DOE's Office of Science and Technology is funding the Accelerated Site Technology Deployment (ASTD) program, formerly known as the Technology Deployment Initiative (see back issues of Initiatives). Projects in the program promise to reduce the cost of environmental management and accelerate cleanup throughout the complex.

Linking two systems to consolidate tank waste
One of the ASTD projects for FY 1998 is the implementation of an integrated cesium removal and evaporator system to concentrate tank waste at Oak Ridge National Laboratory (ORNL). During other deployments planned for the Savannah River Site, the cesium removal and evaporator systems will separately attack different problems.

By joining the cesium removal unit with the subatmospheric evaporator, the ASTD project will efficiently reduce the radioactivity and volume of tank waste. This project contributes to ORNL's effort to consolidate its tank waste into a few designated tanks in preparation for the site choosing private-sector contractors to treat and dispose of ORNL's tank waste. Both systems have already been successfully demonstrated separately. A full-scale demonstration of the cesium removal technology was funded jointly by DOE's offices of Science and Technology (OST, EM-50) and Waste Management (EM-30) and conducted at ORNL in September 1997. This system is composed of three compact, skid-mounted modules—one for collecting feed liquids, one for an ion-exchange treatment, and one for dewatering the cesium ion-exchanger. Each module has secondary containment and modular radiation shielding. A key component of this unit is the effectiveness of the ion-exchange material, crystalline silicotitanate (CST), an inorganic ion-exchange material that was developed in laboratory tests through the combined efforts of Sandia National Laboratories, UOP Molecular Sieves, and Texas A&M University. During its demonstration, the unit removed 1,000 curies of cesium from 30,000 gallons of surrogate waste using 70 gallons of CST.

A full-scale demonstration of the subatmospheric evaporator was also funded jointly by OST and EM-30 at ORNL in April 1996. This system is composed of five compact, skid-mounted modules—each having secondary containment and modular radiation shielding. The evaporator successfully reduced the volume by 25 percent of 22,000 gallons of Oak Ridge high-activity tank waste.

CST-the cutting edge of cesium removal
CST inorganic resins are intended for one-time use, thus eliminating the secondary waste generated during reprocessing of organic ion exchangers and permitting the design and operation of a much simpler facility. The standard ion-exchange material is organic resins that remove not only cesium, but similar chemicals such as calcium and magnesium. Sharon Robinson, technical lead for the project at ORNL, notes that "CST is designed specifically to remove cesium; it's highly selective for cesium. This project will be DOE's first deployment of CST."

When CST snares hazardous components in addition to cesium or other radioactive material, it must be treated as a mixed waste. One way to do this is to vitrify, or make glass out of, the CST. The Savannah River Technology Center has determined that CST can be effectively vitrified if necessary to comply with mixed waste requirements. Robinson notes that when the cesium removal unit is used at Savannah River or Hanford, heavy metals are expected to be in the waste stream. Vitrification at these sites will be a viable way to encapsulate and solidify CST. However, the CST used for the ORNL project isn't expected to contain hazardous materials in addition to cesium, so vitrification won't be required. ORNL plans to dispose of its cesium-loaded CST at the Nevada Test Site.

From orange juice condenser to tank waste evaporator
Robinson describes the procurement of the evaporator as "an off-the-shelf technology" but OST had to adapt the technology for use in a radioactive environment. Robinson says the evaporator has been used in the food industry for condensing orange juice. "You're taking something from an environment like that to something that is radioactive where you have to do totally remote operations, and you're dealing with an entirely different stream going through the evaporator."

Benefits of a cesium removal and evaporator merger
The integrated system's first step is removal of cesium from the tank waste stream, followed by the evaporator's role of concentrating the resulting cesium-free waste. Sole reliance on the evaporator would concentrate cesium in the distillate of the evaporator, creating a more complicated and less efficient process. ORNL procured both systems as modular units. Robinson says "You bring them in, hook them up, put temporary shielding around them, operate them and then move them to another site and operate them again." This saves DOE from developing a huge infrastructure that is not adaptable to particular wastes and may quickly become outdated.

Consolidating tank waste
The cesium removal and evaporator system is aiding an ORNL effort to consolidate tank waste and move it from inactive and unsafe facility tanks to double-shelled tanks. Tank supernates and process water from sluicing operations will be treated, resulting in concentrated solutions with lowered radioactive levels. ORNL issued a call for proposals and is preparing to award a contract to a private-sector firm for treating, packaging, and transporting the concentrated tank waste to the Waste Isolation Pilot Plant, which is not yet open. DOE's regulatory agreement with the state of Tennessee requires that all consolidation activities be completed in FY 2000 to support the privatization effort.

What's happening now
Oak Ridge is currently phasing in the implementation of the project. So far this year, ORNL has installed the evaporator and run it for four campaigns, during which 83,000 gallons of waste was reduced by 50 percent. The cesium removal and evaporator equipment had been tested previously so ORNL has been buying additional equipment to operate the combined system in series. Currently, the equipment is being installed. The plan is to begin operating the integrated system in series beginning in January 1999 and running through 2000.

Looking ahead to Savannah River
The second deployment of the technologies is planned at the Savannah River Site. ORNL is now developing the specifications for two SRS applications that will use each technology separately. SRS will take the knowledge gained at ORNL and apply it to its Consolidated Incineration Facility evaporator, which began processing mixed waste in April of 1997. A result of this process is a secondary waste stream called blowdown, containing dissolved solids. Considerable cost savings can be realized if blowdown can be concentrated by evaporation before stabilization. The Defense Waste Processing Facility also emits a recycle stream at the rate of 3 million gallons per year. A task is currently under way, using data gained through work done on the cesium removal demonstration, to establish specifications for a proposal to create an integrated unit to remove cesium, mercury, and solids. This reduction of waste would reduce costs and risks at SRS. Savannah River will be putting out procurement specifications for the two systems this fall. ORNL will also evaluate additional applications past the second deployment. Robinson believes integrating the systems will require less energy, reduce foaming and scaling problems, and ultimately concentrate more waste than the baseline approach.

Cost savings
The cost of this project is $21 million spanning four years. ASTD will provide $9.4 million, and the remainder will be EM-30 funds from ORNL and SRS. Operational costs will be reduced by $84 million, and the remediation schedule at Oak Ridge will be accelerated by eight years. Additional deployments at Hanford and Idaho National Engineering and Environmental Laboratory will substantially increase cost savings. According to an independent life-cycle cost analysis, $667 million could be saved if Hanford uses CST ion exchangers as opposed to the baseline organic ion exchangers to treat tank supernate.

For more information on the cesium removal and evaporator ASTD project at Oak Ridge, contact Sharon Robinson at (423) 574-6779, ssr@ornl.gov.