CoryOndrejka

[Correction] as noted below, this type of reactor -- unlike US Navy ones -- can remain critical even with dropped rods. So a better statement here would be that the operators would immediately notice a reduction in criticality. thus power and heat. Then it's a process/policy question about shutdown timing.

Yup, this is me focusing on US Navy reactors, which is my experience. For them, a rod would already take you sub critical.

The dropped rods already shut down the reactor in the sense that it is sub critical. It still has enough leftover heat that it will continue to produce steam for a while, but it would have been almost instantly clear to the operators what had happened.

I don't know this plant. In navy submarine reactors like the S5W, you have 440V/3-phase power holding the clamp. If you dropped a rod due to a power or clamp malfunction, usually you'd simply shut down the reactor, drop all the rods and mechanically re-engage the clamp. It could take a few hours which isn't fun because no power which probably means submarine/snorkel depth to run the incredibly noisy diesel, but no step was particularly hard or dangerous.

and for the curious who didn't what Chernobyl on HBO, other types of reactors have brief criticality increases on rod insertion, which is somewhere between bad, BAD, and OMFGWTFBBQVERYBAD. In the Chernobyl's case, they entered a criticality region known as "prompt criticality" which is where power doubling can happen at prompt neutron rates (e.g. milliseconds or faster). Very very bad. In the case of pressurized water reactors, this isn't what happens. Every moment of control rod descent is reducing criticality.

Exactly what I would have answered :)

Of course, but that's not what happened here. For a pressurized water reactor, there are maintenance and procedural questions about why the rod was dropped. People will likely get fired over this. But from a standpoint of reactor and radiological safety, this is largely the design operating correctly and prioritizing radiological containment.

Dropped rods are an incident but one that occurs because of pressurized water reactors being very default safe. Controls rods are one way the criticality of a reactor is controlled and US reactors (in general) will go sub critical if even one rod is fully inserted into the core. You will likely have heard of a reactor scram (which goes back to the safety control rod ax man) where in an emergency, all the rods are dropped back into the core, greatly reducing its criticality. In some cases, an interruption of electrical power will cause a rod (or three) to drop accidentally. This is a "dropped rod" incident and will force a reactor shut down because it is now sub critical.

Lots of knock on effects -- sub critical, let heat in the primary loop, less steam and electricity generated in the secondary loop, etc -- but generally a non event that you practice for.

There's no reason this would lead to a radiological event or more significant casualty.

> in fact in one of Jeff Barr's AWS user meetups in Second Life

There's so much about that phrase that makes me smile. Easy to forget that Second Life was also one of the earliest users of AWS, S3 first. Jeff Bezos had personally invested in our 2005 round (a round that made Linden Lab a unicorn before that was a thing) and pointed us at Jeff Barr and the work coming from AWS.

In return, Jeff Barr started hosting AWS meetups in Second Life -- this was the era of lots of groups setting up Second Life outposts, from Jonathan Coulton to Reuters.

The whole “wheelie to jump cars” but “wheelie require touch on analog stick” is a mechanic I’m shocked other action race games never copied. So much fun to press your luck.