Materials management strategies for VVER reactors - Materials' Ageing and Degradation in Light Water Reactors - page 299

Table 8.7 Attributes for the defi nition of commodity groups

Safety classifi cation Type of SSC Medium Material

Safety Class 1
Safety Class 2
Safety Class 3

Valve body
Pump body
Pipe and pipe
elements
Heat exchanger
Tank

Borated water
Prepared water
River/sea water

Stainless steel
Cast stainless steel
Carbon steel

Non-safety class,
failure of which may
inhibit intended
safety function

Steam, gas-steam
mixture
Acid or alkali
Oil, other

The pipelines, pipe elements (elbows, T-pieces), valves and heat exchang-
ers can be grouped into commodity groups according to type, material and
working environment. The SCs within a group have the same degradation
mechanism and approximately the same operational and maintenance
history. It is very reasonable to develop specifi c ageing management pro-
grammes addressing the ageing of commodity groups. The defi nition of the
commodity groups is decided by applying the attributes given in Table 8.7 in
all reasonable combinations.

Ageing management peculiarities of the VVER-440/213 plants

A peculiarity of the VVER-440/213 design is the extremely large number
(over one hundred thousand) of safety-classifi ed SSCs because of the design
features and methodology of safety classifi cation.
After screening out the active and short-lived systems from the total
safety-classifi ed SSCs, approximately 38 000 mechanical, 6500 electrical and
2000 structural SCs have been identifi ed to be in scope at the plant in Paks,
Hungary.
Ageing management of mechanical commodities might be ensured
approximately by nine vessel specifi c, nine pump-specifi c, 14 valve-specifi c,
22 heat-exchanger-specifi c, 15 piping specifi c, nine fi lter-specifi c programmes.
There are also 15 special components requiring individual AMP. The num-
ber of structural commodities exceeds 25. The AMPs and their hierarchical
structure is plant specifi c, demonstrating that Paks NNP practise an adapta-
tion of best international practice to VVER-440/213 instead of a copy-paste
approach. At the same time, the Paks NPP is utilizing the ageing experi-
ence of other plants and elements of an adequate ageing management pro-
gramme are in line with international practice.
The specifi c approach practicable in the case of the VVER-440/213 plants
can be shown in the example of ageing management of civil structures.
The VVER-440/213 design differs very much from the usual architecture
of PWRs. In the example of the Paks NPP, practically all buildings, earth

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