Nuclear submarines can provide fraudulent nations with a path to nuclear weapons. But neutrinos can help detect attempts to switch from boats to bombs.
Neutrinos, light subatomic particles released by reactors that power nuclear submarines, could reveal the alteration or removal of nuclear fuel for malicious purposes, physicists said in a document adopted in Physical examination letters. Most importantly, this monitoring can be done remotely while the submarine is in port with the reactor off.
To ensure that countries without nuclear weapons do not develop them, international inspectors monitor the use of many types of nuclear technology around the world. Nuclear submarines are particularly worrying. Many use highly enriched uranium, a powerful type of fuel that can be used relatively easily. But the submarines are protected from surveillance by a door. Unlike nuclear power plants, nuclear submarines are used for secret military purposes, so physical checks could violate the country’s national security.
“Neutrino-based methods can significantly reduce intrusion by taking measurements at a distance without requiring physical access to the ship,” said nuclear scientist Igor Jovanovic of the University of Michigan at Ann Arbor, who was not involved in the study.
These particles – in particular their variety of antimatter, antineutrino – flock to crowds of operating nuclear reactors. The particles interact weakly with other matter, allowing them to pass through solid material, including the submarine’s hull. So a neutrino detector placed near a submarine can detect what’s going on inside, say neutrino physicists Bernadette Cogswell and Patrick Huber of the Neutrino Physics Center at Virginia Tech in Blacksburg.
Earlier, scientists suggested using neutrinos to detect other nuclear abuses, such as nuclear weapons tests (SN: 20.08.18).
But submarines, often in motion, are difficult to monitor with stationary instruments. When ships are in port, their nuclear reactors may be shut down. So the researchers came to a decision: they will look at neutrinos produced by the decay of various chemical elements or isotopes that remain after the shutdown of the reactor. A detector located in the water about 5 meters below the submarine reactor can measure neutrinos produced during the decay of certain isotopes of cerium and ruthenium. These measurements will reveal whether the nuclear material has been removed or exchanged.
This method of monitoring a shut down reactor is “very clever,” said physicist Ferenc Dalnoki-Veres of the Middlebury Institute for International Studies in Monterey, California.
But the idea will still require buying from each country to agree with detectors in submarine locations. “Something like that would be much better if it didn’t require cooperation,” said physicist Giorgio Grata of Stanford University.
Submarine surveillance may become more urgent in the near future. So far, all countries that have nuclear submarines already have nuclear weapons, so the question was hypothetical. But that is ready to change. The United States and the United Kingdom, two nuclear-weapon states, announced last September that they were concluding a security co-operation agreement with Australia and would help the country., a country without nuclear weapons, acquire nuclear submarines.
There is no suspicion that Australia will use these submarines as a cover for a nuclear weapons program. But “you still have to worry about the precedent it sets,” Cogswell said. So, she says, monitoring nuclear submarines is new. “The question was how the hell to do that.”