Numerical analysis of the Sodium–Water Reaction in a minichannel to evaluate the safety of a Printed Circuit Steam Generator

Abstract

ABSTRACT 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.