3 ms·
pebble bed reactors. to quote wikipedia which expalins it better than i can; "When the reactor temperature rises, the atoms in the fuel move rapidly, causing
by smegger001 3y ago
pebble bed reactors.
to quote wikipedia which expalins it better than i can;
"When the reactor temperature rises, the atoms in the fuel move rapidly, causing Doppler broadening. The fuel then experiences a wider range of neutron speeds. Uranium-238, which forms the bulk of the uranium, is much more likely to absorb fast or epithermal neutrons at higher temperatures. This reduces the number of neutrons available to cause fission, and reduces power. Doppler broadening therefore creates a negative feedback: as fuel temperature increases, reactor power decreases. All reactors have reactivity feedback mechanisms. The pebble-bed reactor is designed so that this effect is relatively strong, inherent to the design, and does not depend on moving parts. If the rate of fission increases, temperature increase and Doppler broadening reduces the rate of fission. This negative feedback creates passive control of the reaction process."
- FrustratedMonky 3y agoThank You Yes, guess any built in Negative Feedback would be better than defaulting Positive Feedback. Guess someone could still do some bad design to cause some other type of rupture that would expel radioactive material, but much less possible.
- smegger001 3y agoA rupture is unlikely as most pebble bed designs use helium as the coolent. It being a noble gas it won't react chemically, and unlike water cooled designs it doesn't undergo phase change (liquidgas) so no massive pressure build up. And as there is no oxygen fire is unlikely.