Astroparticle physics methodology applied to nuclear facility monitoring
When monitoring nuclear reactors, the International Atomic Energy Agency (IAEA) has to rely on input given by the operators. In the future, antineutrino detectors may provide an additional option for monitoring. However, heretofore the cumulative antineutrino spectrum of uranium 238 fission products was missing. Physicists at Technische Universität München (TUM) have now closed this gap using fast neutrons from the Heinz Maier Leibnitz Neutron Research Facility (FRM II).
Dr. Nils Haag developed an experimental setup that allowed him to determine the missing spectrum of uranium 238. (Bild: Wenzel Schuermann / TU München)
In addition to neutrons, the fission reaction of nuclear fuels like plutonium or uranium releases antineutrinos. These are also electrically neutral, but can pass matter very easily, which is why they can be discerned only in huge detectors. Recently, however, detectors on the scale of only one cubic meter have been developed. They can measure antineutrinos from a reactor core, which has generated great interest at the IAEA.
Prototypes of these detectors already exist and collect data at distances of around 10 meters from a reactor core. Changes in the composition of nuclear fuels in the reactor – for example, when weapons-grade U-239 is removed – can be determined by analyzing the energy and rate of antineutrinos. This would free the IAEA from having to rely on representations of reactor operators.
Antineutrino spectrum of uranium 238 revealed
In the 1980s the antineutrino spectra of three main fuel isotopes, uranium 235, plutonium 239 and plutonium 241, were determined. However, the antineutrino spectrum of the fourth main nuclear fuel, uranium 238, which accounts for approximately 10 percent of the total antineutrino flux, remained unclear. It had only been estimated using inaccurate theoretical calculations and thus limited the accuracy of the antineutrino predictions.
Dr. Nils Haag from the Chair of Experimental Astroparticle Physics at TU München recently developed an experimental setup at the FRM II that allowed him to determine the missing spectrum of uranium 238. "I needed a high flux of fast neutrons to induce the fission of the U-238," says the physicist. This is why he located his experimental setup at the NECTAR radiography and tomography station of the FRM II – a source of fast neutrons.
Second detector for background-free measurement
The neutrons induce nuclear fission in a film of U-238. The radioactive decay products then emit electrons and antineutrinos. The electrons were investigated using a scintillator – a block of plastics that converts the kinetic energy of the electrons into light. A photomultiplier then translates this into electrical signals.
The nuclear decay also generates gamma radiation that produces unwanted events in the scintillator. Therefore, Haag placed a second detector right in front of the scintillator: a so-called multi-wire proportional chamber. Since only charged particles like electrons trigger a signal in the gas detector, the researcher was able to determine and subtract the proportion of gamma radiation. Haag then inferred the antineutrino spectrum using this background-free measurement data.
Method allows better monitoring of reactor cores
The measurement of the antineutrino spectrum can be used to monitor the status, performance and even composition of reactor cores. "Our results open the door to predict with significantly higher accuracy the expected antineutrino spectrum emitted by a reactor running on a fuel composition reported by the operator," explains Dr. Nils Haag. "Deviations of antineutrino detector measurement data from expected reactor signals can thus be exposed."
The development of this methodology is embedded in basic research on the phenomenon of so-called "sterile" antineutrinos. Comparing previously made measurements and predictions of reactor antineutrino spectra gave rise to the assumption that some of the antineutrinos turned "sterile" after being produced. They were then no longer able to react with other matter. A better understanding of this effect would expand our knowledge of elementary physical processes.
This research was funded by the German Research Foundation (DFG) and the DFG Excellence Cluster "Origin and Structure of the Universe" at TUM.
Experimental Determination of the Antineutrino Spectrum of the Fission Products of U238, N. Haag, A. Gütlein, M. Hofmann, L. Oberauer, W. Potzel, K. Schreckenbach, and F. M. Wagner, Phys. Rev. Lett. 112, 122501 (2014), DOI: 10.1103/PhysRevLett.112.122501,
Nils Haag | Eurek Alert!
Present-day measurements yield insights into clouds of the past
27.05.2016 | Paul Scherrer Institut (PSI)
NASA scientist suggests possible link between primordial black holes and dark matter
25.05.2016 | NASA/Goddard Space Flight Center
A biological and energy-efficient process, developed and patented by the University of Innsbruck, converts nitrogen compounds in wastewater treatment facilities into harmless atmospheric nitrogen gas. This innovative technology is now being refined and marketed jointly with the United States’ DC Water and Sewer Authority (DC Water). The largest DEMON®-system in a wastewater treatment plant is currently being built in Washington, DC.
The DEMON®-system was developed and patented by the University of Innsbruck 11 years ago. Today this successful technology has been implemented in about 70...
Permanent magnets are very important for technologies of the future like electromobility and renewable energy, and rare earth elements (REE) are necessary for their manufacture. The Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, Germany, has now succeeded in identifying promising approaches and materials for new permanent magnets through use of an in-house simulation process based on high-throughput screening (HTS). The team was able to improve magnetic properties this way and at the same time replaced REE with elements that are less expensive and readily available. The results were published in the online technical journal “Scientific Reports”.
The starting point for IWM researchers Wolfgang Körner, Georg Krugel, and Christian Elsässer was a neodymium-iron-nitrogen compound based on a type of...
In the Beyond EUV project, the Fraunhofer Institutes for Laser Technology ILT in Aachen and for Applied Optics and Precision Engineering IOF in Jena are developing key technologies for the manufacture of a new generation of microchips using EUV radiation at a wavelength of 6.7 nm. The resulting structures are barely thicker than single atoms, and they make it possible to produce extremely integrated circuits for such items as wearables or mind-controlled prosthetic limbs.
In 1965 Gordon Moore formulated the law that came to be named after him, which states that the complexity of integrated circuits doubles every one to two...
Characterization of high-quality material reveals important details relevant to next generation nanoelectronic devices
Quantum mechanics is the field of physics governing the behavior of things on atomic scales, where things work very differently from our everyday world.
When current comes in discrete packages: Viennese scientists unravel the quantum properties of the carbon material graphene
In 2010 the Nobel Prize in physics was awarded for the discovery of the exceptional material graphene, which consists of a single layer of carbon atoms...
24.05.2016 | Event News
20.05.2016 | Event News
19.05.2016 | Event News
27.05.2016 | Awards Funding
27.05.2016 | Life Sciences
27.05.2016 | Life Sciences