Activities of boron (B) and silicon (Si) in the Fe-Si-B liquid phase were evaluated by thermodynamic approach to clarify the effect of Si on the stable cesium (Cs) species formation at the temperature range from 1500 K to 2000 K. Although Si exists only as a minor alloying element of the stainless steel (SS) at the initial condition, Si may be controlling element when considering the chemical state of Cs in accidental conditions. The calculated activities were applied to the evaluation of chemical reactions of Cs-Si-O and Cs-B-O systems assumed in the Fukushima Daiichi Nuclear Power Station (FDNPS) unit 2. Consequently, production of 1.27 kg of the Cs-bearing particle at 2000 K was possibly found and it is considered to be specific phenomenon to the FDNPS unit 2 accident progression. Moreover, the following two findings were obtained that the increasing of Si resulted in an increase in activity of B in the melt, and Cs could not be released as CsBO₂; instead, could be trapped on the surface of the SS-B₄C condensed phase as the Cs-B-O species.

通过热力学方法评估了Fe-Si-B液相中硼（B）和硅（Si）的活性，以阐明Si对1500 K至2000 K温度范围内稳定铯（Cs）物种形成的影响尽管在初始条件下，Si仅作为不锈钢（SS）的微量合金元素存在，但在考虑偶然条件下Cs的化学状态时，Si可能是控制元素。计算出的活度被用于评估福岛第一核电站（FDNPS）2号机组中假定的Cs-Si-O和Cs-BO系统的化学反应。因此，在2000年产生了1.27千克的Cs颗粒。可能发现了K，这被认为是FDNPS 2号机组事故进展的特定现象。而且，₂ ; 相反，它可能作为Cs-BO物种被捕集在SS-B ₄ C冷凝相的表面上。