Sourcing extraterrestrial Nuclear fuel

Here is a quote from Paul Spudis who lead the
Clementine Lunar mapping project.

"Even the most KREEP-rich deposits on the Moon are
slim pickings for U mining; typical concentrations are
about 2-3 ppm for Apollo 14 soils and breccias. Some
hyper-KREEP rocks like 15405 (a melt breccia
containing clasts of granite and quartz monzodiorite)
only have U contents of about 5-10 ppm. The problem
is that the types of acitivty that concentrate U on
Earth (hydrothermal; alkaline explosive volcanism) are
absent on the Moon. The best you can do is extreme
igneous differentiation of (approximately basaltic)
magmas."

This is the best link I could find on KREEP chemistry
and evolution:
http://www.minsocam.org/MSA/AmMin/TOC/Articles_Free/2001/Shearer_p238-246_01.pdf

The short answer is KREEP has little inclusions of
'leftovers' in the parts per million range.

Hope this helps.

Cheers, Thor