Investigation of Chemical Effects on Emergency Core Cooling Filtration Head Loss After Loss of Coolant Accident

Integrated tests of head loss through an emergency core cooling filter screen are conducted, simulating reactor building environmental conditions for thirty days after a loss of coolant accident. A test apparatus with five individual loops each of whose chamber is established to test chemical product formation and measure the head loss through a sample filter. The screen area at each chamber is 78.54cm² and reactor building materials can be scaled down according to specific plant condition. A series of tests have been performed to investigate the effects of reactor building spray, existence of calcium-silicate with tri-sodium phosphate (TSP), and composition of materials. The results showed that head loss across the chemical bed with even a small amount of calcium-silicate insulation instantaneously increased as soon as TSP was added to the test solution. Also, the head loss across the filter screen is strongly affected by spray duration and the head loss increase is rapid at the early stage, because of high dissolution and precipitation of aluminum and zinc. After passivation of aluminum and zinc by corrosion, the head loss increase is much slowed down and is mainly induced by materials such as calcium, silicon, and magnesium leached from NUKON™ and concrete. Furthermore, it is newly found that the spay buffer agent, tri-sodium phosphate, to form protective coating on the aluminum surface and reduce aluminum leaching is not effective for a large amount of aluminum and a long spray.