Scope of ageing management

The scope of the review covers the following SSCs:

• SCs relevant for safety — Classes 1, 2 and 3

• those non-safety SCs which can jeopardize the safety functions.

The non-safety-related SSCs which can jeopardize the environment (oil pipelines and tanks, containers for storing different chemical substances)

Table 8.3 Concept for ensuring long-term operation

Ensuring

Safety functions/ Production/ Functioning of

performance economy the operating

organization

Review, assessment and amendment of the plant programmes Reconstitution of the TLAAs

— All systems, structures and components (SSCs) have to

be covered by certain plant programme(s), for example preventive/corrective maintenance, ageing management, scheduled replacement

— All ageing mechanisms have to be considered

— All plant activities have to be considered, that is the

routine activities should be integrated with those specific to LTO

— Synergies have to be utilized PLiM Programme for LTO [14] [15]

• Temperature: in the case of organic materials, commonly used as insu­lation and/or sealing parts of components, high temperature is the main factor of ageing

• Radiation: inside the containment, y-rays are mainly taken into account. The most sensitive material is PVC and the least sensitive is XLPE. Therefore, PVC insulated cables are not used for safety-related func­tions inside the containment. Neutron radiation is be considered only for copper parts located next to the reactor, where these parts may be activated

• Pressure changes: extreme pressure changes may occur in loss-of-cool — ant conditions and may endanger the proper operation of systems and components by affecting the sealing materials of some equipment

• Humidity: humidity in the containment may change for several reasons, for example leakage or pipe breakage, unintended operation of fire extinguishing appliances. Penetrating humidity may result in malfunc­tion of electrical and I&C equipment.

• Steam: under LOCA conditions, steam may condense on the surface of equipment causing rapid temperature rise and it may also penetrate into the equipment.

• Chemicals: the applied chemicals (boric acid, hydrazine, etc.) may pene­trate into seals of electrical equipment, reducing dielectric strength, and causing corrosion.

• Seismic events: seismic effects and vibration may degrade the func­tionality of certain electrical and I&C equipment (relays, transmitters, motors, etc.)

Identification of the ageing mechanisms for civil structures and structural

components is discussed by Katona et al. (2009a). Examples are given in

Table 8.5 on the basis of Hungarian regulatory guide No. 1.26.