Environmental Engineering Reference
In-Depth Information
localised in a few places (notably on bends and in the fitting zone). In 1994,
experiments started at the U.S. Farley-2 NPP with addition of zinc into the
primary circuit coolant to reduce the intensity of SCC. A few more nuclear
power plants in the U.S. and Germany joined these experiments later. The
largest amount of experience was obtained at the Diablo Canyon nuclear
power plant, where zinc was added during three cycles. It is concluded in
Ref. 125 that the intensity of SCC slightly decreased, but it was stressed
that the results of laboratory studies are contradictory. This type of SCC
may appear in the form of circular cracks. Defects of the primary circuit
in HSG are extremely rare. The PGV-1000 system did not show a single
case of plugging due to these defects. In PGV-440, these defects led to
plugging of several HET (less than 10). They were found in several units,
and not in all SGs. No apparent localisation was observed and no defects
were not found in the bends.
Wear of anti-vibrational
spacing grating
Deformation of U-
shaped bends
Stress corrosion of
bends
Wear of cold filament
ICC and CC on external
surface
TCC in the straight
sections
TCC in the straight
sections
CC in area with max.
stresses in the bend
CC in the seals
Corrosion fatigue
Seal
ICC in lattice area
CC in the
depression
area
ICC and CC in the
lattice area
Distribution of ICC
in thickness of
perforated plate
Deformation in the
area of the perforated
plate
Formation of defects
in perforated plate
Circum-
ferential
cracks in
perforated
plate
Inlet
nozzle
Outlet nozzle
Wear in the
preheated zone
Distribution of ICC in the thickness of the perforated plate
Damage in the slurry
area
Pitting
ICC in slurry
Propagation of CC CC in the circum-
ferential direction
ICC in slurry
ICC - intercrystalline corrosion,
CC - corrosion cracking,
TCC - transcrystalline corrosion
9.1
Scheme of localisation mechanisms for 600MA and 08Cr18Ni10Ti
steels.
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