The High Flux Isotope Reactor at Oak Ridge National Laboratory. (Image credit: Genevieve Martin, Oak Ridge National Laboratory via Flickr/CC BY 2.0)


Spotting neutrinos is an exciting scientific challenge in and of itself, but it might also be a national security issue.

Neutrinos — and their antineutrinos counterparts — are elusive, elementary particles that travel through the vast majority of the cosmos unaffected.

Scientists have devised sophisticated tests to detect neutrinos near nuclear reactors as one method of trying to comprehend neutrinos. This is because neutrinos are known to be created during nuclear reactions when radioactive material decays.

To avoid interference from cosmic radiation, detectors had to be buried far below at first. Eventually, scientists devised detectors that could work above ground.

Physicists can trace the signature of particular neutrinos as part of the neutrino detection and measuring process, which might offer information useful for nuclear safety, confinement, and disposal. According to experts, refining this information might reveal if a nuclear reactor is creating weapons-grade plutonium, where it is being produced, and whether stored plutonium is being destroyed in line with a deal.

Today, as politicians in the United States debate whether to re-engage in nuclear treaty discussions with Iran and North Korea, neutrino detector experiments — one of which has ties to Yale — might provide one of the tools for monitoring nuclear activity.

Yale is a primary collaborator in the Precision Reactor Oscillation and Spectrum (PROSPECT) project, a well-known neutrino detection partnership based at the US Department of Energy’s Oak Ridge National Laboratory at Tennessee’s High Flux Isotope Reactor (HFIR).

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PROSPECT investigates electron antineutrinos generated by nuclear reactions inside the reactor. The objective is to find a brand-new type of substance known as “sterile antineutrinos.” PROSPECT brings together more than 60 scientists from ten universities and four national laboratories.

Professor and chair of physics Karsten Heeger, director of the Wright Lab, and principle investigator for PROSPECT, spoke with YaleNews about how the experiment might give a new tool for securing nuclear reactors.

This discussion has been shortened and modified.

What is the scientific link between neutrino detection and nuclear program monitoring in another country?

What we’ve demonstrated is that we can detect not just the presence of neutrinos coming from a reactor, but also the isotope from which they originate. The isotopic makeup of fuel in nuclear reactors varies as it burns. The energy distribution of neutrinos flowing out of the reactor has changed as a result. We can establish a fingerprint of the isotopic composition within a reactor by taking accurate measurements of the neutrino spectrum from the reactor. Of course, this is the most important characteristic since it allows you to ask, “Can you identify whether highly enriched gasoline is being diverted for other purposes?” In a reactor, you can essentially analyze nuclear fuel burnup and enrichment.

When did the issue of neutrino detection’s nuclear safety become a major consideration?

This is being looked into right now, although the notion has been around for a long. People have considered putting the detector near a reactor, or even within one. However, it was never apparent if the technology would evolve far enough to extract useful information from the reactors. Now that we’ve demonstrated that it’s feasible, we’re looking into various applications.

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Why was it so difficult to get relevant data?

Because neutrinos produce such a tiny signal and there is a lot of ambient background interference, such as cosmic rays from the atmosphere, neutrino detectors have traditionally required a lot of shielding – what we term “overburden.” This has always been a stumbling block. When you try to take a measurement near a reactor or adjacent to one, you’re inundated with all of this background noise from the surroundings.

Even in the presence of these backgrounds, the PROSPECT detector has proved that we can make an accurate measurement of the neutrinos and energy that flows out of the reactor. We created a detector using a unique detecting liquid [a lithium-doped liquid scintillator] that allows us to confidently extract the neutrino signature. PROSPECT results were recently published as an editor’s suggestion in the journal Physical Review D. PROSPECT is also room-sized, which is a significant aspect. It is small enough to fit within the reactor building. We’ve calculated that we could load it onto a truck and transport it to a reactor.

In the immediate future, how likely is it that neutrino detection will play a role in nuclear monitoring?

Some experimental efforts have been made in this direction, and a recent study is attempting to filter through various applications. However, we do know that organizations such as the International Atomic Energy Agency (IAEA) have built monitoring instruments for inside reactor facilities that are less expensive than neutrino detectors.

So, what’s the point of going down this road?

I believe it provides you with the opportunity to engage in scientific collaboration with other nations, which is something that cannot be measured. “How do you engage with places like North Korea?” we often question. You can monitor things, but what you really want to do is include the technological and scientific communities. We may construct a detector for scientific purposes near to a nuclear plant, and you can begin working with the scientific experts there and forming partnerships. This offers you a lot more information than just monitoring.

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Is it surprising that neutrino science has advanced to the point where it’s being addressed in terms of national security?

It took us 25 years to get the first neutrino measurement. Even 20 years ago, no one would have imagined that a precision measurement could be made using a detector that wasn’t buried deep down. However, we’ve seen incredible progress. I believe that neutrino physics has now reached a stage where politics, societal effect, and fundamental science have all collided.

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