In situ determination of low-level concentrations of 137Cs in soils

A revision is presented of the peak-valley method for the in situ determination of low-level concentrations of 137Cs in soils in which its vertical distribution is uniform or quasi-exponential, and relaxation coefficients within the range 3.5-15 g/cm2. In tests of soils that satisfied these conditions, the revised method was found to reproduce the real 137Cs concentrations to at least within the same order of magnitude, and with uncertainties of less than 40%. Finally a protocol is proposed to improve in so far as possible the precision of assays of this radionuclide in soils in which its presence is relatively low-of the order of a few kBq/m2.