Viewing a single comment thread. View all comments

PHATsakk43 t1_jc3bqm4 wrote

Reply to comment by Hiddencamper in Why were the control rods in the reactor featured in the HBO series 'Chernobyl' (2019) tipped with graphite? by Figorama

I've worked around BWRs but never been an operator at one (my fleet had a two unit station BWR, while the rest were PWRs.)

I stand corrected in that case. Does make perfect sense when you game it out, as you can basically put a shitload of positive reactivity into a BWR.

I have heard of situations similar to Chernobyl at naval plants (all rods out, waiting on xenon decay, below POAH), but again, that was all stories as I only operated new naval plants as well.

4

Hiddencamper t1_jc3czqr wrote

A full power BWR has a void defect around 40% of your total reactivity. When you scram, those voids go away, and you recover all of that reactivity. Voids are dominant in a BWR. The rule of thumb is Doppler 10^-5, moderator temp 10^-4, void coefficient 10^-3. So you always have enough to start back up in a BWR. And actually, especially if it’s a fast restart, more xenon helps a lot with getting to target rod pattern as it’s one of the things that impacts thermal limits and PCIOMR.

5