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Science communication is important in today's technologically advanced society. A good part of the adult community is not science saavy and lacks the background to make sense of rapidly changing technology. My blog attempts to help by publishing articles of general interest in an easy to read and understand format without using mathematics. I also give free lectures in community events - you can arrange these by writing to me.

Saturday, 31 January 2015

Part 5: Contamination of the Environment as a Result of Nuclear Weapons Development

Contamination of the Environment as a Result of Nuclear Weapons Development

We are talking of radioactive contamination here.  This happens in two ways: Contamination at the reactors and facilities that produce Pu-239 and highly enriched U-235.  Nuclear weapons tests have contributed to radioactive fallout and has been politically more damaging causing international outrage.
Both the US and Soviet programmes were conducted with the aim to produce the bomb as soon as possible.  Safety of the personnel, environment and people nearby did not have a high priority and then there are always 'enthusiastic' officers who, with lax controls, did not hesitate to undertake dubious scientific experiments on lab workers, soldiers, prisoners etc.

First we have some slides to show the important facilities in USA and USSR and then describe the sort of contamination that was caused by the programmes. The US Pu-239 production was at the Hanford (Richland), WA site; HEU facilities were at Oar Ridge, TN.  The bomb was designed at Los Alamos, NM.  The Soviet bomb was designed at Sarov (Arzamos).

It might be fair to say that the radioactive contamination has been much more serious in the Soviet Union than it is in the USA.

Friday, 30 January 2015

Part 4: Atom Spies - Klaus Fuchs and Others

Atom Spies - Klaus Fuchs and Others

The atomic bomb was developed in the USA during the tense atmosphere of WWII.  The discovery of fission of uranium in 1938 had made the nations aware of the feasibility of an explosive device of immense power. The need to find what other countries are doing was paramount.
USA through their ALSOS spy programme could ascertain that the German atom bomb programme was not making much progress.  In fact a decision was made by Hitler that the bomb will take too long for it to be useful for the ongoing war.
The main spy ring was operated by the Soviet Union who were a friendly power during the war. The KGB operated a sophisticated espionage system largely through their embassies.  In fact, USA turned a blind eye to most of the spying activity during the war.
The most notable of the spies was Klaus Fuchs and in the following some details are given about him.

Part 3: Countries with proven Nuclear Capabilities

Countries with proven Nuclear Capabilities
Nuclear bombs are complex devices.  Having designed one, it is not guaranteed that it would work as expected.  Testing the device is necessary and sophisticated monitoring procedures are followed to ascertain the results of the test. International community is also able to detect and deduce much useful information about any tests that are performed.
The following couple of pictures show different types of tests and where the tests have been performed and the countries responsible.

Notice that the yield of the tests has been 510 MT which is almost 100 times all the bombs used in WWII
The nuclear arsenal is huge.  At the peak of the arms race - in 1970s - USSR and USA had about 80,000 warheads.  Assuming a warhead of 1 MT explosive capacity that is 80,000 MT of TNT equivalent or 16,000 times the bombs used in WWII.  This is more than sufficient to destroy all population centres in the world.

Wednesday, 28 January 2015

Part 2: Development and Testing of the Hydrogen Bomb

Development and Testing of the Hydrogen Bomb

Uranium and plutonium fission bombs have an upper limit of about 500 kT of TNT equivalent for the maximum explosive energy that they can deliver. On the other hand, a fusion bomb can deliver much more explosive energy.  Most nuclear bomb arsenals now have fusion or H-bombs.

Edward Teller was the scientist at Los Alamos, NM who was very  enthusiastic about the development of H-Bomb even during the phase when everybody was working on getting the fission bomb going. After WWII ended in 1945, USA was the only country with nuclear capability and the work on new and bigger bombs did not receive much support.  However, the Soviet Union tested their fission bomb in 1949 and this event triggered the race to have bigger and better bombs. USA and USSR started work on the H-Bomb.
Initial designs used liquid deuterium which made the bomb too heavy and difficult to be delivered to the target.  H-Bombs with Lithium Deuteride were much better.  The largest H-Bomb ever tested was by USSR in October 1961, the Tsar Bomba, and produced more than 50 MT of energy.

 In the staged design, the fission primary creates energy in the form of powerful X-rays which are focused on to the secondary fusion stage.  Ablation of the tamper surrounding the secondary stage contributes greatly to the pressure that squeezes the secondary. A spark plug in the secondary stage provides yet more compression of the LiD core.
The main reactions in the fusion bomb relate to the production of tritium by neutron bombardment of lithium-6.  Tritium and deuterium fuse to produce 17.59 MeV energy.  Lithium-7 (93% of natural lithium) also produces tritium and increases the yield of an H-Bomb by significant amount.

Part 1:The Fission Bomb based on U-235 and Pu-239.

The Fission Bomb based on U-235 and Pu-239.