[en] The Institute of Hot Chemistry of the Nuclear Research Center Karlsruhe has developed an experimental method to determine the ratios of noble fission gases in the ppm range with uncertainties of a few percent. This is especially of interest for the Xenon isotopes 131 and 134, the ratio of which is different for U235 and Pu239 fission. For KNK II with the Uranium/Plutonium fuel of the test zone assemblies and the Uranium fuel of the driver zone assemblies, a comparison of measured and calculated ratios could therefore allow to distinguish between a failure in one of the two zones with different fuel type. In this report the experimental method is explained and experimental results are presented for one special fuel failure in KNK II

[en] A pair of pliers is described, which is suitable for gripping nuclear reactor fuel elements whose heads have a complicated mechanical structure. The pliers are characterised at the gripping end by gripping arms separated by slits, where the slits are inclined to the axis of the pliers and to plane at right angles to the axis or are arranged to be at least approximately helical or screw shaped. (HP)

[en] In order to be able to replace several separate rods (fuel rods or absorber rods), in a fuel element, a special grab is introduced, which consists of several individual gripping devices and is operated by spring loading. (TK)

[en] The aim of this study was to investigate the formation and properties of heavy organic phases resulting from the TBP-degradation in an uranium evaporator. For this purpose we concentrated uranyl nitrate solutions from 70 g/l to a final concentration of approx.= 480 g/l in a circulation evaporator. These solutions contained different amounts of organic material. In several experimental runs we used - TBP-saturated solutions - TBP-saturated solutions containing 0,2 vol% 30% TBP/dodecane as organic entrainment - TBP-saturated solutions with 20 ml UO₂(NO₃)₂ x 2 TBP complex added as heavy organic phase. The heavy organic phase formed during a run was analyzed for the TBP- and HDBP content at the end of the experiment. In several cases also determinations of H₂MBP, H₃PO₄, acid, uranium and density were carried out. Additionally every sample was analyzed by a combination of DTA/TG. The appearance of a heavy organic phase could only be observed when organic entrainment was present. Its nature seemed to be a mixed uranium-TBP-HDBP complex. At a TBP/HDBP ratio of about 1:1 this complex was relatively stable under our experimental conditions. This observation was confirmed by the behaviour of the UO₂(NO₃)₂ x 2 TBP complex which proved to be stable only after the uptake of HDBP. The thermochemical properties of the residues were quite similar to these of the UO₂(NO₃)₂ x 2 TBP complex. An exothermal degradation step occurred only at temperatures over 190⁰C. Nevertheless the enthalpy of that step was lower than in the case of the pure uranium/TBP complex because of the uptake of HDBP. (orig.)

[en] This concerns the improvement of the composition of a reflector ceiling of graphite blocks for a pebble bed reactor. The reflector ceiling is composed of single blocks which are superposed in several layers. In order to improve security it is proposed to fasten the blocks of each layer separately by a bar- or tube shaped anchoring rod. Each anchoring rod is separately coupled. (UWI)

[en] Short communication

[en] The ARIES-IV Nested Shell Blanket (NSB) Design is an alternate blanket concept of the ARIES-IV low activation helium-cooled reactor design. The reference design has the coolant routed in the poloidal direction and the inlet and outlet plena are located at the top and bottom of the torus. The NSB design has the high velocity coolant routed in the toroidal direction and the plena are located behind the blanket. This is of significance since the selected structural material is SiC-composite. The NSB is designed to have key high performance components with characteristic dimensions of no larger than 2 m. These components can be brazed to form the blanket module. For the diverter design, we eliminated the use of W as the divertor coating material by relying on the successful development of the gaseous divertor concept. The neutronics and thermal-hydraulic performance of both blanket concepts are similar. The selected blanket and divertor configurations can also meet all the projected structural, neutronics and thermal-hydraulics design limits and requirements. With the selected blanket and divertor materials, the design has a level of safety assurance rate of I (LSA-1), which indicates an inherently safe design

