Study on Melt Coolability and Water Ingression Through Melt Pool in Scaled Down Core Catcher—The Influence of Vessel Angle

Abstract

An ex-vessel core catcher is generally used in advanced reactors to mitigate core melt scenarios by stabilizing and cooling the corium for prolonged period by strategically flooding it. The side indirect cooling along with delayed top flooding of water ensures that the water interacts with the oxidic components only after melt inversion. However, water ingression either through the top of melt pool or through the crust–vessel gap may lead to unoxidized metal–water interaction in the melt leading to hydrogen production. To avoid this deleterious scenario, water ingression into the bulk of the melt is to be avoided. In this study, a series of experiments using a scaled down core catcher has been conducted to study the phenomena of melt coolability and water ingression by varying the bottom vessel angle of the core catcher. Three different angles of the bottom plate were considered: 10, 20, and 30 deg. The melt used was a corium simulant in the form of CaO–B2O3.The transient temperature history of melt pool, inside and outside vessel surface temperatures along with the post-test evaluation of the test section reveals that the bottom angle has an effect on water ingression and the resultant melt eruption at different locations. The tests conducted showed that the scaled down core catcher with 10-deg inclination of the bottom plate does not exhibit water ingression, whereas the 20- and 30-deg angle-scaled down core catchers showed water ingression and subsequent melt eruption.