re: #124 goddamnedfrank

AFAIK our only totally graphite moderated and water cooled design was the B-Reactor at Hanford. Later designs, even where graphite was the primary moderator, utilized water as both as an additional moderator and coolant, creating a negative void coefficient that helped prevent power excursions. The two biggest design flaws of the RBMK design at Chernobyl were:

A.) The positive void coefficient, meaning that as water turned to steam inside the reactor chamber it stopped absorbing neutrons which let more neutrons be slowed by the graphite which lead to more fission leading to more neutrons + more heat -> more steam -> wash, rinse, explode. This was why the automated systems that the crew disabled for the test and set minimum safe number of control rods that they idiotically removed in an effort to salvage the test were so crucial.

B.) They put graphite extensions on the bottoms of the boron absorber rods and those rods moved through water filled columns. So when the SCRAM was initiated those graphite extensions first displaced neutron absorbing water with neutron moderating graphite, which initially caused an increase in reactivity before the boron slid into position and could stop it.

Even worse, they didn’t tell the plant operators any of this shit, so they had no idea that the fucking nuclear reactor they were in charge of had several massively counter-intuitive behaviors baked in.

Yep. Dyatlov is on record saying that the RBMK-1000 shouldn’t have been in service, that had he known about its misbehaviours, he hadn’t done the safety test to begin with, or SCRAMmed at the tiniest sign of instability. Them keeping the incidents at Ignalina low-key is one of the reasons the Chernobyl staff didn’t know.

Also, recent research suggests that the cause of one of the explosions in Unit IV was not steam, but a “fizzle”, i.e. an incomplete nuclear detonation. That’s one thing which Western designs have several safety margins against in their designs.