Quote:
Originally Posted by LSainsbury
Wasn't is somthing to do with a steam valve that failed?
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They were buggering about with the reactor.
The water pumps on that type of reactor had backup diesel generators, but they took 40 seconds to get up to speed, so that would be 40 seconds of no water pumping around a nuclear reactor.
So they were testing to see if the momentum in the reactor's turbine was enough to cover the power shortfall.
They'd performed the same operation on another reactor without anything going wrong because they'd left the safety systems active that time. It hadn't worked though, there wasn't enough power produced.
With reactor 4 they'd made improvements to the power so were trying again.
The experiment was delayed until the night shift because a normal power station had gone offline and they needed the power for the grid.
The night shift were inexperienced, most drafted from coal power stations, and not suited to run the experiment.
They didn't even realise the reactor shutdown had been postponed so continued following the original plan, causing the shutdown to be too rapid.
To compensate they withdrew most of the control rods.
Even though only a third of the power required for the experiment was being produced, they continued on.
They increased water flow, which required removing the remaining control rods, as water and the gas produced by the rapid shutdown were absorbing neutrons like the rods should do.
When they turned off the steam to the turbine to let it's momentum power the pumps, the water flow dropped, the neutron absorbsion dropped.
The reaction increased.
Pockets of steam were produced in the cooling lines, increasing the reaction.
The neutron absorbing gas that had been produced was burnt off, increasing the reaction.
They tried to shut the reactor down by re-inserting the rods, but that took up to 20 seconds, and by design flaw reduces the coolant, actually increased the reaction.
The boron rods melted, the steam exploded, and radioactive waste was spread across the continent.
So what caused it?
Untrained staff pulling the control rods out of a badly designed nuclear reactor while trying to see if the turbine spinning could power the coolant pumps.
It wasn't a case of happy running reactor one minute, big explosion the next, the staff caused the explosion.