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Thursday, December 5, 2019
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HELSINKI, Mar 17 2011 (IPS) - In the 1970s Japan, the United States, France, Germany, Britain, the Soviet Union, and China were all developing major breeder reactor programmes. Breeder reactors are nuclear power plants that produce more nuclear fuel than they consume generating electricity.
All of these programmes were later abandoned because there were too many problems and too many potentially dangerous situations. The only partial exception was China, which never officially abandoned its breeder reactor programme. But even in China such plans entered a practical standstill.
More recently the idea has been re-awakened by concerns related to global warming. Many governments have started to see nuclear power as a partial solution to our carbon dioxide problem. Our present nuclear reactors, however, can only provide for a minuscule part of our energy needs: two percent if only the power is counted and six percent if we also classify the waste heat as energy.
This cannot be expanded much with the present reactor types. Even though the Earth’s crust contains a lot of uranium, rich uranium ores are relatively rare, and many of them exist in densely populated areas. The natural deposits that are concentrated enough to be harnessed might last for eighty or one hundred years for the present number of nuclear reactors.
Natural uranium contains 140 atoms of uranium 238 for each atom of uranium 235. Nuclear reactors can only utilise uranium 235, but breeder reactors can convert uranium 238 to plutonium 239, which can be used as a nuclear fuel. Besides this, they can convert thorium to uranium 233, and thorium is five times more abundant than uranium.
In practise this means, that if we want to multiply the production of nuclear power, we have to use breeder reactors.
However, all the breeder reactors which have been constructed, thus far, have used liquid sodium or lithium as their coolant. Both metals explode when they contact water or air. It is very difficult to construct the cooling pipes of a breeder reactor in such a way that they cannot be damaged by a very large tsunami. On land the pipes can be protected by concrete, but at some point they must be contact with sea water so that the superheated sodium inside the pipes can be cooled down before it goes back to the reactor.
The underwater parts of the system are almost inevitably vulnerable to a tsunami wave, which first makes the water withdraw and then comes back with a vengeance. One small tear in one of the pipes and the whole cooling system would be utterly devastated by a series of sodium explosions. More complex cooling arrangements are of course possible, but they do not really solve the problem.
In our present water-cooled reactors, the production of heat drops to a small fraction almost instantly if the coolant is lost. But, at least in the Indian fast breeder designs the production of heat increases if the supply of coolant is interrupted. Expressed in technical jargon, many breeder reactors have a positive and not a negative coolant void coefficient. This multiplies the risks in dangerous situations.
Above all, breeder reactors use highly-enriched nuclear fuels. The fuel of our present nuclear reactors contains 2-4 percent of uranium 235. This kind of fuel can only produce tiny nuclear explosions, even in extreme situations. The first explosion in Chernobyl was technically a nuclear detonation, but it was not much larger than the following hydrogen and steam explosions, because the fuel only contained 1.8 percent uranium 235.
In contrast breeder reactor fuel typically contains 15 to 30 percent and sometimes up to 60 percent fissile isotopes like uranium 235, uranium 233 or plutonium 239. This means that if a breeder melts, we cannot exclude the possibility that a steam or hydrogen explosion would produce a small nuclear detonation and vaporise the whole reactor. The radioactive fallout produced by such an accident would be incredibly lethal and might cause continent-wide devastation.
The construction of breeder reactors would also multiply the risks related to nuclear terrorism. Weapons-grade uranium contains 93 percent uranium 233 or 235, but it is possible to make a crude nuclear weapon from breeder reactor fuel containing 10 percent uranium 233 – and most designs would use a far higher percentage. Thus every shipment of fuel to a breeder reactors will give the terrorist organisations a new chance of acquiring a nuclear weapon.
A few years ago, Japanese nuclear companies and research facilities produced scary proposals about mass-producing tiny, lithium-cooled nuclear reactors. The idea was that these Rapid-L reactors – containing uranium 235 enriched to 60 percent- would act as the power sources for individual office buildings and large blocks of flats.
After the recent devastation in several Japanese nuclear power plants, it is unlikely that these programmes will ever be carried out.
But India is already constructing a 500-megawatt sodium-cooled breeder reactor to Kalpakkam, on the coast of Tamil Nadu. The final goal of India’s nuclear programme is to construct 600 gigawatts of breeder reactors by 2050. This would assumedly mean either 1200 Kalpakkam-sized reactors or 600 larger ones.
These breeders would have to be located in coastal areas because they need huge amounts of cooling water and India already has a growing problem with its freshwater resources.
If the programme is carried out, the human species will soon have an official expiry date, for the first time in our history. That will be the day the next giant tsunami hits a major stretch of India’s coastline. You can’t get any farther from the teachings of the Mahatma. (END/COPYRIGHT IPS) (*)
(*) Risto Isomaki is an environmental activist and awarded Finnish writer whose novels have been translated into several languages
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