Regional Basic Professional Training Course in Korea

Regional Basic Professional Training Course (BPTC) on Nuclear Safety
content of copper and phosphor that show the relation between neutron fluency and a
parameter that describes the state of embrittlement. With regard to the design of the
power plant, the material chosen, and the expected loads, an end of life fluency is
estimated. During the design it has to be shown by calculations, that if the pressure vessel
wall reaches the end of life fluency, the state of embrittlement has still a safety gap to a
critical embrittlement. The calculations use the standard curves and have to include worst
‐case loads from incidents.
That the material fits the standard curve has to be verified by a surveillance program.
From the original material of the reactor pressure vessel wall and core weld specimens
for tensile test and charpy‐V test are manufactured. One part of the specimens is tested
directly; two other parts are put in the pressure vessel together with monitors for
temperature and neutron fluency. The position chosen is near the core where the neutron
flux density is higher than in the position of the wall. In this way the specimens reach the
end of life fluency much earlier then the pressure vessel wall.
When the specimens reach half the end of life fluency and the end of life fluency
respectively they were removed from the reactor pressure vessel to be tested. The change
of the material parameters depending on the fluency is a measure for the embrittlement.
12.4.4. In‐service inspection
For mechanical components, the aim of the in‐service inspection is to verify the integrity
of barriers. This is done by proving the absence of defects in the walls of pipes and
vessels. The extent of the examination should consider the design of the components, the
material properties, the fabrication method and the experience of past examinations. The
methods used are:
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