Preliminary assessment of the radiological consequences of the hostile military occupation of the Chornobyl exclusion zone.

The Russian invasion of Ukraine in February 2022 put the radiological well-being of the people in Ukraine under unprecedented threat due to massive shelling, looting of facilities holding radioactive material, and potential physical disturbance of radioactively contaminated areas. Before the shutdown a few days after the occupation, the gamma-detectors in the ChEZ recorded sharp increases in the gamma-background in several areas which indicated some non-typical processes taking place on its territory.
The State Nuclear Regulatory Inspectorate of Ukraine (SNRIU) and its technical support organization, the Scientific and Technical Center for Nuclear and Radiation Safety (SSTC NRS), as well as the rest of the professional nuclear community in Ukraine and worldwide, recognized the potential for movement of the radioactive contamination by Russian military machinery and personnel to areas outside the ChEZ, creating locally contaminated spots. Certain apprehensions were caused by the inventory performed after the liberation of the ChEZ which revealed the theft of calibration sources and radioactive samples from laboratories located in Chornobyl. 
As soon as this information became available to the public, it caused a wide response and anxiety, as a result of which SNRIU made a decision to conduct a radiation survey of the liberated territories in the Kyiv region. The survey was conducted between June and December 2022 by SSTC NRS specialists with the support of DSA. The survey covered over 50 settlements and a limited part of the ChEZ, and combined continuous gamma-dose rate measurements by detectors installed in the laboratory vehicle with additional manual measurements at specified points. 
The survey found no deterioration in the radiation situation in the liberated territories, and no contaminated objects, radiation sources, or other radioactive material removed from the ChEZ. Measurements of Cs-137 soil contamination in the ChEZ matched the pre-war results. The direct impact on the public in the surveyed territories was negligible, and the radiation consequences of forest fires during the occupation were very small, too. However, due to damage to the radiation monitoring system, explosive hazards, and destruction of transport infrastructure, the consequences of the occupation by Russian troops will be long-term.