OAK RIDGE, Tenn., Oct. 17, 1996 -- A nonintrusive inspection technique that probes samples with neutrons can analyze the content of coal and cement and detect explosives and drugs. It also shows promise for locating plastic and wooden land mines.
Developed by The Department of Energy's Oak Ridge National Laboratory (ORNL) and Western Kentucky University (WKU) researchers, the pulsed fast-thermal neutron analysis system bombards a sample with pulses of fast and slow, or thermal, neutrons. Fast neutrons collide with some atoms, triggering the release of gamma rays. Between pulses, thermal neutrons are captured by other atoms, causing emission of gamma rays. Detectors measure energies of the combined gamma rays, which are unique for each element.
Gamma-ray fingerprints permit accurate determinations of concentrations of hydrogen, carbon, oxygen, nitrogen, chlorine, sulfur, and other elements in samples. Using both fast and slow neutrons allows detection of a greater number of common elements. For example, carbon can be readily identified using fast, but not slow, neutrons; the reverse is true for chlorine. The technique's power lies in its ability to measure elemental content, on-line, during industrial operations.
Negotiations are under way to install a prototype pulsed-neutron generator system at an operating coal-fired power plant. "The coal industry has a strong need for this on-line analytical capability," says Frederick J. Schultz, co-developer of the new technique. "To accurately price coal or blend it to make it cleaner, it helps to know the sulfur content. To operate a coal power plant as efficiently as possible, it is important to know how much carbon and oxygen are in the coal. To reduce fouling and slagging in boilers, it is wise to burn coal low in chlorine."
Because chlorine is a "poison" in crystallization of cement, manufacturers of cement have also expressed an interest in on-line analytical capability for quality and process control.
WKU researchers led by George Vourvopoulos have demonstrated the techique's ability to distinguish between actual and mock explosives in munitions shells in military proving grounds to speed up environmental restoration and to inspect pallets of rice, sugar, or coffee for cocaine and other contraband materials. ORNL researchers are investigating whether the technique can also guide the safe removal of land mines.
This research is funded by DOE's Experimental Program to Stimulate Competitive Research.
ORNL, one of DOE's multiprogram research laboratories, is managed by Lockheed Martin Energy Research Corporation. # # # Written by Carolyn Krause