Environmental Engineering Reference
In-Depth Information
instrumentation and control (I&C) systems. These units have a very suc-
cessful operational history and excellent safety features. A comprehensive
lifetime management programme was launched in the very early stages of
operation, and has allowed LTO of the Loviisa units. The Armenian reac-
tor also represents a modifi cation of VVER-440 with an enhanced seismic
capacity. The shut down Units 3 and 4 at Kozloduy NPP, Bulgaria represent
an intermediate type between 230 and 213 series.
It should be noted that, the VVER-440s have certain inherent safety
characteristics that are superior to most modern PWR plants, for example
robust design, large water inventory in the primary system relative to the
reactor power and large volume of the confi nement.
8.2.2 Basic design features of the VVER-1000
The VVER-1000 model exists in several versions. The 'small series' plants
could be considered as pioneers of this model. The VVER-1000/320 is the
large series version of the design. Developed after 1975, VVER-1000/320
type plants are operated in Bulgaria, the Czech Republic, Russia, Ukraine
and China. Modernized versions of VVER-1000 plants are under construc-
tion in fi ve countries (Bulgaria, China, India, Iran and Russia).
In regard to lifetime management, the VVER-1000/320 plants have great-
est practical importance. The 'small series' plants show some specifi c design
features, but the lifetime management practice of these plants does not dif-
fer essentially from the VVER-1000/320 version.
The VVER-1000 is a four loop PWR with horizontal steam generators.
Each loop consists of a hot leg, a horizontal steam generator, a main circu-
lating pump and a cold leg. Main isolating valves on the hot and cold legs of
each loop equip the non-standard VVER-1000 primary loops. The standard
V-320 design and the new clones of the VVER-1000 do not have isolating
valves on the primary loop. A pressurizer is connected to the hot leg of
one of the loops and the spray line to the cold leg. Operating conditions
are
T
hot
=322 ° C,
T
cold
=290 ° C,
p
=15.7 MPa. The reactor, the primary and the
safety systems are all placed within a full pressure, dry, pre-stressed concrete
containment.
The design bases, and also the technical solutions applied, are very similar
to the PWRs operated in Western countries. The safety concerns about the
VVER-1000 plants are discussed in detail in IAEA reports (1996b; 2000).
The main safety concern regarding the VVER-1000 plants lies in the qual-
ity and reliability of the individual equipment, especially the I&C equip-
ment. The plant layout has weaknesses that make the redundant system
parts vulnerable to hazardous systems interactions and common cause fail-
ures by fi res, internal fl oods or external hazards. At all plants, many of these
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