Saturday, 28 March 2009

It happened 30 years ago: Three Mile Island accident

Three Mile Island accident

Three Mile Island 
Three Mile Island
A partial meltdown at the Three Mile Island nuclear plant near Harrisburg, PA, occurred thirty years ago today, on March 28, 1979. The cooling system in one of the nuclear reactors failed, causing overheating and a partial melting of the uranium core. Backlash from the incident brought protests and demonstrations against nuclear power; some 200,000 attended a rally in New York City. Nuclear plant production came to a halt in the US and the Nuclear Regulatory Commission established stricter guidelines and safety measures on the plants already in existence.


"None of us are nuclear experts, but we know that if there is a melt-down and breach of containment, that's clearly the most odious thing that could happen." — William Scranton 

Question of the Day

Can an improperly managed nuclear power plant explode like a nuclear weapon?
No, it cannot. No mismanaged nuclear plant, no nuclear plant accident of any kind, can cause a massive nuclear explosion like the blast of a nuclear weapon. To understand this, begin with the idea that fissionable material requires a certain minimum amount (critical mass) of it to be brought together to spontaneously initiate fission, to make it go critical. In a nuclear weapon, the subcritical masses are driven together and held together for an extremely short interval of time by conventional explosives. The result of driving and holding the critical mass together is that it goes critical and instantly right through that to supercritical. This causes the nuclear chain to build exponentially and the number of fissions per unit of time goes through the roof. Boooooom. Maximum fission burn and big yield. 

In a non-bomb situation, subcritical masses of fissionable material are brought together without being blasted together. They achieve criticality and fission begins instantly. Enough fissions will occur to generate enough heat to separate the critical mass to make the whole thing go subcritical. That will be the only goal of the fission reactions — to separate the critical mass into something subcritical. ... More

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