Results 1 - 10 of 338
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[en] INVAP performs design activities using a calculation suite, which is a set of codes of the different disciplines that includes, also, a set of procedures and methodologies that take into account the whole process of design including regulatory aspects, analyst qualification and the validation of computer codes as well. INVAP is in continuous development and validation of the calculation suite used for design and optimization of nuclear facilities, including also the improvement of the procedures and the training and retraining of the analyst. The IAEA Coordinated Research Programs (CRP) plays an important role in the V&V process allowing and promoting the strong interaction between data providers and benchmarkers of different countries, which strongly enhances the sharing of knowledge and the learning process of analysts. It also enables other important issues like: i) the comparison of different calculation codes and methodologies, ii) establishing procedures for the qualification of the computational tools and users, iii) the transference of know-how in the area of innovative methods in RR and iv) the minimization of user effects. This paper describes the validation of our calculation line and our experience in the qualification of the analyst and other side effects, based on the INVAP experience in the participation in the IAEA CRP’s. INVAP proposed scheme for the eight evaluated benchmarks is to develop alternate calculation approaches that consider not only the diverse paths of the calculation suite but also diverse specialists for each path. (author)
[en] Newport News Shipbuilding (NNS) is on a mission to achieve and sustain world-class performance and maintenance excellence for Facilities Support. Our Computerized Maintenance Management System (CMMS) installation was 17 years old, and legacy data structures were inadequate to support collection of accurate reliability data. The Facilities Asset Mobile Environment (FAME) project includes three major segments - Mobile Hardware, Information, and Process Upgrades supported by the CMMS. By implementing the FAME project, NNS is making significant strides in improving Mean Time Between Failures (MTBF) and Mean Time To Repair (MTTR). (authors)
[en] Ray optics have proven to be an effcient and versatile tool to describe dielectric optical microcavities and their far-field emission based on the principle of ray-wave correspondence. Whereas often the well-known ray-optics at planar interfaces yields reasonable results, semiclassically and boundary-curvature induced corrections will become more important as the cavity size is further reduced. In this paper, we summarize the various ray optics descriptions of optical microresonators, in addition paying special attention to the differences that arise between chaotic versus non-chaotic (integrable or nearly integrable) resonator geometries, respectively. Whereas the far-field pattern in the chaotic case is known to be determined by the overlap of the unstable manifold with the leaky region, it results from the emission of trajectories with the smallest nonzero decay rates in the non-chaotic situation. We present an enhanced ray optical description, extended by wave-inspired (semiclassical) corrections, and discuss their consequences for the ray dynamics. In particular, we find clear indications for the presence of attractors resulting from the non-Hamiltonian character of the extended ray dynamics in phase space. We illustrate their impact on the far-field emission and show that it can considerably differ from the conventional ray description result. (paper)
[en] Accurate and reliable nuclear data libraries are essential for calculation and design of advanced nuclear systems. A 1200 fine group nuclear data library Hybrid Evaluated Nuclear Data Library/Fine Group (HENDL/FG) with neutrons of up to 150 MeV has been developed to improve the accuracy of neutronics calculations and analysis. Corrections of Doppler, resonance self-shielding, and thermal upscatter effects were done for HENDL/FG. Shielding and critical safety benchmarks were performed to test the accuracy and reliability of the library. The discrepancy between calculated and measured nuclear parameters fell into a reasonable range. (authors)
[en] The detection of special nuclear material at ports and borders is one of the primary missions of the Department of Homeland Security's (DHS) Domestic Nuclear Detection Office (DNDO). In support of this mission a large-scale modeling and simulation effort has been undertaken with the goal of providing a comprehensive tool-kit that addresses the complexity of problems involved with developing and maintaining technologies deployed to global nuclear detection architecture (GNDA) nodes. An important objective of DNDO's mission is to characterize detector system performance before deployment. In the effort to support this mission, the latest version of MCNP has been used to perform detectability studies of highly enriched uranium (HEU) to populate a database that will be used for the tool-kit. The characterization method used in the implementation of the database is the receiver operating characteristic (ROC). A ROC curve shows the limits of detectability of a given system as well as an overall metric of the efficacy of a detection system. This is accomplished by comparing total detector count distributions to the count distribution produced by background alone. For an in-depth explanation of the theory behind the MCNP production of ROC curves please refer to the paper, 'How To Use The Receiver Operating Characteristic Tally Option in MCNP6'. Building a useful database requires an expansive parameter space. The current tool-kit use nine parameters, which if varied with just 5 options each, results in nearly two million simulations to run. Depending on the set of parameters these simulations can take a few hours or a few weeks to complete. This computational cost necessitates the use of scaling algorithms to interpolate between the data contained in the database. The tool-kit employs a discrete event method to simulate the movement and detector response of special nuclear material (SNM) through a GNDA node. Given the nature of a discrete event simulation, constant motion of SNM must be split up in to discrete spatial detection points. The fidelity required of the spatial splitting to achieve a properly converged answer is investigated here for a neutron detection system. The detector used was a SNAP-3 neutron detector in front of a sphere of SNM in the presence of background radiation. A parameter study has been performed to determine the spatial fidelity required for ROC curve convergence for moving objects in a discrete event simulator. It appears that 5 points is the minimum number of detection points with 7 points needed for one of the parameter sets. The convergence worsens with increases to detection length but appears to improve with increasing detector distance. These results will help future work involving quantifying the accuracy based on given tolerances and parameters. (authors)
