Interview: DOE's nuclear bloodhound

By SCOTT R. BURNELL, UPI Science News   |   March 17, 2002 at 12:42 PM

UPTON, N.Y., March 11 (UPI) -- Radiation has never been high on most people's "must-have" lists, and the Sept. 11 terrorist attacks only heightened worries about the possibility of backpack nukes finding their way into major cities.

Ralph James, however, has made a career of seeking out the energetic subatomic particles and rays emanating from some of the most dangerous elements on the planet. James, associate director for energy, environment and national security at the Department of Energy's Brookhaven National Laboratory, is focused on creating smaller, cheaper, easier-to-use radiation detectors.

His work commands the attention of the White House and Congress, where recent hearings have focused on the consequences not only of nuclear weapon detonations, but of conventional explosions contaminated with radioisotopes.

The technology James works with is far more complex than the film badges or chattering Geiger counters Hollywood has long used to signify the hunt for uranium or plutonium. His devices involve semiconductor chips capable of spotting isotopes by their individual radiation "fingerprints."

The effort to safeguard the nation from rogue nukes might be hard-pressed to find a better bloodhound -- James has earned awards from the research and development community the past four years for his work to improve both the chips and the detectors.

Prior to Brookhaven, he worked at both Sandia and Oak Ridge National Laboratories. He earned his bachelor's degree in physics at the University of Tennessee and a master's in physics at the Georgia Institute of Technology before switching to applied physics, where he earned both an additional master's and his doctorate at the California Institute of Technology.

James spoke to United Press International during a conference at Brookhaven, where he gave a presentation on the accelerated effort to more widely deploy radiation detectors across the United States.

Q. You mentioned the development effort is underway for advanced sensors. On Capitol Hill, there's been a lot of talk not only of nuclear weapons smuggling, but also the possibility of radiological attacks. Phrases have been thrown around such as "a sensor on every lamp post," and this would appear to be the sort of technology that's going to fill that role.

A. You need to have something that's relatively inexpensive to be able to disperse them in such a widely distributed manner. You're also going to have something that doesn't have the operational constraints imposed by our really good detectors today that need this cryogenic cooling -- they just won't work in an unattended fashion for long periods of time. You're after something that's low-power, battery operated, very compact in size, long-term operation unattended, no maintenance; all those things are going to be required to make this happen. This (chip) technology really fits the bill.

Q. Can we discuss the technology in a little more detail? What direction is it taking?

A. The technology direction is very simple. We need sensors that are more sensitive, to detect radiation from a greater distance. This is very important if we're going to have this distributed network or even just checking in airports, tunnels and such. We also need detectors that have great specificity, where they can uniquely identify isotopes that are of great interest to us while not interrupting the flow of commerce with the sources that aren't of such concern.

We live in a world that's filled with radiation; it's in the walls, the floors, coming from space. So if we just have a dumb detector that senses radiation, we're going to constantly get false alarms. If this brings about an emergency response, we have a big problem. What we need is something that can discern special nuclear materials that might be part of something with nuclear yield. These are cases of plutonium-239, uranium-235, the ones people know about; (we have to spot these) materials from a wide range of naturally occurring isotopes. We can determine by a specific signature those isotopes that present the greatest risk to our citizenry, versus those that are shipped by the hundreds for a variety of nuclear medicines, gauging and other tasks.

Q. By signature, you mean empirical study has come up with a ratio of alpha to beta to gamma particles and rays that will signify a particular isotope?

A. That's not exactly how this works. Most of these materials emit X- and gamma-ray radiation. The rays are fairly penetrating and escape most shielding; charged particles, like alphas and betas, do not. We've got to detect based on gamma rays or neutrons. The gamma rays have telltale signatures associated with each nuclei, and each isotope has its own nuclei.

Q. Particular frequencies?

A. Yes, they really are frequencies. We refer to "energies" for the gamma emissions, but you can think of them as frequencies. Just as you can tune your radio to find the frequency of your favorite station, you can identify each isotope by tuning into the unique energies associated with the emissions. We can spectrally "window" and determine if (a source) is plutonium-239, a great concern for nuclear weapons, or something like americium-241, which is in practically every smoke detector in the Unites States.

Q. So this sort of system would seem to imply a network of simple detectors in a port of entry or an airport cargo terminal, designed to note the passage of something that's radiating in the proper energy bands and sound the alarm.

A. If you have limited resources, and we all do, and you're trying to have the maximum reduction of risk, you typically would focus on transportation choke points. These are the obvious things -- airports, seaports, train depots, tunnels, bridges and such. That's not going to give all the layers of defense you want, so you'll have to couple that with other things and this is where cost becomes a major issue.

Where'd you like to deal with this is with a sort of distributed network system. With any major city, if (the detectors) are cheap enough, you could put them with every fireman, every policeman, even with every postal worker. Now you have all these people going out in all these different regions with sensitivity to radiation. These individuals need just two signals, a warning that there's elevated radiation and another that might denote danger. You'd have a very strong network, it would be extremely difficult to move things around when you've got that many people. We see this happening in the future; eventually, you could see the detectors all coupled together (and) processing information.

As technology advances, you could see these attached to GPS devices, so that when something occurs, the detector could communicate with a central location that then checks to see if other detectors (have gone off). That would give you a very high level of confidence that something's going on that we should look into.

Q. Understandably there's a very high interest level (in these detectors), a very high effort level. Given the resources being put into this, what's a reasonable timetable to expect this type of network?

A. There are a couple of issues -- cost and the technology advancements. The detectors are available now, but there's a matter of cost. With economies of scale, you expect those costs to come down. It's also a big effort within Brookhaven to work with Russian labs to help them with material control and accountability. In terms of when we may be able to see these larger resources, I'm sure that's being discussed, but I'm not in a position to offer precise information.

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