Emission Impossible

Monitoring radiocarbon emissions (carbon-14, typically in the form of carbon dioxide and methane) from nuclear reactors is no easy task. Laboratory-based methods to detect carbon-14, including accelerator MS and liquid scintillation counting, are effective, but are not easily used online – neither are they sufficiently adaptable to monitor atmospheric samples. Guillaume Genoud and colleagues at the VTT Technical Research Center in Finland set out to fill the gap by using an automated laser spectroscopy-based system to detect traces of carbon-14 containing gases in atmospheric-like samples (1). “We employed an optical method to ensure a compact, rapid, and more affordable way of detecting trace gases,” says Genoud. “Mid-infrared cavity ring-down spectroscopy (CRDS) was chosen to provide the highest levels of sensitivity.”

The CRDS instrument was coupled with an advanced, two-part sampling system; a cryogenic trap extracts carbon dioxide from the air sample, while a catalytic unit converts methane into carbon, which allows the approach to discriminate between radiocarbon in organic or inorganic molecular form.

Monitoring radiocarbon emissions (carbon-14, typically in the form of carbon dioxide and methane) from nuclear reactors is no easy task. Laboratory-based methods to detect carbon-14, including accelerator MS and liquid scintillation counting, are effective, but are not easily used online – neither are they sufficiently adaptable to monitor atmospheric samples. Guillaume Genoud and colleagues at the VTT Technical Research Center in Finland set out to fill the gap by using an automated laser spectroscopy-based system to detect traces of carbon-14 containing gases in atmospheric-like samples (1). “We employed an optical method to ensure a compact, rapid, and more affordable way of detecting trace gases,” says Genoud. “Mid-infrared cavity ring-down spectroscopy (CRDS) was chosen to provide the highest levels of sensitivity.”

The CRDS instrument was coupled with an advanced, two-part sampling system; a cryogenic trap extracts carbon dioxide from the air sample, while a catalytic unit converts methane into carbon, which allows the approach to discriminate between radiocarbon in organic or inorganic molecular form.

Genoud’s research has been conducted in a laboratory so far, but he’s confident of its eventual utility: “There isn’t anything preventing its use in a real setting for in situ radiocarbon monitoring.” In fact, preliminary studies in nuclear facilities are already underway – and the results will be published shortly.

Looking ahead, Genoud would like to enhance the device’s sensitivity. “By increasing sensitivity below 1 part-per-trillion, we’ll be able to monitor not only emission from nuclear facilities, but also use this method for other applications where C-14 is diluted in atmospheric samples,” he says. And that could take the system even further afield. “One would, for instance, be able to determine the origin of greenhouse emissions as radiocarbon can be used to discriminate between fossil and biogenic emissions– key to developing more accurate climate models and predicting future changes.”