Correction of a radioactivity measurement using particles from atmospheric source

Apparatus for determining an amount of radioactive material within a body of material, the apparatus comprising:

• one or more detectors that measure a characteristic of radioactive material, the one or more detectors providing a preliminary measure of the amount of radioactive material within a body of material by directly and/or indirectly measuring emissions generated by the radioactive material;
• one or more first detectors positioned above a measuring location, the one or more first detectors detecting one or more types of particle from an atmospheric source which have not passed through the body of material to give a first value;
• one or more second detectors positioned below a measuring location, the one or more second detectors detecting one or more types of particle from an atmospheric source which have passed through the body of material to give a second value;
• a processor for processing the first value and second value to give a factor, wherein the factor is an expression of density and wherein the factor is a function of the second value divided by a product of a calibration factor and the first value, the processor further applying the factor to preliminary measure of the amount of radioactive material within the body of material to obtain a corrected measure of the amount of radioactive material within the body of material.

A method of determining an amount of radioactive material within a body of material, the method comprising:

• determining a preliminary measure of an amount of radioactive material within a body of material by directly and/or indirectly measuring emissions generated by the radioactive material;
• using a second detector to detect one or more types of particle from an atmospheric source which have not passed through the body of material to give a first value;
• using a first detector to detect one or more types of particle from an atmospheric source which have passed through the second detector and the body of material to give a second value;
• processing the first value and second value to give a factor, the factor being an expression of density and being a function of the second value divided by a product of a calibration factor and the first value;
• and
• applying the factor to the preliminary measure of the amount of radioactive material within the body of material to obtain a corrected measure of the amount of radioactive material with the body of material.

A method of establishing an error in a factor, the factor being used in a method of correcting a measure of radioactive material within a body of material, the method comprising:

• determining a preliminary measure of an amount of radioactive material within a body of material by directly and/or indirectly measuring emissions generated by the radioactive material;
• using a second detector to detect one or more types of particle from an atmospheric source which have not passed through the body of material to give a first value;
• using a first detector to detect one or more types of particle from an atmospheric source which have passed through the second detector and the body of material to give a second value;
• processing the first value and second value to give the factor, the factor being an expression of density and being a function of the second value divided by a product of a calibration factor and the first value;
• applying the factor to the preliminary measure of the amount of radioactive material within the body of material to obtain a corrected measure of the amount of radioactive material with the body of material;
• and
• determining the error in the factor by:
• considering the first value as being accurately measured, considering the calibration factor as being accurately known and considering the second value as being the first value multiplied by a probability, the probability being that of a particle contributing to the first value and to the second value.