Although demand for a critical gas used in radiological detectors and for other purposes is outstripping the annual production of Helium-3 (He-3), it won’t impact deployments this year and in FY ’11 of radiation portal monitors (RPMs), a Department of Homeland Security (DHS) official tells Congress.
The RPMs already have sufficient He-3 tubes, which are a critical component of the radiation detection systems, a Dr. William Hagan, acting director for the Domestic Nuclear Detection Office (DNDO), tells the House Science and Technology Subcommittee on Investigations and Oversight. An RPM consists of a neutron detector, which use the He-3 gas in tubes, and a gamma detector, which uses a plastic scintillator.
The demand for He-3 ramped up following 9/11, in particular with the establishment of DHS and the accelerated production and deployment of RMPs at the nation’s ports of entry the past seven years. The gas is also in oil and gas exploration, low-temperature scientific research, medical imaging and other uses.
“The current and future He-3 supply will fail to satisfy the demand of interagency partners and the commercial sector,” Hagan says. “Only approximately one-tenth of the current demand for He-3 will be available from the Department of Energy’s National Nuclear Security Administration for the foreseeable future, and neutron detectors using He-3 are already becoming difficult to procure.”
He-3, which is rare and low in natural abundance, is created through the decay of tritium used in nuclear weapons, with harvesting typically occurring through the refurbishment and dismantlement of these weapons.
“Without development of alternative sources for He-3, use of this gas will be constrained seriously in the foreseeable future as accumulated stockpiles are drawn down,” Dr. William Brinkman, director of the Office of Science for the Department of Energy, tells the panel.
Alternative Materials
Alternative sources of supply for He-3 and alternative materials for neutron detection are being explored although these efforts have only been accelerated in the last year or so, Hagan says.
“At present we are working with the commercial sector to identify alternative detection products that have potential for near-term commercialization,” Hagan says. “Our DNDO exploratory research projects that address other detection materials with neutron capabilities have also been accelerated.”
Hagan says that DNDO has identified several materials that can be used with the neutron detectors for RPMs. These are Boron Triflouride-filled proportional counters which were used for neutron detection before He3 but is a hazardous material, making it a tough choice for end users, he says. Testing on the technology shows that it is a low cost replacement, he says.
Other technologies include Boron-lined proportional counters, Lithium-loaded glass fibers, coated non-scintillating plastic fibers, and a new scintillating crystal composed of Cesium-Lithium-Yttrium-Chloride, which has both neutron and gamma detection capabilities, Hagan says. He-3 is not used in gamma detectors, which are another component to RPMs. Some of the technologies may have better neutron detection capabilities than He-3, he says.
At one time DNDO had hoped by now to be replacing, or at least complementing, the use of RPMs with a new generation of systems to screen cargo containers for radiation, the Advanced Spectroscopic Portal (ASP). However, that program has faced numerous delays and this year Homeland Security Secretary Janet Napolitano decided that the technology would be used for secondary screening instead of primary screening, which will limit the number of systems that will be needed (TR2, March 3). However, ASP must complete testing and still be certified for use.
Hagan says that if the ASP systems eventually are used in secondary screening, then “DHS can reuse the He-3 from the existing RPMs that are being replaced and use it for the ASP units.”
Hagan also says that in addition to RPMs, smaller detection devices such as handheld radioisotope identification devices and backpack detectors also use small volumes of He-3. A “redesign of current equipment will be necessary over the next several years, once new neutron detection technologies have been identified,” he says. “As such, DNDO plans to work with the device manufacturers to develop new technologies, integrate them into systems, and test them for suitability in the field.”
Between now and then though, DNDO will still have to request “modest allocations” of He-3 from the government stockpile for use in the human portable systems until the alternatives are ready, Hagan says.
For some applications it will be difficult to replace He-3, particularly oil and gas exploration, which requires the high sensitivity and reliability of helium-based devices in often rugged underground conditions in deep wells.”
“It is likely that without Helium-3, exploration for new reserves, development drilling of existing fields, and logging of both new and existing wells will be severely curtailed until an alternative technology is developed,” Thomas Anderson, product line leader at General Electric [GE] Energy, Reuter Stokes Radiation Measurement Solutions, tells the panel.
The hearing was held by the subcommittee to examine the He-3 supply crisis, which only became known publicly last fall when Hagan testified before the panel that the a White House-led group restricted DNDO from using the gas in further RPM production (TR2, Nov. 25, 2009).