Modeling of the Savannah River Site High Level Waste

Three evaporators are used to reduce the volume of waste in the waste tank farm at the Savannah River Site (SRS). Evaporators are crucial operation in the SRS waste processing and management system. Using the Aspen Custom Modeler (ACM) software package marketed by Aspen Technology, Inc., the evaporator dynamic flowsheet models have been constructed to simulate the behavior of the evaporator systems. The evaporator models are used to assist operations and planning. The models account for the basic arrangement and flowpath for the evaporators: 1) Feed system, 2) Concentrate system, 3) Overheads system, and 4) Steam system. This paper provides a detailed description of the model development, and presents the result of a typical simulation scenario. BACKGROUND The SRS tank farm has a system of evaporators to reduce the volume of the waste. There are currently three operational evaporators designated as 2F, 2H and 3H. The 2F and 2H evaporators were built in the late 70’s and identical in their capacities, general construction, and mode of operation. The 3H was built in the 90’s and is similar to the 2F and 2H evaporators except it is about five times larger than 2F/2H. The Evaporator System provides the dewatering facilities required to continue material production and waste solidification programs at SRS. The Evaporator System evaporates water from liquid radioactive waste so that less tank volume is needed for long term storage. The Evaporator System concentrates both high-heat and low-heat liquid wastes from various feed sources consisting of mainly water and a variety of radionuclides and some inorganic salts in soluble or suspended form. The basic arrangement of the Evaporator System can be divided into four sub-systems: Feed system, Concentrate system, Overheads system, and Steam system. The evaporator flowsheet to be modeled is shown in Figure 1. Feed Tank Drop Tank Evaporator Sludge Salt Supernate Supernate Steam Steam to Tube Bundle