Check out
CDEX's detection technology, base on UV and X-ray fluorescence.
Full Disclosure: I used to work there, but quit because my boss was an ass. However, the tech does work. Amazingly, (or not so, depending on your familiarity with the physics of UV-fluorescence) it does. Scanning solids was a little more difficult, and actually scanning liquids is much easier.
They had an man-portable X-ray mine detector. The downside was that the operator got serious dosage of X-rays.