Environmental Engineering Reference
In-Depth Information
it possible to optimumly solve a number of problems of operational
inspection. The most important features are the definition of inspection
sites and settings, inspection frequency, determination of requirements for
the sensitivity of technical means of inspection, determination of norms of
defects of metal, definition of the level of reliability of equipment after
testing and repair, etc.
Here are two examples of determining the optimum inspection frequency:
for VVER-1000 RPV and the casing of a pressuriser of the VVER-440
reactor.
7.4.5 ISI optimum frequency for VVER RPV
The purpose of design analysis is to determine the optimum inspection
frequency of a cylindrical part of the reactor casing for a design life of 30
years. The probability of failure of the reactor pressure vessel was assessed
by the criterion of the resistance to brittle fracture taking into account
metal embrittlement due to radiation. The income from the operation of the
VVER-1000 reactor in 30 years was taken to be
D
0
= 4 · 10
8
roubles (in
prices of 1983 when the analysis was performed). The inspection costs
for 30 years were defined as the wages of 30 people for 30 years with
overhead costs taken also into account (
Y
i
= 1.8 · 10
7
roubles). The cost
of repairs was assumed to be
Y
r
= 10
Y
i
(assuming that the LBB concept
holds for reactor pressure vessel and complete destruction of the body
will not take place). The ratio of inspection and repair times was
t
r
/t
i
= 10. The analysis was performed for two cases: inspection combined
with scheduled preventive maintenance and refueling; the reactor was
shutdown for inspection.
The analysis results are reported in Fig. 7.18 in which the curves 1 and
2 correspond to the following values:
7. 1 8
Results of determination of the optimum frequency of flaw
inspection of a reactor pressure vessel for the case described by
equation [7.4).
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