For the first time, the SNO+ experiment showed that neutrinos emitted by a nuclear reactor more than 240 km away could be detected using plain water.

Science

Neutrinos are subatomic particles that interact extremely weakly with matter. They come from different types of radioactive decay, for example in the core of the Sun and nuclear reactors. Also, neutrinos cannot be blocked; they can effortlessly go to a detector far from the core of a nuclear reactor and even penetrate the Earth itself.

Therefore, very large and highly sensitive instruments are required to capture the small signals from neutrinos. The recent SNO+ experiment showed that only a detector filled with water could detect reactor neutrinos, although neutrinos produced only very small signals in the detector.

To influence

The SNO+ measurement shows that remote nuclear reactors can be observed and controlled using something as simple and inexpensive as water. Reactors cannot protect the neutrinos they produce. This means that the SNO+ measurements are proof of the idea that such water detectors can play a role in containment.

Like SNO+, such detectors need to be very clean of radioactivity, large (SNO+ contains 1,000 tons of water), and capable of detecting the very small amount of light produced by neutrinos. However, the use of water means that very large detectors are possible and there is a real possibility of “seeing” reactors even very far away.

To continue

Scientists have long believed that the tiny signals (as few as 10-20 photons) produced by reactor neutrinos in a water detector would make these neutrinos impossible to detect, especially when the detector is far from the reactor and the speed of these signals is low. Very low. .

Confident that the detector was clear of even traces of radioactivity and had a lower energy threshold than any water detector, SNO+ was able to see these signals and indicate that they came from nuclear reactors at least 240 kilometers (150 miles) away. ) far. Measurement was still quite difficult as backgrounds (fake events) from residual radioactivity and neutrinos created in the atmosphere by cosmic rays had to be identified and eliminated.

Water detectors have a number of advantages. They are inexpensive and can be very large, making them useful for monitoring reactors across international borders. Improvements in such monitoring are being tested in other collaborations, including the use of water-based liquid scintillators or “loading” gadolinium into the water, both of which will increase the size of the signal. Source