242 research outputs found
Simulation of alpha dose for predicting radiolytic species at the surface of spent nuclear fuel pellets
In many countries, spent nuclear fuel is considered as a waste form to be disposed of in underground disposal. Under deep host rock conditions, a reducing environment prevails. In the case of water contact, long-term radionuclide release from the fuel depends on dissolution processes of the UO matrix. The dissolution rate of irradiated UO is controlled by oxidizing processes facilitated by dissolved species formed by alpharadiolysis of water in contact with spent nuclear fuel. To understand the effect of the radiation, the information of the dose rate at the surface of the fuel and its proximity is needed. α particles contribute strongly due to their high linear energy transfer. However, their dose rate and the energy deposition at the fuel surface are difficult to measure. Cylindrical fuel pellets as used in fuel rods show specific features, such as the rim zone, where a higher Pu concentration and a different porosity of the fuel matrix is present. The a particle dose rate was determined by simulations with the code MCNPX with focus on the rim zone of a pellet. As a result a 40% increased dose level in the rim zone exists in comparison to the center of a pellet. The potential dominant and inhomogeneous α-dose distribution is supposed to have a strong impact on radiolysis phenomena and in turn on an inhomogeneous dissolution of elements over the surface
Geochemisches Verhalten der Radionuklide im Multibarrierensystem nuklearer Endlager. Geochemical behavior of radionuclides in the multi-barrier system of a nuclear waste repository
Modellrechnungen zum Korrosions- und Auslaugverhalten von zementierten Abfallprodukten. Dokumentation des Programms DIFMOD
EURATOM EC 7th framework program. Collaborative project \u27redox phenomena controlling systems\u27. 1st annual workshop proceedings
Time-dependent Hamiltonian estimation for Doppler velocimetry of trapped ions
The time evolution of a closed quantum system is connected to its Hamiltonian
through Schroedinger's equation. The ability to estimate the Hamiltonian is
critical to our understanding of quantum systems, and allows optimization of
control. Though spectroscopic methods allow time-independent Hamiltonians to be
recovered, for time-dependent Hamiltonians this task is more challenging. Here,
using a single trapped ion, we experimentally demonstrate a method for
estimating a time-dependent Hamiltonian of a single qubit. The method involves
measuring the time evolution of the qubit in a fixed basis as a function of a
time-independent offset term added to the Hamiltonian. In our system the
initially unknown Hamiltonian arises from transporting an ion through a static,
near-resonant laser beam. Hamiltonian estimation allows us to estimate the
spatial dependence of the laser beam intensity and the ion's velocity as a
function of time. This work is of direct value in optimizing transport
operations and transport-based gates in scalable trapped ion quantum
information processing, while the estimation technique is general enough that
it can be applied to other quantum systems, aiding the pursuit of high
operational fidelities in quantum control.Comment: 10 pages, 8 figure
Berechnungen und Sensitivitaetsbetrachtungen zur Aktivitaetsfreisetzung aus einem ersoffenen Endlager fuer radioaktive Abfaelle anhand eines einfachen Stoerfallmodelles
An ion trap built with photonic crystal fibre technology
We demonstrate a surface-electrode ion trap fabricated using techniques
transferred from the manufacture of photonic-crystal fibres. This provides a
relatively straightforward route for realizing traps with an electrode
structure on the 100 micron scale with high optical access. We demonstrate the
basic functionality of the trap by cooling a single ion to the quantum ground
state, allowing us to measure a heating rate from the ground state of 787(24)
quanta/s. Variation of the fabrication procedure used here may provide access
to traps in this geometry with trap scales between 100 um and 10 um.Comment: 6 pages, 4 figure
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