[en] Information is provided on the technical studies that have been implemented for evaluating the containment integrity of the single-shell waste storage tanks. The major areas of study are an analysis of storage tank integrity, a failure mode analysis, and storage tank improvements. Evaluations of tank structural integrity include theoretical studies on static and dynamic load responses, laboratory studies on concrete durability, and experimental studies on the potential for exothermic reactions of salt cake. The structural analyses completed to date show that the tanks are in good condition and have a safety margin against overload. Environmental conditions that could cause a loss of durability are limited to the waste chemicals stored (which do not have access to the concrete). Concern that a salt cake exothermic reaction may initiate a loss of containment is not justifiable based on extensive testing completed. A failure mode analysis of a tank liner failure, a sidewall failure, and a dome collapse shows that no radiologic hazard to man results. Storage tank improvement studies completed show that support of a tank dome is achievable. Secondary containment provided by chemical grouts and bentonite clay slurry walls does not appear promising. It is now estimated that the single-shell tanks will be serviceable for the storage of salt cake waste for decades under currently established operating temperature and load limits