[ RadSafe ] Californium vs. Americium

[Brennan, Mike (DOH)]

Hi, Franz.

While I can not speak with certainty about the first several atomic weapons, I can speak (though only in very general terms, due to security issues) about more modern nuclear weapons, as I served aboard one of the U.S. Navy's nuclear powered ballistic missile submarines as an Assistant Weapons Officer (and qualified as a Weapons Officer before I left the boat for a shore tour as an instructor at Officer Submarine School).  While I neither confirm nor deny that there were nuclear weapons on board, I can state that the missiles were loaded into the tubes and remained there for a number of years before being rotated off for servicing.  

"Arming" at one point meant inserting some component, but that is no longer the case for most systems.  For example, the torpedo we used (with a conventional warhead) did not arm until after it had been launched and had traveled some distance from the submarine.  For the larger artillery pieces, the shell does not arm until some preset time after it has been fired, and been subjected to several different accelerations that would be impossible to accidentally reproduce on the ground.  In many modern weapon systems the arming sequence requires both operator input of some type of encrypted permission and the meeting of a number of environmental parameters.  

I also can speak with some authority that neither U.S. Naval nuclear reactors nor the commercial reactors I am familiar with use Po-210-Be as a neutron source for start-up.  I can not speak for either the very early reactors or non-US. designs.

I haven't had any professional involvement with Po-210, other than as one of the far down-stream daughter products of radon.  I understand that it does still have some industrial applications, but I have no first hand experience to base that on.  I do know that it is a impressive choice as an assassin's weapon.  You are completely correct that Pu-238 isn't even in the same league as Po-210 as "the deadliest substance in the world" (though there are several nerve agents I would put forward, or small pox virus if we are opening up the field to include bio).



-----Original Message-----
From: Franz Schönhofer [mailto:franz.schoenhofer at chello.at] 
Sent: Thursday, June 28, 2007 3:45 PM
To: Brennan, Mike (DOH); 'radsafe'
Subject: AW: [ RadSafe ] Californium vs. Americium

Mike,

I agree, that Pu-238 might be a better choice, but I know for sure, that Po-210 has been used together with Beryllium as neutron source in nuclear bombs and in nuclear reactors to start the chain reaction. Po-210 was and still is produced by neutron irradiation of Bi-209 (naturally occurring).
Natural occurring Po-210 in uranium ores is only abundant in minute amounts and you might know, that Marie Curie had to use many tons of pitchblende residues to isolate it and you might know that she called it polonium because her native country was Poland (which then for a long time did not really exist). 

Additional hints: When the nuclear reactor at Windscale, England burnt in Oktober 1957 also large amounts of Po-210 were emitted - the reactor was also used to produce Po-210 and this is very volatile. 

I do not believe, that nuclear bombs are stored fully assembled and several occasions confirm my belief: Several accidents are known (e.g. Palomares, Spain and Thule, Greenland) where nuclear bombs fell to the ground from airplanes. It was always communicated, that these bombs had not been armed.
In the reports about the nuclear bombs exploded over Hiroshima and Nagasaki there was always mentioned that the bombs were armed during flight. In the excellent book "Picturing the Bomb" about the Manhattan Project it says, that the bomb was finally assembled during flight. It would not be a good idea in the light of the now prevailing concerns in the USA about terrorism not to inherently secure the bombs by not having them fully assembled. 

Another hint is, that polonium is still produced. I do not believe that the Po is still widely used as a static eliminator, so what should the production otherwise be good for? 

BTW replacement of the extremely poisonous Po-210 by plutonium (238) would be of occupational health significance, though our green friends always claim that plutonium is the deadliest substance on this world. No, its Po-210!

Some information I found confirmed by using at Google "neutron sources polonium".

Best regards,

Franz

Franz Schoenhofer, PhD
MinRat i.R.
Habicherg. 31/7
A-1160 Wien/Vienna
AUSTRIA


-----Ursprüngliche Nachricht-----
Von: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] Im Auftrag von Brennan, Mike (DOH)
Gesendet: Donnerstag, 28. Juni 2007 23:21
An: radsafe
Betreff: RE: [ RadSafe ] Californium vs. Americium

Hi, Franz.

Are you sure it isn't Pu-Be rather than Po-Be?  I am sure that one could use Po-210 and make a compact source with high output, but the 140 day half life means that you would have to use it quickly, before it decayed too much.
That doesn't sound too good for nuclear weapons, that usually are left inside their delivery systems for many years at a time.  Pu-238, on the other hand, has a really nice half life for doing all sorts of things where you want to balance specific activity and longevity.  

Though both Po-210 and Pu-238 are good from the point of view of not having screaming hot gammas, which I understand was the biggest problem with RaBe sources. 

-----Original Message-----
From: Franz Schönhofer [mailto:franz.schoenhofer at chello.at]
Sent: Thursday, June 28, 2007 1:52 PM
To: Brennan, Mike (DOH); 'radsafe'
Subject: AW: [ RadSafe ] Californium vs. Americium

Mike (and others interested),

Far from being an expert on neutron sources I remember that Cf-252 is used as a single source of neutrons because of spontaneous fission - as you pointed out. I never heard that its alpha-particles were used to generate neutrons together with Be. 

Po/Be neutron-sources have been and are obviously still used in nuclear reactors and in nuclear bombs. 

The first neutron-sources were obviously Ra-Be mixtures. I doubt they are still used.

Using DU as a source for alpha-particles would - if it were possible - not reduce the quantity of DU stored significantly.....