多点定点配管減肉計測によるベイズ推定を用いた配管破損確率定量評価および損傷リスク評価の検討

抄録

If a piping system in the reactor coolant circulation system of a nuclear power plant were to fail, the reactor would lose its cooling function, and radioactive materials would be discharged to the outside. In particular, the drainage plant of the Fukushima Daiichi NPP has many unknown parameters, such as the action of external forces and the state of the internal fluid, and there is uncertainty about the state of wall thinning progress and lifetime consumption status. Therefore, it is significant to control the wall thickness appropriately, and remote monitoring is desirable considering the work environment. However, the inspection data of wall thickness reduction by sensors has errors, and the number of measurement points is limited from the viewpoint of cost and other factors. Therefore, this study proposes a method to quantitatively evaluate engineering risk by considering the probability of failure of piping systems and the consequence of failure, based on the data from multiple fixed-point wall thinning monitoring. In this paper, the effectiveness of the proposed method is clarified for a piping system of a cooling water circulation system, and the effects of measurement error, number of measurement points, and candidate settings of wall thinning progression on the evaluation accuracy of wall thinning progression and failure probability are examined.