For years, scientists explored the idea of turning radioactive waste into glass and isolating it underground. However, one of the most complex questions remained unanswered. How would different glass compositions perform under varying storage conditions and over the centuries?
In 1995, Pacific Northwest National Laboratory scientist Pete McGrail attended a glass corrosion conference in Utah where the scientists concluded that traditional testing methods didn't work because they didn't accurately simulate underground storage conditions.
While he maneuvered a rental van through a blinding snowstorm, McGrail confesses that his mind was in overdrive thinking of possible solutions, not the icy roads. By the trip's end, he had a concept that after three years of development would become an answer.
McGrail's Pressurized Unsaturated Flow (PUF) system provides the first cost-effective, real-time method for testing waste forms that might safely be used at future disposal sites.
Scientists using PUF study the flow, transport, and reaction processes in systems not fully saturated with water. A flaw in many conventional testing methods is that they rely on whole samples completely submersed in water, which is different than the realities of underground storage where water percolates through the soil. "Conventional tests are simple to perform but often provide misleading data regarding long-term stability of waste forms," McGrail said.
In a specially designed apparatus patented in 1999, a column is filled with glass pebbles. As water partially fills the column, it flows over and past the pebbles—a better replication of how water would interact with glass in real-world conditions. Varying amounts of pressure and heat are applied to accelerate the weathering process.
The PUF system is fully computerized and any changes in water distribution and effluent chemistry are tracked to a tenth of a second. Compared with traditional testing methods, unstable glasses are detected about 50 times faster, saving time and money.
After experimenting with glass, McGrail began applying the PUF system to examine ceramics being developed for storing plutonium at the proposed national repository in Nevada. "The accelerated weathering possible with the PUF system is important for evaluating ceramics because we need to determine in only a few years whether their stability is affected by radiation that damages their crystal structure over thousands of years," McGrail said.
As part of his research, McGrail needed more information about pore and grain structure changes during PUF tests. To "see" into opaque materials, the idea of using tomography came into play. Like a CAT scan (computerized axial tomography), x-ray microfocus tomography (XMT) provides non-destructive imaging, but at much higher resolution. McGrail received funding from several sponsors and opened the XMT laboratory in Richland, Wash. in 1999.
"Our equipment can handle samples up to six inches in diameter and still see features down to one one-thousandth of an inch," McGrail said. "Synchrotron x-ray sources can achieve even better resolution than our techniques, but they are cost prohibitive for routine applications."
Future applications of PUF and XMT are being explored. One adapted PUF technique would examine ways to enhance recovery of natural gas from hydrates trapped in the Arctic and deep ocean. Another project involves global carbon management. The XMT is finding applications in vadose zone and fuel cell research, bioremediation, micromechanical device operations and inspection of germinating seeds.
RF tags on the right track for tracking
On treasure maps, an X marks the spot where the riches are buried. At Pacific Northwest National Laboratory, researchers have learned that tiny radio frequency tags can mark much more than location when it comes to tracking valuable goods.
Laboratory researchers have been developing RF tags that are ideal for tracking and monitoring a wide variety of items including clothing, pharmaceutical products and computer equipment. Radio frequency tags offer real advantages over bar-coding techniques to track inventory. For example, RF tag systems don't require line-of-sight access to the items. Tags can be affixed to or embedded within items, allowing whole storerooms of inventory to be counted in a matter of minutes whether the items are stored in boxes or containers, stacked in piles or strewn about in a cluttered area.
"With our new technology, the capability exists to read more than 500 tags in one second," said Ron Gilbert, a technical group manager at Pacific Northwest who leads the technology development. "This dramatically speeds up the inventory process, and could quickly determine if high-value items such as tools or equipment were missing."
The tags store unique information that can be read and changed as needed. For example, an item's age could be checked or its condition and location updated each time it is inventoried.
RF tag interrogators—units that contain an antenna, a transmitter and a decoder—create an RF signal that activates the tags. The interrogator then can decode the data from the tag.
Pacific Northwest's systems are on the cutting edge of long-range reading and writing capabilities. Some systems can be read from hundreds of meters away. With range like this, Gilbert and his colleagues developed an RF tag system for the Army that could be used to locate night vision goggles from the air when they're left on the field after training exercises. The same system could also disable the expensive equipment if it is taken without proper authority.
Beyond tracking inventory and locating items, the RF tags developed at Pacific Northwest also have the unique ability to monitor inputs and control outputs. With sensors incorporated into the systems, the tags can relay temperature and humidity measurements, or automatically control valves and switches if certain conditions exist. These features make this technology ideal for tamper detection, monitoring changing conditions and for remotely activating or disabling devices.
Pacific Northwest National Laboratory has developed radio frequency tag systems for many government and military applications, but according to Ron Gilbert who leads efforts in this area, these examples barely scratch the surface of potential uses. "These same technologies can be used in a wide range of applications," he said. "Our RF tags could be used on automobile parts, medical products, perishable food, sensitive documents—anything that needs to be tracked and monitored."
The genuine article
In the early 1990s, Pacific Northwest collaborated with Lawrence Livermore National Laboratory to develop a small, flexible RF tag that could be embedded in clothing. The project was part of the American Textile Partnership, or AMTEX, a multimillion-dollar agreement between the U.S. Department of Energy and America's textile industry. The tag was developed to inventory and manage clothing at department stores and to authenticate name-brand products such as designer jeans.
Loaded with information
Pacific Northwest engineers developed an RF tag system to track small arms inventory for the U.S. Army. The tagged weapons can be easily inventoried in cluttered environments such as warehouses and can be disabled if removed without the proper authority.
A brake in the action
A prototype system to monitor the temperatures in the brakes of F-16 aircraft is being developed for the Air Force. In this system, an RF tag is connected to tiny sensors inserted into an existing wear pin that monitors brake pad wear. The tag collects temperature readings from the sensor and relays it to ground crew members, helping them and the pilot prepare for the risks associated with high temperatures caused by locking the brakes in hard landings.
Dog tags go digital
A prototype for the U.S. Navy of the Tactical Medical Coordination System, also called TacMedCS, will quickly store, record and transmit information about an injured person's medical condition. The same size as a conventional military identification tag, an RF tag encapsulated in rubber could contain an electronic record of a person's medical history and condition that could be read and updated in the field. This system could improve the speed and effectiveness of assessing injuries, administering treatment and transporting patients.