Chornobyl radiation spikes are not due to military vehicles disturbing soil

On 25^th February 2022, increased gamma radiation dose rates were reported within the Chornobyl Exclusion Zone (CEZ). This coincided with Russian military vehicles entering the Ukrainian part of the CEZ from neighbouring Belarus. It was speculated that contaminated soil resuspension by vehicle movements or a leak from the Chornobyl Nuclear Power Plant complex may explain these spikes in radiation dose rates. The gamma dose rate monitoring network in the CEZ provides a crucial early warning system for releases of radioactivity to the environment and is part of the international safeguards for nuclear facilities. With the potential for further military action in the CEZ and concerns over nuclear safety, it is essential that such anomalous readings are investigated. We evaluate the hypotheses suggested to explain the apparent gamma dose rate increases, demonstrating that neither military vehicle-induced soil resuspension nor a leak from the Chornobyl Nuclear Power Plant are plausible. However, disruption of the Chornobyl base-station's reception of wireless signals from the gamma dose rate monitoring network in the CEZ may potentially explain the dose rate increases recorded.

Monitoring alkyl pyrazines in roasted hazelnuts by SHS-GC-IMS: IMS response assessment and standardization

Gas chromatography coupled with ion mobility spectrometry (IMS) is an analytical tool which is rapidly becoming widespread in the analysis of food volatiles. Despite this increasing popularity, an assessment of the IMS response for several flavor compound classes is not yet available. This study focuses on alkyl pyrazines and their determination in roasted hazelnut pastes. These Maillard reaction products are crucial to determine the aromatic profile of roasted foods and are suitable markers for industrial roasting monitoring. The instrumental response of 8 alkyl pyrazines was studied using a model matrix and a matrix matching approach. The results showed a relevant effect of the pyrazine ring substitution pattern on the concentration-response curve trends, highlighting that an external standardization of the IMS response is required to make possible relative abundance comparisons between analytes. A response standardization was therefore developed and applied to determine alkyl pyrazines in samples with different roasting intensity and geographical and botanical origin.

A Monte Carlo detector response model for the IRIS PET preclinical scanner

PET preclinical studies require high spatial resolution due to the limited size of the animal under investigation. To achieve this target, iterative image reconstruction algorithms are commonly preferred over the analytical methods because they offer the possibility of accurately modeling the whole imaging process. In this work, we propose an accurate factorized system matrix for the INVISCAN IRIS preclinical PET scanner to be used with an iterative algorithm. The model includes two components: the geometric component and the detector response of the system. The main innovative aspect of the work is the creation of the detector matrix using a Monte Carlo simulation, with a particular focus on the optimization of the simulation process to reduce the calculation time. The new system model is compared with the current IRIS model to evaluate the image quality, following the NEMA Standards NU 4-2008. The comparison showed an enhancement of the image quality, in terms of uniformity and recovery coefficients. This work confirms that the inclusion of the detector response into the system model leads to improved reconstruction results.

A brachytherapy photon radiation quality index Q(BT) for probe-type dosimetry

INTRODUCTION

In photon brachytherapy (BT), experimental dosimetry is needed to verify treatment plans if planning algorithms neglect varying attenuation, absorption or scattering conditions. The detector's response is energy dependent, including the detector material to water dose ratio and the intrinsic mechanisms. The local mean photon energy E¯(r) must be known or another equivalent energy quality parameter used. We propose the brachytherapy photon radiation quality indexQ(BT)(E¯), to characterize the photon radiation quality in view of measurements of distributions of the absorbed dose to water, Dw, around BT sources.

MATERIALS AND METHODS

While the external photon beam radiotherapy (EBRT) radiation quality index Q(EBRT)(E¯)=TPR10(20)(E¯) is not applicable to BT, the authors have applied a novel energy dependent parameter, called brachytherapy photon radiation quality index, defined as Q(BT)(E¯)=Dprim(r=2cm,θ0=90°)/Dprim(r0=1cm,θ0=90°), utilizing precise primary absorbed dose data, Dprim, from source reference databases, without additional MC-calculations.

RESULTS AND DISCUSSION

For BT photon sources used clinically, Q(BT)(E¯) enables to determine the effective mean linear attenuation coefficient μ¯(E) and thus the effective energy of the primary photons Eprim(eff)(r0,θ0) at the TG-43 reference position Pref(r0=1cm,θ0=90°), being close to the mean total photon energy E¯tot(r0,θ0). If one has calibrated detectors, published E¯tot(r) and the BT radiation quality correction factor [Formula: see text] for different BT radiation qualities Q and Q0, the detector's response can be determined and Dw(r,θ) measured in the vicinity of BT photon sources.

CONCLUSIONS

This novel brachytherapy photon radiation quality indexQ(BT) characterizes sufficiently accurate and precise the primary photon's penetration probability and scattering potential.

Thermal neutron response of a boron-coated GEM detector via GEANT4 Monte Carlo code

In this work, we report the design configuration and the performance of the hybrid Gas Electron Multiplier (GEM) detector. In order to make the detector sensitive to thermal neutrons, the forward electrode of the GEM has been coated with the enriched boron-10 material, which works as a neutron converter. A total of 5×5cm² configuration of GEM has been used for thermal neutron studies. The response of the detector has been estimated via using GEANT4 MC code with two different physics lists. Using the QGSP_BIC_HP physics list, the neutron detection efficiency was determined to be about 3%, while with QGSP_BERT_HP physics list the efficiency was around 2.5%, at the incident thermal neutron energies of 25meV. The higher response of the detector proves that GEM-coated with boron converter improves the efficiency for thermal neutrons detection.

Photodiode array to charged aerosol detector response ratio enables comprehensive quantitative monitoring of basic drugs in blood by ultra-high performance liquid chromatography

Quantitative screening for a broad range of drugs in blood is regularly required to assess drug abuse and poisoning within analytical toxicology. Mass spectrometry-based procedures suffer from the large amount of work required to maintain quantitative calibration in extensive multi-compound methods. In this study, a quantitative drug screening method for blood samples was developed based on ultra-high performance liquid chromatography with two consecutive detectors: a photodiode array detector and a corona charged aerosol detector (UHPLC-DAD-CAD). The 2.1 mm × 150 mm UHPLC column contained a high-strength silica C18 bonded phase material with a particle size of 1.8 μm, and the mobile phase consisted of methanol/0.1% trifluoroacetic acid in gradient mode. Identification was based on retention time, UV spectrum and the response ratio from the two detectors. Using historic calibration over a one-month period, the median precision (RSD) of retention times was 0.04% and the median accuracy (bias) of quantification 6.75%. The median precision of the detector response ratio over two orders of magnitude was 12%. The applicable linear ranges were generally 0.05-5 mg L(-1). The method was validated for 161 compounds, including antipsychotics, antidepressants, antihistamines, opioid analgesics, and adrenergic beta blocking drugs, among others. The main novelty of the method was the proven utility of the response ratio of DAD to CAD, which provided the additional identification efficiency required. Unlike with mass spectrometry, the high stability of identification and quantification allowed the use of facile historic calibration.