The NERVA engines of the Apollo era were pretty dirty as were the Aircraft
Nuclear Propulsion (ANP) engines that were ground-tested between 1956-61.
The ANP tests released about 4.6 million curies of radioactive stuff into
the atmosphere (the Hiroshima bomb released about 3 million curies). Of
course, the ANP release was negligible compared to the radioactivity
released in the 1950s by above-ground nuclear weapons tests.

The really big release of radioactivity in the NERVA program occurred on 21
Jan 1965. NASA and the AEC (who were jointly developing the NERVA engines)
decided to see what would happen if one of these 1000 megawatt+ (thermal)
reactors was pushed to the limit. In the Transient Nuclear Test (TNT) a Kiwi
B-4E reactor was deliberately driven to overload (without hydrogen
propellant flowing through the core). The resulting thermo-mechanical (not
nuclear) explosion vaporized 5-15% of the reactor core and scatted reactor
parts over a circular area of 4 nautical mile radius. The radioactivity from
this extremely dirty test in the Nevada desert north of Las Vegas was
tracked to LA and out over the Pacific Ocean.

NERVA along with the Apollo program was cancelled in 1972 by the Nixon
Administration. All of the NERVA/Phoebus reactors and engines wound up
buried in the Nevada desert. During the Star Wars days of the 1980s, the
SDIO planned to resurrect the pebble-bed nuclear reactor/engine for use in
the upper stages of a heavy lift launch vehicle that would orbit the massive
laser and particle beam battle stations envisioned by the Star Wars
enthusiasts (I spent about 6 years working on the the neutral particle beam
payload). The pebble bed bit the dust along with most of the other exotic
Star Wars stuff in 1993 when the Clinton Administration came to town.
Testing a nuclear engine these days would be a nightmare because of the
environmental concerns.

All of this ancient history is covered in Chapter 25 of my recent (2002)
book on U.S. manned spaceflight in the 20th century

Later
Ray Schmitt



"David Findlay" wrote in message
u...
Was NERVA type or other nuclear engines ever considered for the space
shuttle? Do they generally release any radioactive materials or is this
completely contained? Is it still contained in failure modes? Thanks,

David