on the Characterization, Monitoring, and Sensor Technology Crosscutting Program

About the focus areas
The U.S. Department of Energy's Office of Environmental Management has established an integrated approach for addressing waste issues based on problem, or focus, areas. The focus areas are subsurface contaminants; mixed waste characterization, treatment, and disposal; radioactive tank waste remediation; deactivation and decommissioning; and plutonium stabilization. Three crosscutting technology areas support the focus areas: characterization, monitoring, and sensor technology; efficient separations and processing; and robotics.

The DOE site project activities described in the draft Accelerating Cleanup: Paths to Closure identifies many needs for characterization, monitoring, and sensor technologies in the areas of

• locating and characterizing wastes and waste sites before treatment;
• monitoring waste retrieval and remediation processes;
• characterizing and monitoring waste treatment processes, products, and effluents; and
• long-term compliance monitoring after site closure.

The importance of characterization and monitoring is widely recognized. Although characterization and monitoring technologies can be extremely expensive, inadequate characterization often leads to even more costly remedial decisions, including insufficient cleanup through overly conservative strategies. Without monitoring technologies, problems with a process cannot be determined in time to make changes necessary to ensure product quality. The mission of the Characterization, Monitoring, and Sensor Technology Crosscutting Program (CMST-CP) is to deliver appropriate and economical characterization, monitoring, and sensor technologies to the DOE offices of Waste Management, Environmental Restoration, and Facility Transition and Management (EM-30, -40, and -60, respectively).

To ensure that available DOE and other national resources are focused on the most pressing needs, the Office of Science and Technology (EM-50) concentrates on development within its four focus areas, all of which have characterization and monitoring development needs. Technology that is developed for one focus area can often be adapted to solve problems in another. Working in concert with the focus area teams and EM site users, CMST-CP identifies technology gaps, integrates technology development, and leverages resources to achieve synergy in developing and providing cost-effective solutions.

Highlights of recent CMSP-CP successes follow.

LIFI lights up contamination
Scientists at DOE's Special Technologies Laboratory are developing laser-induced fluorescence imaging (LIFI) to find and map environmental pollutants. An optical technique that detects fluorescence generated by pollutants irradiated with laser light, LIFI addresses the need for rapid survey tools to monitor sites remotely, identify contaminant "hot spots," assist in cleanup activities, and monitor remedial progress. In the future, if regulatory sensitivity can be achieved and verified through field tests, LIFI may be used to verify site cleanup.

Both handheld and airborne LIFI systems have been designed, fabricated, and tested. The handheld system evolved from a field-transportable system demonstrated at the East Tennessee Technology Park (the former Oak Ridge K-25 Site) for detection of uranium at the uranium cylinder storage yards. The handheld system was recently demonstrated at the Fernald Plant 1 Complex, where LIFI readings were correlated with standard radiological survey instruments. Current work is focused on further reducing the size and weight to be a backpack-mounted uranium-survey tool. The completed backpack portion—everything but the cable and handheld head and connecting cable—will stand less than 18 inches tall and weigh less than 32 pounds.

LIFI was recently tested at Disney's EPCOT Center to see whether it can detect and identify plants stressed by disease, exposure to toxins, and other phenomena. Another test applied LIFI to detect heavy metals in soils and plants in Poland. Researchers hope the system will be able to help farmers keep watch over their crops and help federal agencies detect hazardous material leaks before these problems become serious. A new means of deploying LIFI technology known as "Spotlight LIFI" is being developed for improved airborne signature detection.

From a (safe) distance—GammaCam^TM
GammaCam^TM, a gamma-ray imaging system manufactured by AIL System, Inc., is designed to provide two-dimensional information on the position and relative strengths of gamma-ray radiation fields located from a few feet to several hundred feet from the observer. The system was developed under the sponsorship of the Department of Defense Advanced Research Projects Agency (ARPA) Technology Reinvestment Project, with the ARPA and CMST-CP as joint program managing organizations.

GammaCam^TM consists of a portable sensor head that contains both gamma-ray and visual imaging systems and a portable computer for control. Because the system can be positioned outside the radiologically controlled area, the radiation exposure to personnel is significantly reduced and extensive shielding is not required.

GammaCam^TM was demonstrated in December 1996 as part of the Chicago Pile-5 Research Reactor Large-Scale Demonstration Project. The system performed well in providing two-dimensional color images of gamma radiation fields superimposed on corresponding black and white images. Using GammaCam^TM to determine shielding requirements and positioning promises to significantly reduce the radiation dose received by operating technicians, especially in high-radiation areas. GammaCam^TM can also provide useful information on the relative strengths of the various sources and their locations from outside the radiological area.

Go ask Alex
Quantrad Sensor's Alloy Expert—Alex, for short—is a portable, handheld X-ray fluorescence (XRF) metal alloy analyzer. The battery-operated Alex provides fast, accurate, and reliable analytic results in seconds. The analysis is based on a proprietary algorithm developed in conjunction with the U.S. Naval Research Laboratory and funding from CMST-CP.