[en] We presents and experimental investigation on the effects produced by broad band soft X-rays (combined with a small fraction of vacuum ultra violet photons and possibly secondary elec-trons) on the surface of three moons of giant planets: Europa, Titan and Enceladus. Such environ-ments are constantly exposed to space ionizing agents (UV and soft X-rays photons, electrons and ions) allowing photodissociation processes, surface photochemistry and prebiotic chemistry. The processing of such spatial ices have promoted an enhancement in the chemical complexity, similar what may have happened in the early earth triggering the arising of life. (paper)

[en] Magnetic monopoles, predicted by Dirac, entered a new paradigm with the discovery of emergent monopoles within dipole lattices known as bulk and artificial spin ices. The observation of monopoles in certain artificial systems, and their absence from other similar structures, is a significant puzzle. Connected artificial spin-ice structures attract much attention in terms of the possibility to read states electrically, and offer the possibility of monopole defect control via well-understood domain wall processes. Nevertheless, full comprehension of the underlying processes is lacking. Here, we establish one of the overriding components. We demonstrate using high-resolution scanning transmission x-ray microscopy (STXM) the cooperative process associated with two transverse domain walls that creates the monopole defect in NiFe. The feature size of the array is large compared to the exchange length in the ferromagnet, and the two transverse domain walls give a rich internal structure to the monopole defect vertex. The magnetic Coulomb repulsion between two domain walls carrying the same sign of magnetic charge stabilizes the monopole defects at fields greater than the depinning field for a single wall at that vertex. These observations allow us to form an overview of monopole defect control possibilities from extrinsic pinning as in Co arrays (the extreme extrinsic limit being isolated bar structures) to intrinsic pinning captured here.

[en] Highlights: • Co-optimization of CO₂–EOR process under geological uncertainty is presented. • Multi-objective function is developed for CO₂-EOR Co-optimization process. • Polynomial response surface model optimized using a neural network optimizer. • Operational control variables are optimized to increase CO₂ storage and oil recovery. - Abstract: This paper presents an integrated numerical framework to co-optimize EOR and CO₂ storage performance under uncertainty in the Farnsworth Unit (FWU) oil field in Ochiltree County, Texas. The framework includes a field-scale compositional reservoir multiphase flow model, an uncertainty quantification model and a neural network optimization process. The reservoir flow model has been constructed based on the field geophysical, geological, and engineering data. Equation of state parameters were tuned to achieve field measured fluid properties and subsequently used to predict the minimum miscible pressure (MMP). A history match of primary and secondary recovery processes was conducted to estimate the reservoir and multiphase flow parameters as the base case for analyzing the effect of recycling produced gas, infill drilling and water alternating gas (WAG) cycles on oil recovery and CO₂ storage. A multi-objective optimization model was defined for maximizing both oil recovery and CO₂ storage. The uncertainty quantification model comprising the Latin Hypercube sampling, Monte Carlo simulation, and sensitivity analysis, was used to study the effects of uncertain variables on the defined objective functions. Uncertain variables include bottom hole injection pressure, WAG cycle, injection and production group rates, and gas-oil ratio. The most significant variables were chosen as control variables to be used for the optimization process. A neural network optimization algorithm was utilized to optimize the objective function both with and without geological uncertainty. The vertical permeability anisotropy (Kv/Kh) was selected as one of the uncertain parameters in the optimization process. The simulation results were compared to a scenario baseline case that predicted CO₂ storage of 74%. The results showed an improved approach for optimizing oil recovery and CO₂ storage in the FWU. The optimization model predicted that about 94% of CO₂ would be stored and most importantly, that this increased storage could result in about 25% of incremental oil recovery. The sensitivity analysis reduced the number of control variables to decrease computational time. A risk aversion factor was used to represent results at various confidence levels to assist management in the decision-making process. The defined objective functions were shown to be a robust approach to co-optimize oil recovery and CO₂ storage.