Use of neutron-capture prompt gamma-ray activation analysis in environmental and energy research

Reactor-based neutron-capture prompt γ-ray activation analysis (PGAA) can be used for several trace elements (e.g., B, Cd, Sm, Gd), but it is mainly a major and minor element method. Among the 15 to 20 elements that can be determined in a particular type of sample, the major elements C, H, N and S can usually be measured in coals and biological samples and the elements of geochemical interest, Na, Al, Si, K, Ca, Ti, Fe and others in rocks, coal and other crustal samples. When used along with instrumental neutron activation analysis (INAA), the combined techniques can be used to analyze for 40 to 50 elements in crustal samples. Suggestions for further development of reactor-based PGAA include: the need to reduce low-energy γ-ray backgrounds for observations of species having intense lines only at low energy, more development of biological and special materials applications, the use of beam choppers to look for very short-lived species, and demonstrations of analyses of samples too large, precious or hazardous to be irradiated inside reactors. The greatest potential for applications of PGAA may be in the use of systems detached from reactors, i.e., those using 252Cf or other isotopic neutron sources. This may be the only method for elemental analyses of large, inhomogeneous process streams in various industries, power plants, etc. Fluxes comparable to those of external beams from reactors are feasible with the use of mg quantitites of 252Cf. Practical systems for use on coal have been developed. Many other applications would be possible: field prospecting for valuable ore deposits, studies of nutrients in soil and plants, in situ measurements in remote locations such as planetary surfaces, mines, bore holes, etc