The SNO+ detector 2 kilometers deep in a mine in Ontario, Canada. Credit: Image courtesy of the SNO+ Collaboration
The SNO+ measurement reveals that remote nuclear reactors can be observed and kept track of with something as simple and economical as water. This indicates SNO+s measurement is evidence of the concept that such water detectors could play a role in making sure nuclear non-proliferation.
SNO+ is funded by the Department of Energy Office of Science, Office of Nuclear Physics and has gotten financing from the National Science Foundation and the Department of Energy National Nuclear Security Administration through the Nuclear Science and Security program.
The Impact
The SNO+ measurement reveals that distant nuclear reactors can be observed and kept an eye on with something as basic and economical as water. Reactors can not protect the neutrinos they produce. This means SNO+s measurement is proof of the concept that such water detectors might play a role in ensuring nuclear non-proliferation.
Like SNO+, such detectors would still need to be very clean of any radioactivity, large (SNO+ contains 1,000 lots of water), and able to detect the tiny quantity of light that the neutrinos produce. Making use of water, however, implies that large detectors are possible and a genuine alternative for “seeing” even really remote reactors.
Summary
Researchers long believed that the tiny signals (simply 10-20 photons) produced by reactor neutrinos in a water detector would make it impossible to discover those neutrinos, especially when the detector was far from the reactor and the rate of these signals was extremely low.
By guaranteeing that the detector was clean from even trace amounts of radioactivity, and by having an energy limit lower than any water detector ever built, SNO+ had the ability to see these signals and show that they originated from atomic power plants at least 240 kilometers (150 miles) away. The measurement was still quite tough, as backgrounds (phony events) from residual radioactivity, and from neutrinos developed in the atmosphere by cosmic rays, needed to be recognized and removed.
Water detectors have several advantages. They are economical and can be large, making them helpful for keeping an eye on reactors across international borders. Improvements to such monitoring, including utilizing water-based liquid scintillators or “loading” the water with gadolinium, both of which would boost the signal size, are being checked by other partnerships.
Reference: “Evidence of Antineutrinos from Distant Reactors Using Pure Water at SNO+” by A. Allega et al. (The SNO+C ollaboration), 1 March 2023, Physical Review Letters.DOI: 10.1103/ PhysRevLett.130.091801.
This work is from the SNO+ Collaboration, a global partnership of roughly 100 researchers from the United States (the University of Pennsylvania, the University of California at Berkeley and Lawrence Berkeley National Laboratory, the University of California at Davis, Brookhaven National Laboratory, Boston University, and the University of Chicago), Canada, the United Kingdom, Portugal, Germany, China, and Mexico. SNO+ lies in SNOLAB, the Canadian underground laboratory.
SNO+ is funded by the Department of Energy Office of Science, Office of Nuclear Physics and has actually received financing from the National Science Foundation and the Department of Energy National Nuclear Security Administration through the Nuclear Science and Security program. Financing in Canada comes from Canada Foundation for Innovation, Natural Sciences and Engineering Research Council, Canada Institute for Advanced Research, Queens University, the Ontario Ministry of Research, Innovation and Science, the Alberta Science and Research Investments Program, the Federal Economic Development Initiative for Northern Ontario, and the Ontario Early Researcher Awards.
The SNO+ detector 2 kilometers deep in a mine in Ontario, Canada. The image shows the ropes that hold the 12 m-diameter acrylic vessel filled with 1,000 heaps of water and the light sensors that identify small amount of light from neutrino interactions. Credit: Image thanks to the SNO+ Collaboration
For the really very first time, the SNO+ experiment has shown the capability to discover neutrinos emitted by a nuclear reactor located more than 240 km away using plain water.
The Science
Neutrinos are subatomic particles that show exceptionally weak interaction with matter. They originate from various types of radioactive decay, such as those occurring within the suns core and in nuclear reactors. Furthermore, its difficult to block neutrinos; they can effortlessly journey from an atomic power plants core to a distant detector, and even permeate the Earth itself.
To catch the minuscule signals from neutrinos, gadgets of immense size and high level of sensitivity are required. The SNO+ experiment just recently showed that a detector filled simply with water can detecting reactor neutrinos, regardless of the truth that the neutrinos create only small signals in the detector.