Environmental Engineering Reference
In-Depth Information
Welded joint: 17
Parent metal: 10
Flange seal: 2
1.26
Location of damage to the pipelines of the primary circuit
of NPP with PWR reactors.
based accident was applied in the design of NPP which is based on the
assumption that the main pipeline of the NPP fails extensively during
service plant, i.e. it is assumed that the probability of failure of the pipeline
is equation to 1
3, etc.
.
It is obvious that underestimation of the unreliability of passive elements
may result in lower estimates of the risk indicators NPP, and if the data on
the reliability of passive components are overestimated the PSA will lead
to overly conservative safety requirements.
Quantitative data on the probability of failure of equipment and pipelines
are needed not only for PSA. These data are of interest also for other tasks.
The limiting states of equipment and pipelines of the NPP are determined
by the criteria of strength, criteria of destruction, operating conditions,
and the state of the structure. Calculation of the maximum permitted
stress makes it possible to solve only one part of the problem of rational
selection of sizes of installations, namely: to determine the conditions
under which the installation should fail. The second, equally important
part of the problem is the question how to ensure that these conditions do
not occur, i.e. provide sufficient safety of equipment for the entire period
of its operation. This issue was solved, until recently, by introducing
more or less arbitrary factors - safety factors. A number of studies was
published in recent decades in which it was attempted to theoretically
develop more or less accurate methods for determining the safety factors
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