- #1
Totam
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I am new to nuclear.
you could answer me one question : why do people say "fission", I thank you
you could answer me one question : why do people say "fission", I thank you
From Merriam-Webster's dictionary - Etymology: Latin fission-, fissio, from findere to splitTotam said:I am new to nuclear.
you could answer me one question : why do people say "fission", I thank you
Astronuc,Astronuc said:Let's not forget Lise Meitner's contribution to the discovery of fission.
Otto Hahn won the Nobel Prize in Chemistry in 1944 for "his discovery of fission of heavy nuclei". I think Meitner and Strassman should have shared the prize. :grumpy:
Sir James Chadwick had discovered the neutron in 1932. He won the 1935 Nobel Prize in Physics for the discovery.
Morbius said:Astronuc,
Yes - Meitner was really the first to understand / explain what was happening.
Hann and Strassman were the first to fission U-235; but that's not what they were trying to do. They were trying to transmute Uranium to the next higher element, subsequently called Neptunium.
Instead, they got fission products - but didn't understand what was happening.
Meitner understood what was happening - but the hope was that Hahn, et al would not realize what was happening - because it points the way toward developing nuclear weapons. So Meitner wasn't going to announce her interpretation of the Hahn experiment - it would just put Hitler's Germany on the right path to having nuclear weapons.
Dr. Gregory Greenman
Physicist
Astronuc,Astronuc said:So technically, Meitner discovered fission!
Morbius said:Astronuc,
Hahn and Strassman later, independently; came to the same conclusion that
Meitner did. The indications that they had done so led Leo Szilard and members
of the Uranium Committee to press FDR to start the Manhattan Project. That's
when Szilard wrote the famouns "Einstein letter" that was sent to FDR over
Einstein's signature.
Edward Teller was always proud of the fact that he drove Szilard to his meeting
with Einstein, since Szilard didn't drive.
Dr. Gregory Greenman
Physicist
Grogs,Grogs said:They had a great show on this recently. It was one of the 'Ten Days That Changed the World' on the History Channel. It started with Teller and Szilard driving to Einstein's house to ask if he'd sign the first letter, then progressed through the first and second letters, the CP-1 reactor, and all the way to the dropping of the first bomb on Hiroshima.
Hafnium is used in control rods because it a neutron absorber. One can also use Cadmium and Boron as control absorber - and they don't have the high temperature characteristics that Hafnium has - characteristics that are not needed in control rods.
Astronuc,Astronuc said:Boron is used in control rods in LWRs normally in the form of B4C, and it can be enriched from 20% B-10 to more like 55%. But the problem with B-10 is the (n, [itex]\alpha[/itex]) reaction which produces He.
Also, PWRs use Ag-In-Cd, but Ag can be expensive and In and Cd are toxic. In addition, Ag-In-Cd swells and creeps.
Hf (in the recrystallized form) is attractive because it does not swell, it is relatively inexpensive as a by-product of the production of nuclear grade Zr, it has good high temperature properties, and it does not produce gas. One downside is that Hf absorbs hydrogen and it will swell if that happens. Hf was withdrawn from the commercial nuclear market because of hydrogen absorption and swelling problems in PWR control rods, however it is used in some modern BWR control blades.
Astronuc,Astronuc said:Anyway on PWR vendor did use Hf in the control rods. Unfortunately, SS is rather porous to H, and the H from the coolant found its way to dry Hf, which sucked up the H and began to swell as a result of HfH2 formation. The control rods swelled and cracked - a big NO-NO! The Hf rod were withdrawn from service.
Astronuc,Astronuc said:One way to mitigate hydrogen absorbtion in Hf and for that matter Zr and Ti is to allow the surface to oxidize. I believe the naval control rods have a different geometry than commercial, since the fuel has a different geomentry. All that those details remain classified,
Nuclear fission is a process in which the nucleus of an atom splits into two or more smaller nuclei, releasing a large amount of energy.
Nuclear fission typically involves heavy elements such as uranium or plutonium. These elements have unstable nuclei that can easily split apart.
Nuclear fission is primarily used in nuclear power plants to generate electricity. It is also used in nuclear weapons to create large explosions.
The main risks associated with nuclear fission are the release of radioactive materials and the potential for accidents or meltdowns. These can have harmful effects on the environment and human health.
Nuclear fusion is a process in which two smaller nuclei combine to form a larger nucleus, whereas nuclear fission involves the splitting of a larger nucleus into smaller ones. Fusion requires extremely high temperatures and pressures, while fission can occur at more manageable conditions.