Development of in-situ mineral exploration methods by means of 252Cf

The neutron induced γ radiation of natural mineral samples has been investigated with high-resolution Ge(Li) diodes both in reactor beam and 252Cf experiments. To test the utility of 252Cf for in-situ exploration, a simulated bore-hole facility for scheelites and a seawater tank for manganese nodules have been used. Sensitivity and precision related to background and calibration problems seem to allow the quantitative determination of small percentages of W, Ti, Ni, Cu, Co, Mn, and Fe in a few minutes. A calibration method is given which is based on internal γ-ray lines only. For an in-situ experiment in 500 m deep water-filled boreholes near Mittersill, Austria, a versatile probe was constructed. Because of the module technique utilized, this probe can be mounted in different arrangements to allow for three experimental modes: XRF, (n,γ), and NAA. (U.S.)