on the Tanks Focus Area

The nation’s highest cleanup priority is remediation of nearly 300 radioactive waste tanks at five DOE sites. These tanks hold nearly 90 million gallons of differing waste containing 650 million curies. Differing waste types and unique compositions require specialized technologies for safe storage, removal, treatment, and disposal of tank contents in an environmentally acceptable manner. The Tanks Focus Area is the central organization within the Office of Science and Technology managing development and deployment of technology to close DOE radioactive storage tanks. TFA draws on a broad spectrum of resources to develop safe, cost-effective solutions to site technology needs.

Since its establishment in 1994, TFA has enabled the ongoing development and implementation of approximately 100 technologies, accounting for approximately 100 deployments. This contribution has resulted in significant reductions in risk and schedule, with a net cost savings of approximately $250 million to date. TFA anticipates that savings from future deployments of existing TFA technical solutions will amount to billions of dollars.

Close interaction with users
TFA’s success in implementing new technical solutions is due in large part to close interaction with cleanup programs managers and other science and technology programs to bring together valued expertise, resulting in many deployments and technical assistance efforts. TFA works to accelerate technology deployments—while reducing environmental management costs and technological risk—by

Program benefits from independent experts
TFA’s Technical Advisory Group, an independent review and advisory panel, provides a national resource base of experts that can be quickly accessed to provide review, technical assistance, and support to the program. Seventeen senior subject-matter experts in tank waste remediation from industry, universities, and national laboratories serve on the TAG, whose review and input supports the TIMs in developing and executing a technically defensible program.

Independent reviews focus on technical feasibility/validity and relevancy in meeting the needs of users and TFA. These reviews are typically conducted on "new starts" or projects in the early stages of the technology maturity cycle. Two types of independent technical reviews are conducted—reviews by the TFA TAG, as well as peer reviews by the American Society of Mechanical Engineers as defined under OST guidelines. Relevant experts selected by ASME perform reviews of proposals, new starts, and ongoing projects that meet certain requirements.

TFA technical assistance spans the country
The expertise of the TIMs, along with that of the TFA TAG, has resulted in numerous requests for technical assistance, including the following:

Technology developments
Pit Viper reduces radiation exposure at Hanford
Under a project funded by TFA and the DOE Office of River Protection, Robotics Crosscutting Program staff at PNNL and Oak Ridge National Laboratory (ORNL) are developing a robotic Pit Viper system (Tech ID 2195) that will be used in tank valve pits at the Hanford Site to remotely retrieve contaminated equipment and clean out contaminated pits. The Pit Viper system consists of several components, including a backhoe, control trailer, video equipment, and a dexterous manipulator arm. This equipment recently underwent testing at Hanford’s Hazardous Material Management and Emergency Response (HAMMER) cold-test facility.

The French manufacturer of the arm visited Hanford to provide basic training on the arm and illustrate removal techniques as required for maintenance, positioning the arm inside the pit mockup, and placing sleeving on the backhoe boom and the arm. Training on the manipulator arm by the manufacturer is a key activity in support of deploying the system at Hanford. This system will reduce personnel exposure, decrease costs for riser pit decontamination, and enhance riser pit access to support deployment of tank waste retrieval and transfer equipment.

Probes help prevent tank leakage at Hanford and Savannah River
To combat corrosion in double-shell tank walls and improve the corrosion control process, TFA has worked with partners at the Hanford Site to develop and deploy an electrochemical noise–monitoring device called the Corrosion Probe (Tech ID 1985). This probe “listens” to the sounds of electrochemical reactions during the corrosion process and interprets them to detect the type and extent of corrosion taking place.

For the Savannah River Site (SRS), a corrosion–inhibitor monitor has been developed to continuously measure concentrations of nitrate, nitrite, and hydroxide ions, which are the key to minimizing corrosion in steel tanks. Data from this instrument—the Raman Probe (Tech ID 2015)—minimizes sampling requirements and chemical additions to the tanks. TFA is funding efforts to integrate the Raman Probe with the Corrosion Probe to notify operators when corrosion is occurring, enabling them to take quick and effective actions while minimizing and refining corrosion inhibitor added to the waste.

Pipeline plugging prevention
and unplugging
TFA is working with the Characterization, Monitoring, and Sensor Technology Crosscutting Program and Florida International University (FIU) to develop a system to reduce the risk of pipeline plugging during tank waste retrieval activities. The Dual Coriolis Monitor (Tech ID 2970) detects weight percent changes in suspended solids by continuously monitoring the density of tank waste being transferred through pipelines. This real-time monitored data, coupled with a better understanding of solids formation and plugging chemistry in pipelines, will ensure safe and cost-effective retrieval operations. Experience from an ORNL deployment of the Dual Coriolis Monitoring System in FY 2000 was integrated into a demonstration test loop at FIU to produce a prototype planned for deployment at SRS in FY 2002.

TFA is also working with Industry Programs to sponsor a demonstration of pipeline unplugging methods at FIU using specially constructed testbeds (Tech ID 2367). Several effective means of removing simulated blockages in pipelines were demonstrated. One used sonic resonance to apply varying vibration frequencies, breaking the bond holding the blockage to the pipe. Another method used water pressure and scouring inserts called "pigs" to remove blockages.

Processing of vitrification expended material accelerated
The West Valley Demonstration Project’s removal and vitrification of liquid high-level waste from underground tanks generates “vitrification expended material,” radiological waste material in the form of used equipment and instruments that have come into contact with high-level waste slurry and molten HLW glass. In an Accelerated Site Technology Deployment effort, TFA has funded the Vitrification Expended Material Processing System (Tech ID 2383) to sort, segregate, size-reduce, chemically and radiologically decontaminate, and package all materials and equipment that have been declared waste.

Accelerated deployment of expended materials processing cuts costs by reducing the volume of waste requiring management and storage following vitrification. The system has potential for processing similar waste already in storage and other high-activity wastes being generated as part of WVDP. Subsequent deployments are possible at sites that process HLW, including the Hanford Site, Oak Ridge Reservation, SRS, and INEEL.

Regenerable HEPA Filter to save time, cost, and exposure at DOE sites
TFA is partnering with the Savannah River Technology Center High Level Waste Division and the National Energy Technology Laboratory to investigate the use of regenerable filter media on high-level radioactive liquid waste tank exhaust systems. The media would have filtration performance characteristics equivalent to conventional disposable high-efficiency particulate air filters.

Westinghouse Savannah River Company tested two types of filter media: sintered metal and monolith ceramic. These media were subjected to a hostile environment to simulate tank ventilation systems conditions. Test results showed that both filter media were insensitive to high humidity or moisture conditions and were easily cleaned in situ. The filters regenerated to approximately clean filter status even after numerous plugging and in situ cleaning cycles. Both the sintered metal and ceramic filters passed the challenge test with conventional HEPA filter efficiency (99.97% or greater) each time.

The sintered metal and ceramic filters not only can be cleaned in situ, but also hold great potential as a long-life alternative to conventional HEPA filters. An in situ regenerable system may also find application in recovering nuclear materials, such as plutonium, collected on glovebox exhaust HEPA filters. This innovative approach of an in situ regenerative filtration system may be a significant improvement upon the shortfalls of conventional disposable HEPA filters having the potential to significantly reduce cost and personnel risk.

For more information, see the TFA Web site at http://www.pnl.gov/tfa.