[DBrow]

At the Sandia Nuclear Museum they have (had?) mockups of several space power Snap-like RTGs. One used Co60 in a gadget with variable fins to maximize radiant cooling. The source for this would have been pretty hot, I think it had over 4 grams of cobalt (4 KCi), which even after twenty years (a little less than 4 half-lives) would have been lethal in a few hours, at 500 curies the dose rate at a meter would be well over 100 REM/hr. If Sr90 had been the source, the half life is 27 years, and the source strength would be higher than for Co.

I saw a Snap-7 with a charge of Sr90 and its shielding was pretty big, the whole thing was like a fireplug. It put out about 2KW of electricity. I think the shielding was U238.

If the dose rate was hundreds of REM/hr (seems likely from the facts in the story) the stuff probably was not Pu. We played around with thulium RTGs for a while, they'd be hot.

Another possibility is that the cans were Ir192 field radiography sources, removed from their shielding for theft. Half life is only 70 days.

Sometimes Cs137 was used in RTGs, and sometimes used in radiography. Pretty penetrating stuff, between Co and Ir in photon energy, and the halflife is 33 years.

I doubt we will know what the capsules are until they are found. Should be pretty easy if they are that hot!

[Robert A Cook PE]

I can't recall the details of the story ... but pieces of Soviet-era SNAP reactors were recovered from "Canada" (obviously a "wide" crash/survey zone) after one of their RORSAT's crashed in the Yukon/Northwest Territires.

I assume "somebody" used an aerial radiation survey ... but no details other than that they recovered the reactor.