looks like a retrace back to 1.70 ish imo, page-19

2x prompt fission neutron hehehe....and how many companies in the World do have access to a PFN tool ???? :)))))))


A Prompt Fission Neutron (PFN) tool is used to
overcome this disequilibrium, giving a true reading
without the need to drill core holes. The PFN tool was
first developed by Sandia Laboratories and Mobile R
& D for the oil exploration industry in the 1970s.


When the patent expired in 1999, it became available
to the uranium exploration industry, though there are
still only about half a dozen of them being used worldwide today.

They are complex, heavy, difficult and potentially dangerous to use and they are expensive, costing about $0.5m each. They tend to be custom built for the end user. Untroubled by the patent, the Russians developed a similar tool and called it the KND System.

This has been actively used in ISL mines in Kazakhstan.
A PFN tool is a down-hole instrument measuring 3m
in length and weighing about 50 kg. Inside is a pulsed
neutron source about the size of a light bulb.

High voltages accelerate deuterium ions into a tritium target and this produces 14MeV neutrons which are emitted into the rock to test for uranium. Epithermal neutrons collide with the country rocks and slow down to form thermal neutrons.


If they find an atom of 235U it causes slow fission at the atomic level, which produces a characteristic 2MeV neutron. Thermal flux and epithermal flux generated by the fission reaction are read by the PFN tool. The ratio of epithermal to thermal neutrons is directly proportional to 235U levels. Only 235U is naturally fissionable in the natural environment.


Use of the PFN tool and the re-estimation of uranium
grades can result in variations being plus or minus
30% or more when compared with gamma ray log
calculations. So far, at 4 Mile, six holes have been
tested with the PFN tools. It is believed that there has
been no significant downgrading of grades as a result
of the tests.