Neutrinos can ensure that a submarine’s nuclear fuel will not be a weapon

Nuclear submarines can provide rogue states with a path to nuclear weapons. But neutrinos can help detect attempts to switch from boats to bombs.

Neutrinos, light subatomic particles released from reactors that power nuclear submarines, can expose the alteration or removal of nuclear fuel for disgusting purposes, physicists report in an article adopted in Physical review letters. Importantly, this monitoring can be done remotely while the submarine is in port with the reactor shut down.

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. Of particular concern are nuclear submarines. Many use highly enriched uranium, a powerful type of fuel that is relatively easy to use in weapons. But submarines are protected from slit control. Unlike nuclear power plants, nuclear submarines are used for secret military purposes, so physical checks can violate a country’s national security.

“Neutrin-based techniques can significantly reduce intrusiveness by making measurements at a distance, without the need for physical access to the ship,” said nuclear scientist Igor Jovanovich of the University of Michigan at Ann Arbor, who was not involved in the study.

These particles – in particular, their kind of antimatter, antineutrinos – flow en masse from existing nuclear reactors. Particles interact weakly with other matter, allowing them to pass through solid material, including the submarine hull. So a neutrino detector located next to a submarine can detect what’s going on inside, say neutrino physicists Bernadette Cogswell and Patrick Huber of the Center for Neutrino Physics at Virginia Technology Center in Blacksburg.

Previously, scientists have suggested using neutrinos to detect other nuclear crimes, such as nuclear weapons tests (CH: 08/20/18).

But submarines, which are often in motion, are difficult to control with stationary devices. If ships are indeed sitting in port, their nuclear reactors could be shut down. So the researchers came up with a solution: they looked at neutrinos that are formed as a result of the decay of various chemical elements or isotopes that remain after the reactor is shut down. The detector, located in the water about 5 meters below the submarine reactor, could measure neutrinos formed during the decay of certain cerium and ruthenium isotopes. These measurements would reveal whether nuclear material has been removed or altered.

This method of monitoring a shut down reactor is “very smart,” says physicist Ferenc Dalnaki-Veres of the Middlebury Institute for International Studies in Monterey, California.

But the idea will still require purchases from each country to agree on detectors at submarine berths. “Something like this would be much better if it didn’t require cooperation,” says physicist Giorgio Grata of Stanford University.

Submarine monitoring may become more relevant soon. So far, all countries that have nuclear submarines already have nuclear weapons, so the question was hypothetical. But that needs to change. The United States and the United Kingdom, two nuclear-weapon states, announced last September that they are concluding a cooperation agreement with Australia and will help the country, state without nuclear weapons, acquire nuclear submarines.

There is no suspicion that Australia will use these submarines as cover for a nuclear weapons program. But “you still have to worry about the precedent it sets,” Cogswell says. So she says monitoring nuclear submarines is a new important one. “The question was how the hell to do it.”

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