Posted on: Thursday, April 14, 2005
Key ingredient in 'dirty bombs' removed from UH
By Johnny Brannon
Advertiser Education Writer
Radioactive material that had been used for decades at the University of Hawai'i in agricultural research — but that now carries national-security implications — has been removed and disposed of, according to the National Nuclear Security Administration.
• What it is: Cobalt (chemical symbol Co) is a metal that may be stable (nonradioactive, as found in nature), or unstable (radioactive, manmade). The most common radioactive isotope of cobalt is cobalt-60.
• What is cobalt-60 used for? Cobalt-60 is used in many common industrial applications, such as in leveling devices and thickness gauges, and in radiotherapy in hospitals. Large sources of cobalt-60 are increasingly used for sterilization of spices and certain foods. The powerful gamma rays kill bacteria and other pathogens without damaging the product. The product is not left radioactive. This process is sometimes called "cold pasteurization." Source: U.S. Environmental Protection Agency The 100 sources, or individual pieces, of cobalt-60 were removed at the university's request, because they had greatly weakened over time and were no longer being used in research, she said.
UH spokesman Jim Manke said the material had not posed any danger to the public, and that the university did not possess any more of it.
Federal authorities are concerned that cobalt-60 could be used to manufacture a crude radioactive weapon, or "dirty bomb," if obtained by terrorists. Such devices combine a conventional explosive, such as dynamite, with radioactive material. The NNSA has launched a national Radiological Threat Reduction Program to recover and secure materials that could be used to make such weapons.
"The removal of these radiological sources has greatly reduced the chance that radiological materials could get into the wrong hands," said Paul Longsworth, NNSA deputy director for nonproliferation. "The University of Hawai'i, its surrounding neighbors and the international community are safer today as a result of this effort."
A private contractor with expertise in removing, packaging and transporting cobalt-60 completed the removal on March 28, and it was permanently disposed of at a secure facility on Tuesday, the NNSA said.
The material was used in an irradiation process to treat tropical fruit, such as papayas and rambutan, Sakimoto said. The research was discontinued last year after a professor who oversaw the effort retired, she said.
"They were testing different kind of fruits to see how much radiation they would have to give it to kill insects, but keep the fruit in a marketable condition," Sakimoto said.
Irradiation is used by some food processors to kill bacteria and other pathogens that could otherwise result in spoilage or food poisoning. Cobalt-60 is the most commonly used radionuclide for food irradiation, according to the U.S. Environmental Protection Agency.
There is one commercial food irradiation facility in Hawai'i, on the Big Island, but it does not use cobalt-60, according to the state Department of Agriculture.
Scientists measure radiological activity, or strength, by a unit called the curie, which is defined as 37 billion disintegrations per second. Sakimoto said the cobalt-60 at UH measured at 1,000 curies.
"For research, it's a small amount," she said.
Reach Johnny Brannon at jbrannon@honoluluadvertiser.com or 525-8084.
The substance, called cobalt-60, was loaned to the university in the 1960s by the U.S. Atomic Energy Commission, and was kept at a lab on the Manoa campus near the Agricultural Engineering Building on Maile Way, UH radiation safety officer Irene Sakimoto said.
About cobalt-60
