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If by fail safe you mean that powering off the reactor makes it cool down then the Navy uses fail safe reactors. Water is used as the moderator to absorb radiat
by dickholesalad 4y ago
If by fail safe you mean that powering off the reactor makes it cool down then the Navy uses fail safe reactors. Water is used as the moderator to absorb radiation. When water is heated its density decreases (edit), thereby making it a less good moderator of radiation. This effect lowers reactor reactivity and heat output. This effect is combined with various devices to produce what is called an inherently safe design. Losing power will not make the reactor have a fuel element failure or melt down.
- whearyou 4y agoFail safe means that in a catastrophic failure of the reactor’s regulatory systems it stops functioning rather than overloads. Entropy trends it to not working rather than working too much - for example a gas furnace will stop burning if the systems running the furnace stop working and are unable to provide more gas to the burn chamber. Is that how Navy reactors work?
- dickholesalad 4y agoChernobyl used a neutron moderator with a positive temperature coefficient of reactivity (liquid sodium), while U.S. Navy reactors use water, which has a negative coefficient of reactivity. The more energy you put into the water surrounding the reactor, the less reactive it allows the reactor to be. This has a stabilizing effect on the system. U.S. Navy reactors are inherently stable and inherently safe. To answer your question directly, yes entropy will trend toward making the reactor produce less heat with no intervention.
- pfdietz 4y agoChernobyl did not use liquid sodium. It was a graphite moderated thermal spectrum reactor with water as the coolant.
- dickholesalad 4y agoI appreciate the correction. I had fusion of knowledge with a different reactor accident. https://allthingsnuclear.org/dlochbaum/nuclear-plant-accidents-sodium-reactor-experiment/ https://allthingsnuclear.org/dlochbaum/nuclear-plant-acciden...