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Push to purge cesium irradiators gains momentum

24 October 2017

Government subsidies and nonprofit advocacy encourage institutions to replace devices containing materials that could be used in a dirty bomb.

Cesium blood irradiator
Cesium blood irradiators like this one are being phased out in favor of x-ray devices. Credit: NNSA

A nonprofit-led initiative to eliminate a widely used medical and research device containing an isotope that could be used in a dirty bomb has received an important boost. On 11 October, a dozen New York City institutions announced that they will replace all but 2 of the 30 cesium-137 irradiators in the city. Separately, California institutions agreed late last month to phase out 11 of the state’s 100 irradiators.

About 550 of the nation’s estimated 800 irradiators are used at hospitals and blood banks to sterilize blood prior to transfusions, according to the Nuclear Threat Initiative (NTI), which helped organize the New York and California efforts. The remainder are used to irradiate small animals and cells in biomedical research.

A fission by-product, 137Cs has a half-life of 30 years and emits beta and gamma rays. Due to its talcum powder–like consistency, the isotope is considered particularly attractive to would-be radiological bomb makers. If dispersed by an explosive device in a densely populated area, the material would have severe economic and human health consequences. Nearby buildings would be contaminated and possibly require demolition. Cleanup to meet human habitation standards could take years.

The Food and Drug Administration has approved x-ray equipment made by two US manufacturers as alternatives for blood sterilization. The devices cost around $250 000, but the Department of Energy’s National Nuclear Security Administration will pay half of that. The NNSA also will remove and dispose of cesium irradiators for free, saving institutions $100 000 or more in disposal costs.

Andrew Bieniawski, a vice president at NTI, says the organization has set a goal to have all US cesium blood irradiators phased out by 2025. Worldwide, there are believed to be more than 2000 of the devices, he says. France and Norway have replaced all their irradiators, and Japan, spurred by the Fukushima nuclear disaster, has done away with 80% of its total. But Bieniawski is pessimistic that Russia, India, and China will phase out their cesium sources.

X-ray blood irradiator
The Icahn School of Medicine at Mount Sinai in New York installed a new x-ray blood irradiator. Credit: Mount Sinai

Jacob Kamen, associate professor of radiology at the Icahn School of Medicine at Mount Sinai in New York, says his institution is in the midst of replacing all four of its irradiators. “We decided the best risk is not to have risk,” he says. The x-ray devices also offer the advantage of providing radiation at a wide range of energies, as opposed to cesium’s single peak-energy emission. Ninety-eight percent of research users at the school have already switched to x rays, Kamen says, and the remainder are finishing up their experiments on the cesium equipment.

Mount Sinai had previously upgraded security protections for its irradiators, at a cost of around $700 000, with help from an NNSA grant. It also hired a full-time technician to irradiate samples from all researchers, in order to restrict the number of people with access.

The 12 New York City institutions agreed to dispose of 28 cesium sources. The one holdout, Memorial Sloan Kettering Cancer Center, is considering replacing its two devices. The citywide phaseout is expected to be completed in 2020.

California governor Jerry Brown and NTI obtained commitments in late September to replace 11 of the 100 irradiators in the state. Most of the pledges were from the University of California, which has 40 units on multiple campuses, says Bieniawski. Owners of 11 others agreed to further explore the NNSA incentives program.

Bieniawski says the hope is to replicate the New York phaseout model in other large cities considered particularly attractive to terrorists, such as Los Angeles, Boston, Chicago, and Houston. Some top executives of hospitals and medical centers aren’t even aware they have the irradiators, he says, and insurers don’t offer any policies that would cover an institution’s liability in the event a dirty bomb is fashioned from a stolen irradiator.

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