Nuclear fusion, ITER and Aditya

  Mar 13, 2020

Nuclear fusion, ITER and Aditya

What is nuclear fusion?

Without fusion, there would be no life on Earth. What we see as light and feel as warmth is the result of a fusion reaction in the core of our Sun: hydrogen nuclei collide, fuse into heavier helium atoms and release tremendous amounts of energy in the process. In the extreme density and temperature of the stars, including our Sun, fusion occurs. Fusion is the process that powers the sun and the stars: when light atomic nuclei fuse together to form heavier ones, a large amount of energy is released. 

Where does it take place naturally?

In the Sun's core, where temperatures reach 15,000,000 °C, hydrogen atoms collide at very high speeds and fuse. The fusion of light hydrogen atoms produces a heavier element, helium.
The mass of the resulting helium atom is not the exact sum of the initial atoms, however—some mass has been lost and great amounts of energy have been gained. This is what Einstein's famous formula E=mc² describes.

Every second, our Sun turns 600 million tonnes of hydrogen into helium, releasing an enormous amount of energy.

How can it be done in the laboratory?

Twentieth-century fusion science identified the most efficient fusion reaction in the laboratory setting to be the reaction between two hydrogen (H) isotopes deuterium (D) and tritium (T). The DT fusion reaction produces the highest energy gain at the "lowest" temperatures. It requires nonetheless temperatures of 150,000,000 degrees Celsius—ten times higher than the hydrogen reaction occurring in the Sun.

Although different isotopes of light elements can be paired to achieve fusion, the deuterium-tritium (DT) reaction has been identified as the most efficient for fusion devices. ITER and future devices will use the hydrogen isotopes deuterium and tritium to fuel the fusion reaction. 

Deuterium can be distilled from all forms of water. It is a widely available, harmless, and virtually inexhaustible resource. In every cubic metre of seawater, for example, there are 33 grams of deuterium. Deuterium is routinely produced for scientific and industrial applications.
What is the `breeding’ of tritium?

Tritium is a fast-decaying radioelement of hydrogen which occurs only in trace quantities in nature. It can be produced during the fusion reaction through contact with lithium, however: tritium is produced, or "bred," when neutrons escaping the plasma interact with lithium contained in the blanket wall of the tokamak.

Lithium from proven, easily extractable land-based resources would provide a stock sufficient to operate fusion power plants for more than 1,000 years. What's more, lithium can be extracted from ocean water, where reserves are practically unlimited (enough to fulfill the world's energy needs for ~ 6 million years).

Global inventory for tritium is presently around twenty kilos, which ITER will draw upon during its operational phase. The concept of "breeding" tritium within the fusion reaction is an important one for the future needs of a large-scale fusion power plant.

Fusion research is aimed at developing a safe, abundant and environmentally-responsible energy source. 

What are the challenges?

The challenge before the fusion community is to hold a sufficiently dense and hot plasma (a collection of electrons and ions) for a sufficiently long time to obtain net power output.

Also, to find a way of maintaining the temperature that is more than 100 million degrees Celsius.  

What is ITER?

ITER, International Thermonuclear Experimental Reactor is an international nuclear fusion research and engineering megaproject that is being built in southern France.

Designed to demonstrate the scientific and technological feasibility of fusion power for peaceful use, ITER will be the world's largest experimental fusion facility.

ITER is also a first-of-a-kind global collaboration. Europe will contribute almost half of the costs of its construction, while the other six members of this joint international venture (China, India, Japan, Korea, Russia and the US), will contribute equally to the rest. 

How is Institute for Plasma Research (IPR), Gandhinagar involved?

The nodal agency for the project in India is Institute for Plasma Research (IPR), Gandhinagar. ITER reached 58 per cent of completion and is likely to start generating power by 2035.The construction and assembly of all units to be completed by 2025.

As an ITER member, India is responsible for about 9 per cent of in-kind contribution to the ITER project. This contribution is in the engineering and development of key components, including cryostat, cooling water systems, radio frequency heating sources among others. An India-built cryostat base and lower cylinder are ready for installation at ITER by mid-2019. 

What is Aditya?

ADITYA is a medium size tokamak (fusion reactor) installed at the Institute for Plasma Research in India. 

What do member countries get?

The member countries of ITER will get no-cost full access to the Intellectual Property of the project to use it for themselves. This project is an attempt to be able to supply energy to the world at a competitive rate.