PFN (Prompt Fission Neutron) Technology

What is it?

  • Prompt Fission Neutron is a logging technology used for assaying uranium mineralization around a borehole. PFN technologies have played an important part in discovering, and bringing to production, some of the best uranium deposits in the world.
  • For years, the primary method of uranium logging has been the detection of gamma radiation, however, a conventional gamma log of a formation in disequilibrium will produce an incorrect estimate of the uranium in the deposit. PFN technology solves this issue by instead using neutron activation to detect uranium in drill holes.
  • The recovery and analysis of core samples is both expensive and time consuming and often is used only to confirm the presence of uranium indicated by significant natural gamma radiation.

Why Is It A Competitive Advantage?

  • The use and ownership of PFN technology provides enCore with a clear competitive advantage by providing the ability to perform real-time assays for uranium that cannot be achieved using conventional logging, coring, and assay methods. This technology is unavailable to many other uranium exploration and development companies.
  • The PFN equipment and supporting technology owned by enCore includes:
    • Associated proprietary intellectual property, including all internal details of the tools, circuit board diagrams, firmware code, software, manuals and instructions.
    • The sole right to utilize the license of the PFN technology globally.
    • PFN downhole wireline probes.
    • Gamma downhole wireline probes with single point resistivity, spontaneous potential and deviation.
    • Heavy-duty logging trucks with logging and associated equipment.
    • Power supplies, computers, communication equipment, and other technology.

How Does it Work?

  • The PFN tool creates very fast neutrons (14MeV) and fires 108 neutrons per second into the formation.
  • The neutrons emitted by the PFN tool excite, at an atomic level, in-situ uranium atoms surrounding the drill hole, inducing fission creating fast (epithermal) neutrons and slow (thermal) neutrons.
  • The ratio of epithermal to thermal neutrons is specific for uranium, allowing the U3O8 ore grade to be accurately calculated.
  • This provides a relatively inexpensive and instantaneous means to accurately assay in-situ ore grades over large areas, and allows for accurate orebody mapping, resource estimation, and wellfield planning.


  • Cost: PFN provides a significant advantage to extracting uranium by reducing costs associated with uranium exploration, delineation, and production drilling.
  • Time: the much shorter observation time of the PFN method offers the possibility of faster, real-time assay logging as opposed to conventional gamma logging and coring techniques.
  • Accuracy: without PFN, it is easy to miss large areas of high-grade uranium resources within a deposit if under disequilibrium.
  • Dealing with disequilibrium: Many young uranium deposits in the U.S have a certain degree of disequilibrium, meaning the radioactivity measured in drill holes using both traditional total gamma and spectral gamma methods does not accurately correspond to ore grade. Without accurate in-situ measurement of uranium, significant high-grade ore has been missed using conventional downhole logging techniques. PFN technology solves this issue by instead using neutron activation to directly detect uranium in drill holes.

“PFN technology is far superior to traditional downhole gamma measurements where an array of different elements emits a collective gamma signature which may or may not correlate well with the actual uranium content.”


In the hope of eliminating problems associated with conventional logging techniques, alternative methods of direct detection of uranium were made as early as 1961 and in October 1974, under contract with the U. S. Energy Research and Development Administration (ERDA) field off ice in Grand Junction, Colorado, Sandia Laboratories began the first phase of a project to evaluate the PFN technique. Field evaluation of the prototype PFN system began in January 1976.  Both Sandia Laboratories and Mobil R&D in south Texas further developed and refined the PFN system during the mid to late 1970’s.  During the 1980’s, the technologies were refined and methods for calibrating the results for subsurface conditions were designed.  The US Patents for the PFN expired in 1999, and the PFN system was subsequently developed for commercial use by GeoInstruments, Inc., and its successors. enCore currently owns the rights to this technology.