An interesting fact I found in the book Atomic Accidents, A history of nuclear meltdowns and disasters by James Mahaffey. http://amazon.com/Atomic-Accidents-Melt ... inw_strp_1
Talking about atomic test engines for aircraft specifically HTRE-3, High Temperature Reactor Experiment-3.
Quote " Hold onto your seat. Three quarters of the free world's supply of mercury was used to shield HTRE-3. At the end of the project it had to be released slowly back into the market to prevent an economic crash in the liquid metals trade."
HTRE-3 was one test reactor for powering 2 jet engines. Can you imagine an aerial explosion involving a nuclear reactor with all of the radioactive materials and mercury raining down on your head. This was tested in late 50's early 60's.
This book will scare the heck out of you as it lists a lot of problems associated with the birth of nuclear power.
Leonard