Root Cause Analysis of the Power Generation Capability Decrease After the 5^th Refuelling Outage of Ling Ao 2

The power generation capability of Unit 2 of Ling Ao Nuclear Power Plant has been decreased about 6MW after its fifth refueling outage in 2008. This paper investigates the activities which may influence the unit capability in the outage, compares the related parameters before and after the outage, and then analyzes its root causes. From the root cause analysis, it can be found that the replacement of orifices which measure the feedwater flow was the main reason for the capability decrease. Finally, some modification measurements have been provided to recover the unit capability.