Liquefaction interaction between oxidized Zircaloy and other fuel assembly components of BWR in the early stage of fuel assembly degradation

Tokushima, Kazuyuki; Shibata, Hiroki ; Kurata, Masaki ; Sawada, Akihiko*; Sakamoto, Kan*

Two type tests were performed to examine the prevention effect of the oxide layers to liquefaction interaction between Zircaloy and core component materials. The oxide layer of Zircaloy was clearly confirmed to prevent the liquefaction interaction under the temperature of melting point of stainless steel even if the oxide layer on Zircaloy of approximately 30 micro meters, which is thinner than it is predicted to be formed under typical accident condition. The oxide layers were able to be formed even in the region where the gas flow is significantly limited by narrow arrangement. Although the oxide layers at the inner position of upper end plug was hard to form, the prevention effect of the oxide layers was sufficiently observed. The axial variation of the thickness of the oxide layers was observed. It suggested that variation of partial pressure of HO should be considered to evaluate the growth rate of the oxide layers for detail.