Steven Aftergood at the Federation of American Scientists presents Fifty Years of Space Nuclear Power "A plutonium fueled RTG that was deployed in 1965 by the CIA not in space but on a mountaintop in the Himalayas (to help monitor Chinese nuclear tests) continues to generate anxiety, not electricity, more than four decades after it was lost in place. See, most recently, "River Deep Mountain High" by Vinod K. Jose, The Caravan magazine, December 1, 2010." (MeFi previously)
Nanda Devi - India's second-highest peak, at 25,645 feet (7816m), sits in a "sanctuary," surrounded by 21,000-foot+ lesser mountains. This has made it even more of a challenge to climb. Among those who took up the challenge were a 1965 CIA team trying to set up a plutonium-powered device to spy on China's nuclear testing program. That expedition retreated in the face of bad weather, leaving the device on the mountain. When they returned the next spring, it was gone. The Nanda Devi Sanctuary supplies water to the Ganges River, and there were fears that the four pounds of plutonium in the device could escape into the watershed. Those fears have been confirmed.