The Risks of Laser Isotope Separation (LIS)
- Dr. Mark Raizen, University of Texas at Austin
- Dr. Francis Slakey, American Physical Society
Over the last 15 years I’ve criss-crossed the globe and witnessed its full range of stories. And when you see dust kick up from the bare feet of a tribeswoman walking 5 miles to get water, you realize that we face enormous global challenges, including climate change, pandemics and access to clean water, to name just a few. Regardless of our individual views on any of those issues, I’m sure that we can all agree on one thing: let’s not add more challenges to the list. We have enough to deal with.
So, when the research that we carry out has the possibility of creating significant risks, then we should pause, reflect, and make sure that we don’t add yet another burden to an already challenged world.
Biologists did just that – pause and reflect – in exemplary fashion a few months ago when they confronted the H5N1 issue. Concerned about potential security risks associated with publishing particular work on airborne transmission of avian flu, the relevant community of biologists put a self-imposed pause on research to consider the implications and challenges. It was thoughtfully done, with only modest reluctance from some scientists, and with benefit to all.
We are now at a moment when it would be fruitful for the relevant members of the physics and engineering communities to carry out a similar examination of the risks and benefits of some areas of isotope separation research.
So far, we’ve gotten lucky in uncovering when countries are developing nuclear weapons programs. However, new isotope separation technologies are emerging that are smaller, more efficient and harder, if not impossible, to detect. The technologies are in various phases of development, from basic research to commercialization. Consider this:
Global Laser Enrichment, a joint
venture of General Electric-Hitachi, is construct-
ing and evaluating a laser-based method of uranium enrichment (SILEX) that
is substantially more efficient and could leave little prospect for detection if
stolen and acquired by a rogue group.
Professor Raizen has developed a method
of single-photon isotope separation
using a magnetic trap and low-power laser excitation for a more efficient method
to develop much-needed medical isotopes. His technique isn’t intended to enrich
uranium, although the potential may well be there.
These developments raise the same issue: the on-going push for greater efficiency in isotope separation carries associated proliferation risks.
These risks of more efficient isotope separation are well known to the U.S. government. For example, the SILEX technology under development in North Carolina was the subject of a multi-agency proliferation-assessment report. The report conceded that “Laser-based enrichment processes have always been of concern from the perspective of nuclear proliferation… a laser enrichment facility might be easier to build without detection and could be a more efficient producer of high enriched uranium for a nuclear weapons program.”
The report ominously stated that it seemed likely that the technology would “renew interest in laser enrichment by nations with benign intent as well as by proliferants with an interest in finding an easier route to acquiring fissile material for nuclear weapons.”
So the risks of enrichment technology are well documented, and the consequences of the proliferation of the technology are clear and present, most immediately in Iran.
Of course, the easiest path for our research community would be to claim that these risks are someone else’s responsibility – we are scientists after all, not police. Yet, the biologists didn’t take that easy path. They broadened their sense of responsibility outside of the lab. They paused, considered, deliberated. And there is a practical reason for doing this. If scientists don’t consider the risks, we leave it to others to decide. And we may not like what they conclude.
What would we conclude from pausing and carrying out our own “stress test”? I can’t predict the outcome. In the case of the biologists, they strengthened their system with a centerpiece called the National Science Advisory Board for Biosecurity that monitors “dual-use research of concern” and it has received enthusiastic endorsements from scientists. The biologists came out of the process stronger. So can we.
We live in exciting times, as we learn to control the physical world on the atomic and molecular scale. Efficient isotope separation is one example of a wider range of capabilities that include the assembly of new materials on the nanoscale, one atom at a time. These are powerful developments that can bring many benefits to mankind, but can also be intimidating to some. In particular, the topic of efficient isotope separation can evoke a fear of nuclear proliferation, but is that really true?
In fact, our methods will actually be used to reduce the risk of proliferation. How can that be? Consider Technecium-99m (Tc-99m).
This short-lived radio-isotope is used for medical imaging and is a major tool in nuclear medicine. Today, all Tc-99m is produced using weapon-grade uranium as a target in a nuclear reactor. The need to use such weapon-grade uranium poses a serious risk of proliferation, and the U.S. has led a worldwide effort to halt this mode of production by 2016. An alternative is to enrich a stable isotope, Molybdenum-100, which can be converted to Tc-99m by a clean nuclear process. You can read more about this topic in an excellent article by Dr. Tom Ruth. Our method of laser isotope separation can be used to produce enriched Molybdenum-100, and will therefore be an important tool in stopping nuclear proliferation.
Could our method be used for enrichment of uranium? That is a valid concern, and we should certainly pause and reflect, as suggested by Dr. Slakey. My best guess is that the application of our method to uranium is unlikely to be competitive with existing methods.
The basis for our approach is laser activation of the magnetic state of an atom, requiring a relatively simple atomic structure. Uranium has a very complex structure which may not be amenable to this new process. It is perhaps tempting to say that a method for enriching one isotope could also be applied to another. However, each element is unique in its physical and chemical properties. For example, the starting point for most atomic laser separation projects is to heat the solid material and vaporize it, forming an atomic beam. According to unclassified documents on the laser uranium separation project, it took years to find materials that do not react chemically with hot uranium metal. In contrast, many elements, such as calcium or ytterbium, are routinely used in atomic beams in research laboratories and do not have those problems. Similarly, the atomic structure and required lasers are unique to every atom. A good analogy is to say that not all fruit are the same. In fact, uranium and calcium are as different from each other as apples and oranges.
In conclusion, with so many evident benefits we should not fear the future. We should look instead to the past and be inspired by the words of the great Marie Curie who said: “I am one of those who think like Nobel, that humanity will draw more good than evil from new discoveries.”
Updated July 17, 2012 1:15 PM