Sellafield Ltd is a nuclear decommissioning Site Licence Company (SLC) controlled by the Nuclear Decommissioning Authority (NDA), a government body set up specifically to deal with the nuclear legacy under the Energy Act 2004. From 2008–2016, it was operated under licence from the NDA by a third party Parent Body Organisation called Nuclear Management Partners (NMP). Since the termination of the NMP contract it has been brought back under direct governmental control by making it a subsidiary of the NDA.Sellafield Ltd's main aim is to manage the decommissioning of the Sellafield facility in Cumbria, England, on behalf of the NDA. The company employs more than 13,000 workers and its focus is to deliver accelerated nuclear decommissioning and clean-up programmes. It is also involved in nuclear fuel production and reprocessing, and international nuclear decommissioning and transportation.
Density functional theory (DFT) provides a powerful tool for describing the electronic properties of materials, however, self-interaction errors in semilocal functionals complicate the accurate modeling of correlated materials. The DFT + U method is a popular and computationally cost-effective solution for mitigating self-interaction; though, this reduces the ab initio aspect of DFT calculations, as the outcome now becomes dependent on the user's choice of U parameters. Atomistic modeling of plutonium dioxide (PuO2) is employed to provide insight into its evolution in storage or into its properties as mixed-oxide fuel. There is no single U parameter that can reproduce all the experimental properties of PuO2 accurately and, as such, it is important that the U parameter is selected with careful consideration. In this work, we use noncollinear DFT + U simulations to thoroughly examine the defect chemistry of PuO2 using U = 4 and 7 eV, in order to understand the implication the choice of U parameter can have on the predicted defect chemistry. We find that both U parameters predict the same intrinsic defect chemistry, with the main discrepancy being on the preferred charge state of the oxygen vacancies: +2 for U = 4 eV and neutral for U = 7 eV. Additionally, we show that the choice of U can impact the defect formation energies and preferred charge states of a dopant. When uranium is placed onto a plutonium lattice site, it tends to favor the neutral and +1 charge state (indicative of U4+ and U5+) with U = 4 eV, whereas with U = 7 eV the -1 and neutral charge states are more stable.
Delayed γ-ray spectroscopy was performed for evaporation residues produced in the ^{58}Ni+^{96}Ru reaction. A new isomer in _{ 70}^{150}Yb (Z=70, N=80) with a half-life of 0.62(5) μs was identified at an excitation energy of 2872(2) keV. Its spin-parity is assigned as (10^{+}) and a decay scheme is proposed based on a strong analogy with that of the isotonic _{ 68}^{148}Er. Previously, the 10^{+} isomers were observed in the N=80 even-Z isotones from the neutron-rich _{ 46}^{126}Pd to the neutron-deficient _{ 68}^{148}Er. For the first time, by combining experimental data and comprehensive large-scale shell-model calculations, we clearly identify the configurations of these isomers and demonstrate that they all exhibit seniority structures. These findings firmly establish a configuration change in the 10^{+} isomeric chain, from a pair of maximally aligned 1h_{11/2} neutrons (holes) to a pair of maximally aligned 1h_{11/2} protons around the Z=64 subshell closure. This transition serves as a unique isomeric relay underpinning the persistence of the isomeric chain.
This study investigates the erosion behavior and modeling of glass particle beds under impinging jet conditions, with a focus on particle size effects and the onset of cohesion. Ultrasonic profiling is implemented to scan and measure static crater profiles. Results indicate that particle size significantly affects crater dimensions, ring peak formation, and overall crater shape. The smallest glass particles (d 50 = 35 mu m) studied deviate from the trends in crater size, yield stress, and analytical modeling established using larger particles, indicating the onset of cohesion effects at this small particle size. The standard erosion parameter worked well for modeling cohesionless particles down to a certain size limit, beyond which cohesive forces become significant. A new parameter, E tau based on particle critical shear stress, is introduced for erosion modeling in this study. The transition to cohesive behavior observed in the smallest glass particles is successfully accounted for using E tau.
Delayed gamma-ray spectroscopy was performed for evaporation residues produced in the 58Ni + 96Ru reaction. A new isomer in 150 70Yb (Z = 70, N = 80) with a half-life of 0.62(5) mu s was identified at an excitation energy of 2872(2) keV. Its spin-parity is assigned as (10+) and a decay scheme is proposed based on a strong analogy with that of the isotonic 148 68Er. Previously, the 10+ isomers were observed in the N = 80 even-Z isotones from the neutron-rich 12646Pd to the neutron-deficient 14868Er. For the first time, by combining experimental data and comprehensive large-scale shell-model calculations, we clearly identify the configurations of these isomers and demonstrate that they all exhibit seniority structures. These findings firmly establish a configuration change in the 10+ isomeric chain, from a pair of maximally aligned 1h11/2 neutrons (holes) to a pair of maximally aligned 1h11/2 protons around the Z = 64 subshell closure. This transition serves as a unique isomeric relay underpinning the persistence of the isomeric chain.
