posted at http://www.awgnet.com/aviation/avi_wash.htm
The Energy Dept. is sounding out NASA about reviving work on space nuclear power systems. Energy is proposing a $4.4-million space fission reactor technology evaluation in Fiscal 2001, and wants to work with NASA to identify specific long-term power and propulsion requirements, according to documents obtained by the Federation of American Scientists. Energy foresees fission energy in a Mars outpost, exploration of outer planets and deployment of observatories in deep space. The last major U.S. space nuclear power effort, called SP-100, was terminated in the early 1990s after nearly $500 million had been spent.
İSeptember 6, 1999 The McGraw-Hill Companies, Inc.
In contrast to RTGs like those of the Cassini Saturn-bound spacecraft carrying 72 pounds of plutonium-238 ( T½ = 87.7yrs.), a fission reactor for space application could be built that contains much less radioactivity during the risky launch phase. As little as a couple of hundred grams of Americium-242m ( T½ = 152 yrs.) with BeO moderator would make a reactor core with enough excess reactivity that could enable it to run for several years at multi-kilowatt power level. Total radioactivity at launch would be about 200-times less than using Pu-238. Neutron & gamma radiation is a problem for spacecraft electronics once the reactor is powered up, but the technique of shadow-shielding, with long separation boom, is a solution which avoids a great weight penalty....
A similar type of system (much larger, for different applications) is described in the Canadian Nuclear FAQ, at URL http://www.ncf.carleton.ca/~cz725/cnf.htm#g4