Antineutrino detector developed by SINP scientists will trail over weapon-grade plutonium production

The first industrial antineutrino detector, three dimension model.

The first industrial antineutrino detector intended for monitoring of nuclear reactors is being developed in SINP MSU by the team of PhD. Alexander Chepurnov (according to RFBR Grant 12-02-12129). Scientists from RSC Kurchatov Institute, INR RAS and VNIIA (N.L.Dukhov All-Russia Institute of Automatics) take part in this project.

Nuclear reactors of the atomic power stations are the most powerful sources of antineutrino on the Earth, therefore the operation of the atomic power stations can be effectively monitored by means of antineutrino detector. Antineutrino has low probability of interaction with matter and very high penetrating power: it can loosely fly through steel and concrete hundreds of meters thick carrying exact information about the processes in the center of nuclear reactor. At the same time they do not influence on the people.

Application of antineutrino for monitoring of power atomic stations was offered in 1970s by the scientist of Kurchatov Institute of Atmoic Power (now RSC Kurchatov Institute) Professor L.A. Mikaelyan. In 1980s ths method was proved by a number of remarkable experiments carried outby the team of Mikaelyan on the base of Rovena atomic power station.

Up to 2000 the methods of antineutrino detection based on liquid scintillators has been improved up to so high level, that it became possible not only to carry out large-scale fundamental studies by means of big-volume detectors (DoubleCHOOZ, Reno, DayaBay), but also to manufacture an industrial antineutrino detector. Other materials used as active volume for antineutrino detection (solid plastic scintillators, super-pure semiconductor materials and liquid gases) are used only for fudamental research.

As Alexander Chepurnov told us: "We use liquid scintillator based on linear Alkyl Benzene, which has large neutron capture cross-section and high transparency. It provides high efficiency of beta-decay products, which are used for antineutrino detection in the active volume".

Currently the scientific team leaded by Chepurnov has finished the first stage of the development of the industrial antineutrino detector: samples of liquid scintillator are ready for the tests, photomultipliers have been already tested and electronic tract of photomultipliers data procession was assembled. Two 30-liters prototypes were manufactured for preliminary tests on structural materials compatibility with liquid scintillator, development of industrial design solutions and tests of the properties of photomultipliers and liquid scintillators of different types.

The case of the antineutrino detector produced of low-background stainless steel will consist of three zones. It will provide an opportunity for suppression of background radiation of photomultipliers and diminishing of the effect of "efflux of gammas" produced by inverse beta-decay reaction. Suppression of the outer background produced by space muons, neutrons and gammas from the reactor will be achieved by means of multi-layer passive protection and active protection produced from plastic scintillator. Total size of the detector is 2.5x2.5x2.5 meters. Total volume is 15 cu.m., volume of the basic target is 1 cu.m. The detector is intended for industrial purposes, therefore it will be collapsable and after assembling and tests it will not require any service.

How the nuclear reactor will be monitored?

Chain fission proceeding in the active zone of the nuclear reactor is accompanied by irradiation of electronic antineutrino during beta-decay of fission fragments overloaded with neutrons. On the average during one act of fission about 6 antineutrino are emitted.

By intensity and density of antineutrino flux the detector will be able to measure variation of thermal power of the reactor, evaluate fuel composition and the rate of plutonium-239 production, which can be used in order to pull plutonium-239 out for nuclear weapons production.

The most important is that besides additional control over the nuclear reactor processes, during several hours the antineutrino detector is able to determine unapproved shutdown of the reactor, which can be used in order to pull plutonium-239 out for nuclear weapons production.

As reference: the most widespread fuel at the atomic power stations is the fuel in the form of tablets consisted of the mixture of uranium-238 2-5% enriched with uranium-235 in the form of sintered uranium dioxide UO2 with diameter of 9-10 mm placed into cylidric protective shell, produced from zirconium alloy. The fuel is uranium-235. Very important point is that during the process of the nuclear reactor operation uranium-238 under the influence of neutrons produces plutonium isotopes, which can be pulled out of the fuel for nuclear weapons production.

The manufacturers suppose that the industrial antineutrino detector can become a safe additional instrument of IAEA (International Atomic Energy Agency) in order to solve a problem of nonproliferation of fission materials. It will be remembered that the basic function of IAEA is to provide control over the nuclear facilities and materials by means of studies of the corresponding records, tests of work of the nucleas facilities operators, spot-check measurements in "key points" of the facilities. Realization and following implementation of the industrial antineutrino detector the Agency will get an opportunity for permanent real-time control over the using of fission materials. In iеs turn the state will have independent data indicating correspondence of the materials application to the agreement with IAEA.

"All components and details of the first antineutrino detector are planned to be produced by the first half of 2014. Assembly and tests of the detector, measurements of its physical properties will be lasted during the whole 2014. The next stage will include planning and carrying out of a demonstration experiment at the atomic station", - Alexander Chepurnov told us.

He also added that the antineutrino detector will be set up in SINP MSU. Probably it will cause a question: how the detector can be used in the Institute if there are no atomic reactors there? In fact field of application of the detector is very wide. The scientists will be able to develop and study the properties of new liquid scintillators, to study photomultipliers and other detecting instruments, develop and test electronic devices and software for data collection and procession systems. It will also possible to teach students modern methods of nuclearradiation registration at the highest level and will help them to be ready for participation in large-scale international experiments and collaborations.

"In perspective we plan to take part in the international projects, because the future SINP MSU detector is a small copy of big detectors, such as DayaBay, Reno and DoubleCHOOZ. We have all the elements of big detectors. We have largescale plans and a lot of things to do, therefore we invite students and and other interested persons to take part in the project on the development and production of the first industrial antineutrino detector", - Alexander Chepurnov said.

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