Thursday, February 6, 2014

1. Physics concepts like in nuclear energy fission method is used to extract nuclear energy but very difficult to mange the nuclear waste and to control the reaction. So fusion energy using Helium 3 is very much safe. Moreover helium 3 is efficient resource of energy as 1 tonne of helium 3 is enough for power needs of India for 1 year.

2. Space exploration – Helium 3 is released by sun but out atmosphere does not let helium 3 reach earth, so very negligible resources. But moon does not have any such atmosphere and has abundant resources of energy. So the novel concept of space exploration comes into picture.

3. International Politics – Russia started experiments in 2005 and by 2015 expecting substantial results. NASA has also planned to make a re-entry in lunar missions for Helium 3 exploration. China is also in the race and expecting to do landing by 2020. India should not miss the opportunity looking at its limited energy resources and environmental problems.


Normal helium has 2 protons and 2 neutrons in its nucleus, giving it an atomic weight of 4.
Now, if you take out one of neutrons, you get helium-3. This happens once in a while in very energetic nuclear reactors, especially the sun. The sun produces helium by fusing hydrogen atoms together, but about one in every ten thousand helium atoms comes out missing a neutron.

He3 casts lustful eyes upon that neutron in the deuterium, and will grab it if it gets a chance. 

The Mixture:

He3 is used in a reaction with deuterium to produce energy:

This is a nuclear fusion reaction. The deuterium and helium-3 atoms come together to give off a proton and helium-4. The products weigh less than the initial components; the missing mass is converted to energy. 1 kg of helium-3 burned with 0.67 kg of deuterium gives us about 19 megawatt-years of energy output.

The fusion reaction time for the D-He3 reaction becomes significant at a temperature of about 10 KeV, and peaks about about 200 KeV. A 100 KeV (or so) reactor looks about optimum.

A reactor built to use the D-He3 reaction would be inherently safe. The worst-case failure scenario would not result in any civilian fatalities or significant exposures to radiation.

Note: MeV and KeV are measures of energy, standing for mega-electron volts and kilo-electron volts, respectively. In nuclear physics, these terms are used to refer to the amount of energy in a nuclear reactor. One electron volt is the energy acquired by one electron falling through a potential of one volt, equal to approximately 1.609 E-19 

Lunar Supply Potential

In their 1988 paper, Kulcinski, et al., estimate a total of 1,100,000 metric tonnes of He3 have been deposited by the solar wind in the lunar regolith. Since the regolith has been stirred up by collisions with meteorites, we'll probably find He3 down to depths of several meters.

The highest concentrations are in the lunar maria; about half the He3 is deposited in the 20% of the lunar surface covered by the maria. To extract He3 from the lunar soil, we need to heat the dust to about 600 degrees C. 

The Energy

That 1 million metric tonnes of He3, reacted with deuterium, would generate about 20,000 terrawatt-years of thermal energy. The units alone are awesome: a terrawatt-year is one trillion (10 to 12th power) watt-years. To put this into perspective, one 100-watt light bulb will use 100 watt-years of energy in one year.

That's about 10 times the energy we could get from mining all the fossil fuels on Earth, without the smog and acid rain. 

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