Rehearsals for full-scale melt-down

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with public opinion running skyhigh after the calamitous meltdown at Three Mile Island, something had to be done.

You will be relieved to know that as result, scientists at the US National Engineering • Laboratory (Idaho) were instructed to alter their . expensively scheduled safety programme and to further investigate the type of accident occurring at Harrisburg. The tests involved simulated accidents in a one-sixtieth scale thermal reactor.

The programme-named the Loss of Fluid Test (LOFT)-refers to an unfortunate loss of vital reactor cooling water and is carried out on the basic Light Water configuration (this reactor type uses 'light' water as both coolant and moderator).

Prior to Three Mile Island LOFT researchers had = 1762 by Tony Allen within a minute.

But Three Mile Island involved minor leakage from a damaged relief valve that wasn't spotted for 90 minutes so the LOFT schedule was redirected towards this type of breakdown, adn more specifically, into analysis of operator response times.

So what did the experts find?

Strain

The key points are summarised thus. In sharp confrast io previous experiments of a minute or so, one small leak test was timed at 90 minutes while another lasted It was reasoned that LOFT did not reveal any flaws in existing nuclear technology although every reactor type carried its own set of potential malfunctions. However, unmoderated 'fast' reactors do generate mechanical failures absent from thermal LWRs, so that during a scram there is a definite risk of a core re-alignment creating an intense radio-active surge ... and nuclear explosion.

Significantly, was admitted that the 250 reactor-years of crisis-free operation of LWRs (so far) have limited value in determining the accident rate for the year 2000. menace, especially so since 90% of American reactors are of the Harrisburg mode (i.e. LWRs).

And, as they point out, investigation of that $1 billion radio-active disaster has yet to be carried out!

Nevertheless, the longterm direction of energy supply is going increasingly toward nuclear power and continued massive profits for. Exxon, Westinghouse, Rio Tinto Zinc, etc. A fast reactor programme alone will screw American workers for a cool $200 billion unless they scram it first!

Source: Bulletin of the Atomic Scientists Nuclear Engineering International.

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Organiser, Thursday 1982

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