RE: The "From" bug strikes again :-)

["Franta, Jaroslav" <frantaj@aecl.ca>]

Jim Muckerheide [mailto:jmuckerheide@delphi.com] wrote on Wednesday August
09, 2000 9:51 AM
<SNIP>
 The Farm Hall transcripts clearly establish that <SNIP> (e) they thought
that "plutonium" was probably
element 91. 

 Citation: Klotz, Irving M. Captives of Their Fantasies: The German Atomic
Bomb Scientists J. Chem. Educ. 1997 74 204.
>>>>>>>>>>>>>>

COMMENT :

Jim,

Element 91 is Protactinium.

As I wrote in my 1993 letter in Physics Today, far from being indicative of
the Germans' ignorance of A-bomb matters, their repeated references to
protactinium in fact displays a surprizing degree of awareness of the
practical aspects of procuring approximately correct quantities of the only
naturally occurring element that has a fast fission crossection in the 1.5
barn range, which is about the same as plutonium-239.

Protactinium's very low mineralogical abundance - about the same as radium -
is undoubtedly what made them reluctant to believe American claims of an
A-bomb. Their obvious ignorance of the nuclear properties of plutonium-239
and uranium-235 on the other hand, was probably due to the former's total
absence from the mineral world and the latter's unavailability in an
isotopically pure form (unlike protactinium, which is 100% isotope 231).
Unlike the Americans, the German scientists did not even have cyclotrons -
used to produce the first tiny samples of Pu.

Also, Pu-239 and Pa-231 have similar radioactive half-lives: 33,000 years
for Pa-231 versus 24,000 years for the "deadly radioactive" Pu-239. This,
combined with the fact that they are both alpha particle emitters, gives
them roughly the same degree of radiotoxicity.

Another interesting snippet I came across while sifting through some of my
old photcopies of reference materials :

"British researchers... isolat[ed] ...some hundred grams of  231Pa from the
sludge left over from uranium processing" for inorganic chemistry research.

and :

231Pa "occurs in pitchblende in the amount of 300mg/ton, about the same as
radium." 

...this from J. C. Spirlet et-al. Whatever the "sludge" source of the
British chemists was, I doubt that it represented a significant fraction of
the total produced in uranium mines around the world. The implication being
that multi-kilogram quantities of  231Pa (enough for a small U-Pa fueled
fast-breeder reactor, or possibly even a bomb core or two, depending on the
"design sophistication") could potentially be extracted by a sufficiently
determined organisation - without ever having to overcome any sort of
nonproliferation safeguards. (Also, Pa happens to be a much better-handling
metal than Pu, with a much higher m.p., like Th)

Jaro
frantaj@aecl.ca

References:

1.  I. Klotz, "Germans at Farm Hall Knew Little of A-Bombs," Physics Today,
October 1993, pp. 11, 13, 15 and 135.

2.  Logan, J.L., "Heisenberg, Goudsmit and the German 'A-Bomb'," Physics
Today, May 1991, pp.15, 90, 91.

3.  Garber, D.I. and R.R. Kinsey, Neutron Cross Sections, Vol II: Curves
[Brookhaven National Laboratory (BNL-325), Upton, NY, 1976], 3rd ed.,
pp.450, 456-457

4.  Srinivasan, M. et al, "Systematics of Criticality Data of Special
Actinide Nuclides Deduced Through the Trombay Criticality Formula," Nuclear
Science and Engineering, July 1989, pp.295-309.

5.  J. C. Spirlet et-al, "Preparation and Purification of Actinide Metals,"
Adv. in Inorganic Chemistry, Vol. 31, pp. 1-41, 1987.
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