SCIENCE REPORTER, November 2010 13

Pooran Koli, K.M. Gangotri, Urvashi Sharma, MukeshBhimwal, Amit Mahawar & Mahesh Bhimwal

Feature Article

IT was only in 1939 that Hans Bethe and others showedthat production of stellar energy is thermonuclear(nuclear fusion) in nature. They showed that at atemperature of around 108 K, which is present at the

center of the sun and other stars, four hydrogen nucleicombine to form one nuclei of helium with mass loss (Δm)which gets converted into stellar energy quantitativelyaccording to Einstein’s mass-energy relation, E = Dmc2,where E is energy produced and c is light velocity in vacuum.

There are two types of fusion—uncontrolled andcontrolled. In uncontrolled nuclear fusion, vastamount of energy in uncontrolled manner isreleased causing destruction only—the hydrogenbomb is an example. Thus uncontrolled nuclearfusion is not of use for constructive purpose. Incontrolled nuclear fusion, the vast energy isreleased steadily so it can be used for peacefulpurposes, say, the nuclear fusion reactors.

Hydrogen constitutes about 70% mass of thesun and other stars. The three isotopes of hydrogen(protium- 1H

1, deuterium- 1H2, and tritium- 1H

3)and light isotope of helium (2He3) constitute thefuel of the nuclear fusion process.

Protium is the fuel in nuclear fusion occurring instars. The natural abundance of protium is about99.984%. This protium may be used as fuel forimitation of stellar energy on earth.

Deuterium is formed as an intermediate speciesin nuclear fusion processes in stars. The naturalabundance of deuterium is about 0.016%. The ratioof deuterium to protium is 1:6900 in hydrogengas.

The natural abundance of deuterium is in the ratio 1(D):7000 (H). The ratio gives an impression that abundanceof deuterium is very low but this abundance of deuteriumis enough for electricity generation as energy intensity ofdeuterium fuel is very high.

Tritium is an unstable radioactive isotope (half life 12.4years). It is found in nature only in minor traces –1 (T) : 1018

(H). In nature, Tritium is believed to be formed by neutronbombardment of atomic nitrogen gas.

Fusion technology holds the promise of being able to meetthe future energy needs of the planet. But a lot still needsto be done before the technology is perfected.

A Limitless Source of EnergyFUSION

Nuclear Fusion

DeuteriumHelium

Energy

Tritium Neutron

SCIENCE REPORTER, November 201014

Feature Article

Light helium is rare on earth (natural abundance 0.000137%).The abundance of helium-3 (a stable nuclei) is thought to begreater on the moon. A little amount of helium-3 can supplyvast energy. The fusion of He-3 with He-3 gives the third-generation fusion fuel, and fusion of deuterium with He-3constitutes second-generation fusion fuel. The fusion ofdeuterium with deuterium or deuterium with tritium isfirst generation fuel.

Among all fuels, deuterium is the ideal andprincipal raw material for fusion reactors because:� Deuterium is non-radioactive, and inert & denserthan hydrogen. So it is relatively easy and safe toproduce, handle and store deuterium gas. Further, theby-products like oxygen formed during production ofdeuterium can be used in the medical field, sea diving,welding, etc. Tritium is radioactive so its productionand storage involves radiation hazards.� Deuterium is a renewable fuel as it is obtainablefrom water. This way, deuterium is as close as thenearest body of water. The ocean and other waterbodies contain more than 25 million tons of deuterium.Thus, water bodies provide inexhaustible amount ofdeuterium as source of energy.� Burning of one deuterium nuclei through fusionproduces about 7.2 MeV energy (when deuteriumalone is used as fuel). So 18 g of water producessufficient amount of heavy water and in turn sufficientdeuterium to produce about 1022 MeV energy. If fusionreactors operate at 50% efficiency then 18 g ordinarywater has capacity to produce about 222 KWH powersufficient to operate one cooler, one TV, onerefrigerator, tube lights and electric bulbs for onemonth for a family.

Products of Nuclear FusionThe products of nuclear fusion are vast amount ofenergy and some particles with by-product helium—an inert, non-polluting, non-radioactive and non-

greenhouse gas. Helium finds many uses:(a) As cryogenic rocket fuel;(b) In superconductivity as mercury on cooling by

liquid helium becomes superconductive at 4 K;(c) For filling tyres of airships and balloons for

meteorological observations as it is non-inflammable with lifting power being equal to 92%of that of hydrogen gas;

(d) Mixture of helium with oxygen is used for sea-divers for respiration, and in treatment of certainrespiratory diseases like asthma;

(e) For providing inert atmosphere in the welding ofmetals or alloys that are easily oxidized.

Hurdles in Nuclear FusionThe energy intensity of renewable sources like wind, ocean,etc. is very low. So, fusion is a renewable, clean, commercialand limitless source of energy capable of meeting industrialand household power needs.

But then what is stopping us from using nuclear fusionas an energy source? Fusion involves some inherentproblems like creation of plasma state, and fusion of positive

The expert committee on integrated energy policyof Planning Commission in its recent report hasestimated that India’s electricity generationcapacity would need to go up six to seven foldfrom the current installed capacity of around 1.15lakh MW to between 7.8-9.6 lakh MW by 2031-32

The energy intensity of renewable sourceslike wind, ocean, etc. is very low. So, fusion isa renewable, clean, commercial and limitlesssource of energy capable of meetingindustrial and household power needs.

