“The core concept of transmutation – which was formulated as early as mid 20th century – consists of irradiating the actinides by fast neutrons. The highly stimulated nuclei that are generated this way suffer a fission, which leads to relatively short-lived nuclei, which in turn rapidly disintegrate into stable isotopes. Then, they cease to be radioactive,” explains Professor Helmut Leeb from the Atomic Institute of the Austrian Universities.
Thus, the required radioactive waste isolation time of several millions years could be decreased to 300 and up to 500 years. The technological progress made in the last decades has made the transmutation possible at the industrial level.
An efficient transmutation of radioactive waste requires the development of new facilities. In addition to specially designed fast reactors, the Accelerator-Driven Systems (ADS) present a new potential concept. This is an undercritical reactor, which cannot sustain any chain reaction. The neutrons necessary for stationary operations are supplied by a proton accelerator with a spallation target located in the reactor core. “During the spallation, the atomic nuclei of the target (mainly lead) are broken with high-energy protons, while a large number of neutrons are normally released, neutrons which are necessary for the stationary operation of the reactor. If the accelerator is turned off, the chain reaction ceases,” added Leeb. Worldwide studies are based on the assumption that at least two decades will be necessary to transfer this concept to the industrial level, a concept which is fully understood at the scientific level.
An essential prerequisite for this development is a thorough knowledge of the neutrons’ interaction and reactions with other materials as available to date. Therefore, in the year 2000, the n_Tof facility became operative at CERN (Genf), which is a unique facility in the world, suitable especially for measuring the reactions of radioactive materials when bombarded with neutrons. Between 2002 and 2005, a large number of radiative captures and fission reactions, previously insufficiently known, were measured as part of an EU project, in which nuclear physicists from TU Vienna were considerably involved. After the conditional pause occasioned by the construction of the Large Hadron Collider at CERN, now at the end of September 2008, the consortium will start the operations at the upgraded n_TOF facility with a new target. The first series of experiments are neutron radiative captures on iron and nickel, which are analyzed by Viennese nuclear physicists (from TU Vienna and the University of Vienna). In addition to accurate reaction data for transmutation facilities, the results are also of interest for Astrophysics.
An alternative nuclear fuel, which leads to a reduced incidence of radioactive waste, is the “thorium-uranium cycle.” Leeb: “Thorium is a potential nuclear fuel, which may be incubated into a light uranium isotope, whose fission generates basically no actinide. Furthermore, thorium can be found approximately five times more often than uranium. However, special reactors must be still developed for this, reactors that would be appropriate for the reaction pattern and for the somewhat harder gamma radiation. India is one of the countries that already host experiments with thorium in reactor cores.
Significantly more productivity in USP lasers
06.12.2016 | Fraunhofer-Institut für Lasertechnik ILT
Shape matters when light meets atom
05.12.2016 | Centre for Quantum Technologies at the National University of Singapore
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
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