Many nuclear facilities like nuclear power stations and the cooling ponds and recycling plants of used nuclear fuel have been constructed on coastal areas. When nuclear facilities are situated near the sea, sea water can provide for much of the cooling required by the plants. This reduces the consumption of freshwater. However, the construction of nuclear facilities on coastal zones also exposes them to storm surges and tsunamis.
It is now more or less generally accepted that much of the extra heat remaining on our planet because of the atmosphere’s increasing greenhouse gas concentrations will be channelled into more powerful storms. On the Saffir-Simpson scale a category 5 hurricane is defined as a storm with wind speeds exceeding 249 kilometres per hour and strong enough to rise the sea level (temporarily) by at least 5.5 metres. In bays and fjords the temporary rise of sea level can be much more, especially if there are rivers that are flooding because of the heavy rains. Such hurricane storm surges are produced by the combined effect of two different factors: the strong winds push the surface water forward and against the shores, and the low-pressure area inside the storm adds to the height of the surge. The first factor is the more significant one.
At the North Atlantic there have been a little bit more than one large tsunami wave in a century. The most well-known events took place in 1929, 1755, 1607 and 1580. The tsunami of 1755 destroyed Lisboa, Cadiz, Huelva, and hundreds of smaller towns at the Spanish, Portuguese and Moroccan coasts. The Buran Peninsula tsunami (in 1929) was 7 metres high on long stretches of Canada’s coastline and rose to 27 metres in some bays. It was triggered by a relatively small (Magnitude 7 on the Richter Scale) earthquake, which caused a 200-cubic-kilometre submarine landslide.
After the last ice age the melting of the Fennoscandian ice sheet was relatively slow and took thousands of years of time. However, the melting of the continental ice sheet was still able to cause very large earthquakes, at least 8.5 and possibly much more on the Richter scale. These earthquakes were caused because a continental ice sheet is so heavy that it depresses the crust under it, sometimes by more than one kilometre. When the ice melts the ice sheet becomes less heavy and the crust begins to bounce back. The Swedish scientists have found traces of at least 13 tsunami events triggered by these earthquakes at the Baltic Sea, 12,400 to 4,000 years ago. According to the Swedish scientists some of these waves were “large” (about 20 metres high) and a few were “very large”.
The Fennoscandian ice sheet melt slowly because the melting process was only influenced by natural factors. During our own time the melting of the Greenland and West Antarctic ice sheets could happen in a much shorter time, because of the influence of various human activities. We are increasing the atmosphere’s greenhouse gas concentrations and we are increasing the cirrus cloud cover (which has a strong warming impact on climate).Besides this we are also producing huge amounts of soot and dust which accelerate the melting of the glaciers by making the surface layer of the glaciers darker. Dust and soot reduce the reflectivity of snow and ice so that the glaciers can absorb more solar radiation.
Many scientists are now saying that the major part of the Greenland ice sheet could disappear in a couple of centuries and possibly in less than a century. If this happens, the Greenland ice sheet will melt dozens of times faster than the Fennoscandian ice sheet did. Such a process would, with a probability of exactly 100 per cent, cause a number of extremely violent earthquakes. Such earthquakes would be very likely to cause huge submarine landslides along the eastern coast of Greenland. There are enormous amounts of loose sediments, brought by the annual melt waters, which have been piling on Greenland’s coastal margins for more than a hundred thousand years. The edge of the ice sheet in Eastern Greenland has been remarkably stable for a very long time. For this reason there haven’t been any major earthquakes in the region after the last ice age, and the first major event can easily trigger substantial underwater landslides.
The scientists of Geomar, a famous ocean research institute in Kiel, Germany, have also warned that the warming of the sea water could lead to the destabilization of the so called methane clathrate deposits on continental slopes. This might also cause huge submarine landslides and tsunamis.
High storm surges or the tsunamis triggered by the melting of the clathrate beds and the Greenland ice sheet constitute a potential danger for the coastal nuclear facilities. A tsunami or a storm surge hitting a nuclear power plant could easily halt the diesel and electric engines of a reactor’s cooling system. In the worst-case scenario the nuclear fuel inside the reactor would burn and spread into the atmosphere in the form of highly radioactive aerosols. The main problem is the zirconium alloy cladding of the nuclear fuel rods, because it can catch fire and liberate most of the radioactivity inside the nuclear fuel into the atmosphere in the form of small and nanoparticles which can easily be inhaled in the lungs, but which can then stay inside a human body for years or for decades.
Three generals of the US Air Forces (see Nichelson-Medlin-Stafford: Radiological Weapons of Terror, Air University Air Command and Staff College) made, in 1999, an investigation of what would happen if a group of terrorists would use conventional high explosives to pulverize ten kilograms of used nuclear fuel just taken out from a nuclear reactor. According to the study the radioactive fallout produced by such a Dirty Bomb of three million curies would be able to kill most of the unprotected inhabitants of New York, Washington DC, Philadelphia and Baltimore if the winds would blow towards their direction. A large nuclear reactor can contain 150 tons of nuclear fuel with 300,000,000 curies of radioactivity per ton. Some of the proposed new reactors would be even larger and might finally contain two or three times more radioactivity for each ton of nuclear fuel. As a Dirty Bomb such a reactor would be 17,000 times more effective as the radioactivity dispersal device in Nichelson’s, Medlin’s and Stafford’s scenario. The accident of Chernobyl only released 50 million curies of radioactivity into the environment.
The cooling ponds outside the reactors’ containment shields are probably the most vulnerable spots. The fuel rods stored in them are typically thousands of times less radioactive than the nuclear fuel which has just been taken out from the reactor. However, even this fuel is still so hot that its zirconium alloy cladding will catch fire if the pumps stop functioning and the water in the cooling ponds evaporates so that the fuel rods will be exposed. A typical cooling pond of a nuclear power plant contains 20-50 times more radioactive Cesium 137 than what was released in Chernobyl, and this could easily be released into the atmosphere in a fire caused by a tsunami or a storm surge accident.
It would be very important to improve the sea defences of the nuclear facilities which have been constructed on the coastal areas of the Atlantic. If the governments decide to construct new nuclear power plants, they should not be sited on low-lying coastal zones.