Wow you got you some markov chains, Monte Carlo, Gamma Radiation, what a fun dissertation. I especially liked the bit about how the NaI detector is not a sphere and sensitivity depends on incident angle. I would never have thought of that. You even did a trip to ORNL, how cool is that!

Walking around with a Giger counter while wearing a hazmat suit seems like fun too, but I suppose it would freak people out. This seems like a much more stealthily way to locate a lost source.

Actually, someone walking around with a detector and us localizing in real time is what the current state is. There's been a lot of development since this dissertation to let it run in real time, and to integrate with tactical radiation detectors that the military/police/civil defense teams tend to use. Unfortunately that's mostly unpublished work at present.