By Alberto Perego
Nuclear fusion is what powers the sun and the stars. It is often seen as a thing of the future, partially enveloped in a cloud of dreams and science fiction. However, it is quite reassuring that experiments concerning this powerful energy source are being conducted in a top tech lab at MIT by over 100 professional scientists, engineers and PhD students. Fusion produces all the elements of the periodic table, and allows for the combination of lighter elements into heavier ones using a 100 million degree superheated gas called ‘plasma’. The MIT team is trying to devise a successful way of isolating the hot plasma from the ordinary matter using strong magnetic fields. The challenge is to successfully isolate the plasma in a vacuum vessel, as it is several times hotter than the sun’s core and therefore hard to contain. The MIT scientists used an Alcator C-Mod Tokamak nuclear fusion reactor to heat up the plasma using radio frequencies reaching 35 million degrees Celsius, or approximately twice as hot as the centre of the sun. The plasma lasted for about 2 seconds, and it set a new record of 2.05 atmospheres for plasma pressure in a magnetic confinement device. The Alcaletor C-Mod has been in operation for 23 years and it’s a rather fitting event that it should set a last new record just before deactivation. The also set the former 2005 record at 1.77 atmospheres.
Why is this experiment relevant? Fusion could be the ultimate source of clean energy. In a push for clean energy, nuclear is often seen as a good alternative to burning hydrocarbons. The aim of nuclear scientists is to create a self-sustaining nuclear fusion reaction, like those constantly happening on the sun and on other stars. The scientists strive to perfect self-sustaining fusions as in this way it would be possible to create energy using much less energy. As of now it takes quite a lot of energy to force nuclei to fuse using traditional nuclear fission reactors.
After the 2011 earthquake that hit Japan, and following the terrible environmental repercussions created by the Fukushima nuclear disaster, nuclear power has been lacking appeal on the energy scene. Lately, things have changed, and it seems that we are set to see a strong come back of nuclear energy. The World Nuclear Association (an organisation representing a mix between trade union and lobbying agency for the companies involved with nuclear energy) provides data and analysis which seems to express a certain optimism for a revival in the popularity of nuclear power plants. This optimism is particularly linked to the use of nuclear power plants as a cleaner option to produce baseload electricity as opposed to coal or other fossil fuels.
Electricity demand is increasing twice as fast as overall energy use, and it is likely to rise by more than two-thirds during the period up to 2035. In 2012, 42% of primary energy used was converted into electricity. Nuclear power provides about 11% of the world’s electricity, and 21% of electricity in the OECD countries. If we look at the Chinese new five-year plan, we can see how this new super state is increasingly choosing to use nuclear energy for its baseload electricity needs. As of now, the People’s Republic of China has 35 nuclear power reactors in operation, and another 20 reactors are currently under construction. Moreover, additional reactors are planned, including some of the world’s most advanced. The Chinese government would like to double its nuclear capacity to at least 58 GW by 2020-21, then up to 150 GW by 2030.
However, nuclear, at least in its current fission from, is not totally clean, for it creates nuclear waste, which is a very long run problem. The problem of stocking nuclear waste is stretched on such a long term that it is indeed quite difficult for human beings to grasp it. The oldest man-made buildings on our planet are about 5000 years old, and they are not exactly in a good shape. Nuclear waste will be radioactive and harmful for thousands of years, and disposal techniques are being developed all over the world. In the USA, the plans to transform the Yucca Mountains into an underground long-term depository have been in place since the late 1980’s. Finland has four nuclear reactors providing nearly 30% of its electricity, and a fifth reactor is under construction. Here, provisions for radioactive waste disposal, are well advanced. Olkiluoto is an island off Finland’s West coast where the Finnish authorities allowed for the creation of a €3-billion (US$3.2-billion) storage facility. This site will be operational beginning in 2023. It will pack up to 6,500 tonnes of uranium into copper canisters, which will be lodged into a network of tunnels cut out of the granite bedrock 400 metres underground. Moreover, the canisters will be packed in with clay. Finnish authorities estimate that the facility will be sealed in 2120, and it should safely isolate the waste for several hundred thousand years, until the radiation levels will be harmless.
Long-term storage is a fundamental problem to solve, if we want to use nuclear energy safely. Fortunately, fusion could solve the waste disposal problem in a more permanent way. The MIT experiment was made in a small size reactor, but there are plans to replicate and use this technology on a much larger scale. In Southern France, a huge reactor capable of using fusion is being built. Named ITER, it will produce 800 times more energy than MIT’s device using magnetic fields similar to MIT’s. If successful, it would be a huge step forward towards clean nuclear energy.
http://news.mit.edu/2016/alcator-c-mod-tokamak-nuclear-fusion-world-record-1014
http://www.nei.org/issues-policy/nuclear-waste-management/disposal
http://www.nature.com/news/why-finland-now-leads-the-world-in-nuclear-waste-storage-1.18903
ENERPO Journal 