Answer to Question #1754 Submitted to "Ask the Experts"

Q

I am concerned about nuclear contamination should a terrorist detonate nuclear-related materials in this country. As a result I would like to buy a detection device such as the badges that workers wear in nuclear facilities. I am interested in your opinion as to which is the most-sensitive and least-expensive (emphasis on sensitive) material to detect radiation: sodium iodide or cadmium telluride? Any additional comment is welcome.

A

There are many federal and state agency, and privately employed, health physicists who are concerned about the country's readiness to respond to a nuclear weapon of mass destruction or radiological dispersion device (RDD). I believe you may not be a professional health physicist, but a very concerned individual. Given the media attention to "dirty bombs," since 9/11, this doesn't surprise me. First, you should be aware that many local and county emergency responders have basic radiation survey instruments (Geiger-Mueller [GM] counters). State hazardous material responders often have the same, but with more sensitive thin mica window "pancake" style probes that can detect alpha, beta, and gamma radiation. Secondly, state radiation control program staff members have the same sensitive "pancake" probes on their GM counters and often have portable gamma spectroscopy equipment for radioactive material identification.

Should a terrorist detonate an RDD, I believe it would be detected in a relatively short period of time. There are hundreds of nuclear power plants and thousands of radioactive materials licensees that perform routine contamination monitoring. Additionally, there are national air sampling programs for the same and, perhaps as an unplanned benefit, many metal scrap dealers and landfills are installing very sensitive radiation-detection equipment to protect their physical assets from lost "general license" sealed sources. These detectors may provide an early warning to an unknown release. Local and state radiation protection officials would be first to respond to any radiological event.

You should also be aware that there are many federal assets available to the states in an emergency, such as 24-hour radiological assistance program teams, aircraft and helicopters with radiation monitoring capability, dispersion modeling groups, etc. And as I understand it, many of these local, state, and federal programs are being reviewed and strengthened in light of our current threat environment. The message I wish to convey is, there are many health physicists at all levels of government, at national laboratories, and within private institutions who are working very hard to ensure nuclear facilities and materials are secure, materials are detected from illegal trafficking into the United States and should it happen, an RDD would be detected and mitigated promptly. I can't recommend that a private citizen spend money to purchase any type of radiation-detection or monitoring device. However, if you would like to obtain training and volunteer for local radiological emergency response, there are many training programs available in areas that have nuclear power plants or major transportation routes. I'd suggest starting by contacting your local or state emergency response organizations to get involved. If you still think you want an instrument of your own, I'd recommend a GM counter with a "pancake" type probe. You could pick up an old Civil Defense CDV700; don't pay more than $25 as they built millions and most states are dumping them. I believe both Health Physics Society Affiliate Members SE International and Canberra Industries build a retrofit pancake probe for the CDV700. A solid NaI or CdTe probe will only see gammas, and a pancake (though not as sensitive to gamma rays) will detect alpha, beta, and gamma radiation. If I had one instrument to bring to an event scene, it would be a GM with a pancake probe. Great question, thanks.

David J. Allard, CHP
Director, PaDEP Bureau of Radiation Protection