Environmental Engineering Reference
In-Depth Information
unit 2 of the Balakovo NPP. Due to the positive experience with using this
technology at the Balakovo NPP and increasing relevance of the problem of
ensuring the integrity of the steam generator tubes in other plants, it became
necessary to generalise the experience obtained at the Balakovo NPP and
apply it to all nuclear power units with VVER-440 and VVER-1000 reactors
with damaged steam generator tubes.
This work was done in 2003 and resulted in a guidance document RD
EO-0552-2004 'Guidelines on the application of system methodology to
ensure the integrity of steam generator heat exchanger tubes of NPP with
VVER-440 and VVER-1000 reactors (hereafter guidelines). In 2004, the
guidelines were adopted by all nuclear power plants with VVER reactors
for experimental use until 2007 inclusive.
In fact, the guidelines were adopted only for those units of nuclear
power plants which contained a steam generator with damaged tubes. There
were six such units in Russia. In one unit, the guidelines were not used for
organisational reasons.
Four inventions were made in developing the system technology to
ensure the integrity of the pipes and are protected by patents [145-148].
These patents form the basis of RD EO-0552-2004.
Results of application of the guidelines
The most severe consequences of unreliable work of steam generator tubes
are associated with the need for an unscheduled shutdown of the unit to
eliminate leaks between circuits. Thus, one of the main objectives of the
guidelines is to ensure the reliability of the steam generator tubes on the
basis of the criterion of resistance to the formation of leaks in the circuits
(primary-secondary leakage) during operation (with the unit at power) or,
in other words, avoiding unplanned shutdowns of the units due to leaks un
the circuits. The above problem can be solved with high efficiency through
by the application of the system technology prescribed by the guidelines.
In all cases, the operation of the steam generator tube bundles of these
units after the adoption of the guidelines was successful, with no unplanned
shutdowns due to unacceptable leakage from the primary to secondary
circuits.
Figure 9.36 shows the change in the number of unplanned shutdowns
of the units before the guidelines were adopted and after that. The Figure
shows that all the units where the guidelines were adopted did not have
any unplanned shutdowns (curves 1, 2, 4 and 5). The exception is one unit
on which the guidelines were not adopted for a number of organisational
reasons (curve 3). On this unit there were two unplanned shutdown (curve
3) during this period.
An unscheduled shutdown occurred on unit 3 of the Novovoronezh
nuclear power plant in 2008 and was associated with the termination of
the use of the guidelines for organisational reasons during the planned
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