Neutron Incident at the Chornobyl NPP Shelter Object: Study of the Causes and Impacts of Safety in the New Confinement

On April 26, 1986, the fourth accident in the history of nuclear energy took place at the fourth power unit of the Chernobyl Nuclear Power Plant. As a result of the accident, was formed fuel-containing materials, which are the main source of environmental danger of the Shelter. Some of the clusters are potentially nuclear hazardous and need to be monitored and analyzed. This paper presents a comprehensive analysis of the available experimental data on the neutron anomaly recorded in June 1990 on the periphery of clusters of fuel-containing materials located inside room 305/2 of the Shelter object. Particular attention is paid to the available data on the chronology of this event, determining its causes, restoring the natural dynamics of neutron flux density, as well as describing the most likely processes that accompanied this incident. In conclusion, it is suggested that, given all available data, this event can be consistently interpreted as a cold critical incident in the amount of material being shared.