courtesy Outlaw Labs
Get rid of dirty bomb ingredient
The US government should take steps to promote the replacement of radioactive cesium chloride radiation sources, a potential "dirty bomb" ingredient used in some medical and research equipment, with lower-risk alternatives, says a new congressionally mandated report from the US National Research Council
Cesium-137 in the form of radioactive cesium chloride in stainless steel capsules is used in self-contained irradiators at hospitals and universities for blood irradiation and in biomedical and radiation research, as well as other industrial uses. Approximately 1,300 radioactive high-activity cesium chloride devices, nearly all of them self-contained irradiators, are in use across the United States, and the number appears to be increasing. Replacements for radioactive cesium chloride and some other high-risk radioactive materials used in commercial devices are available, but they are more expensive, creating little incentive for users to switch.
The report was requested by Congress because of concerns that devices containing cesium-137 and other high-risk radionuclides could be stolen for use in a terrorist attack. The committee that wrote the report was asked to examine the uses of high-risk radiation sources and to identify lower-risk alternatives.
The U.S. Nuclear Regulatory Commission and some state agencies with authority to license and regulate devices that contain radiation sources adopted an international hazard ranking system, which is based on the potential of a radiation source to harm human health. A source is categorized as "high risk" if it could lead to the death or permanent injury of unshielded individuals who are exposed for a few minutes to up to a few hours.
Direct exposure by one of the sources studied by the committee -- whether accidental or intentional -- would likely not cause mass causalities. Yet, dispersal of the source, as would occur in some kinds of radiological attacks, could contaminate an area, including the land, buildings, and infrastructure, rendering it uninhabitable for an extended period of time. While the economic and social disruptions caused by such an incident are difficult to quantify, these long-term exposure hazards should be considered when evaluating risk because they go beyond immediate fatalities, the committee noted.
Eight radionuclides account for more than 99 percent of the sealed sources that pose the highest security risks in the United States. Cesium-137 in the form of cesium chloride poses greater concern than the others because it is widely used in significant quantities and is soluble and dispersible. If ingested or inhaled, it delivers a dose to the whole body. The concern about the availability of sources is exacerbated by the lack of permanent disposal options, which increases the likelihood that unwanted cesium-137 will remain in storage where it could be vulnerable to theft, the committee emphasized.
For most applications, radioactive cesium chloride can be replaced by lower-hazard alternatives that will not change the performance of the medical and research equipment, the committee found. Such options include using less hazardous forms of radioactive cesium, radioactive cobalt, and X-ray generators. However, less hazardous forms of radioactive cesium sources are not yet commercially available, and making them available may require cesium-source producers to modify production processes. Cobalt-60 may be substituted for some applications, but it would require more expensive shielding and more frequent replacement. Devices using X-ray generators instead of radioactive material are already commercially available as substitutes for some applications, but they are slightly more expensive and require more maintenance.
To phase out the use of current radioactive cesium-chloride sources, the committee presented a number of options. One option is the U.S. government could stop licensing new cesium chloride irradiators, including discontinuing their import and export. The government could also create incentives for owners to decommission and dispose of their current sources and devices. Additional incentives could lower the cost of replacement technologies or encourage device makers to develop and promote lower-hazard replacement technologies.
As another option to speed replacement, the government could create incentives to buy back used irradiators, basing the price on the device's age. In turn, owners of the devices could pay for more of the disposal costs, which could be as much as or more than the purchase price of a less hazardous device. The committee did not make a specific recommendation about the magnitude of a desirable buy-back price; however, the estimated capital cost of a replacement X-ray irradiator device is $200,000, slightly higher than the current cost of a cesium chloride irradiator.
In addition to actions related to radioactive cesium chloride, the U.S. government should adopt policies that provide incentives -- market, regulatory, or certification -- to facilitate the introduction of replacements and reduce the attractiveness and availability of other high-risk radionuclide sources, the committee recommended.
This study was sponsored by U.S. Nuclear Regulatory Commission. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies. They are private, nonprofit institutions that provide science, technology, and health policy advice under a congressional charter. The Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering.
