Activity under Chornobyl NPP Sarcophagus as Forecasted, No Hazard Exists: Experts

Some increase in the neutron flux density was recorded in one of the Chornobyl NPP Unit 4 (Shelter) rooms by sensors of the Integrated Automated Monitoring System installed in the New Safe Confinement. The information disseminated by some mass media about fission reactions that pose a danger of new accidents is factually incorrect.

“There are no actual nuclear reactions. There is an increase in the neutron flux density. The entire Shelter is equipped with a great number of sensors to monitor gamma radiation and neutron flux. Increasing neutron flux density was observed for some time. And this is not something that happened unexpectedly”, told Yuriy Ovdiyenko, Head of Neutronic Processes Department of the State Scientific and Technical Center for Nuclear and Radiation Safety in his comments for the website.

According to Ovdiyenko, this process was forecasted by calculations performed with the computer models to analyse the phenomena occurring in the fuel-containing materials in the sarcophagus developed by dedicated research organizations.

Dynamics of Neutron Flux Density: (a) near the nuclear-hazardous accumulation in Shelter room 305/2 and (b) on the remote periphery. Figure courtesy of the Institute for Safety Problems of Nuclear Power Plants, National Academy of Sciences of Ukraine

According to the ChNPP Press Service, increased neutron flux density was recorded in room 305/2, and the Institute for Safety Problems of Nuclear Power Plants (National Academy of Sciences of Ukraine) had predicted this process even before the New Safe Confinement was installed. This process was caused by loss of water by a humidified layer of black lava-like fuel-containing materials located above (elevation +9.00 ÷ + 9.70) the potentially nuclear-hazardous accumulations of fuel-containing materials.

To monitor the condition of neutron fluxes, the Program for Monitoring of Shelter Fuel-Containing Materials (Shelter Nuclear and Radiation Safety) has been ongoing since 2018. “Specific operational limits and limits of safe operation were established for each of the sensors. These limits are still very far from being exceeded”, added Yuriy Ovdiyenko.

The Institute for Safety Problems of Nuclear Power Plants further predicted that the contribution of nuclear-hazardous accumulations of fuel-containing materials to neutron activity would be constant. Should the limits of safe operation in terms of neutron flux density be exceeded, a neutron-absorbing solution will be introduced into the area with increased neutron flux density. This is provided for by the Shelter Technical Specifications. Editorial Board