225-B Pool Cell 5 Liner Leak Investigation

This document describes the actions taken to confirm and respond to a very small (0.046 ml/min) leak in the stainless steel liner of Hanford`s Waste Encapsulation and Storage Facility (WESF) storage pool cell 5 in Building 225-B. Manual level measurements confirmed a consistent weekly accumulation of 0.46 liters of water in the leak detection grid sump below the pool cell 5 liner. Video inspections and samples point to the capsule storage pool as the source of the water. The present leak rate corresponds to a decrease of only 0.002 inches per week in the pool cell water level, and consequently does not threaten any catastrophic loss of pool cell shielding and cooling water. The configuration of the pool cell liner, sump system, and associated risers will limit the short-term consequences of even a total liner breach to a loss of 1 inch in pool cell level. The small amount of demineralized pool cell water which has been in contact with the concrete structure is not enough to cause significant structural damage. However, ongoing water-concrete interaction increases. The pool cell leak detection sump instrumentation will be modified to improve monitoring of the leak rate in the future. Weekly manual sump level measurements continue in the interim. Contingency plans are in place to relocate the pool cell 5 capsules if the leak worsens