Evaluation of chemical effects on fuel assembly blockage following a loss of coolant accident in nuclear power plants

Abstract

After a loss of coolant accident (LOCA) in a pressurized water reactor (PWR), the chemical environment inside containment is complex; there is a potential trend for some materials to be corroded by high-temperature alkaline water. The subsequent corrosion products may be recirculated through the sump strainers using the emergency core cooling system (ECCS), and ultimately transported into the reactor core. This phenomenon would aggravate the blockage and head loss across the fuel assembly, thereby prohibiting decay heat transfer. To analyze the potential impact of “chemical effects” on flow resistance in the fuel assembly, the specific test loop was established and a series of analysis tests were performed. Four types of chemical precipitates were used in the tests: AlOOH, NaAlSi3O8, Ca3(PO4)2, and Zn3(PO4)2. This study concluded that the AlOOH precipitates could effectively increase pressure drop across the fibrous bed. The final head loss could also be affected by the physical and chemical characteristics of precipitates, such as the particle size, settling rate, and chemistry.