Dr. abdus salam centre for physics approved

[VCheng]

Plutonium is a different material and has nothing to do with Uranium .

Except that Pu-239 is created by neutron bombardment of U-238, usually in a reactor, and recovered by re-processing.

 

[django]

Lol, any person with the knowledge of nuclear science and technology will tell you that Uranium enrichment is actually the only step involved in achieving the manufacturing of a nuclear device. There were hundreds and thousands of other scientist involved in the project but had we not achieved the Uranium enrichment technology, never would we have been able to acquire a self-dependent nuclear program. From nuclear devices to nuclear power plants, even Karachi nuclear plant, every single project owes its debt of existence to Dr Abdul Qadeer Khan.

Coming to the point of work of Dr Abdul Salam, the noble prize was actually given to three scientists in which he was one. So his work was also shared and who knows to what extant he actually contributed and how much blessing were bestowed upon him by Zionist masters as the two (or atleast one) other scientists were jews.

Actually the scientists worked independently of each other.

 

[Falgrine]

Fission devices are either based on U-235 or Pu239. U235 constitute about 0.3-0.7% of the naturally occurring Uranium. The most abundant isotope is U238, which is non-fissionable. Now there are two major approaches to create the fissile material,either you enrich the U235 from the meager 0.3% to 90% or higher, or bombard the U238 with neutrons and transform it to Pu239.

There are two main methods which can be used for enriching Uranium: Gas diffusion and centrifugal enrichment. The first method was used in the Manhattan project (1945) by the US to build its first Nuclear device(Trinity). It is a very energy inefficient method as several diffusion iterations of the gasified Uranium are required to enrich it to the desired levels. The second method started to be studied right after the WWII. It is based on the simple intuition that U235 being lighter in weight will experience less centrifugal force then U238 when rotated at very high speed in a cylinder, and hence will be pushed towards the rim from where it can be collected. The real engineering task is to design such cylinders that have sufficient strength to withstand the enormous G forces which they are likely to be subjected to. Overall centrifugal enrichment is challenging task and it involves a strong cross disciplinary research team with easy access to the materials required. However, this method is not too expensive in terms of the electricity consumption. Laser enrichment is another method which I do not know much of.

The second approach to get the fissile material is to convert the more abundantly found U238 into Pu239. This is done by bombarding the U238 with neutrons. The Uranium decays into Neptunium which has very short half life. Neptunium then decays further into Pu239, Plutonium (see going from Neptune to Pluto ). Anyways, Pu239 can be created in a Fast breeder reactor (FBR) which also produces some electricity but that is not its chief purpose. As compared to the Uranium enrichment, this method is quick and cheap. Hence most nations trying to get the fissile material follow this path. Also U235 nucleus emits 2.5 neutrons while undergoing a fission while Pu239 emit 3 neutrons (or may be its 2 and 2.5). My own conjecture is that this translates to a higher yield for a Plutonium based fission device than the one based on the Uranium. Alternatively, this could mean that the actual fission device using Pu239 can be smaller. Hence can be quite useful for weapons of smaller size/yield (miniaturization like done for TNW ). Remember, we were supposed to get a reprocessing plant for FBR from France when US forced the later to cancel the deal. I think that it was back in 70's before we finally started to enrich Uranium. (As a remark to an earlier comment, I think heavy water is also used in FBRs to slow down the fast neutrons. Correct me if I am wrong).

Now once we have enough fissile material, it does not mean that we have a working bomb. A critical mass (not less) of the fissile material has to undergo the neutron bombardment,just at the right moment, to get the chain reaction started. US did this in two ways. The Little boy based on U235 was a gun type device, where two masses of Uranium were kept apart. The smaller amongst the two was fired towards the larger one with the simultaneous neutron source emission. This lead to the start of the chain reaction. The second method is more complex as it requires very precise firing of the neutron source. Device based on this method is called a implosion type device. Fatman (second dropped bomb) was based upon this technique. Conventional high explosives are placed around the fissile material in form of a broken sphere. Just before the detonation, the explosive is detonated which causes an implosion, leading to the compression of the fissile material present inside the sphere. Once the fissile material is compressed enough, a neutron source is triggered. The resulting neutron shower causes the start of the chain reaction. The precise timing of the neutron triggering is the key issue.

Hope I was clear enough in the presentation.

@Syed.Ali.Haider, @WAJsal