[en] As one of the key components of nuclear reactor design and safety analysis software for Pressurized Water Reactor (PWR), the advance of the core-analysis code indicates the nuclear power development of the corresponding country. Hence, Nuclear Engineering Computational Physics Lab. (NECP) developed a PWR core-analysis code NECP-Cypress. Currently, it contains several modules including a generalized cross section module, a diffusion module using the Variational Nodal Method (VNM), a depletion-calculation using the traditional macroscopic module, a thermal-hydraulics module solving the single channel heat transfer equation and 1D heat conduction equation. With the VNM employed, NECP-Cypress can eliminate the control rod cusping effect and provide a better pin power reconstruction. In this paper, we firstly introduce the modules of the code NECP-Cypress. Secondly, two large-scale PWR core benchmarks were employed to demonstrate the ability of the code by comparing with SIMULATE-3, including the BEAVRS problem and a pseudo CAP1400 reactor core problem. (authors)
[en] The variational nodal method (VNM) as implemented in the VARIANT code has been widely employed to fast reactor cores, but much less so for thermal reactors. In what follows we report the initial phase of development of the PANX code (Purdue - Argonne - Northwestern - Xi'an) for three-dimensional pin resolved PWR transport calculations. In two dimensions, prototype modifications of VARIANT using finite elements to obtain heterogeneous nodes and quasi-reflected interface conditions to reduce the high angular-order interface conditions, have been successfully employed to the 2D C5G7 benchmark. In three dimensions, however, the polynomial interface conditions employed in VARIANT smear fuel and coolant at each axial interface, leading to lack of convergence as the axial mesh is refined. This problem is also encountered in the 2D/1D approximations in MOC based methods. The intent of this work is to eliminate these interface homogenization effects from VNM calculations. For clarity, in this work we examine these phenomena in diffusion theory. The next stage of development will incorporate spherical harmonic trial functions to achieve more accurate transport solutions. (authors)
[en] The processing and analysis of remotely sensed imagery (RSI) is a research hotspot in the information field, and building extraction and change detection are some of the difficult problems. In order to make the maximum use of the effective characteristics and design independently the algorithm of feature extraction, an approach to building extraction and change detection from RSI based on layered architecture containing pixel layer, object layer and configuration layer is proposed. In the pixel layer, the input image is over-segmented and under-segmented, respectively, by a quantity-controllable algorithm using super-pixel segmentation to obtain the segmentation object sets, with which the input image is decomposed into shadow layer, homogeneity layer and edge layer, where the buildings are extracted based on the spatial relationship between the feature areas and segmentation objects. In the object layer, for preserving the accurate contour of the buildings, a new segmentation method based on the traditional graph-cut theory and mathematical morphology is introduced, and then, the buildings extracted from each layer are merged. Finally, in the configuration layer, the change information is detected using spatial relationship of buildings between the old image and the new one. The experimental results reveal that the building contour is extracted accurately, and three types of change including the newly built, the demolished and the reconstructed buildings can be detected; in addition, there is no strict requirement for registration accuracy. For the test images, the overall performance F1 of the building extraction is over 85, and the precision and recall of the change detection are both higher than 90%.
[en] The collision between the coal–gangue and the metal plate of the hydraulic support is a typical mechanical contact behavior in the surface coal mining, which will cause vibration in the tail beam and even in the whole hydraulic support. This paper presents a contact analysis of coal–gangue impact on the metal plate to discover how vibration signals are generated and propagated in the collision process. We build a dynamic model for rock impact on the metal plate based on the elastoplastic contact theory, the Drucker–Prager criterion and the Tavares and King particle impact damage model. We establish a finite element model of the impact system between the coal–gangue and the metal plate, conduct contact simulation using the software LS-DYNA and study the stress transfer process on the metal plate contact surface. We compare the parameters of coal and gangue impact on the metal plate and discuss how they are different by calculating the stress and displacement created in the metal plate, kinetic energy of the coal–gangue particles and the total energy of the metal plate. In addition, we study the effect of impact velocity on the vibration response of the metal plate. Results show that the stress wave diffuses outward from the center of the metal plate. The collision frequency, contact position of the rock sphere and re-collision time are random. As the impact velocity increases, the contact responses all increase. This study provides guidance for the analysis of vibration response of coal–gangue impact on tail beam.