Tank 50H Tetraphenylborate Destruction Results

We conducted several scoping tests with both Tank 50H surrogate materials (KTPB and phenol) as well as with actual Tank 50H solids. These tests examined whether we could destroy the tetraphenylborate in the surrogates or actual Tank 50H material either by use of Fenton's Reagent or by hydrolysis (in Tank 50H conditions at a maximum temperature of 50 degrees C) under a range of conditions. The results of these tests showed that destruction of the solids occurred only under a minority of conditions. (1)Using Fenton's Reagent and KTPB as the Tank 50H surrogate, no reaction occurred at pH ranges greater than 9. (2)Using Fenton's Reagent and phenol as the Tank 50H surrogate, no reaction occurred at a pH of 14. (3)Using Fenton's Reagent and actual Tank 50H slurry, a reaction occurred at a pH of 9.5 in the presence of ECC additives. (4)Using Fenton's Reagent and actual Tank 50H slurry, after a thirty three day period, all attempts at hydrolysis (at pH 14) were too slow to be viable. This happened even in the case of higher temperature (50 degrees C) and added (100 ppm) copper. Tank 50H is scheduled to return to HLW Tank Farm service with capabilities of transferring and receiving salt supernate solutions to and from the Tank Farms and staging feed for the Saltstone Facility. Before returning Tank 50H to Tank Farm service as a non-organic tank, less than 5 kg of TPB must remain in Tank 50H. Recently, camera inspections in Tank 50H revealed two large mounds of solid material, one in the vicinity of the B5 Riser Transfer Pump and the other on the opposite side of the tank. Personnel sampled and analyzed this material to determine its composition. The sample analysis indicated presence of a significant quantity of organics in the solid material. This quantity of organic material exceeds the 5 kg limit for declaring only trace amounts of organic material remain in Tank 50H. Additionally, these large volumes of solids, calculated as approximately 61K gallons, present other obstacles upon returning Tank 50H to HLW service. The concerns include the potential for retention of flammable gases, nuclear criticality safety implications, and possible combustible solids formation. A recent document describes the initial results of that work