Waste Tank cooling coil leakage calculations

A high activity Waste Tank cooling coil supply line cracked on September 12, 1991 at the H-Area East pump house, draining the cooling water to the ground. This raised the possibility of draining high-activity waste to the ground by siphon action through the submerged cycling coils since some of the cooling water supply lines are located up to 40 ft. below waste tank liquid level. The following documentation summarizes conclusions and provides details of flow calculation presented earlier during the incident investigation. No plausible reason for a simultaneous rupture of the supply line and the cooling coils inside the tank was identified. Both seismic stresses and water hammer produce relatively low stresses on the cooling coils. A hypothetical simultaneous rupture of the cooling coils inside the tank and the supply line below ground could result in 100 to 200 gpm waste discharge to the ground. Waste discharge from a possible cooling coil corrosion leak would be limited to 20 gal/12-hr shift under maximum possible siphon, based on operating procedures for cooling water makeup which call for coil isolation when a cooling water loss of 40 gal/shaft is identified. This level of discharge is within the existing envelope of accident consequences for Waste Tank Form SAR.