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 300

Table 9.6 Distribution of defects in the heat exchanger tubes of steam generator unit № 1 at the Kola
nuclear power plant

Permissible and critical depth and length of defects*, mm

4 years 30 years

Calculated
estimate

Event Criterion

Sv-10GN1MA Sv-10GN1MA

UONI-

13/55

According
to criterion

According to
criterion

13/55

Acerage Average

Corrosion cracking - 3.2 (16) 3.2 (16) 5.5 (27.5) 3.2 (16) 3.2 (16) 5.5 (27.5)

First 15 (75) - - 7 (35) - -

Formation of Corrosion-fatigue

crack growth**

through-wall cracks

less than 3
(less than 15)

Second 12 (60) 10 (50) 10 (50) 2.5 (12.5) 2.5 (12.5)

less than 3
(less than 15)

Third 2.5 (12.5) — — — —

Critical crack
opening***

Large-scale failure — 19 (95) 19 (95) 21.5 (107.5) 14 (70) 14 (70) 17 (85)

*The results for each criterion include: the permissible or critical depth of the defects, and the values in the brackets are the permissible or
critical crack length with defect density taken into account.
**The permissible defect sizes were determined on the basis of corrosion-fatigue growth of defects with corrosion cracking taken into account.
***Critical defect sizes were determined on the basis of the criterion of critical crack opening with corrosion cracking and corrosion-fatigue
growth of defects taken into account.