Neutron Reflection and Counting
Posted: Tue Sep 27, 2005 1:05 am
The only good thing about a long jet ride on a business trip is the time is affords one to catch up on reading. I flew from Boston to Dallas and Dallas to Guad, Mexico and back last week. During the trip down and back I managed to finish... just as the plane was landing back at Logan in Boston, "The Curve of Binding Energy" by John McPhee.
The book although dated was a good reading and interesting story of Ted Taylor a theoretical physicist who was one of the most inventive nuclear scientist of our time. He miniaturized the atomic bomb, and designed the largest yield fission bomb every exploded. He also contributed to the Fusion bomb and led a scientific effort to build a nuclear-powered spaceship. He also led the fight for safer controls due to the alarmingly available weapons grade uranium and plutonium. He was convinced at a time when others were not that an amateur could make a nuclear bomb.
There were a number of interesting things in the book but one that struck me was that Taylor talked about the importance of "neutron reflection" in the bomb design. He stated that steel is an excellent reflector of neutron especially curved surfaces for reflecting the neutrons back toward the implosion.
Obviously a bomb is far different then the fusion in a fusor but my question is when counting neutrons are you also taking into account those that are not radiated outward but reflected internally and if so how are these being accounted for. It would seem that a good number more "thank goodness" are contained by the SS enclosure.
Also is it beneficial to maintaining the fusion reaction, as it with a bomb to make use of contain and reflect the neutrons created? If so Taylor mentions the importance of a good neutron reflector. He recommends Glasstone's "Sourcebook on atomic Energy," under Nuclear Reactors: Reactor Moderators and Reflectors. He goes on the recommend the use of natural uranium, steel, copper, magnesium, lead, aluminum, beryllium, water, solder, or wax, as neutron reflectors. Such as two stainless steel mixing bowls lined with was and soldered together. A three-inch thickness of was will reflect as many neutrons as an inch and a half of steel. To get good reflection of neutrons you need two-inches of steel. However the best material for neutron reflection is beryllium which is the most poisonous nonradioactive inorganic material on earth. However it is one of the lightest elements and less dense then aluminum, but many more atoms per cubic centimeter making is a great reflector. Beryllium cost about a $100 a pound but is brittle and hard to work. If a SS sphere could be lined with beryllium it would reflect most all the neutrons back toward the plasma… then again the assumption which might be wrong on my part is that these neutrons are needed to maintain the fusion process?
One last point from the book at one point there was a need for more Tritium and the process of making it is very slow and comes mostly from reactors and cost about eight hundred thousand dollars per kilogram. So Taylor proposed putting a large blanket of lithium around a thermonuclear bomb and placing it under ten thousand feet of ice and setting it off. This would provide and underground lake of full of heavy isotopes. This idea didn’t fly, however he had support for ideas like this from folks like Freeman Dyson, John von Neumann and George Gamow.
The book although dated was a good reading and interesting story of Ted Taylor a theoretical physicist who was one of the most inventive nuclear scientist of our time. He miniaturized the atomic bomb, and designed the largest yield fission bomb every exploded. He also contributed to the Fusion bomb and led a scientific effort to build a nuclear-powered spaceship. He also led the fight for safer controls due to the alarmingly available weapons grade uranium and plutonium. He was convinced at a time when others were not that an amateur could make a nuclear bomb.
There were a number of interesting things in the book but one that struck me was that Taylor talked about the importance of "neutron reflection" in the bomb design. He stated that steel is an excellent reflector of neutron especially curved surfaces for reflecting the neutrons back toward the implosion.
Obviously a bomb is far different then the fusion in a fusor but my question is when counting neutrons are you also taking into account those that are not radiated outward but reflected internally and if so how are these being accounted for. It would seem that a good number more "thank goodness" are contained by the SS enclosure.
Also is it beneficial to maintaining the fusion reaction, as it with a bomb to make use of contain and reflect the neutrons created? If so Taylor mentions the importance of a good neutron reflector. He recommends Glasstone's "Sourcebook on atomic Energy," under Nuclear Reactors: Reactor Moderators and Reflectors. He goes on the recommend the use of natural uranium, steel, copper, magnesium, lead, aluminum, beryllium, water, solder, or wax, as neutron reflectors. Such as two stainless steel mixing bowls lined with was and soldered together. A three-inch thickness of was will reflect as many neutrons as an inch and a half of steel. To get good reflection of neutrons you need two-inches of steel. However the best material for neutron reflection is beryllium which is the most poisonous nonradioactive inorganic material on earth. However it is one of the lightest elements and less dense then aluminum, but many more atoms per cubic centimeter making is a great reflector. Beryllium cost about a $100 a pound but is brittle and hard to work. If a SS sphere could be lined with beryllium it would reflect most all the neutrons back toward the plasma… then again the assumption which might be wrong on my part is that these neutrons are needed to maintain the fusion process?
One last point from the book at one point there was a need for more Tritium and the process of making it is very slow and comes mostly from reactors and cost about eight hundred thousand dollars per kilogram. So Taylor proposed putting a large blanket of lithium around a thermonuclear bomb and placing it under ten thousand feet of ice and setting it off. This would provide and underground lake of full of heavy isotopes. This idea didn’t fly, however he had support for ideas like this from folks like Freeman Dyson, John von Neumann and George Gamow.