Materials management strategies for VVER reactors - Materials' Ageing and Degradation in Light Water Reactors - page 298

Table 8.6 Degradation mechanisms which an AMP may address

Low-cycle fatigue Thermal ageing

Irradiation damage Stress corrosion

Boric acid corrosion Wear

Local corrosion General corrosion

Irradiation-assisted stress corrosion Loosening

Swelling High-cycle fatigue

Thermal stratifi cation fatigue Erosion

Erosion-corrosion Microbiological corrosion

Water hammer Groundwater corrosion

Deposition

given structure or component and plant lifetime limiting character of the
given ageing mechanisms.

AMPs addressing a degradation mechanism

Some AMPs are based around addressing a particular degradation mecha-
nism, examples of which are shown in Table 8.6.

Structure- or component-oriented AMP

Applying the graded approach, the SCs can be separated into two
categories:

1 Highly important from a safety point of view, items with complex fea-

tures and ageing mechanisms.

2 Items which have the same type, safety class, identical design features,

materials, operating circumstances and dominating ageing mechanism
could be grouped into commodity groups and for each commodity group
a designated AMP can be implemented, for example pipelines, pipe ele-
ments, valves, heat exchangers, etc.

￿ ￿ ￿ ￿ ￿ ￿

The highly important SCs like the reactor pressure vessel together with
internals or components of main circulating loop (SCs of Safety Class 1 and
some SCs of Class 2) can have dedicated, individual AMPs, for example:

￿ Reactor pressure vessels

￿ Steam generators

￿ Reactor pressure vessel internals

￿ Pressurizers

￿ Main circulation pipeline

￿ Main coolant pumps

￿ Main gate valves.