This is an excerpt from EERE Network News, a weekly electronic newsletter.

August 24, 2005

Anti-Neutrinos Shed Light on the Source of Geothermal Energy

Anti-neutrinos—lightweight particles that interact very weakly with matter—may be the key to understanding nuclear processes that occur deep within the Earth and contribute to geothermal energy production. Anti-neutrinos are the anti-matter counterpart to neutrinos, both of which interact so weakly with matter that they can easily pass straight through the Earth. A specific kind of anti-neutrino, the anti-electron neutrino, is produced when radioactive isotopes decay. Scientists believe that much of the heat generated within the Earth comes from the radioactive decay of two isotopes, uranium-238 and thorium-232. By studying anti-electron neutrinos coming from within the Earth, scientists hope to understand how much geothermal energy is produced from the decay of these isotopes, and how much is left over heat from when the Earth was formed.

To study these so-called "geoneutrinos," an international collaboration of scientists used a neutrino detector called KamLAND (Kamioka Liquid scintillator Anti-Neutrino Detector) that is built deep underground in central Japan. The underground location helps shield the detector from other particles, allowing it to detect the elusive geoneutrinos. In a paper published in the July 28th issue of the journal Nature, the scientists demonstrated the ability of the KamLAND detectors to measure the radioactivity of the uranium and thorium isotopes. Although the initial test was not sensitive enough to precisely determine the amount of heat produced by radioactive decay, the experimental results were consistent with current models of Earth's core, and the study could pave the way for future, more accurate measurements. Scientists from DOE's Lawrence Berkeley National Laboratory (LBNL) participated in the study, which was funded by the DOE Office of Science and the Japanese Ministry of Education, Culture, Sports, Science and Technology. See the LBNL press release.