On 25/02/2021 21:00, newshound wrote:
On 18/02/2021 13:06, jon wrote:
On Thu, 18 Feb 2021 12:39:22 +0000, Steve Walker wrote:

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:

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


I don't like the term "bad design". I'm not sure it is possible to
design and build anything useful that does not have some limitation The operators got confused and took it outside its clearly defined
permissible envelope. Rather like putting a 747 into a vertical dive,
and then trying to pull out at 600 knots. When our experts looked at the
RBMK in the 1970's they decided it would not have been licensable in the
UK presumably because of the lack of interlocks to prevent it being
taken beyond the safe envelope. But as we have seen recently with the
Max 8, safety system design can be cocked up too.

No. It was not the lack of interlocks. It was the basic design of the
reactor. It is nothing like Western reactors - part of it being designed
to use hundreds and hundreds of small pipes, able to be welded by pretty
well any old welder, instead of properly coded welders for the job. The
design was known to a) increase power output as the control rods were
inserted, b) take too long to insert the rods and c) a single failure
could cause damage to nearby channels, defeating the concept of being
safe with two failures (Western licensing would have required more anyway).

Plus the Soviet Union did not even require any containment around the
reactor.

They knew it was unsafe, but did nothing about it. After Chernobyl, they
did make some changes to improve safety - making the basic design safer.
Changes that they could have done years earlier, but no-one dared to
speak out against higher power.

UK companies in the nuclear industry have a policy that anyone - no
matter if they a Nuclear Safety Engineer or a humble labourer, can stop
any job at any time if they think that there is danger ... even if that
job is nothing to do with them, but they are just passing by and see
something.

Also, it wasn't an unauthorised test; but it had not been reviewed as
carefully as it would have been in the UK.

At the time it took place, it was not authorised at higher levels IIRC,
only locally and the test began despite being far outside the parameters
stated as required for the test and well into the danger zone - so it
*was* unauthorised.

As an example of the differences here. To change a single set-point
requires access via a password or key protected control; which in turn
requires documentation declaring what change is proposed, the reason for
it, potential consequences, etc., which is then assessed by multiple
disciplines onsite, in offsite design offices and possibly by the ONR to
ascertain the effects of the change. Only then would it be authorised
and actioned - with a full update of all the existing, relevant
documentation. Then when changed, the change would need to be observed,
checked and recorded.

60 years ago, things would have been different, but these days
everything is *very* tightly controlled.