SCIENCE REPORTER, November 2010 15

Feature Article

charged nuclei against extremely high repulsion betweenthem. To get the plasma state and to overcome nuclearrepulsion during nuclear fusion, nuclei must be broughtvery close together not only by high pressure but also withhigh kinetic energies as required activation energy for fusionis very high. For this, a temperature about 108 K is required.

Nuclear fusion is possible in stars as temperature about108 K is available in stars. On earth, it may be obtained byexploding a fission bomb as in hydrogen bomb. But, thisway of fusion is an uncontrolled process that releasesuncontrolled energy leading to destruction.

For peaceful use of fusion energy, the nuclear fusionprocess has to be controlled. Till now, there is no availablemethod of controlling the release of fusion energy. Acontrolled release of fusion energy is possible in a fusionreactor but its construction is problematic.

The main problem is the manufacturing of a containercapable of containing hot plasma state under the requiredconditions of high temperature and high pressure. So far,there is no manufacturing material that can withstand 108 Ktemperature. Even tungsten (W) having the highest meltingpoint among metals, melts at a mere 3683 K and vaporizesat 5933 K. Further, the contact of plasma with the wall ofcontainer (if it can withstand 108 K temperature) will causeits cooling which in turn will inhibit the fusion process.

Developments in Fusion TechnologyConsiderable efforts have been made to accomplishcontrolled fusion. Scientists have been working forproduction of temperature of the order of 108 K and hotplasma without destroying the container itself and withoutletting the plasma to cool on touching the wall of thecontainer.

The production of high temperature is based onelectromagnetic and laser devices. In electromagneticdevices, the container is surrounded by strong and circularmagnetic fields that repel the plasma and force and compressit away from the sides into the center of the container.Further, the extremely dense flow of current within theplasma heats it up to enormously high temperature.

The high pressure and high temperature developed inthe plasma state of fuel forces plasma particles to fusetogether to produce helium nuclei and enormous energy in

the form of heat. This is known as the ‘Pinch Effect’. On thebasis of this effect, in experimental reactors, fusion has beenobserved for a fraction of a second. Three types ofexperimental reactors, namely – magnetic bottle, tokamakand stellarator have been tried on the same principle i.e.magnetic containment and compression of plasma.

A major step taken towards imitation of stellar energywas the launch of International Thermonuclear ExperimentalReactor (ITER) project at Cadarache in France. ITER will bedesigned for fusion of about 0.5 g of deuterium–tritiummixture in its approximate 840 sq m fusion reactor chamberto produce approximate 500 MW power sustained for up to400 seconds. ITER is based around a hydrogen plasma torusoperating at over 100 millions Kelvin temperature.

The project is anticipated to last for thirty years – 10years for construction, and 20 years for operation. The firstplasma operation is expected in 2016, and a commercialfusion reactor is expected in 2050.

India and Fusion TechnologySeveral Indian research institutions are engaged in differentcomponents of fusion research. Some such institutions arethe Bhabha Atomic Research Center (BARC), Indira GandhiCenter for Atomic Research (IGCAR), Center for AdvancedTechnology (CAT), Institute of Plasma Research (IPR) andPhysical Research Laboratory (PRL).

In 1989, India’s indigenous tokamak named ‘Aditya’was installed at IPR, Gandhinagar. In Aditya, plasma atabout 5 million K can be generated, which however is notsufficient to trigger fusion.

India today has expertise in design, construction andoperation of heavy water plants. India has not only acquiredself-sufficiency in heavy water (a source for fusion fueldeuterium) production but has also acquired surplus forexport. The Heavy Water Board holds the responsibility ofdesign, construction and operation of heavy water plants inIndia.

The expert committee on integrated energy policy ofPlanning Commission in its recent report has estimatedthat India’s electricity generation capacity would need togo up six to seven fold from the current installed capacity ofaround 1.15 lakh MW to between 7.8-9.6 lakh MW by 2031-32 (end of XV plan period). To meet this requirement, Indiais trying to tap non-conventional energy resources includingfusion reactor technology.

Dr Pooran Koli is Assistant Professor and Dr. K.M. Gangotri is Professor ofchemistry, while Urvashi Sharma, Mukesh Bhimwal, Amit Mahawar &Mahesh Bhimwal are Research Scholars in the Photochemistry Lab, Dept. ofChemistry, Jai Narain Vyas University, Jodhpur, Rajasthan–342033. Address:Dr Pooran Koli, 7, University Teachers’ Flat, P.W.D. Road, Jodhpur, Rajasthan–

342033; Email: poorankoli@yahoo.com

There are two types of fusion—uncontrolled and controlled.In uncontrolled nuclear fusion, vast energy in uncontrolled manner isreleased causing destruction only—the hydrogen bomb is an example.Thus uncontrolled nuclear fusion is not of use for constructive purpose.In controllednuclearfusion, vast amountof energy isreleased steadily.