[en] A printed circuit heat exchanger is expected to improve the safety of a sodium-cooled Fast reactor when it is used as the steam generator. To use such a Printed Circuit Steam Generator (PCSG), the Sodium-Water Reaction (SWR) should be evaluated first. Because the diameter and length of a sodium channel in the PCSG are 4 mm and 2 m, respectively, a numerical approach is useful to understand the SWR characteristics in a minichannel. CFD modeling is conducted using commercial code and the SWR in a single sodium channel is analyzed under operating conditions. H₂O at 16.8 MPa and 683 K is injected into the sodium channel through the cracks of different sizes (0.1-1.0 mm). Although the SWR is extreme in the early stage, most of the Na_(l) is pushed towards the inlet and outlet of the channel within 15.3-35.3 ms as H₂O inflowed. The peak temperature is around 1200-1600 K in the early stage of the SWR and the temperature reaches around 683 K. Moreover, the calculated depth of target wastage is around 0.62-3.34 μm. Therefore, the effect of the SWR is negligible in the PCSG core under operating conditions. (author)