The American public’s fears of tritium contributed to the closure of a famous neutron facility. Robert P Crease calls for more understanding of why people fear this isotope
Tritium is one of the most dangerous substances known to modern science.
This is not something that one would suspect at first appearance. Tritium is an ordinary part of the modern environment and is continually produced in the Earth’s atmosphere by cosmic rays. Common consumer products contain it: some wristwatches use tritium in illuminated dials, as do emergency-exit signs that are now standard in office buildings. Tritium is also used in many vital medical-research procedures.
Nor would one suspect tritium’s dangers from reading science textbooks. A soft-beta-ray emitter, tritium is not an external hazard to the body and must be inhaled or ingested to be dangerous. Even then, it passes through the body like water and is excreted quickly. Atom for atom, tritium has a low radiological toxicity, and the biological damage per disintegration is small. While one disintegration of an alpha emitter may deposit 6 MeV, a disintegration of a tritium nucleus deposits 5 keV, making it more than a thousand times less harmful. Environmentally, tritium does not hang around long, having a short half-life of 12.5 years.
Ingested in high quantities, of course, tritium can be lethal, like many chemicals (aspirin, say). But for a radioisotope, tritium’s physical and biological properties are relatively benign.
Toxic tritium tales
Appearances deceive. Consider the following true stories about the damage that tritium has inflicted, or threatens to inflict, on modern science.
In 1997 at the Brookhaven National Laboratory in the US, a small leak of water that contained tritium was found at the spent-fuel pool of the High Flux Beam Reactor (HFBR), one of the most important tools for neutron scientists worldwide. A total of 5 curies of tritium had seeped out – less than a quarter of that inside a single typical emergency-exit sign. The tritium was not in the drinking-water supply. It decayed near the pool and was not a health hazard. Yet the discovery triggered a media and political outcry, in the wake of which the Department of Energy (DOE) fired the lab’s contractor and ordered the reactor to be shut down.
Activists are trying to terminate the National Tritium Labeling Facility (NTLF), funded by the National Institutes of Health, at the Lawrence Berkeley National Laboratory in California. The facility, which labels tritium for research into curing diseases and other purposes, releases a minute amount of tritium in its operations. However, Berkeley’s city council has voted resolutions to shut down the facility because of tritium fears. Activists cited a consultant’s view that a catastrophic fire storm, consuming the entire tritium inventory of the NTLF, could expose a damaging amount to a jogger passing a few metres away. (This possibility was found to be exaggerated by several orders of magnitude.)
Anti-NTLF activists have also targeted a famous museum for closure – the Lawrence Hall of Science at the University of California at Berkeley. The tritium exposure there, due to the nearby NTLF, is about 0.02 millirems a year (one-thirtieth of the level permitted by US regulations). A single round-trip plane flight from Berkeley to New York exposes passengers to more radiation than a year spent living at the museum. Yet the Alameda county school board voted in favour of a moratorium on student field trips to the museum, although the resolution was later modified merely to note “differences of opinion” about the danger.
The National Ignition Facility at the Lawrence Livermore National Laboratory, also in California, has been targeted by activists claiming that its tritium releases (equal to that from an average hospital that conducts in vitro research) will be life-threatening.
All of these stories reveal that tritium poses a potential threat to any modern scientific and healthcare institutions that use tritium or occasionally produce it, in however minute quantities.
Non-toxic tritium tales
Yet tritium is not always harmful. Consider the following stories.
Last year the High Flux Isotope Reactor at the Oak Ridge National Laboratory in Tennessee was discovered to be leaking tritium-containing water. The amount of tritium in the resulting plume appears to be greater than that at the HFBR at Brookhaven, yet the consequences for the Oak Ridge contractor were not severe. Indeed, the Department of Energy wants to upgrade the reactor.
The DOE’s Savannah River site, which has produced tritium and plutonium for the US weapons-production programme, released hundreds of thousands of curies of tritium a year into the environment up until the 1990s. Now it releases less than 50,000 curies a year.
In June 1997 a Brookhaven radiation-protection team received a call from the New Jersey State Health Department about a 16-year-old New Jersey boy who, as a prank, had removed several tritium-powered exit signs from a dump, broken them open and ingested some tritium. His urine samples showed a concentration of 28.6 million picocuries per litre – almost 20 times the peak concentration in the tritium that had seeped from the spent-fuel pool at Brookhaven.
Yet the New Jersey health authorities determined that the incident did not create a health hazard. They also concluded that there was no possibility that the boy could have received enough of a radiation dose to cause an immediate health effect, such as radiation sickness.
The critical point
I have heard scientists speak of public scares involving minute amounts of tritium as cases of irrationality – “modern Salem stories”. This is wrong: there are underlying reasons. Fear of tritium can be generated and exploited in the presence of “social prereceptors” – specific sensitivities to external stimuli. Ideologues can then treat minute amounts of tritium not as a health issue but as a tool to further political agendas or Utopian crusades.
Many scientific instruments – from accelerators to reactors – create tritium in minute amounts. Given this, isn’t an in-depth study of these social prereceptors important to the future of science? Considering that so many public-health institutions – from hospitals to clinical research programmes – use tritium in indispensable ways, isn’t such an analysis of interest to any socially progressive individual?
