Thirty to forty years ago, *muon-induced fission* was a hot topic.
Most of the radioactive heavy metal actinides were found to undergo
prompt or delayed fission when placed in a muon flux. This includes
thorium. The coupling is not huge but it is significant.
However, at that time the economics of producing large numbers of muons
was prohibitive and the field of inquiry dried up. Here is an old paper.
http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/12/609/12609441.pdf
Muons were produced in a beam line for most of these studies. There is
no possibility of a self-sustaining chain reaction, as with neutron
mediated fission, although fission does produce some additional muons.
Thus, a high flux must be maintained.
But... fast forward forty years to Holmlid, and reassess the situation
... What if muons can be produced millions of time easier and cheaper,
using UDD and the Holmlid effect?
If he is correct, a heavy flux of muons is produced via laser instead of
beam line, meaning that size can be reduced greatly and cost and form
factor minimized. When thorium is the target for muon induced fission,
it becomes useful without adding fissile material and it is far more
plentiful than uranium and the proliferation risk disappears as well as
90% of the cost of dealing with neutrons and critical mass.
Win, win, win, win.
This is a paradigm shift in assumptions, leading to something
unexpected. "Small-scale fission courtesy of cold fusion."
Even Holmlid has overlooked the possibility of muon-induced fission of
thorium (at least it does not turn up in a search of his papers.
