Ageing degradation of main components in nuclear power plant Dukovany

The aging problems of the key components of nuclear power plants are outlined in a systematic way, including the ageing factors, ageing mechanisms, their combinations and effects on the integrity of the components, safe operation, and lifetime assessment, and the specific major ageing/damaging mechanisms affecting the key components of the primary and secondary circuits at the Dukovany nuclear power plant are analyzed. The following mechanisms are identified as crucial for the key components: (i) Reactor pressure vessel: beltline region - irradiation embrittlement; nozzle region, main flange, and bolting joints - low-cycle fatigue (LCF). (ii) Reactor internals: core barrel, shroud, etc. - wear, high-cycle fatigue, irradiation embrittlement. (iii) Steam generator: inlet feedwater nozzle - LCF (thermal stratification); other nozzles, primary circuit collectors, flanges and bolting joints - LCF; vessel body - LCF, corrosion; tubes - corrosion; (iv) Pressurizer: nozzles, electrical heaters area - LCF; water level changing - LCF, corrosion; (v) Primary circuit piping: LCF (with thermal stratification for the piping connecting it with the pressurizer); (vi) Secondary circuit piping: steam line - erosion (LCF); feedwater line - erosion-corrosion (LCF). (vii) Heat exchangers - corrosion. (P.A.). 4 tabs