Little Boy initiatiation method.
Eric Erpelding
What is the Monroe effect? and who was Monroe?
--EE
scrumpy
> Does anyone know how the neutron initiators used in the Little Boy
> bomb worked?
> I'm assuming they used an explosive charge to mix beryllium and
> polonium. Was the Monroe effect used as it was in the implosion
> initiators or were the two substances in powder form and explosively
> mixed? Assuming explosive mixing was used, was it detonated by an
> impact sensitive primer or by electronics?
>
> Matt
> §
If I recall correctly,the U235 bullet had a disk of Beryllium on its
front face. While the target had mounted at its rear, a disk coated
with Polonium 210. So when the gun was fired, the two disks came into
hard physical contact they started emitting neutrons. However unlike
an implosion type warhead, an initiator isn't strictly neccassary, as
the insertion is long enough for background neutrons in the U235 to
initiate it. The initiators just merely ensure the the chain reaction
will start in a timely and predictable manner. I believe that should
answer your question but Carey or Allen could probably do a better
job.
Carey Sublette
e_erp...@yahoo.com says...
> >.... Was the Monroe effect used (?)
>
> What is the Monroe effect?
Aka the shaped charge or hollow charge effect. It is the creation of
regions of higher pressure, and the accompanying formation of jets,
where detonation or shock waves collide. Its related to the Mach effect
where higher pressure shocks develop when shock waves reflect off a
surface.
> and who was Monroe?
Charles Edward Munroe (1849-1938), the leading U.S. researcher in
explosives in the late 19th and early 20th century. Professor of
chemistry at the U.S. Naval Academy 1874-1886. Professor of chemistry at
George Washington University 1892-1917. Chief explosives chemist at the
U.S Bureau of Mines 1919-1933.
>
> --EE
md
care...@earthlink.net says...
> e_erp...@yahoo.com says...
> > >.... Was the Monroe effect used (?)
> >
> > What is the Monroe effect?
>
> Aka the shaped charge or hollow charge effect.
And isn't is funny that he could have entered "Monroe
effect" into a search engine and found hundreds of answers
himself. You were too nice to him.
Carey Sublette
@hotmail.com says...
The initiators were a different type of sealed beryllium/polonium device
called Abner(s) using less polonium (since not as strong a neutron flux
was needed, and less tolerance of internal leakage existed) than the
Urchins used in the implosion bombs. The internal design is unknown, but
they were apparently activated by mechanical crushing. They were
designed to be rugged, and were able to withstand being dropped. 40-some
of these were made, and four were used in Little Boy.
Polonium is a volatile and toxic material (and costly), so it could not
be simply coated on an exposed surface.
scrumpy
> nx1...@hotmail.com (scrumpy) wrote in message news:<14d0fc24.02052...@posting.google.com>...
> initiation? When I first asked about the initiator I figured that
> colliding the beryllium into polonium would not have used because the
> neutron production rate would not have been as high as could be gotten
> by explosively mixing the two. I just now remembered that as long as
> the bullet dosn't bounce back from the target it doesn't even need an
> initiator (duh), much less one that puts out a neutron every
> nanosecond or so. So the little boy could have used a simple one, I
> wasn't sure.
>
> thanks,
> matt
> §
I believe there is a description of it in Carey's NWFAQ, I think section four.
Gregory Walker
>
> Polonium is a volatile and toxic material (and costly), so it could not
> be simply coated on an exposed surface.
The word "volatile" does not really do justice to the bizarre behavior of
Polonium-210, its most common isotope. You cannot simply plate polonium
metal onto a surface to make an alpha source. It gives off alpha particles of
such energy that polonium atoms are sputtered out by recoil and
contaminate all surrounding surfaces!
Even so, you can buy nifty anti-static brushes that contain a polonium-210
source for for cleaning dust off photographic film. (Source is
well-contained.)
Gregory Walker gwa...@jump.net
Trinity Atomic Web Site --
<http://nuketesting.enviroweb.org/>
Carey Sublette
nuclearf...@aol.com says...
> initiation? When I first asked about the initiator I figured that
> colliding the beryllium into polonium would not have used because the
> neutron production rate would not have been as high as could be gotten
> by explosively mixing the two. I just now remembered that as long as
> the bullet dosn't bounce back from the target it doesn't even need an
> initiator (duh), much less one that puts out a neutron every
> nanosecond or so. So the little boy could have used a simple one, I
> wasn't sure.
There is a discussion of the development of the gun initiator in Lillian
Hoddeson's _Critical Assembly_, but it doesn't discuss the design.
R ESTEY
Given the problems with Polonium (expense, short half life, tendency to migrate)
could someone use a substitute material as Alpha source. i was thinking of
Americium 241, commonly used in ionization type smoke detectors, material is
common, relatively cheap. Don't know if Americium is strong enough Alpha source?
Peanut Kangaroo
> Given the problems with Polonium (expense, short half life, tendency to migrate)
> could someone use a substitute material as Alpha source. i was thinking of
> Americium 241, commonly used in ionization type smoke detectors, material is
> common, relatively cheap. Don't know if Americium is strong enough Alpha source?
I don't think alpha-Be neutron sources are used now anywhere in the
nuclear weapons. The high flux deuterium plasma discharge tubes are
commonly available, and are by far more preferable initiation method
than that using the alpha-Be source.
-PK
Paul F. Dietz
> Where does one pick up these easily available deuterium plasma
> discharge tubes? I had always though these would be tough to get a
> hold of.
Pulsed neutron generators are used extensively for oil well
logging, where strings of instruments are slowly pulled up
through an oil well on the end of a data cable; neutrons are
used to measure the hydrogen concentation in the formation
around the instrument (and sometimes to measure the elemental
composition of the rock through various gamma-producing
nuclear reactions).
Paul
Carey Sublette
Nuclearf...@aol.com says...
> pkfr...@yahoo.com (Peanut Kangaroo) wrote in message news:<281574e9.02053...@posting.google.com>...
> > reste...@aol.com (R ESTEY) wrote in message news:<57512bcd.02053...@posting.google.com>...
> > > Given the problems with Polonium (expense, short half life, tendency to migrate)
> > > could someone use a substitute material as Alpha source. i was thinking of
> > > Americium 241, commonly used in ionization type smoke detectors, material is
> > > common, relatively cheap. Don't know if Americium is strong enough Alpha source?
The Urchin initiators used around 30-50 curies of polonium. A smoke
detector has 0.9 microcuries (at least mine does) of Am-241, so you'll
need around 33-55 million of them to get similar results. Better get
cracking. But the gamma emissions are too high for a modulated
initiator. The gammas will knock neutrons loose also.
However if a stochastic initiation system is acceptable (the Manhattan
Project seriously considered this option), then mixing beryllium with
someplutonium will work, and commercial reprocessed plutonium will have
its own built in neutron source.
> >
> > I don't think alpha-Be neutron sources are used now anywhere in the
> > nuclear weapons. The high flux deuterium plasma discharge tubes are
> > commonly available, and are by far more preferable initiation method
> > than that using the alpha-Be source.
> >
> > -PK
>
> For a terrorist Beryllium initiators would probably much easier than
> dealing with external neutron intiators, at least I think so, I've
> never tried!
Really strong alpha emitters (with very low gamma emissions) required
for modulated initiators are really hard to come by.
bob
>Where does one pick up these easily available deuterium plasma
>discharge tubes? I had always though these would be tough to get a
>hold of.
--,00.html
dont forget you can also use high enegy photons to initiate fission.... just
pick up a used medical linac and your in buisness...