Re: Cassini Mission and Plutonium RTG's

["Scott D. Kniffin" <Scott.D.Kniffin.1@gsfc.nasa.gov>]

Perhaps I made this worse with my explanation of "pit" sizes.  Too much
knowledge, too little clarity, please allow me to further explain.  

Each bomb is generally only one element and one or two masses of that
element.  Those being U-235 and Pu-239/240 preferably with as little 240 as
possible.  The problem with Pu-238 and Pu-240 is their annoying tendency
towards spontaneous fission.  Pu-239 does SF too, however the frequency is
very, very small in comparison to 238 and 240.  

Where might I get a copy of the document Dr. Raabe mentions?  Sounds
fascinating.

A thousand pardons,

Scott Kniffin


Scott.D.Kniffin.1@gsfc.nasa.gov
RSO, Unisys Corp. @ Lanham, MD
CHO, Radiation Effects Facility, GSFC, NASA, Greenbelt, MD

The opinions expressed here are my own.  They do not necessarialy represent
the views of Unisys Corporation or NASA.  This information has not been
reviewed by my employer or supervisor.  



At 12:49 08/29/97 -0500, you wrote:
>
>On Wed, 27 Aug 1997, Otto G. Raabe wrote:
>
>> Perkins and Thomas ("Worldwide Fallout", pp 53-82, TRANSURANIUM ELEMENTS IN
>> THE ENVIRONMENT, W.C. Hanson, Ed. DOE/TIC-22800, 1980) have compiled a list
>> of all U.S., French, U.K. USSR, and Chinese nuclear tests and releases up
>> to 1980, and conclude: "Since the first nuclear weapons test at Alamogordo,
>> N. Mex., on July 16, 1945, approximately 360,000 Ci of 239,240Pu has been
>> injected into the atmosphere. In addition, 17,000 Ci of 238Pu entered the
>> atmosphere in April 1964 as a result of the high-altitude burnup of a
>> SNAP-9 satellite power source."
>> 
>> Maybe you can answer your question by comparing your calculation with the
>> data provided by Perkins and Thomas (1980).
>
>	--Apparently my problem was in assuming that more than half of the
>fission yield came from plutonium; The numbers you quote imply that only
>about 6% of the fission yield was from Pu and 94% was from Uranium. I am
>surprised at this;  as the old saying goes, "you learn something new every
>day". 
>	 
>