Particle blockage and flow degeneration in Savannah River Site reactor fuel/target assemblies

In the event of a Savannah River Site K-Reactor Loss of Fuel Accident (LOFA), a postulated consequences of a single assembly melting is that the debris from this assembly results in flow blockage of another assembly sufficient to cause the second assembly to fail. Material from this second failed assembly may sufficiently block the flow to yet another assembly, resulting in a cascade of failures. This study addresses, analytically and experimentally, the likelihood that sufficient flow degradation occurs. An experiment was performed in which particles were injected into a stream leading to a prototypic assembly. The flow degradation was measured for different particle size distributions and particle quantities. The analytical portion examines the filtering of the particle debris through the process cooling water loop (some of the larger particles cannot pass through the heat exchangers) and the geometrical conditions necessary to block the holes to the assembly. Based on calculated particle concentrations and the blockage geometry, the probability for such blockage is estimated.