Nuclear power plants have a requirement that if a pipe break occurs in a room, the room’s drainage system must be adequate to prevent water levels from reaching safety related equipment.
This project involved reviewing rooms in several buildings that could have higher inflow rates, due to pipe break, than the values that were assumed in the original design basis. The inflow and outflow rates due to drainage were calculated for each room and each potential line that could break. Based on the flooding event duration the maximum water depth in each room was calculated and compared to the level that could impact safety related equipment. Some lines that were not originally analyzed to resist pipe break during a seismic event were re-analyzed using our pipe stress analysis software to certify them as meeting the pipe break limit criteria. In one complex case, flow into a sump had a back flow condition from sump in-flow from other rooms. To calculate the room water depth, a pipe flow model was created using FATHOM flow analysis software.