Quenching of a stainless-steel rod with a honeycomb porous plate in artificial seawater

The prime concern during a severe accident scenario in a nuclear power plant is to prevent leakage of radioactive material. In case of a fuel meltdown accident, as part of in-vessel retention (IVR) efforts, the reactor pressure vessel cavity is flooded with fresh water to decrease the temperature of the reactor pressure vessel wall, preserving its structural integrity. Improving IVR safety margin requires shortening of the quenching time and enhancement of the critical heat flux (CHF). This work investigates and compares the performance of artificial seawater and distilled water for quenching of a stainless-steel cylinder with a honeycomb porous plate (HPP) attached to the heated surface. Experiments, at atmospheric pressure and saturated condition, with both fluids on the bare surface (BS) and with an HPP with 10 mm in height attached were performed. On the BS, artificial seawater presented a quenching time 13-times shorter than that of distilled water due to a much shorter film boiling region, due to an unstable vapor film and localized solid-liquid contact. When the HPP was employed, the quenching times for both fluids were significantly reduced due to its capillary properties and the separation of liquid and vapor phases near the heated surface. With the HPP, the quenching time in distilled water was reduced by approximately 9-times (from 859 s to 99 s) and in artificial seawater it was decreased from 67 s to 20 s. The best performance observed in the latter case resulted from the absence of film boiling. After experiments in artificial seawater the presence of irregular distributed sea-salts deposits was observed on the cylinder surface. These deposits can improve the capillarity of the surface, what translated in a higher quenching performance for this fluid.