Using probabilistic methods for solving the problem of ensuring leak tightness of heat exchanger tubes of nuclear power plant steam generators - Probabilistic Safety Assessment for Optimum Nuclear Power Plant Life Management (PLiM) - page 308

1) Branching with corrosion traces

1) Non-conditioned
metal

2) Size, up to continuous
3) Orientation, majority along HET
axis

4) Orientation,majority across

5) Propagate from HET surface
6) At other nuclear plants only
when WCR disrupted
7) Located in middle and upper
rows
8) Length up to 8 mm on outer
surface
9) Cracks containS, Cl and Na

1. Very high thermo-
mechanical stresses

3) Disrupted WCR,
chlorides

10) Branching with strong
corrosion traces
11) Orientation along HET axis
12) Dimensions: depth to
continuous, length to 8 mm
13) Situated between spacing
lattices
14) Medium rows of HET
15) Propagate from HET surface

4) Disrupted WCR,
alkali metal ions

5) Disrupted WCR,
pH

6) Salt deposits

16) From secondary circuit
17) Depth up to continuous
18) Depth to diameter ratio ~0.5
19) Ellipsoidal cracks detected
20) Under Cu deposits
21) Lower rows mainly in the
sludge zone

7) Condensate-feed
circuit, suction

￿ ￿ ￿ ￿ ￿

8) Condensate-feed
circuit, corrosion
products

Stage 2. Hypotheses

22) Density
23) Circumference - uniform
24) Below lattices - no;
mostly between

Stage 1. Main features of damage