomparisons of personal dosemeters, EURADOS Working Group 3, “Environmental Dosimetry”, performed the first EURADOS intercomparison for passive ambient dose equivalent, abbreviated H*(10), area dosemeters used for environmental monitoring in 2014 (IC2014env). Such dosimetry systems are generally used to monitor nuclear installations, besides other applications. The results of this intercomparison with a total of more than 500 dosemeters help to better understand influence parameters and the possible accuracy of typical dosimetric measurements using passive dosemeters.

For the upgrade of existing dosimetric early warning networks in Europe spectrometric detectors based on CeBr3, LaBr3, SrI2, and CdZnTe are investigated as possible substitutes for the current detector generation which is mainly based on gas filled detectors. The additional information on the nuclide vector which can be derived from the spectra of gamma-radiation is highly useful for an appropriate response in case of a nuclear or radiological accident. The measured gamma-spectra will be converted into ambient dose equivalent H*(10) using a method where the spectrum is subdivided into multiple energy bands. For each band the conversion coefficients from count rate to dose rate is determined. The derivation of these conversion coefficients is explained in this work. Both experimental and simulative approaches are investigated using quasi -mono -energetic gamma-sources and synthetic spectra from Monte -Carlo simulations to determine the conversion coefficients for each detector type. Finally, precision of the obtained characterization is checked by irradiation of the detectors in different well-known photon fields with traceable dose rates.

To detect radiological incidents, all members of the European Union have installed nationwide radiological early warning networks. Most of the installed detector systems supply only dosimetric information. Novel spectrometry systems are considered to be good candidates for a new detector generation for environmental radiation monitoring because they will supply both nuclide-specific information and ambient dose equivalent rate values. Four different detector types were chosen and compared with each other (LaBr3, CeBr3, SrI2 scintillation detectors, and CdZnTe, a semiconductor detector). As a first step, the inherent background of these detectors was measured in the low background underground laboratory UDO II of PTB. As a second step, the relative detection sensitivity between the various detectors was determined at different energies. Finally, the detectors were exposed to a 4 pi-radiation field of radon progeny in PTB's radon chamber. The obtained results show that the investigated detectors are well suited for environmental radiation monitoring.

As a consequence of the Chernobyl nuclear power plant accident in 1986, all European countries have installed automatic dosimetry network stations as well as air sampling systems for the monitoring of airborne radioactivity. In Europe, at present, almost 5,000 stations measure dose rate values in nearly real time. In addition, a few hundred air samplers are operated. Most of them need extended accumulation times with no real-time capability. National dose rate data are provided to the European Commission (EC) via the EUropean Radiological Data Exchange Platform (EURDEP). In case of a nuclear emergency with transboundary implications, the EC may issue momentous recommendations to EU member states based on the radiological data collected by EURDEP. These recommendations may affect millions of people and could have severe economic and sociological consequences. Therefore, the reliability of the EURDEP data is of key importance. Unfortunately, the dose rate and activity concentration data are not harmonized between the different networks. Therefore, within the framework of the European Metrology Research Programme (EMRP), 16 European institutions formed the consortium MetroERM with the aim to improve the metrological foundation of measurements and to introduce a pan-European harmonization for the collation and evaluation of radiological data in early warning network systems. In addition, a new generation of detector systems based on spectrometers capable of providing both reliable dose rate values as well as nuclide specific information in real time are in development. The MetroERM project and its first results will be presented and discussed in this article.

The European Radiation Dosimetry Group (EURADOS) has been organising dosimetry intercomparisons for many years in response to an identified requirement from individual monitoring services (IMS) for independent performance tests for dosimetry systems. The participation in intercomparisons gives IMS the opportunity to show compliance with their own quality management system, compare results with other participants and develop plans for improving their dosimetry systems. In response to growing demand, EURADOS has increased the number of intercomparisons for external radiation dosimetry. Most of these fit into the programme of self-financing intercomparisons for dosemeters routinely used by IMS. This programme is being coordinated by EURADOS working group 2 (WG2). Up to now, this programme has included four intercomparisons for whole-body dosemeters in photon fields, one for extremity dosemeters in photon and beta fields, and one for whole-body dosemeters in neutron fields. Other EURADOS working groups have organised additional intercomparisons including events in 2014 for eye-lens dosemeters and passive area dosemeters for environmental monitoring. In this paper, the organisation and achievements of these intercomparisons are compared in detail focusing on the similarities and differences in their execution.