Global Ecological Problems and Issues

The primary energy-producing reaction will stop immediately if a water-cooled nuclear reactor loses its cooling water. This is because the water is also acting as a moderator: it is slowing down the neutrons produced by the splitting of the atoms to speeds in which most of them will split other atoms. However, if the nuclear fuel has been in use for some time, it has accumulated a large amount of waste products. These nuclear ashes are a mixture of numerous different radioactive materials including plutonium, each decaying at a different rate. These radioactive waste products that have been accumulating in the nuclear fuel keep on decaying and producing heat even after the reactor has been shut down. If something happens to the nuclear reactor just before it would have been shut down so that the fuel rods can be exchanged, each ton of fuel can keep on producing 1.6 megawatts of heat even after the primary reaction has stopped.

In other words: a large water-cooled nuclear reactor can keep on producing up to 80 megawatts of heat even after the reactor has been shut down. If the cooling pipes have been cut or seriously damaged this heat will not be transferred out of the reactor by the coolant. When you lift a kettle containing water off an electric stove, it does not take very long before the plate has been heated red hot by the current running through it. If a nuclear reactor goes through a loss of coolant accident (LOCA) at the wrong moment, the same thing will happen to it. The nuclear fuel will melt and sink into the ground through the containment shield. This phenomenon has been dubbed "the China syndrome".

The China syndrome has never happened in a nuclear power plant and the probability that it would happen by accident is not very large because the nuclear power plants now have multiple safety systems. However, if somebody wants to sabotage a nuclear power plant on purpose in order to cause a loss of coolant accident, this is very easy to do.

According to a study carried out by majors Scott M. Nichelson and Darren D. Medlin of the US Air Forces terrorists could also do a lot of damage if they were able to capture a single used nuclear fuel rod. If the fuel rod would be detonated with a mixture of diesel oil and nitrogen fertilizer, the radioactive fallout could kill 50-90 per cent of the unprotected population of Washington DC, Baltimore, Philadelphia and New York. Besides this there would be a notable increase in cancer mortality on the whole Wastern Coast of the USA.

However, the most serious problem related to the safety of the nuclear power plants and nuclear fuel reprocessing facilities could still be something else than terrorism. It could be a phenomenon known as megatsunami.

Normal tsunamis are fast-travelling waves caused by volcanoes or earth-quakes. They are typically only a few centimetres or, at most, a few metres high. Even this kind of waves can cause enormous damage in coastal areas.

Geologists and geomorphologists at the University of Wollogong in New South Wales, Australia, have discovered traces of a number of very large but relatively recent tsunami waves around the coast of Australia. The traces include car-sized blocks of rock lifted over 100-metre high cliffs, and smaller debris deposited up to 35 kilometres inland. According to the Australian researchers there has been, an average, one megatsunami wave at intervals of 1000 to 500 years.

Most researchers first assumed, that the megatsunami waves on the Australian coast had been caused by comet fragments or asteroids hitting the Earth. This theory, however, has now fallen out of glory. The record of impact craters on land does not support the hypothesis, it is likely that cosmic collions on this kind of scale are very rare. Moreover, the researchers think that a collision with an asteroid would create a slightly different wave than the ones that have left their marks on the coast of Australia.

This leaves three likely candidates: the destabilization of methane clathrate deposits, the destabilization of Antarctic glaciers and the collapse of volcanoes.

For example a volcano named Cumbre Vieja, on the island of La Palma on the Canary Islands, is expected to collapse when the next major eruption of the volcano takes place. When this happens roughly half a trillion tons of rock will drop in the ocean and create a five hundred metre-high megatsunami wave raging over the Atlantic with the speed of a jet-plane. Earlier collapses of the Canary Island volcanoes have caused similar waves. For example on the Island of Eleuthera, Bahamas, these ancient megatsunamis have washed boulders weighing up to 2000 tons on younger rocks situated tens of metres above the sea level.

However, something like this should only happen once in every one hundred thousand years or so. This means that the most likely cause of the megatsunamis have been the destabilization of methane clathrate deposits or continental glaciers. The destabilization of clathrates can create megatsunamis by causing very large underwater landslides.

Also the melting of glaciers can cause huge tsunami waves. After the last ice age vast amounts of melt water often accumulated behind large ice dams. It seems that large melt-water lakes, the biggest of which may have contained up to one million cubic kilometres of water, have suddenly erupted and flooded to the sea when the ice dam has finally been broken.

According to professor John Shaw of Canada's Alberta University the breaking of the ice dams may have created a situation in which huge masses of melt water have started to run towards the sea under a continental glacier. In such situations a vast chunk of the whole continental glacier can suddenly lose its contact with the base rock. When the contact with bedrock is severed the glacier can slide towards the sea on top of the water. Such glacial surges have probably caused very large tsunamis at the end of the last ice age. They might be the most plausible explanation also for the old megatsunamis which have hit the coast of Australia. This is a very worrying possibility, because the predicted man-made warming of the climate could well trigger similar glacial surges also in the future.

Most nuclear power plants in the North have been built on coastal zones, because they require large quantities of cooling water and because most of the people in the USA and Europe live on coastal regions or relatively close to them.

If there would be a big megatsunami wave triggered by the collapse of glaciers or the destabilization of clathrate deposits, all these nuclear power plants would be destroyed. Even ordinary breaking waves can create pressures of up to 6 kilograms per square centimetre, equivalent to 60 tons per square metre, which is enough to crush very strong steel baulks and plates. Megatsunamis are much larger and much, much faster than ordinary waves and the forces created by them are at least one order of magnitude stronger. The pipelines and other vulnerable structures of the nuclear power plants and cooling ponds have no chance of withstanding such an impact. The radioactivity in the cooling ponds would be released into the environment. The complete melt-down of the actual nuclear reactors would also be likely to produce a very hot pond of molten metal, which might be hot enough to penetrate through the containment shell.

Loss-of-coolant accidents leading to the simultaneous melt-down of a hundred nuclear reactors and the related cooling ponds would be a disaster of almost unimaginable portions, perhaps even the end of the human kind. The amount of radioactive pollution released into the environment could be tens of thousands or one hundred thousand times larger than the radioactive fallout created by the Chernobyl accident.

If building nuclear power means taking big risks, the construction of nuclear power plants on coastal areas during a historical period when global warming is threatening the stability of glaciers and methane clathrate deposits is raving madness. There should perhaps be a huge global boycott against the countries that aim to construct new nuclear power plants on coastal areas.

We do not know exactly how harmful radiation is, but everybody now agrees that radiation does cause some damage. Estimates about the number of cancer deaths caused by man-made nuclear pollution, most of which consists of the fallout from the atmospheric nuclear tests, range from 1 173 600 (International Commission on Radiation Protection) to 61 600 000 (European Committee on Radiation Risk).

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