Patent ID: 7429739

Claim:
A method for determining a dispersion format of a radioactive material within a matrix, wherein said radioactive material is potentially present in a dispersion format which is self-shielding against emissions arising from said radioactive material, the method comprising: measuring emissions from said radioactive material within said matrix at three or more energies selected from energies about 143.8 keV, about 163.3 keV, about 185.7 keV, about 205.3 keV, about 766.4 keV, about 1001.0 keV; determining a ratio of emissions at one said energy to emissions at another said energy in respect of at least two different pairs of said energies; obtaining a ratio value of said ratio of the emissions at the two energies for each of said pairs of energies; comparing one said ratio value to a first threshold value, wherein when one said ratio value is to one side of said first threshold value said dispersion format for said radioactive material in said matrix is determined to be a dispersion format which is self-shielding against emissions arising from said radioactive material; and comparing second said ratio value to a second threshold value, wherein when second said ratio value is to one side of said second threshold value said dispersion format for said radioactive material in said matrix is determined to be a dispersion format which is self-shielding against emissions arising from said radioactive material.