Experimental Study on Nuclear Properties of Water Cooled Pebble Bed Blanket

For the first time, nuclear properties are experimentally examined on the water cooled pebble bed blanket by using DT neutrons with two partial mockups; multi-layered mockup with water and pebble bed mockup. Prediction uncertainties are clarified on tritium production rate (TPR) through the experimental analyses. From the multi-layered mockup experiment, it is found that integrated tritium productions can be accurately evaluated. Calculation methods are discussed on the evaluation for TPR of the pebble bed layer, and the precise modeling method is proposed using the hexagonal close-packed heterogeneous geometry. The integrated tritium productions by the homogenous geometry decrease compared with those by the heterogeneous geometry. It is clarified that evaluations are required on a tritium breeding ratio in the blanket design calculation by the proposed method.