Tungsten Alloy Shielding For Neutron Logging

Tungsten alloy shielding for neutron logging is widely used in neutron logging. Neutron logging consists of a neutron source and a single detector. Many variations were produced utilizing both thermal and epithermal neutrons. In most of the early tools, neutrons were not detected directly. Instead, the tools count gamma rays emitted when hydrogen and chlorine catch thermal neutrons. Since hydrogen has the biggest impact neutron transport so far, the borehole effects on such tools are large. The now-standard compensated neutron-porosity logging tool is a very simple tool. Like a density tool, it consists of a neutron source and two neutron detectors. The tool surveys the size of the neutron cloud by identifying the decline of neutrons between the two detectors. Because neutrons have a much higher penetrating power than gamma rays, the design is much simpler than that of a density tool. It demands little collimation and does not need to be pressed against the borehole wall.

According to the different tools used in neutron logging, neutron logging can be divided into neutron-thermal neutron logging, neutron-epithermal neutron logging, neutron-gamma logging, neutron-gamma ray spectrometry log; while it can also be divided into conventional neutron log, compensated neutron log and sidewall neutron logging in accordance with the structural features of the tools. The neutron sources used by neutron logging are mainly isotopic neutron source and accelerator neutron source (now most often americium-beryllium, although at least one tool uses an accelerator source). Neutron radiation which is generated by the high-energy neutrons can damage personnel in the effective range, and cause blood-forming organ failure, digestive and central nervous system damage, as well as leukemia, cataracts and other diseases.

The neutron radiation and gamma radiation released during the process of neutron logging will harm human health. So it is generally recommended to use tungsten alloy shielding for neutron logging to shield the radiation to protect staffs from radiation damage. Tungsten alloy shielding for neutron logging has a high density. Because the radiation shielding effectiveness of a metal material will increase with the increasing of its density, thus the tungsten alloy shielding for neutron logging has good radiation shielding effectiveness. 

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