Apr 20, 2009There are scores of asset-tracking applications that improve security or save money, time and labor, but it's hard to imagine items for which precise and continuous monitoring is more vital than drums of hazardous nuclear materials. That's why the U.S. Department of Energy (DOE) and its Packaging Certification Program, which certifies safe packaging for hazardous materials, turned to one of the DOE's oldest and largest research centers, the Argonne National Laboratory, in Illinois, to develop a customized, sophisticated approach for using radio frequency identification technology to continuously track radioactive and fissile materials, both while in storage and during transport. The number of drums holding such materials is estimated to be in the tens of thousands.
Spent nuclear materials are stored in facilities such as Argonne's Alpha-Gamma Hot Cell Facility, where irradiated materials from various U.S. research and test reactors are kept in specialized, locked drums. Detailed paper-based records are maintained for each container, says Yung Liu, Argonne's senior nuclear engineer and RFID project manager. These records include the serial number assigned to each drum, what the drum contains and its exact location within the storage area. But the only way to closely monitor the condition of each drum—including the integrity of its seal, and environmental factors that could compromise safety—was with manual inspections (a process that is not performed frequently) to limit personnel's exposure to radiation.
Argonne National Laboratory developed a customized, sophisticated approach for using radio frequency identification technology to continuously track radioactive and fissile materials, both while in storage and during transport. Click here to view a larger version of the image.
Another concern was tracking drums of nuclear materials during transit. While a global positioning system (GPS) was used to track the location of the vehicles carrying nuclear material, the DOE had no way to constantly take inventory of the drums, or to automatically monitor each drum's environmental condition.
Argonne's scientists spent three years developing the RFID system, which was tested during a weeklong demonstration project in April 2008. The system met its goals: to manage nuclear materials for safety, security, accountability, health and environmental protection during storage, transportation and disposal. "The Argonne system can simultaneously monitor thousands of drums 24 hours a day, seven days a week," Liu says. "Any abnormal situation—such as a lost seal, a sudden shock or a rise in temperature or humidity—can trigger an alarm for immediate action." The DOE plans to deploy the RFID system to augment and modernize its existing management systems for nuclear materials. The system has already been installed at the Argonne National Laboratory, and is currently being installed at a test site in Nevada.
To build the solution, the Argonne scientists had to modify the ST-676 active 433 MHz tag made by Savi Technology, as well as develop specialized application software, a database server and Web pages to manage the tag and location data. "Active RFID was our first and only choice for this application," Liu says. The DOE required a method for identifying the drums, without a constant, clear line of sight to each. Passive tags would not have provided the necessary read range, and the metallic content of the drums would likely have interfered with RF signals used for transmitting and collecting data. Plus, the need for sensors integrated into the tag required an onboard power source.
Savi's ST-676 tag—which operates at low power but offers a long read range (approximately 100 meters, or 328 feet)— made it attractive, as did its use of the globally accepted 433 MHz band. What's more, the tag included integrated sensors that monitor the temperature, humidity and shock to which the tag is exposed. And since the tag was made to track and secure cargo containers, it included a locking mechanism that enabled it to act as a security seal.
So even before Liu and his team began customizing the ST-676 tag, they tested its gamma radiation resistance by exposing four tags to constant, potent doses of nuclear radiation over a period of three months. "We remotely monitored the tag and looked for evidence of degradation of the data saved to the tag," Liu states. Two of the four tags showed no degradation, but in two tags, the chip memory began to deteriorate once a certain level of radiation exposure was reached.
Given the much lower radiation exposure limits required in nuclear storage facilities, the team estimated that the tags would remain in service for roughly 17 years before this same memory degradation would occur. Furthermore, given that nuclear material storage areas are generally well below the limits of radiation exposure, the serviceable life of the tags in real deployments would likely be much longer than the 17–year estimate. Based on this result, Liu and his team proceeded with tag development. (He notes that the lab will continue to test later generations of RFID tags, to gauge whether radiation resistance can be improved.)
To modify the tag's form factor, its old housing and locking mechanism were removed and replaced. The new tag's profile is designed to fit snuggly on each of the three types of standard drums in which the DOE transports and stores nuclear material. But because these drums—referred to by the model names 9975, 9977 and ES-3100—each have unique lids, Argonne needed three different designs for the seal part of the tag. So while a common outward-facing housing is used for the tag, there are customized mounting plates and seal sensors for each of the three drum types.
To address the issue of battery life, Liu and his team replaced the single battery that comes factory-issued with the ST-676—which has a three- to four-year life expectancy—with a battery management board. This board accommodates up to four A-size Li–SOCl2 batteries, and it manages the batteries's lifespan using a switching circuit. This ensures that only one battery is activated at any given time, preventing the batteries from unnecessarily draining power when not in use. When all four batteries are nearly drained, the circuit controlling them will send a signal through the tag data to the RFID interrogator, and the reader software will trigger a direction to personnel to replace the tag's batteries, thereby ensuring the tag's continued operation. It's estimated that this customized battery design will enable the tags to operate for more than 10 years under normal use.
