Environmental Engineering Reference
In-Depth Information
8.1
The steam generators in VVER-4403.
no generic need for the heating up of the emergency core cooling water. It
was introduced as an example at Rivne NPP in Ukraine, however it seems
unnecessary at Paks NPP in Hungary.
The critical locations when considering fatigue are the welds of the inner
tubes of the control rod drive nozzles.
Steam generator of VVER-440/213 design
The steam generators in VVER-440 are horizontal (see Fig. 8.1). The advan-
tages of the VVER horizontal steam generator design are the high reliabil-
ity, absence of vibrations, no accumulation of sludge at the tube sheet and
ease of access for maintenance. The SG design has a positive impact on
safety as well, for example the design allows reliable natural circulation,
effective gas removal, large water inventory and essential thickness of the
heat-exchange tubes.
The heat-exchange tubes and the steam generator tube headers (col-
lectors) are manufactured from austenitic stainless steel (18% Cr, 10%
Ni stabilized with titanium) in VVERs, instead of the nickel-based alloys
(Alloy 600 and 690) and higher chromium-containing alloys (Alloy 800) as
used in PWRs. The material of the SG heat-exchange tubes in VVER-440
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