Chornobyl radiation spikes are not due to military vehicles disturbing soil.

On 25th 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.

Dose quantities and instrumentation for measuring environmental gamma radiation during emergencies.

The dosimetry for exposure to gamma radiation in the environment is reviewed, including the factors used to convert measurements of traceable quantities to effective dose equivalent. A value of 0.70 Sv Gy-1 is widely used to convert air kerma or absorbed dose-to-air to effective dose equivalent, but recent work shows that a value of 0.86 Sv Gy-1 is more appropriate for deposited radionuclides. The arguments are reviewed and the implications of using operational dose equivalent quantities defined by the International Commission on Radiation Units and Measurements are considered. For planar deposited sources in the environment, it is shown that the use of ambient dose equivalent quantities without applying conversion factors, could significantly overestimate effective dose equivalent. In contrast, the adoption of the new effective dose quantity defined by the International Commission on Radiological Protection in Publication 60 will have a small impact on conversion factors for gamma radiation in the environment. Practical aspects of measurement are also considered, and five instruments suitable for measuring environmental gamma radiation have been evaluated in the laboratory and in field tests. The instruments include models with scintillation detectors, a Geiger-Müller detector, and a high-pressure ionization chamber, the choice being influenced by those commonly used in European Community countries for routine and emergency monitoring. The main disadvantage of all the instruments is the lack of spectral information, so a straightforward emergency instrument capable of discriminating between natural and artificial radionuclides has also been evaluated.

An IPSM sponsored intercomparison of surface contamination monitoring test results.

An intercomparison using two popular survey meters was arranged to assess the ability of participants to test surface contamination monitors in compliance with the requirements of the Ionising Radiations Regulations 1985. The instruments were circulated and the data returned were compared with the NRPB values. The major inconsistencies were caused by differences in the interpretation of what constitutes 1 Bq of 90Sr+ 90Y and in the conversion of the emission rate from (129)I plaques into a value of equivalent (125)I activity.