The Institute for Safety Problems of Nuclear Power Plants of the National Academy of Sciences of Ukraine has denied media reports that a self-sustaining chain reaction could resume in the Unit Four of the Chornobyl NPP destroyed in 1986.
After the installation in 2016 of the arch on the Shelter Object that covered the destroyed reactor, separate sensors recorded an increase in neutron activity in the aggregates of fuel-containing materials in the melt-through zone of the under-reactor plate, the report says. However, during the entire observation period from the beginning of the arch installation in the design position, no exceedance of normal operation limits was recorded. The level of neutron activity corresponds to the predicted values.
"At present, the sensor readings in all rooms have stable values without an increasing tendency, the current levels do not pose a threat of a self-sustaining fission," the message says.
Context. In an article published on May 5 in the journal Science, it is said that in the Unit Four of the Chornobyl NPP, 35 years after the accident, signs of radioactive fuel fission reactions were recorded.