1. PFN Technology: “Prompt Fission Neutron”
Deposit Evaluation
PFN Technology: “Prompt Fission Neutron”
SXR
Southern Cross Resources Inc

2. PFN: Disequilibrium Problem
Gamma is the traditional tool used to measure eU3O8 grade and evaluate resources… g
Gamma Ray Intensity
214Pb
214Bi
Gamma measures radioactive Bismuth & Lead (the daughter products of uranium decay) not Uranium itself. Disequilibrium occurs when deposits are younger than ~1 million years old and gamma under calls true uranium grade.
…but in some Roll-front deposits uranium is not in equilibrium with its daughters as they are too young.
238U

3. PFN: Schematic Gamma Response
Hole 1
Hole 2
Hole 3
Hole 4
Overlying Clay
Oxidised
Aquifer
Reduced
Aquifer
Tails
Uranium Ore
Nose
Example of gamma response. High levels in the tails, low to no response in the nose.
Basement Clay
Gamma Response

4. PFN: Schematic PFN Response
Hole 1
Hole 2
Hole 3
Hole 4
Example of gamma response. High levels in the tails, low to no response in the nose.
No PFN response in low grade tails as daughters only
PFN response directly measures 235U concentrated in high grade nose

5. PFN: What is PFN Technology?
Down Hole Probe
Pulsed Neutron Source
Haliburton Neutron Generator Tube gives controlled bursts of high energy neutrons 1000 per second.
Drill Hole

6. PFN: Neutron Generator Tube
Haliburton Neutron Generator Tube gives controlled bursts of high energy neutrons 1000 per second.
High voltage accelerates deuterium (2H) ions into a tritium (3H) target
2H + 3H  n + 4He (En = 14.2MeV)
Pulses at 1000 cycles per second & emits ~108 neutrons per second

7. PFN: What is PFN Technology
Down Hole Probe
14 MeV Neutron Flux
Epithermal Neutron
To Thermal Neutron
(by Collision with rock)
Pulsed Neutron Source
Thermal Neutrons Induce Slow Fission of Natural 235U in rocks
PFN neutron detection. Ratio of Thermal (output) to Epithermal (U235 fission product) neutrons is directly proportional to true in-situ uranium grade.
Epithermal & Thermal Neutron Detectors
Ratio gives % 235U
2MeV Prompt Neutrons emitted from 235U fission
Drill Hole

8. Epithermal Neutron Flux
PFN Results
Thermal Neutron Flux
3.52 U3O8 lbs/ft3
Epithermal Neutron Flux
1.48 U3O8 lbs/ft3
0.27 U3O8 lbs/ft3
Ratio of Epithermal to Thermal Neutrons is Directly Proportional to 235U
Only 235U is Fissionable in the Natural Environment
Deposits considered in Isotopic Equilibrium % U
99.27% 238U

9. PFN: Calibration

10. PFN Calibration Results

11. Wireline Log Output Induction & Guard eU3O8 (Black) Natural Gamma
- Define lithology by measuring porosity using EM and Electrical methods. Similar to SP / Resistivity but better suited to highly saline conditions
eU3O8 (Black)
- Calculated from calibrated natural gamma using a number of factors)
Natural Gamma
- Total count natural gamma radiation measured by up to three scintillometers with varying NaI crystals sizes
pU3O8 (Red)
- Direct measure of U235 insitu using ration of epithermal to thermal neutrons – PFN

12. PFN: Advantages
Crucial for most Tertiary Uranium deposits as they are young and suffer extreme disequilibrium
Uses a safe neutron generator rather than a radioactive source
Produces an accurate direct measurement of insitu uranium over narrow intervals
Results are instantaneous
Measures a large sample volume (500mm sphere)
Obviates the need to drill core
Can be used during ISL mining to quantify recovery
Exploration tool – disequilibrium vector towards mineralisation
Colin Skidmore (October 2005)