Elemental analysis and grade verification of unknown alloy parts is essential in disposing of scrap metal in decontamination and decommissioning activities. XRF instruments for these applications must be portable, easy to use, and safe for maximum field ruggedness without compromising accuracy or repeatability.

Alex identifies and accurately determines and displays percent of alloy content for aluminum, bronze, copper, rare earth, steel, stainless steel, titanium, and zinc alloys within seconds. Alex uses a conventional X-ray source, which is safer and more accurate than the isotopic source and eliminates the need for source replacement, leak testing, special licensing, and record keeping.

SEAtrace^TM validates subsurface barriers
SEAtrace^TM uses gaseous tracers to verify impermeable barriers in the vadose zone. Sandia National Laboratories and Science and Engineering Associates, Inc. (SEA) developed SEAtrace^TM with CMST-CP funding support. Integrating autonomous, multipoint soil vapor sampling with data analysis, the system pinpoints leak sources, sizes, and start times. In addition to providing a conservative assessment of initial barrier integrity, the system can also provide long-term monitoring of contaminant soil gases for surveillance of the containment system's performance.

The system injects inexpensive and nonhazardous gaseous tracers into the contained volume of a barrier. The location and size of any leaks in the barrier are quantified by tracking tracer gas concentration histories. The vapor injection and sampling points can be emplaced by direct-push techniques (such as Geoprobes) or the rapid ResonantSonic^TM technique, avoiding excessive drilling costs and secondary waste generation. In field tests, leak location was determined to within as little as 0.1 meter, leak size to within approximately 10 percent, and time the leak started to within approximately 5 percent.

SEA has commercialized the system and is seeking a site for full-scale demonstration.

Heavy metal can't hide from X-ray K-edge detector
Ames Laboratory and Iowa State University's Center of Nondestructive Evaluation are developing an improved nondestructive assay technique to detect and quantify uranium, plutonium, and other heavy metals inside sealed containers or processing equipment. The technique—based on observing the K-edge absorption transition in X-ray transmission measurements—is being developed to maximize sensitivity for detecting heavy metals while minimizing measurement time.

The technique promises to benefit many D&D projects, especially inspecting the vast amount of piping in former gaseous diffusion plants. By monitoring chemical flushing in situ, the technique could minimize the danger of contamination to workers and equipment during disassembly operations, saving time and money and reducing secondary waste.

The system consists of a high-flux X-ray generator, a collimator for minimizing the local radiation hazard and providing the requisite beam characteristics, a monochromator, a real-time imaging detector for simplified alignment, and an energy-dispersive detector for collection of the K-edge data. The raw data is analyzed by the same personal computer that controls the equipment, and the result is available to field personnel. In early tests, a 2-µm layer of uranium was successfully measured through 1 inch of steel, and measurement time was cut in half.

Several opportunities for deployment of the K-edge technology are being explored.

Subsurface imaging by ERT
Electrical Resistance Tomography (ERT) can create two- or three-dimensional visualizations of in situ remediation processes such as air stripping, bioremediation, and subsurface heating. By mapping the movement of liquids in the subsurface, ERT can verify the emplacement and performance of surface and subsurface barriers such as grout curtains. It can also be used to detect leakage from holding tanks and liquid-waste ponds.

ERT employs buried electrodes to measure the potential distribution induced from applied electrical current. ERT images are available for inspection a few hours after the data are collected. The electrodes are inexpensive and robust and can be placed in boreholes or pushed into the ground, reducing the need for drilling.

In 1997, ERT was demonstrated to image the extent of leakage from a colloidal silica barrier at Brookhaven National Laboratory and from a grout barrier at Dover Air Force Base. Potential commercial applications for ERT include subsurface geologic mapping for mining and petroleum industries, nondestructive evaluation of large-scale structures such as dams, and even medical diagnosis.

Improved covers for landfills
The Alternative Landfill Cover Demonstration (ALCD) is a large-scale field test at Sandia National Laboratories (see Initiatives, December 1995). The project will provide alternatives to EPA's landfill cover designs that will be more effective and less difficult and expensive to install in arid and semiarid climates. ALCD is also working to improve regulatory acceptance of alternative landfill cover designs. In addition to CMST-CP support, the project is also receiving FY98 funding from OST's Accelerated Site Technology Deployment program (see article).

Two baseline covers were constructed next to four alternative cover designs for comparison based on performance, cost, and ease of construction. Some of the alternative designs will emphasize unsaturated hydraulic conductivity, increased water storage potential to allow for eventual evaporation, and increased transpiration through engineered vegetative covers. The alternative covers were designed to take advantage of local materials to allow for easier construction of covers at substantial cost savings.

The covers are being monitored for all water balance variables and supporting data. These field-obtained data will be compared with results obtained from predictive computer models for validation of the models. In addition, five years of water balance data would be deemed adequate for regulatory approval of the alternative covers, and this project is expected to complete data collection by the year 2001.

For further information, contact David Hippensteel, CMST-CP field lead, (702) 295-1467, e-mail hippensteel@nv.doe.gov, or visit the Characterization, Monitoring, and Sensor Technology Crosscutting Program Web site at http://www.cmst.org.