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Part 1 of 2 Parts
        One major problem with monitoring the processes inside a nuclear reactor lies in the fact that there is a great deal of dangerous radiation released during operation of the reactor. Now a group of researchers have found a way to use antineutrinos to continuously monitor nuclear fission processes from outside of the reactor.
        A neutrino is a neutral subatomic particle. It has very little mass and a half-integral spin. Neutrinos have very little interaction with normal matter. An antineutrino is the anti-matter version of the neutrino. The fission process inside a nuclear reactor generates antineutrinos. They can easily pass through the densest and thickest shielding around a nuclear reactor core. The flux of antineutrinos coming from a reactor depends on the type of fissionable materials that are fueling the reactor and the power level that the reactors is operating at. Now researchers at the Georgia Institute of Technology (GIT) are investigating a way to use the release of antineutrinos from a nuclear reactor to monitor the fission processes.
        Anna Erickson is an associate professor in Georgia Tech's George W. Woodruff School of Mechanical Engineering. She says, "Antineutrino detectors offer a solution for continuous, real-time verification of what is going on within a nuclear reactor without actually having to be in the reactor core. You cannot shield antineutrinos, so if the state running a reactor decides to use it for nefarious purposes, they can't prevent us from seeing that there was a change in reactor operations.”
      The new monitoring technique can be used with existing pressurized water reactors. It will also be able to monitor future reactor designs which may require less nuclear fuel. It can be used in conjunction with other monitoring techniques. The GIT carried out extensive simulations of reactor operations as part of their research. An article published on August 6th of this year in Nature Communications details the research at GIT.
       Two different types of reactors were evaluated during the GIT research. They used a PROSPECT detector currently deployed at the Oak Ridge National Laboratory's High Flux Isotope Reactor (HFIR). PROSPECT stands for “Precision Oscillation and Spectrum Experiment”. It makes precision measurements of the flux and energy spectrum of antineutrinos emitted from nuclear reactors.
       Erickson said, “Traditional nuclear reactors slowly build up plutonium 239 in their cores as a consequence of uranium 238 absorption of neutrons, shifting the fission reaction from uranium 235 to plutonium 239 during the fuel cycle. We can see that as the signature of antineutrino emission changes over time. If the fuel is changed by a rogue nation attempting to divert plutonium for weapons by replacing fuel assemblies, we should be able to see that with a detector capable of measuring even small changes in the signatures.”
       “The antineutrino signature of the fuel can be as unique as a retinal scan, and how the signature changes over time can be predicted using simulations. We could then verify that what we see with the antineutrino detector matches what we would expect to see."
       Erickson and two of her graduate students use powerful computer simulations to gauge the capabilities of near-field antineutrino detectors. These detectors would be positioned near but not inside the reactor containment vessel. One problem that has to dealt with is the separation of the readings coming from the fission reactors from the readings coming from natural background processes.
       Erickson said, "We would measure the energy, position and timing to determine whether a detection was an antineutrino from the reactor or something else. Antineutrinos are difficult to detect and we cannot do that directly. These particles have a very small chance of interacting with a hydrogen nucleus, so we rely on those protons to convert the antineutrinos into positrons and neutrons.”
Please read Part 2