Environmental Engineering Reference
In-Depth Information
• plugging all leaky pipes detected by other methods (ECT, PHI, etc.)
in SPM;
• control of operating modes of tube bundles on SG1, SG3, SG4 of unit
2 of the Balakovo NPP after SPM 96-97 until the next SPM.
From these data it also follows that the safe operation of SG1, SG3, and
SG4 can be ensured also up to the end of the design life taking into account
the reference inspections carried out in subsequent SPM and implementation
of appropriate measures arising from the results of these inspections.
The safety conditions must be determined more accurately on the basis
of the operation results and SPM. HT pressure p HT1 = 24.6 MPa can be
reduced (to 18-20 MPa), if the conditions precluding sudden steam pipe
rupture are accepted.
The above-described technology used to define the residual life,
reliability and safe operation and development on its basis of appropriate
technical measures proved to be highly efficient when applied to the HETs
of the steam generator on unit No. 2 of the Balakovo NPP.
However, given the large number of similar structural elements - each
steam generator has 11 000 HETs, it is possible to check the accuracy
of probability forecasts. So according to the prediction [150] made in
SPM 96, 2-3 HETs should become depressurised in the section of the steam
generator with the highest degree of damage during a single campaign.In
fact, inspection of integrity, carried out in SPM 98, showed that only two
tubes were depressurised.
The steam generators of unit No. 2 of the Balakovo NPP after SPM
98 worked for another life cycle in 1999 and were then replaced by new
ones because of the large number of plugged tubes and not due to tube
reliability reasons.
In conclusion, it should be noted that the positive results obtained on
unit No. 2 of the Balakovo NPP using a system technology for assessment
and ensuring the required operating life, reliability and safety have been
also used in other nuclear power plants since 2003, including the RD EO-
0552-2004.
The experience obtained in the framework of these studies is summarised
in Ref. 137.
￿ ￿ ￿ ￿ ￿
9.5 Guidance Document RD EO-0552-2004 'Guide-
lines on the application of system methodol-
ogy to ensure the integrity of steam generator
heat exchanger tubes of NPP with VVER-440 and
VVER-1000 reactors' 
The technology to ensure the integrity of the steam generator tubes on
the basis of the system concept of strength safety (hereinafter - system
technology) was developed in 1996-1997 to ensure reliable operation of
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