Study on correlation effect between factors of statistical hot spot factor for HTGR design

Fukaya, Yuji   ; Nishihara, Tetsuo 

A study on Correlation effect between elements of statistical hot spot factor for High Temperature Gas-cooled Reactor (HTGR) Design had been performed. Both of safety and reactor specification can be remained if the uncertainty is correctly propagated by revising hot spot factor. In this context, it is reported for light water reactor design that the propagated uncertainty can be reduced by statistical hot spot factors with numerical statistical approach, that is Monte Carlo method, because correlation effects for each factor can be considered. For HTGR with sleeve covered fuel, it is expected that the fuel temperature also reduces by employing the same approach because the gap between sleeve and fuel compact, which shows significant temperature increase, have direct correlation. In addition, Monte Carlo method treats correlation effect at the price of evaluating contribution of individual factor. Therefore, improved method based on conventional method has been developed in this study. Then, statistical hot spot factor for fuel temperature of HTGR was evaluated by Monte Carlo method and the improved method. As a result, it is not found significant difference between the result of the conventional method and the improved method. Moreover, usage of hot spot factor is investigated and we proposed new one reflecting the investigation.