h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Here's some more general reactor trivia for anyone who might be interested:

Reactor power is controlled via multiple "control rods" that are inserted into the core. The control rods are made of a neutron-absorbant material such as boron carbide. Neutrons being absorbed by the control rod means less neutrons available for fission events, and thus less power. Therefore, lowering rods into the core causes neutron absorption and lower power, and raising rods means the opposite.

United States reactors operate using something called a Prompt Negative Temperature Coefficient (PNTC), which essentially means that as the reactor goes up in power, it becomes less efficient. Therefore, the operator needs to withdraw more and more of the control rod at higher powers in order to increase net reactor power. This is largely a safety mechanism. If left unattended, a powered-up US reactor will gradually decrease in power.

Russian reactors use a Prompt Positive Temperature Coefficient (PPTC), which means that the reactor becomes more efficient as power increases. Drawing control rods therefore becomes a delicate business, and if left alone, a powered-up reactor will increase in power, with potentially catastrophic effects. This system sacrifices safety for efficiency.

There's a lot to be said here. I've worked at a nuclear research reactor for three years now; power at research reactors is (generally) extremely low and no power is produced, meaning no water boiling, no turbine, no steam etc., but the basic principles are the same.

**Frobozz Node #34-C**