Environmental Engineering Reference
In-Depth Information
P
f
5.59
Variation of
n
K
1
c
at
n
σ
= 2.
Table 5.11
Variation of the structural properties of steels (ageing) during
operation of nuclear power plants
Mechanical
properties
Crack
resistance
Microstruc-
ture
Chemical
compound
Steel
Component of nuclear plant
St20, 22K
Main pipeline of RBMK reactor
+
+
+
+
10GN2
10E
Steam line and casing of VVER-
1000 reactor
+
+
+
+
0Kh18N
10E
Main pipeline of VVER-40 reactor
+
+
+
+
48TS
15Kh2N
MFA
High-pressure casing of VVER-
440 and VVER-1000 reactors
+
+
+
+
the normative curve for cyclic crack resistance specified in the document
in Ref. 104.
The experimental results lie below the normative values of cyclic crack
resistance which indicates that long-term operation has no significant effect
on the cyclic crack resistance of the pipes.
This conclusion can also be fully attributed to the static crack resistance
of austenitic steel pipelines. As shown in Ref. 9, the limiting condition
of these pipes with cracks determined by the 'plastic hinge' mechanism
which is controlled by yield strength. It was already shown that long-term
operation has no significant effect on the mechanical properties, therefore,
the static fracture toughness of pipelines made of 08Cr18Ni12Ti steel
Fatigue of specimens of MCP of block 1 of the Novovoronezh NPP after
prolonged use was invsetigated in Ref. 100. The fatigue characteristics
were higher than the minimum values established by the norms.
4
Thus, the
endurance limit according to the test results is equal to 246 MPa
11
, which is
higher than the normative values for steel 08Cr18Ni12Ti equal to 220 MPa.
4
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