the chernobyl power plant went offline on june 17, 2017.
when did the chernobyl power plant go offline?
june 17 , 2017
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the notorious rbmk graphite moderated, water-cooled reactors of chernobyl power plant disaster were designed with a positive void coefficient with boron control rods on electromagnetic grapples for reaction speed control. to the degree that the control systems were reliable, this "design" did have a corresponding degree of "active" inherent safety. the reactor was unsafe at low power levels because erroneous control rod movement would have a counter-intuitively magnified effect. chernobyl reactor 4 was built instead with manual crane driven boron control rods that were tipped with the moderator substance, graphite, a neutron reflector. it was designed with an emergency core cooling system (eccs) that depended on either grid power or the backup diesel generator to be operating. the eccs safety component was decidedly not passive. the design featured a partial containment consisting of a concrete slab above and below the reactor – with pipes and rods penetrating, an inert gas filled metal vessel to keep oxygen away from the water-cooled hot graphite, a fire-proof roof, and the pipes below the vessel sealed in secondary water filled boxes. the roof, metal vessel, concrete slabs and water boxes are examples of passive safety components. the roof in the chernobyl power plant complex was made of bitumen – against design – rendering it ignitable. unlike the three mile island accident, neither the concrete slabs nor the metal vessel could contain a steam, graphite and oxygen driven hydrogen explosion. the water boxes could not sustain high pressure failure of the pipes. the passive safety components as designed were inadequate to fulfill the safety requirements of the system.
passive nuclear safety