Nuclear mattersThe U.S. faces severe helium-3 shortages; nuclear detection, science suffer
The decay of tritium, the radioactive heavy-hydrogen isotope used in nuclear weapons, long produced more helium-3 than could be used; the United States stopped making new tritium in 1988, and so the remaining supply has been dwindling as it decays; the post 9/11 rush to build and deploy radiation detectors, however, increased dramatically the demand on the U.S. declining helium-3 resources — and now scientific research dependent on helium-3 suffers, and soon there will not enough even for security devices
This week, members of the U.S. Congress will consider what to do about a serious shortage of helium-3 that is disrupting both scientific research and nuclear security. Helium-3 is invaluable for some scientific instruments, but supplies have been used up in making security systems to detect dangerous nuclear materials, and production can not be increased. On Thursday, a House subcommittee will try to pin down what went wrong and how to fix the problem.
New Scientist’s Jeff Hecht writes that the decay of tritium, the radioactive heavy-hydrogen isotope used in nuclear weapons, long produced more helium-3 than could be used. The United States, however, stopped making new tritium in 1988, and so the remaining supply has been dwindling as it decays. Around a decade ago, the stockpiles of tritium and helium-3 seemed adequate, with only about 10,000 liters used each year, largely in neutron detection and cryogenics (see NAS: Selling Vast Federal Helium Reserves Is a Mistake,” 9 February 2010 HSNW).
All this changed with the deployment of neutron detectors in security systems searching for illicit plutonium and other nuclear materials. Nearly 60,000 liters of helium-3 were used per year in 2007 and 2008 — about 80 percent for neutron detection.
“Everyone who uses helium-3 is getting pinched,” says William Halperin of Northwestern University in Evanston, Illinois. He had not realized there was a shortage until 2008, when he could find no gas for his cryogenics lab.
“Without helium-3 we will not have a means for refrigeration to do scientific research below 1 kelvin. It’s absolutely necessary,” Halperin says. Existing refrigerators will continue working, but new ones can not be built, which is preventing the study of quantum computing and other fields that require extreme cold.
“There are labs in Germany and Japan that have half-built instruments and can’t buy neutron detectors,” says Ron Cooper of the Oak Ridge National Laboratory in Tennessee. Oak Ridge is planning a second large array of neutron detectors for its Spallation Neutron Source. The first used 4,000 liters of helium-3, but that much gas won’t be available again.
Hecht writes that lithium and boron also can be used in neutron detectors, so Oak Ridge is developing a lithium-based instrument. It will be less sensitive, however, than one based on helium-3.
The Pacific Northwest National Laboratory in Richland, Washington, is also developing new types of boron-based detectors, one using tubes filled with boron trifluoride gas, the other tubes coated with boron. Neither is as sensitive as a helium-3 detector, says Daniel Stephens of the lab, but like helium-3 both are blind to gamma rays, which can confuse other neutron detectors.
