Neutron Rem Detector Response Changes due to Activation of Components

Area of Science:

• Nuclear instrumentation
• Radiation detection and measurement

Background:

• Neutron rem detectors exhibit a response increase after prolonged neutron flux exposure, known as the "soak factor."
• The underlying physical mechanism for this phenomenon has remained unexplained.

Purpose of the Study:

• To investigate and identify the primary cause of the increased response in neutron rem detectors.
• To elucidate the mechanism behind the "soak factor."

Main Methods:

• Gamma-ray spectroscopy was employed to analyze activated components of neutron rem detectors.
• Instrument response was tested under varying neutron flux rates and accumulated fluence levels.

Main Results:

• Activation of copper (Cu) in the brass collar of the gas-filled detector tube is proposed as the primary cause.
• While manganese (Mn) was detected, it was not found to be a significant contributor to the response increase.
• Photon pulses from activated components, coinciding with neutron pulses, contribute to the elevated readings.

Conclusions:

• Copper activation in detector components is the main driver of the "soak factor."
• The increased indicated neutron dose rate is attributed to decay photons from activated copper.
• Understanding this effect is crucial for accurate neutron dosimetry.