Environmental Engineering Reference
In-Depth Information
9
Using probabilistic methods
for solving the problem of ensuring leak
tightness of heat exchanger tubes of nuclear
power plant steam generators
The problem of the integrity of heat exchanger tubes (HET) of steam
generators (SG) for the above-described probabilistic methods is of
considerable interest because:
- there are a number of similar elements; for example, the number of
HETs in a VVER-1000 reactor is 44 000;
- there is a large amount of damage, for example, the number of
damaged HETs reaches hundreds and thousands of tubes;
- the dynamics of damage is very high and the effectiveness of measures
taken to ensure integrity becomes noticeable very quickly (within a few
days to several years of operation);
However, the large amount of statistical material and its rapid change
makes it possible to determine the effectiveness of an approach.
This chapter provides three examples of practical application of
probabilistic methods:
- Monte Carlo method (section 9.2);
- method based on the binomial distribution law (section 9.3);
- a generalised method that takes into account the residual defects
(section 9.4).
9.1 Ensuring the leak tightness of tubes of
vertical and horizontal steam generators
Nuclear power plants used steam generators (SG) of fundamentally different
designs: horizontal (HSG) - in Russian projects, vertical (VSG) - in Western
countries, the USA, Japan, Korea and in other countries. These designs have
evolved considerably over many years and in most cases the evolution was
stimulated by problems arising during operation. One major problem was the
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