Literature review on experiments and models associated with degradation and oxidation of boron carbide control material during severe accidents
Zheng, X.
; Ishikawa, Jun
; Ito, Hiroto; Tamaki, Hitoshi
; Maruyama, Yu 
Boron carbide (B
C) is one kind of neutron absorbing control rod/blade materials used in light water reactors (LWRs). In Fukushima Daiichi Nuclear Power Station (NPS), all units used B
C as absorber material. The degradation of control rod/blade will affect the early phase of in-vessel core melt progression. Furthermore, the release of carbon compound gases including carbon dioxide (CO
) as well as boron compounds due to the oxidation of B
C with steam is possible to affect source terms of radioactive materials. Past experiments related to B
C degradation and oxidation and numerical modeling in severe accidents codes are investigated in the current report with a main view to apply the acquired knowledge into the modification of THALES-2 developed at JAEA as an integral severe accident analysis code. The eutectic interactions of B
C with other materials such as stainless steel and Zircaloy will lower the melting point of control rod/blade. The Nagase's correlations for eutectic interaction are selected as one of candidates to be applied into THALES-2. The oxidation reaction of B
C with steam will release considerable amount of thermal energy, and form CO
, boric acids and boron oxide, which could make an impact onto source terms by changing the pH value of a water pool where those dissolve. The IRSN correlation is chosen to be used in the modeling of oxidation reaction in THLAES-2.