Sustained concrete attack by low-temperature, fragmented core debris

Four experiments were performed to study the interactions between low-temperature core debris and concretes typical of reactor structures. The tests addressed accident situations where the core debris is at elevated temperature, but not molten. Concrete crucibles were formed in right-circular cylinders with 45 kg of steel spheres (∼3-mm diameter) as the debris simulant. The debris was heated by an inductive power supply to nominal temperatures of 1473 K to 1673 K. Two tests were performed on each of two concrete types using either basalt or limestone aggregate. For each concrete, one test was performed with water atop the debris while the second had no water added. The results show that low-temperature core debris will erode either basalt or limestone-common sand concretes. Downward erosion rates of 3 to 4 cm/hr were recorded for both concrete types. The limestone concrete produced a crust layer within the debris bed that was effective in preventing the downward intrusion of water. The basalt concrete crust was formed above the debris and consisted of numerous, convoluted, thin layers. Carbon dioxide and water release from the decomposition of concrete were partially reduced by the metallic debris to yield carbon monoxide and hydrogen, respectively. The overlying water pool did not effect the reduction reactions