BASED ON INFORMATION AVAILABLE TO DATE, WE CAN CONSTRUCT AT 1:23 AM, APRIL 26, 1986 AN EXPLOSION OCCURRED AT THE EXPLOSION IS SAID TO HAVE OCCURRED IN THE BUILDING WHICH AS A RESULT OF EXPLOSION, THE ROOF OF THE REACTOR BUILDING FIRE DAMAGE CAUSED A BREACH OF REACTOR CONTAINMENT INITIAL RADIOACTIVE RELEASE SUBSEQUENT INITIATION OF GRAPHITE FIRE O THERE ARE MANY POSSIBLE SCENARIOS FOR CHERNOBYL THAT CAN LEAD TO THE DAMAGED CORE. = 0 WE STILL DO NOT KNOW ABOUT THE ACTUAL SEQUENCE OF EVENTS WERE. SOME POSSIBILITIES ARE: - EXPLOSION/FIRE IN TURBINE OR REACTOR BUILDING ULTIMATELY CAUSES LOSS OF CONTROL (COOLING) TO CORE. LEADS TO CORE UNCOVERY AND MELTDOWN - EXPLOSION/FIRE IN TURBINE OR REACTOR BUILDING CAUSES FAILURE OF REACTOR BUILDING AND DAMAGES REACTOR ROUGH DESCRIPTION OF A HEATUP SCENARIO - PRIMARY COOLANT WATER BOILS OFF - WITH REACTOR SHUT DOWN, NO HEAT GENERATION IN GRAPHITE - FUEL AND GRAPHITE COOL AND APPROACH QUASI-THERMAL EQUILIBRIUM - FUEL UNCOVERS OVER SEVERAL HOURS AND HEATS UP - FUEL CLADDING OXIDATION AND FAILURE - FUEL ASSEMBLY CASING FAILURE NEAR TOP OF CORE - HIGH PRESSURE-HIGH TEMPERATURE STEAM AND OTHER GASES PRESSURIZE THE GRAPHITE CAVITY - FAILURE OF GRAPHITE CAVITY ALLOWS AIR INGRESS TO CORE REGION - GRAPHITE FIRE STARTED AND A CHEMICAL (GAS) EXPLOSION IS POSSIBLE - GRAPHITE CONTINUES TO BURN OVER A LONG TIME |