R&D plan for development of oxidation-resistant graphite and investigation of oxidation behavior of SiC coated fuel particle to enhance safety of HTGR

Development plan of high burnup fuel for high temperature gas-cooled reactors in future

“…One of the design extension conditions (DECs) for the HTGR is the large amounts of air/water ingress accident [23]. It is desirable that the behavior, under severer conditions than those assumed accidents, can be understood for evaluation of safety of HTR50S, though, the large amount of air/water ingress will be prevented in the HTR50S by the containment vessel [24].…”

“…The experimental identification of the condition to form the layer with stable oxide, i.e., silicon dioxide (SiO 2 ), for SiC layer of the CFPs is the most important data [23]. It should be noted that SiC layer is thinned and finally vanished in some oxidation conditions [23].…”

“…The experimental identification of the condition to form the layer with stable oxide, i.e., silicon dioxide (SiO 2 ), for SiC layer of the CFPs is the most important data [23]. It should be noted that SiC layer is thinned and finally vanished in some oxidation conditions [23]. In addition to the identification of the oxidation mode described in [23], the mechanical strength of the oxidized CFPs are also important data and is planned to be obtained.…”

“…It should be noted that SiC layer is thinned and finally vanished in some oxidation conditions [23]. In addition to the identification of the oxidation mode described in [23], the mechanical strength of the oxidized CFPs are also important data and is planned to be obtained. The formation of the stable oxide layer on the SiC layer does not mean that the oxidized CFPs can confine the harmful materials whatever happens.…”

“…The results of this research item are essential for the design of the naturally safe HTGR (see Section 4), which JAEA proposed after the accident at the Fukushima Daiichi Nuclear Power Station [23,26,27]. The specifications of the CFPs of the naturally safe HTGR are not determined yet, but the mode and the rates of the oxidation of the coating layers would be independent on the specifications.…”