Evaluation of Saltstone Mixer Paddle Configuration for Improved Wear Resistance.

摘要

At the Savannah River Site (SRS), the Saltstone Production Facility (SPF) receives low level waste (LLW) salt solution from Tank 50H for treatment and disposal. At the SPF, the LLW is mixed with premix (a cementitious mixture of portland cement, blast furnace slag, and Class F fly ash) in a 10-inch Readco-Kurimoto continuous mixer to produce fresh (uncured) saltstone that is transferred to the Saltstone Disposal Facility (SDF) for permanent disposition in the Saltstone Disposal Units (SDU) (previously referred to a vaults). In March 2011, dry feeds began backing up in the chute that feeds the 10-inch Readco-Kurimoto continuous mixer. The dry feeds were setting off both the 2 foot and the 7 foot indicators in the premix chute to the Readco-Kurimoto mixer during multiple days of processing. When the 7 foot indicator is tripped, the SPF enters into shutdown. During troubleshooting of the process, the Readco-Kurimoto mixer was cleaned and inspected and wear was found in the area where the screw augers and the first set of mixing paddles meet. The wear to the paddles eliminated the self-cleaning capabilities of the paddles and augers, leading to a build-up of grout between the paddles/augers and the barrel. This build-up acts as an orifice which reduces the throughput capabilities of the premix through the mixer. Waste solidification Engineering (WSE) has tasked Savannah River National Laboratory (SRNL) with investigating the degradation mechanism that causes wear to the paddles, using a 2-inch Readco-Kurimoto continuous mixer, and recommending alternative materials of construction for the mixer paddles; and determining whether a different paddle configuration will minimize wear without affecting the product through the mixer. The results of the alternative material request are documented elsewhere. As documented in the Task Technical and Quality Assurance Plan, the focus of this report is to recommend a paddle configuration that will minimize wear in the 10-inch Readco-Kurimoto mixer in use at the SPF.