Ferrocyanide is a chemical that was added to some single-shell tanks between 1954 and 1957 to remove cesium from the liquid wastes. Concern over ferrocyanide surfaced in the 1980s as the old single-shell tanks began to leak and liquid was pumped from them, leaving a thick sludge. Scientists were concerned that temperatures might increase and heat the sludge waste high enough for it to burn or explode. Thermocouples in the tanks indicated that the temperatures were low, but precautions were needed to ensure that work in the tanks would not significantly increase the temperature. Rigid safety controls were established on work inside as well as outside the tank farms.
Several tanks are on more than one list.
The large mixer pump installed in this tank in July 1993 to mitigate gas build-up continues to perform flawlessly. Tank farm hazards and potential safety concerns have been more thoroughly identified and analyzed, and a new Basis for Interim Operations prepared. This greatly improved safety authorization basis will be implemented this fiscal year. While we are celebrating significant progress in resolving safety issues within the TWRS Program, we can't lose sight of the many challenges that remain.