Estimation of Leak Rate from the Emergency Pump Well in L-Area Complex Basin

Abstract

This report provides an estimate of the leak rate from the emergency pump well in L-basin that is to be expected during an off-normal event. This estimate is based on expected shrinkage of the engineered grout (i.e., controlled low strength material) used to fill the emergency pump well and the header pipes that provide the dominant leak path from the basin to the lower levels of the L-Area Complex. The estimate will be used to provide input into the operating safety basis to ensure that the water level in the basin will remain above a certain minimum level. The minimum basin water level is specified to ensure adequate shielding for personnel and maintain the ''as low as reasonably achievable'' concept of radiological exposure. The need for the leak rate estimation is the existence of a gap between the fill material and the header pipes, which penetrate the basin wall and would be the primary leak path in the event of a breach in those pipes. The gap between the pipe and fill material was estimated based on a full scale demonstration pour that was performed and examined. Leak tests were performed on full scale pipes as a part of this examination. Leak rates were measured to be on the order of 0.01 gallons/minute for completely filled pipe (vertically positioned) and 0.25 gallons/minute for partially filled pipe (horizontally positioned). This measurement was for water at 16 feet head pressure and with minimal corrosion or biofilm present. The effect of the grout fill on the inside surface biofilm of the pipes is the subject of a previous memorandum