People's Democracy

 An Artificial Sun On Earth?

Raghu

LAST week major world and nuclear powers meeting in Washington took further steps, but encountered a major hurdle, along the road towards a dream project for a nuclear reactor or power-generation system based on fusion rather than the conventional fission-based power plants. The US, Canada, European Union, Russia, Japan, China and South Korea committed themselves firmly to the International Thermonuclear Experimental Reactor or ITER Project, the acronym being Latin for “the way”, which, at an estimated US 10 billion dollar (Rs 47000 crore) is the largest international collaborative research and development Project since the Space Station. But they also failed to decide upon where to locate the Project, the two main contenders being France and Japan, with geo-political considerations playing the main role in the postponement of this decision.

Before we discuss the various issues involved and their implications, let us first clarify some of the basics. Put simply, fission reactions are based on splitting atoms releasing huge quantities of energy as during the first nuclear bombs dropped on Hiroshima and Nagasaki. Fusion reactions, on the other hand, are based on forcing the nuclei of atoms together releasing even greater amounts of energy, as in the Hydrogen Bomb but also, more commonly, as in the sun and the stars.

In nuclear power plants as against nuclear bombs, the problem lies in controlling the enormous amounts of energies released and harnessing it for generating electricity rather than for unleashing a gigantic explosion. In conventional fission-based plants, energy is generated by triggering a chain reaction of splitting uranium atoms if left to itself, this chain reaction will build up to an explosive release of energy as in a bomb but, in a power plant, the reaction is moderated and controlled so that the heat generated can be used to produce steam which drives turbines to generate electricity. Scientists and engineers have achieved this over the previous six decades and more, and have also tried, with mixed success, to tackle the accompanying environmental problems and the even more serious problem of handling the hazardous wastes.

But harnessing fusion to generate power on a commercial scale is still a distant goal. Since this is tantamount to replicating the energy-generating mechanism in the sun and the stars, fusion-based nuclear power generation has been likened to having an artificial sun on Earth.

POWER FROM FUSION

In a fission reaction, a heavy atom such as that of Uranium is bombarded with neutrons (electrically neutral particles from the nucleus of an atom) which split the atom into roughly equal parts, release two or three more neutrons and large amounts of energy. If there is a critical mass of Uranium, such that there are always sufficient numbers of atoms left to be split, a chain reaction results.

Atoms of lighter elements too can be used to produce energy. In such a reaction, negatively charged electrons are separated from the nucleus of an atom, which now has residual positive charge, and which is then forced to join with another similarly charged nucleus. When the two charged nuclei join, they combine to form a new element with slightly less mass than the original, this “lost” mass being converted into energy as per Einstein’s famous equation. In the sun and in stars, for instance, hydrogen atoms join together to form a new element, helium, and release enormous amounts of energy.

The problem is that, to make charged nuclei come together, they must be provided sufficient energy to overcome the force with which the similarly charges are repelled from each other. In the sun, this is achieved due to the prevalent high temperatures of over 15 million degrees Celsius and the high pressures over 100,000 times that on the earth’s surface. In a nuclear reactor, it has not been possible anywhere near the levels of pressure generated in the sun but, to compensate, higher temperatures are possible. In order to achieve the energy levels required to generate and sustain fusion reactions in a reactor, temperatures of around 100 million degrees Celsius, or 10 times the temperature in the sun, is required. In experimental reactors, temperatures of around 300 million degrees have been achieved!

At such high temperatures, the electrically charged gases form a state of matter called a plasma, a form of gas that has a great deal of energy looking for a way out. This brings in a new problem, that of how to contain the plasma. Controlling the whirls and eddies of the plasma and keep it burning like a miniature sun has been a formidable task for nuclear scientists and engineers. Our sun generates sufficient energy to sustain all human, animal and plant life on our planet and who knows where else in our solar system. The energy of sun and of other stars in the universe are generated by nuclear fusion and the goal of trying to reproduce this system on earth is indeed tempting. But taming the power that lights up the cosmos is a daunting challenge.

ADVANTAGES OF FUSION

Fuels commonly used in fusion reactors are deuterium and tritium, both isotopes of hydrogen, and both non-radioactive. Deuterium occurs naturally in sea water from which it is extracted, which is why all fusion reactors are located on coasts. Tritium does not occur naturally but can be made within the reactor itself from lithium, the lightest metallic element (but heavier than hydrogen or helium) which is used as a blanket to control the speed of the fusion reaction by slowing down the neutrons released from the fusion of deuterium and tritium to form helium. Lithium also is abundantly available on the earth's crust all over the world, thus promising an almost limitless availability of material for fusion reactors.

Fusion has several other advantages over fission. Quantities of raw material used are very low, with grammes of material being used compared to kilogrammes in fission reactions. 1 gramme of fusion fuel could produce as much energy as 10,000 kg of fossil fuel. The fusion process has in-built safety features: fusion reactions require leak-tight confinement and if any leakage takes place, this results in extinguishing the plasma, like a candle getting blown out if the door is opened, and stopping the energy generation. There is no chain reaction in fusion unlike in fission where the danger is of the chain reaction going out of control. In fusion, if excess plasma gets generated, temperatures will rise beyond the limit (close to which they are operating in reactors) after which the fusion reactions start winding down by themselves. Fusion processes are also limited by the quantum and rate of refueling without which the plasma gets rapidly extinguished: also, many conditions together must be satisfied and failure of any one leads to energy loss and plasma extinguishment. Further, reaction products from fusion are either absorbed by the surrounding lithium or are non radio-active like helium. There are no hazardous wastes produced, minimal exhaust releases into the environment and de-commissioning poses no long-term or other hazards, all making fusion power a highly attractive proposition.  

