Experimental study on eutectic reaction between lower head of reactor pressure vessel and molten pool using simulant materials

Abstract

The eutectic reaction between core materials is an important behavior during reactor severe accidents because it will affect the accident progression. To comprehend the eutectic reaction between molten corium and the lower head of the reactor pressure vessel, this study conducted a series of simulated experiments. Liquid bismuth (Bi) and lead (Pb) rods, chosen for their relatively low eutectic point of 398.5 K, were utilized in a self-designed apparatus. For a more comprehensive understanding, various experimental parameters, including the temperature of Bi pool (548–578 K), temperature of Pb rod (548–578 K), charged gas pressure (0.002–0.006 MPa), weight of load block (3.3–7.3 kg) and style of baffles (type A, type B) were varied. Upon analyzing the experimental observations and quantitative data gathered, we investigated the influence of experimental conditions on the reaction rate. It is found that the temperature of the Bi pool exerts a notably positive influence on the eutectic reaction rate constant, regardless of the baffle pattern and the initial Pb rod temperature, while the role of Pb rod temperature seems to be insignificant. In experiments employing baffle A, both the weight of the load block and gas pressure significantly impact the reaction rate constant. Conversely, in the case of baffle B, their impact is insignificant. Knowledge and evidence gained from this study will be applied to future preparation of high-temperature experiments that involve actual reactor materials. Furthermore, this study furnishes experimental data aimed at enhancing and validating the eutectic reaction related model within the severe accident analysis code for water-cooled reactors.