Summary

Science and Technology Class 06

A Brief Discussion on the Last Class (5:13 PM)

Three staged Nuclear Programme of India (5:37 PM)

The three-stage program was envisaged by Dr Homi Jehangir Bhabha, who is considered the father of India's nuclear program.
He realized the limitations being faced by India.
India has some uranium and a huge amount of thorium, found in the monazite sands of Kerala.
To make India Self-sufficient, in fissile material, three stage program was envisaged.
In the First stage Pressurized Heavy water reactor with heavy water as moderator and coolant will be used.
Enriched Uranium in the reactor will produce fission-based energy.
However, uranium-238 will not go to waste.
It can absorb a neutron and get converted into Uranium 239.
In the second stage, a fast breeder reactor will be used.
It will use liquid sodium as a coolant and no moderator.
Plutonium-239 recovered from the first stage will be used as fissile material along with Thorium-232.
Thorium can convert into Uranium-233, by absorbing a neutron.
It doesn't use a moderator, because even though fast neutrons are not good at causing fission, they readily convert thorium to uranium.
it is called a fast breeder because the production of Uranium-233 occurs faster than the fission of Plutonium-239.
In the third stage, Uranium-233 recovered from the second stage, would be the main fissile material, along with thorium.
Thorium can convert into Uranium which will be used in the third stage itself.
The third stage can go on for 400-500 years, producing 100 Gigawatts of electricity.

Challenges in the Three-Stage Nuclear Programme (5:56 PM)

The first fast breeder reactor was supposed to become operational in Kalpakkam, Tamil Nadu, but it still is not operational.
There have been many challenges to the three-stage program, such as
(a) Spent Fuel reprocessing, is technologically challenging and expensive.
(b) India is still not part of the Nuclear Supplier Group.
In the past, this restricted supply of uranium to India from other countries.
(c) There has been a powerful pressure group, against the production of Nuclear power.
Because of the opposition to nuclear projects many projects were delayed.
(d) Some accidents from the past such as Chornobyl Disaster, 1986 have further intensified opposition to Nuclear power.
(e) Historic Nuclear deal with the US, in 2008 and a waiver from NSG seemed like nuclear power production will take off, however in 2011, because of the Fukushima disaster triggered by Tsunami, in Japan, there was global opposition to Nuclear power.
(f) Cost of renewable energy especially solar energy, started coming down in the last decade, and the government focused more on that.

Nuclear Fusion (7:17 PM)

Nuclear Fusion involves the fusion of lighter nuclei, to form a heavy nucleus at a very high temperature.
This is a natural process inside the core of stars, where at high temperatures, hydrogen nuclei fuse to form helium nuclei.
In the process, energy is released, which can be calculated using einstein's mass-energy equivalence, E=mc^2.
4 Hydrogen nuclei fuse to form two helium atoms, 2 positrons, and huge energy.
Fusion happens at very high temperatures because when nuclei are closer, there is a powerful electromagnetic repulsion, which has to be overcome.
Nuclei require very high energy, hence very high temperature, so that they can come closer enough for strong nuclear force to start acting and nuclei can fuse.
On Earth, many experiments are going on to attain nuclear fusion.
Recently a fusion experiment at Lawrence Livermore Lab, in California, US was able to achieve a net energy gain using fusion for the first time.
To do this, we used about 200 laser beams, in a very small volume containing deuterium and tritium, so that they can fuse.
Such a setup is called Inertial fusion.
Another approach is to have magnetic fusion, using a device called a Tokamak.
It is a toroid shape device that uses a powerful magnetic field, to contain deuterium and tritium plasma, at very high temperatures, so that they can fuse.
For example, the International Thermonuclear Experimental Reactor (ITER). It is a collaboration between various countries and is situated in France. It aims to produce 500 MW of fusion power.
Other examples are China's Artificial Sun (Experimental Advanced Superconducting Tokamak (EAST)), Joint European Torus(JET), Aditya Tokamak, Steady State Superconducting -1 (SST-1), Steady State Superconducting -2 (SST-2).

Benefits of nuclear Fusion (7:36 PM)

Both Fusion and fission are clean sources of energy, but fusion has additional advantages.
(a) It produces more energy than fission for equal mass.
(b) There is no risk of a reactor meltdown because the quantity of fuel in the reactor is very small which doesn't allow the chain reaction to happen.
Also, fusion requires a lot of prerequisites, if any of the parameters are not fulfilled, fusion will automatically stop.
(c) Fusion doesn't produce long-lived radioactive waste.
(d) Fusion doesn't require enriched material, thus, Tokamak cannot be used for any type of nuclear weapon.
(e) Raw material for fusion is deuterium, which can be found in any water source, and tritium which can be made in the lab.

Topics for Next Class: Radioactivity