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The Close technology, which is used to measure the flow of subatomic particles (ie antineutrinos) in nuclear reactors, enables continuous remote monitoring and is designed to detect changes in fuel that may indicate the transfer of nuclear material. Monitoring can be done from outside the reactor vessel, and the technology may be sensitive enough to detect whether individual fuel assemblies need to be replaced.
The technology can be used in existing pressurized water reactors, and can also be used in future designs that do not require frequent fuel additions. This technology can be used as a supplement to other monitoring technologies, including sending people to check. Researchers at the Georgia Institute of Technology conducted extensive simulations to confirm the potential use of ground anti-neutrino monitoring technology for current and future reactors.
Anna Erickson, associate professor at the George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, said that anti-neutrino detectors provide a solution that can continuously and real-time verify what is happening inside a nuclear reactor without having to really Enter the core of the reactor. You ca n’t block anti-neutrinos, so if the country that runs the reactor decides to use it for evil purposes, they ca n’t stop us from seeing the reactor ’s operation change.
The research, which will be published in the journal Nature Communications on August 6, has received partial funding from the National Nuclear Regulatory Commission (NRC). The study evaluated two types of reactors and anti-neutrino detection technology based on the prospect detector of the Oak Ridge National Laboratory High Flux Isotope Reactor (HFIR).
Antineutrino is a basic subatomic particle, which has extremely small mass and no charge. They can pass through the shielding layer around the core of the nuclear reactor, which is part of the nuclear fission process. The flux of antineutrinos produced in a nuclear reactor depends on the type of fissile material and the power level at which the reactor operates.
Because uranium 238 absorbs neutrons, conventional nuclear reactors slowly accumulate plutonium 239 in its core, thereby transferring fission reactions from uranium 235 to plutonium 239 during the fuel cycle. Ericson said: "We can see that the characteristics of anti-neutrino emissions will change over time. If a rogue country tries to change the fuel by replacing the fuel assembly to transfer the plutonium used for weapons, we You should be able to see this with a detector that can measure small changes.
She said that the anti-neutrino feature of this fuel can be as unique as a retina scan, and that this feature can be predicted to change over time through simulation. Then, we can verify that the anti-neutrino detector we see matches what we expect to see.
In this study, Eriksson and newly graduated doctors Christopher Stewart and Abdalla abu-jaoude used high-fidelity computer simulation technology to evaluate the near field Anti-neutrino detector capabilities. One of the challenges is the particles generated by the division fission and the particles from the natural background.
She said: "We will measure energy, position and time to determine whether anti-neutrinos from the reactor or other substances are detected." Anti-neutrinos are difficult to detect and we cannot do this directly. The chances of these particles interacting with hydrogen nuclei are very small, so we rely on these protons to convert antineutrinos into positrons and neutrons. "
Nuclear reactors currently used for power generation must be refueled regularly. This operation provides opportunities for human inspection, but future generations of nuclear reactors may not be refueled for up to 30 years. Simulation results show that sodium-cooled reactors can also be monitored using anti-neutrino detectors, although their characteristics are different from current pressurized water reactors.
One of the challenges ahead is to reduce the size of the anti-neutrino detector so that it is portable enough to fit into a car that may pass a nuclear reactor. The researchers also hope to improve the directionality of the detectors so that they can focus on the emissions from the core of the reactor, thereby improving their ability to detect small changes.
The detection principle is similar in concept to the retinal scan used for authentication. In retina scanning, the infrared beam passes through the human retina and blood vessels. Compared with other tissues, the retina and blood vessels have a higher light absorption capacity. Then extract these mapping information, and compare with the previous retina scan, and then store in the database. If the two match, you can verify the identity of the person.
Similarly, nuclear reactors continuously release anti-neutrinos, and the flux and spectrum of these anti-neutrinos change with specific fuel isotope fission. Some antineutrinos interact with nearby detectors through reverse decay. Compare the signal measured by the detector with the reference copy of the reactor, initial fuel, and fuel consumption stored in the database; if a signal exactly matches the reference copy, it indicates that the core inventory has not been secretly changed. However, if the antineutrino flux of the disturbed reactor is sufficiently different than expected, this may indicate that a transfer has occurred.
When the reactor turns from burning uranium to plutonium, the emission rate of antineutrinos at different energies changes with operating life. The signal from the pressurized water reactor includes a repeated 18-month operating cycle and a three-month refueling interval, while the signal from the ultra-long cycle fast neutron reactor (UCFR) represents continuous operation, excluding maintenance interruptions .
Eriksson said that preventing the proliferation of special nuclear materials suitable for weapons is a long-term concern of researchers in many different institutions and organizations.
She said: "From the mining of nuclear materials to the processing of nuclear materials, at each step of the process, we must pay attention to who is processing these nuclear materials and whether these nuclear materials will fall into unlawful hands. The actual situation is more complicated, Because we do n’t want to prevent the use of nuclear materials to generate electricity, because nuclear energy contributes a lot to non-carbon energy. "
Eriksson said that this paper shows the feasibility of the technology and the continued development of detector technology should be encouraged.
She said: “One of the key points of this research is to analyze the transfer at the assembly level in detail, which is very important for us to understand the limitations of anti-neutrino detectors and the potential impact of possible policies. People will be encouraged to study future systems in more detail. "
(Originally from: Daily Science China New Energy Network Synthesis)
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