ITER PROJECT

For over five decades, efforts have been underway in various countries to harness fusion energy for power generation. Putting these diverse efforts together, USA, Europe (including mainly Britain, Germany, France, Italy, Switzerland and Spain), Japan and Russia got together over a decade ago to form the ITER Project under which various engineering design activities (EDA) have been carried out between 1992 and 2001. Canada, South Korea and China joined in later, China being the latest entrant, with the US re-entering under the George W Bush administration after an earlier withdrawal by the Clinton administration.

ITER has been described as the boldest nuclear initiative since the infamous Manhattan Project which developed the nuclear bomb during the second World War. Its goal is to design and develop the first-ever production-scale fusion system to produce energy at the level of a conventional power plant. However, given the limited state of current knowledge and experience with the technology, the ITER Project will not deliver a full-fledged running power plant but will produce 500 MW (mega-watts) of power for 500 seconds or longer during each fusion experiment.

In doing so, ITER’s mission is to demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes. It will demonstrate moderate levels of power multiplication i.e. generating more energy than is put in, demonstrate essential technologies in a system integrating the necessary physics and engineering, and test important elements essential for the harnessing of fusion as a practical energy source. ITER will thereby provide, in a single but multi-dimensional and integrated experiment,  the next major step towards a commercial-scale pilot plant which would be the next task. The experimental technology demonstrator under the ITER is expected to begin construction in 2006 and become operational in 2014. However, fusion research is expected to take another 20 years before it comes up with an operational and economically viable commercial-scale power plant.

TECHNOLOGIES IN ITER

The technologies involved have developed over several decades since the end of World War II. The basic problem confronting scientists was, although collision between nuclei released substantial energy, a large amount of energy was required to generate the plasma and therefore, could energy output be made greater than energy input. Soon ideas from nuclear physics, astrophysics and plasma physics came together to provide a realistic possibility. But there were huge engineering problems involved in designing and building a reactor, chief among which was how to contain and control the plasma in the absence of the massive gravity available in the sun and the mostly larger stars and the obvious difficulty of any containing material being able to withstanding the million-degree temperatures generated.

Among many approaches being pursued by American, British and Soviet experimental physicists and engineers, Soviet researches provided the crucial breakthroughs. Sakharov and Tamm first suggested that the plasma could be contained within a magnetic field. Soviet experimental successes with this approach were first revealed to an astonished world in 1956 by Kurchatov. By the time the "Atoms for Peace" conference was held in Geneva in 1958, the genie was out of the bottle, fusion was no longer a secret and information started getting shared in the global scientific community.

In the early '70s, the Soviets had built a reactor in the shape of a doughnut or vada i.e. a tube forming a circle with a hole in the middle. This design was called a "tokamak" after a Russian snack of that shape. Tokamak reactors soon came to be adopted worldwide and were further developed, the most advanced perhaps being the Joint European Torus (i.e. the toroidal doughnut shape) or JET reactor at Culham, UK, set up under the European Fusion Development Agreement, then becoming the flagship programme of the ITER Project and the world's largest and most powerful fusion reactor, which started operation in 1983. In 1981, JET demonstrated the generation of over 1 MW of power in a short burst. Other important experimental fusion reactors are in Japan, the second-largest after JET, France, Germany, Canada and Spain.

While these various national projects were gradually incorporated into ITER, to take the concept of fusion power to the next stage required an experiment so large that it could only be conceived as an international co-operative venture. And this is where the present phase of the ITER comes in along with the requirement of commencing work on a single-site experimental reactor.

SITE SELECTION

Even the most naive person could have foreseen that, although the ITER agreement calls for arriving at a consensus on the ITER site based on objective criteria and a transparent decision-making process, the decision would inevitably be one guided by geo-political considerations.

Four sites were initially short-listed: Clarington in Canada, Cadarache in France, Vandellos in Spain and Rokkasho-mura in Japan. Of these Clarington, where a nuclear power station is situated 60 kilometres east of Toronto on Lake Ontario, was dropped first, despite noisy threats by Canada to opt out of ITER if its site was not selected, since Clarington did not offer as many advantages as the other sites brought to the table. The Vandellos site in Spain lost out just before the Washington conference because Spain was not seen as having the depth of research expertise and experience that France and Japan had, leaving these two countries to clash in the finals. 

France has strengths in nuclear fusion research and in related science and engineering, and the reactor at Cadarache, located in southern France in the Provence region, also holds the record for the highest power generation through fusion. Cadarache was also endorsed as the EU's candidate at a European meeting prior to the Washington conference where it was supported by Russia, China and the UK. But the US, whose definition of the "evil empire" seems to include France these days, raised a resounding NO! Japan's Rokkasho-Mura site, located in the northern tip of the main Hokkaidu island, also has a strong and distinguished fusion research record but is located in a seismically sensitive area. Japan has of course offered to meet all the costs if its site is chosen whereas the Eu has pledged 2.4 billion Euros if Cadarache is selected. Its bid was supported in Washington by the US and South Korea. If money and geo-politics are to be the decisive factors, Japan is likely to breast the tape first while the US pulls France back!

In any case, the ITER Project is expected to be underway fairly soon. And despite the usual doomsayers, who see red anytime anything nuclear is mentioned. Nuclear power, especially from fusion, still holds great promise and, for all the scare-mongering, the last word on nuclear energy has not been spoken. Research on nuclear energy must continue and, in this field, cannot be done at a small laboratory scale. Nuclear energy, especially from fusion, is an option the world needs to keep open.