Term from the field of nuclear material monitoringOrganisational and physical test methods enabling the monito...; source materials are uraniumNatural radioactive element with the atomic number 92. The n... which contains the naturally occurring isotopeAtoms of the same atomic number (i.e. the same chemical elem... mixture, uraniumNatural radioactive element with the atomic number 92. The n... where the U-235 content is below the natural content and thorium.