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Pulsed neutron uranium borehole logging with epithermal neutron dieaway

Conference ·
OSTI ID:4046130
Both prompt fission neutrons and delayed fission neutrons can be used for logging uranium boreholes. This paper describes a uranium logging system, using a pulsed neutron generator, which detects and assays uranium by the measurement of prompt fission neutrons. The system development began with a feasibility study which included experimental meaxurements in uranium test pits at Grand Junction, Colorado, and computer calculations of the epithermal neutron return in the presence of uranium. A Monte Carlo neutron transport code and a 21 group, one-dimension, time-dependent, discrete-ordinates neutron transport code have been used to calculate the effects of borehole geometry and rock matrix parameters on the epithermal neutron dieaway. Some experimental and analytical results are described. A prototype logging probe, 70 mm in diameter, was built and field evaluation began in January 1976. The physical and operational characteristics of the probe and the uphole equipment are described. Some logging results are shown which were obtained in an area in which disequilibrium is known to exist. Although the field experience with the probe has been brief, the results have been significant. They imply that a relatively accurate assay of low-grade uranium ore can be obtained with this method provided that proper calibration factors are determined, and a neutron output of about 10$sup 10$ n/s is used. A neutron tube is being developed for uranium logging that will generate 10$sup 10$ n/s when operated at 100 pulses per second. (auth)
Research Organization:
Sandia Labs., Albuquerque, N.Mex. (USA)
NSA Number:
NSA-33-029086
OSTI ID:
4046130
Report Number(s):
SAND--75-5991; CONF-760316--1
Country of Publication:
United States
Language:
English