Today I visited Utah’s TRIGA: a nuclear reactor located in the building where I’ve had an office for about nine years. I’ve had a low-grade fascination with these devices since reading about them many years ago in one of Freeman Dyson’s books. Unlike powerplant reactors, which rely on elaborate safety systems, the TRIGA series is fueled by uranium zirconium hydride, “which has a large, prompt negative thermal coefficient of reactivity,” according to Wikipedia. So, as it heats up, the reaction is damped, making any sort of meltdown highly unlikely. This kind of built-in safety is quite elegant, and — as a specialist in embedded software — makes me far more comfortable than would an engineered system.
Ben, a PhD student in nuclear engineering, showed me around and answered lots of questions. I even got to borrow a dosimeter and look down into the core. The coolest part — and this is something I’ve wanted to see for a long time — was the blue glow of Cherenkov radiation: light caused by neutrons escaping the core faster than the speed of light in water. It was also interesting to see ripples on the surface of the water, caused by convection as the reactor dumped heat into the pool. Although almost no radiation escapes the pool, it was still nice to see a 0.0 reading on the dosimeter on exit (not sure what the units were, perhaps millirems).