Liu and his team have left an empty space within the tag housing for the addition of a radiation dosimeter sensor. This sensor, which would trigger alerts in the event that the tag is exposed to unsafe levels of radiation, is still under development.
The software includes a graphical interface that illustrates the drums while they are both in storage and in transport, based on tag reads. By logging onto a secure DOE server, offsite personnel can employ this interface to watch the tagged drums' movements in real time. The interface also relays alarms, triggered by sensor reads—such as if a seal sensor detects an attempt to open a drum. And it allows a user to click on a specific drum and access all of the location and sensor data that the software has logged about that drum, based on tag reads.
The Argonne system can simultaneously monitor thousands of drums every day. Click here to view a larger version of the image.
The weeklong demonstration project that the DOE conducted in April 2008 showed that the customized tags worked as expected. But that was just one of many, equally important objectives. The goals were to demonstrate that the RFID tags could be read during transit, that the tag data (which includes sensor readings) could be integrated with location data collected through a GPS system, and that this combined information could then be sent through a satellite or cellular communication network to authorized parties. In addition, the demonstration needed to show how the sensors act as eyes and ears, triggering alerts whenever environmental conditions surpassed set parameters.
For the demonstration, 14 empty drums (of all three drum styles) were loaded onto a conventional 18-wheel tractor-trailer. Each drum was outfitted with an RFID tag. An interrogator was installed within the trailer, under the ceiling and above the drums. The interrogator was hard-wired to a computer, a GPS antenna and a cellular/satellite modem. An engineer in the cab of the truck operated the equipment, and a secondary vehicle containing additional staff followed the truck on each leg of the trip. Back at the Argonne National Lab, network and security staff monitored the demonstration through secure Internet links.
For the first leg of the journey, the truck drove from the Argonne National Lab to Savannah River National Laboratory, located in South Carolina. This took two days, and included a demonstration for moving the drums into and out of a storage facility. The second leg involved moving the drums from Savannah River to Oak Ridge National Laboratory, in Tennessee, where the drums were again moved into and out of storage. Finally, the drums were brought back to Argonne and placed into storage at that facility.
The sensors were purposely triggered during the trip—twice by hand-tapping the tags (to induce the vibration sensor), and twice by momentarily loosening the drum nuts (to trigger the seal sensors). In each case, the sensors communicated the event to the tag's onboard memory, and the tag conveyed the information to the RFID interrogator mounted within the truck. Based on this data, ARG-US triggered alerts—e-mail and text messages—sent over both the cellular and satellite links, to appropriate personnel. When responding to the alerts, employees were able to log into the ARG-US software and view a representation of the truck on a map view of the highway, to ascertain exactly where and when the sensor was triggered. If a real-world incident were to occur, alerts could also be transmitted to local emergency response teams, based on the event's location, to ensure the fastest possible response.
The truck location data stream also proved accurate and reliable. It was determined that having a satellite-based communication capability was important, because the cellular-based data link sometimes failed when the trucks were in highway zones without cellular coverage (data was cached when this occurred, so no information was lost).
The interrogator was hard-wired to a computer, a GPS antenna and a cellular/satellite modem. Click here to view a larger version of the image.
The security of the ARG-US software and DOE servers is another major concern. The DOE indicates it is addressing this issue by deploying backup data centers and servers at separate physical locations, to "preclude system disruption during natural disasters and/or terrorist attacks."
Going Forward With RFID
Based on the success of the demonstration project, the RFID system will likely be used for many tracking and environmental monitoring applications throughout the DOE—both for nuclear materials and other hazardous materials. At the Nevada test site, the goal is to use the collected tag data to decrease the frequency of physical drum inspections from each year to every five years. The DOE also intends to employ the RFID system for tracking cross-country nuclear material transports.
The Argonne lab is presently seeking a patent for the new tag design, though Liu says it is not in the business of mass-producing RFID tags. The DOE is looking to the commercial sector to begin offering RFID tags based on the Argonne design. While Savi has been a major supplier to the U.S. government—particularly the U.S. Department of Defense—for the past 15 years, it will not be its sole supplier of active 433 MHz RFID systems going forward (see U.S. Defense Department Picks Four for RFID III). To ensure not only that devices from various providers conform to the ISO 18000-7 air interface standard that the Savi and Argonne tags follow but also that they can interoperate with each other, the DOE has joined with Savi and a number of tag makers, chipmakers and other stakeholders in the development of an industry alliance, known as Dash7 (see Dash7 Seeks to Promote RFID Hardware Based on 18000-7).
Outside of the safety and national security benefits, through greater monitoring and accountability of the nuclear materials, the DOE hopes the RFID tracking system will also lead to business benefits in the form of greater operational efficiency and labor reductions.