Radioactive Boyscout

[Marlin]

David Hahn tried to build a breeder reactor in his parents backyard shed. This is not news to many of us on Nukeworker but now for the "rest of the story". When he failed to perform in an academic environment his parents pressured him to enlist in the Military and even though he was interested in nuclear power he served on the Enterprise as a spud pealing seaman, his commanding officers took great pains to keep him away from the nuclear works on the U.S.S. Enterprise. After his tour in the Navy David enlisted in the Marines. The EPA believes he exceded his life time exposure to thorium but David has refused offers to be monitored at Fermilab.


http://www.wesjones.com/silverstein1.htm

[Rifleman]

I have one question if anyone cares to answer it...

"Dr. Hahn" built what he thought was, and has been reported to be, a "neutron gun"

As it decays, americium-241 emits alpha rays composed of protons and neutrons. David put the lump of americium inside a hollow block of lead with a tiny hole pricked in one side so that alpha rays would stream out. In front of the lead block he placed a sheet of aluminum. Aluminum atoms absorb alpha rays and in the process kick out neutrons. Since neutrons have no charge, and thus cannot be measured by a Geiger counter, David had no way of knowing whether the gun was working until he recalled that paraffin throws off protons when hit by neutrons. David aimed the apparatus at some paraffin, and his Geiger counter registered what he assumed was a proton stream. His neutron gun, crude but effective, was ready.

It is my understanding that an Alpha-N reaction does not produce neutrons in a collated beam aligned with the incident alpha beam...

so my question is,

this "neutron gun" was actually a neutron sprinkler was it not?  Producing a spherical aray of neutrons as the alpha beam entered the aluminum... or the brillium rod in his later derivation, neutrons were produced and emmited in all directions.  with out neutron shielding, or reflection... no "neutron beam' could be acheaved...

is this kid a walking talking source right now... Who gives a rats backside about his lifetime exposure to Th232... I'm worried about the dose comming off him from activation of Potassium, Iron, Carbon...

anyone, anyone?

[thenuttyneutron]

I agree that a neutron beam would have been hard to make.  If he had read any reactor engineering materials, he would have probably made his neutron source by mixing the Am-241 with Beryllium in a sphere.  Making it the right size would increase the neutron yield.  If he had then encased it in a graphite shell he would have had a very good point source for neutrons.  He had the Thorium Blocks and could have succeeded in his attempts to make a reactor by mixing the Th-232 with more graphite powder and making a blanket surrounding the neutron source.

It may have taken several years for enough fuel to be breed in to the blanket to make a critical system, but I think it could have worked if he had made the Th232/C blanket large enough to prevent the source neutrons from leaking.  It would have smoldered and had an increasing neutron count rate very similar to 1/M.  Instead of rods being pulled it would be the increasing amount of fuel that would be changing the reactivity.  The next problem before he gets the critical system is shielding.  Those U233 atoms have some nasty gamma emitters.  Maybe it is because I know enough to not be dangerous, but I would never have tried this.  This guy knew enough to be dangerous.

[Rifleman]

well I think shielding... or the lack there of, is a common missed safety concern through out the entire story. 

It also doesn't appear that there was any glove box or other type of containment so everything was going everywhere.  How on earth do you extract lithium metal out of batteries in an oxygen atmosphere with out lighting the entire works on fire? (class D that is)  Reducing Th02 with lithium metal and a blow torch in an uncontroled atmosphere?!?!

the kid was brilliant in some areas, scarry stupid in others.  With out a doubt, quite the con artist, that is for sure.

this is without a doubt a "don't try this at home kids" situation.  I'm just saying his "maybe 5 years" estimate may be off by an order of magnitude or so.

[thenuttyneutron]

I'm just saying his "maybe 5 years" estimate may be off by an order of magnitude or so.

Yep, several years in my post is an abstract amount of time.  I am too lazy to figure out the amount of time needed to make his reactor.  If he made a neutron source of 1e13, a rather large source, it would take a very long time to make the fuel.  With a large enough blanket and sub critical multiplication, it would be shorter than just a simple calculation of fuel production over time.  The fuel production would have accelerated over time.