Anti-neutrinos for peace

14 March 2008

American researchers have developed a potential new tool to monitor the status of nuclear reactors. Based on an anti-neutrino detector, it could even be located outside the reactor building.


Antineutrino symbol 
Hard to spot.
A team of scientists from Lawrence Livermore National Laboratory and Sandia National Laboratory said the device - similar in size to a washing machine - could help in nuclear safeguards checks like those carried out by the International Atomic Energy Agency.


Anti-neutrinos are neutral particles that interact with other matter only through gravitational and weak forces, and so are very difficult to detect. However, about six anti-neutrinos are released every time a uranium atom is split to release energy, so the number coming from a nuclear reactor is so large that a cubic-meter scale detector can record them by the hundreds or thousands per day. The detector can even be located tens of metres from the reactor itself.


The detector provides a direct measurement of the operational status of the reactor and measures the reactor's thermal power. LLNL said the detector could even determine the operational amount of plutonium or uranium necessary to run the reactor and place a direct constraint on the amount of fissile material the reactor creates throughout its lifecycle.


Some types of uranium reactor fuel could in theory be useful in weapons, while plutonium - also theoretically useful for weaponry - is created during operation. For these reasons, strict international controls administered by the IAEA ensure the materials are always accounted for.


In previous years, the group tested an early prototype detector at the San Onofre Nuclear Generating Station, a nuclear power plant in California, USA. By comparing anti-neutrino detection records with publicly available data on the power plant, researchers were able to confirm the continuous and stable operation of the detector for yearlong periods, with remote and automatic data collection and detector calibration.


"There was no evidence for long-term drifts or other confounding detector problems that could have compromised the detector performance," said Adam Bernstein, leader of LLNL's advanced detectors research group. Berstein plans to publish a paper on the research in the Journal of Applied Physics.