True-coincidence correction when using an LEPD for the determination of the lanthanides in the environment via k0-based INAA.

As part of a recent study on the environmental effects caused by the operation of a coal-fired power station at Sines, Portugal, k0-based instrumental neutron activation analysis (INAA) was used for the determination of the lanthanides (and also of tantalum and uranium) in plant leaves and lichens. In view of the accuracy and sensitivity of the determinations, it was advantageous to make use of a low-energy photon detector (LEPD). To begin with, in the present article, a survey is given of the former developments leading to user-friendly procedures for detection efficiency calibration of the LEPD and for correction for true-coincidence (cascade summing) effects. As a continuation of this, computer coincidence correction factors are now tabulated for the relevant low-energetic gamma-rays of the analytically interesting lanthanide, tantalum, and uranium radionuclides. Also the 140.5-keV line of 99Mo/99mTc is included, molybdenum being the comparator chosen when counting using an LEPD.