Low radioactive nucleon density measurer

Abstract

A nuclear density gauge and test method is provided for measuring density material in a relatively thin zone beneath a surface of the material. The gauge comprises a gauge housing and a substantially planar base on said gauge housing adapted to be positioned on a surface of the material sample. A gamma radiation source having a characteristic primary energy and an activity of no more than 100 microcurie is mounted within the housing and cooperates with the base for emitting gamma radiation through the base and into an underlying material sample. An energy selective gamma radiation detector is mounted within the gauge housing and in laterally spaced apart relation from the gamma radiation source. The gamma radiation detector is operable for quantifying the energy level of the detected gamma radiation. Shielding is provided within the gauge housing between the source and the detector for preventing gamma radiation from passing directly from said source to the detector. An analyzer is connected to the detector for detecting gamma radiation counts in a predetermined energy spectrum having a lower limit of 0.1 MeV or greater and an upper limit which is less than the characteristic primary energy of said source. The density of the sample is calculated based upon the gamma radiation counts obtainedby the analyzer within the predetermined energy spectrum.

Description

technical field [0001] The present invention relates to the measurement of density, and more specifically, the present invention relates to a test instrument and a test method for measuring the density of a sample by gamma rays. The invention is particularly suitable for measuring the density of thinner zone layers located below the sample surface. Background technique [0002] In the asphalt paving industry, the density of asphalt pavements is often measured using a portable nuclear gauge. Typically, asphalt pavers are laid in relatively thin layers, for example on the order of about 1 to 2 inches in thickness, on a prepared road bed or on an existing paved surface. Therefore, there is a need to measure the density of pavement samples in thinner zones below the pavement surface, for example, at a depth of 1 to 3 inches. To this end, nuclear gauges have been developed for directly measuring the density of thin-layer paving materials. Nuclear "thin layer" gauges of this ty...

AI Technical Summary

Problems solved by technology

[0003] Although the gamma-ray source in these gauges is very low in radioactivity, in the millicurium range, and it can be used safely by operators with ordinary precautions and safeguards, regulatory agencies still have restrictions on the maintenance, transportation, storage, and use of such gauges. instruments and restrictions on qualified personnel operating such instruments

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