Search - Number 16 - 25 YEAR-EVOLUTION OF “SHELTER” OBJECT FUEL-CONTAINING MATERIALS COMPREHENSION: LFCM FORMATION SCENARIOS AND PHYSICAL CONSIDERATIONS

25 YEAR-EVOLUTION OF “SHELTER” OBJECT FUEL-CONTAINING MATERIALS COMPREHENSION: LFCM FORMATION SCENARIOS AND PHYSICAL CONSIDERATIONS
Cover not present 25 YEAR-EVOLUTION OF “SHELTER” OBJECT FUEL-CONTAINING MATERIALS COMPREHENSION: LFCM FORMATION SCENARIOS AND PHYSICAL CONSIDERATIONS
Category: Number 16
Publication: 16
Summary

25 years passed since the known heavy nuclear accident held on Chornobyl NPP facility in 1986. The paper contains critical review analysis of known concepts purposed on identification of physical mechanisms responsible for lava-like fuel-containing materials (LFCM) formation and includes a comprehensive analysis of existing data, involving new author's experimental data on both a quantitative accounting of high-temperature interaction of overheated nuclear fuel with design materials of channel reactor construction and LFCM fluidity on temperature dependence data. As a result, it was established, that long-year wide-disseminated concepts based on the picture of preliminary uranium-zirconium eutectic formation in active stage of accident are fundamentally flawed because of extremely low uranium dioxide with zirconium chemical interaction intensity, even at high temperatures. Leading chemical-physical mechanism responsible for LFCM formation was dissolving of zirconium-made fuel envelopes in melted silicates became feasible because of such materials in channel reactor construction design as serpentine and sand filling. The temperature level just below 1200 ?С turned out to be sufficient for black and brown LFCM formation; an effective temperature for main lava streams dissemination was estimated as 900 ± 50 ?С as well. High intensity of uranium fuel with melted silicates interaction (when in air atmosphere, even at moderate temperatures) was a key moment, which led to irradiated fuel fractioning accompanied with further wide dissemination of its high-radioactive components into the environment. The heavy radio-ecological consequences of the accident, comparing with other known nuclear accidents, are mainly caused by crucial faults in the USSR channel reactor design. The non-contradictive concept, explaining the main features of processes, which dominated in the active stage of accident, is also discovered.

Keywords: heavy nuclear accident, irradiated nuclear fuel, fuel-containing materials.

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