On 18/02/2021 12:21, Tim Streater wrote:
On 18 Feb 2021 at 12:03:48 GMT, Steve Walker
wrote:

On 17/02/2021 17:03, michael adams wrote:

In pointing out the "mistakes" that they made Tim Streater is merely reinforcing
the point - of how easy it is, without the benefit of hindsight for people who aren't
particularly stupid to make "mistakes".

Chernobyl was not a mistake, it was known bad design, there was reliance
on operators to avoid a particular operating regime due to that design
constraint, there was no safety system to prevent such operation and
someone chose to carry out an unauthorised test, within that regime,
outside even the test's pre-determined parameters.

My understanding (which is now a bit flaky as it's a while since I read up on
it) was that the operators actually didn't know that the regime they were
moving the reactor to was dangerous. To move it there they had to disable all
the kit designed to prevent them moving it there.

The kit to stop them working there was a chart recorder, at the opposite
end of the control room, no actual hard-wired safety system.

And that operating region would not have been a problem, except for the
physical reactor design, which was known to be defective.

In addition the design of the control rods was bad. The tips of the rods
actuallly did the opposite of what the rod is intended to do. It increased
reactor output instead of shutting it down. By the time they were scramming
the reactor, or trying to, the rod channels had distorted so the rods jammed
part-way-in. That just made it all worse.

Yes, the rods could not be inserted fast enough, so as they started to
go in, they slowed enough neutrons to the speeds required for a
sustained reaction and increased output, just when they had nowhere to
get rid of the heat. That did, as you say, result in distortion that
prevented them being pushed fully in and stopping the reaction.

Again a known problem with the design, that the Soviets simply ignored.