Construction of the new safe confinement (NSC) above the Shelter over destroyed Chornobyl NPP unit 4 is under completion. The NSC Arch was launched and installed in its design position in November 2016. The NSC design is based on boundary conditions for current and potential hazardous impacts from the Shelter. The NSC should withstand these boundary conditions to protect NSC personnel and the environment. The goal of this work is analyze the factors that determine safe state of the Shelter as a part of NSC. The paper presents results of the following analyses: boundary conditions for current and potential hazardous Shelter impacts (release of radioactive substances, release of radiation, hypothetical criticality emergencies, collapse of structures, fire etc.); factors that characterize the Shelter state and are associated with boundary conditions (dust generation in degradation of fuel- containing materials (FCM), degradation of most Shelter structures, dynamics of changes in water-humidity conditions and water accumulations etc.). Upon the analyses, approaches have been identified to determine conditions and criteria to ensure safety of the Shelter under NSC. It is pointed out that additional study is required for FCM degradation processes, Shelter internal structures with FCM accumulations, fire sources in arears with high levels of radioactive contamination etc.
Keywords: Shelter, new safe confinement, fuel-containing materials.
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