Probabilistic Safety Criteria and Core Degradation Mechanism

摘要

As nuclear power plant age, degradation of structure, systems and components can be expected to occur. The understanding of the effect of the age related degradation is important to ensure safe operation of the nuclear power plant. The pressure tubes in CANDU reactors are critical components and its failure has consequences of concern. These cold worked Zr-2.5% Nb pressure tubes may degrade due to ageing mechanisms like creep and delayed hydride cracking. It is important to periodically monitor the serviceability these tubes over the service life. This paper discusses the estimation of the allowable conditional failure probability of the pressure tubes for meeting the risk informed regulation criteria of the US-NRC regulatory guide RG. 1.174.