> Overall things are rarely as clear cut as they might appear at first glan=
ce.
> If you want to give the construction crew some flexibility for the sake o=
f
> efficiency, you have to accept a certain number of failures like the Kans=
as
> City walkway collapse.

In that case overloading a nut by a factor of two (more or less)
killed a number of people.
I'd feel that less than a factor of two over maximum possible loading
is excessively low for a walkway - that's the sort of margins that you
go to space on. And, when you DO go to space on a 1.5:1 safety margin
(or 1.2:1 in some cases) , you find people doing up nuts with a force
calibrated certified traceable nut driver, counting the turns and
recording them in a log.

In my Comet example the addition of a single pop-rivet (in any one
instance) killed an aircraft full of people at a time.

In the case of a nuclear accident people have a different attitude to
the fundamental nature of the hazard which MIGHT be released if the
pipe is moved, nut substituted, rivet added or whatever. Those who
want to bravely press ahead with such projects discount the "stupid
illogical" aversion to things like cancer and mutagenesis. After all
dealing with Thalidomide and nuclear reactor accidents and Bhopal
events and ... is  what liability insurance is for, isn't it.

Bhopal is probably quite an apposite example -

             http://en.wikipedia.org/wiki/Bhopal_disaster

it is in the news again at present, with 'victims' still proclaiming
their victimhood (those who are still alive) and those who they
believe to be responsible still demonstrating that they don't believe
they are. The disaster occurred in December 1984. Litigation is
ongoing. In June THIS YEAR 8 defendants were found guilty of whatever
in the Manhattan District Court (and an Indian one) and sentenced to
the maximum sentence allowed by law - 2 years imprisonment and a $2000
fine. (On of the 8 is beyond caring as he's dead already). As "the
system" has taken TWENTY SIX YEARS to obtain a conviction and legal
matters are not yet settled, it is possible  that most involved  will
be dead before justice considers itself  to be done.The incident
killed 3000 / 4000 / 15000 people (choose one from available data).
500,000 people were injured - or more, or less.

This system contained 40 + tons of a horribly dangerous chemical. If
it had escaped and/or had had water added it could cause a vast number
of deaths and injuries. It did, it was, it did. Water got into the
tank due to [[insert pet opinion here]]. May have been bad
maintenance, carelessness, human error, sabotage ... .

Quoting:
Factors leading to the magnitude of the gas leak include:

Storing MIC in large tanks and filling beyond recommended levels
Poor maintenance after the plant ceased MIC production at the end of 1984
Failure of several safety systems (due to poor maintenance)
Safety systems being switched off to save money=97including the MIC tank
refrigeration system which could have mitigated the disaster severity

Overall its an apt enough metaphor of how a potentially horrifically
dangerous system which was able to be safe enough to be used in a
densely populated area under proper conditions but also capable of
killing and injuring many, was 'allowed" to approach its worst case
result.

Anyone wishing to demonstrate that this is NOT a good metaphor and
case study for nuclear safety probably should look at their
protestations from the viewpoint that they will be selling their ideas
to.  It's easy to be so sure of your position as to fail to see the
other point of view. That works both ways in this and many other
situations - but the people on one side tend to have profit as their
bottom line and the people on the other the lives of their families
and themselves. That's not meant to 'slang' profit as a driver - just
note that it influences how things are seen.

If told that there under the bold new deregulated lean mean efficient
low cost construction regime  is a chance of a Bhopal like event for
you and your family, but involving radioactive by products, BUT that
the prospect is very small, and that actuaries have signed off on it,
and that they are fully able to compensate you, or your estate, in the
most unlikely event of something going wrong, who will be happy to
live on their boundary? James is one who would, he's said before now.
So too the residents of Sellafield apparently :-(. Rather they than I,
I'm afraid.


 http://en.wikipedia.org/wiki/Bhopal_disaster

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