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 321

Start of operation See comment 3

Operating time, years

Comment. 1. Total application time of the guidelines - more than 100 SGs/year;

2. Curve 2 - the guidelines were not used; 3. Failure because use of the

guidelines was interrupted.

9.36 Dynamics of unscheduled shutdowns prior to and after
applying RD EO-0552-2004: 1) Balakovo nuclear power plant unit
2; 2) Kalinin nuclear power plant, unit 1 (the guidelines were not
used ); 3) Novovoronezh nuclear power plant, unit 3: 4) Novovoronezh
nuclear power plant, unit 4: 5) Kola nuclear power plant, units 1
and 2.

shutdown in 2007 for routine maintenance. This case illustrates that all
the guidelines should be used with high care, otherwise the process of
unplanned degradation of steam generator tubes would resume.

Other results obtained during the development and application of system
technology to ensure the integrity of steam generator tubes
Termination of unexpected process of stress corrosion cracking of steam
generator tubes

￿ ￿ ￿ ￿ ￿

Figure 9.37 shows the dynamics of growth in the number of leaky pipes in
a steam generator with damaged pipes. It is seen that before applying the
guidelines the number of leaky pipes was increasing with acceleration. After
applying the guidelines, the rate of growth in the number of leaky pipes fell
almost to zero.

Guaranteed elimination of the possibility of sudden pipe rupture with a
large leak of coolant during operation

Excluding the possibility of sudden pipe rupture with a large leak of coolant
during operation is of great importance for the safety of NPP as this may be