A flow-dependent estimation of constriction size distribution in gap-graded soils: an integrated statistical approach

The clogging-unclogging process in gap-graded soils is a result of the migration of seepage-driven fines, which subsequently induces measurable changes in the local hydraulic gradients. This process can be temporally observed in the variations of Darcy's hydraulic conductivity (K). The current study proposes an integrated statistical Monte Carlo approach combining the discrete element method and 2D computational fluid dynamics simulations to estimate the flow-dependent constriction size distribution (CSD) for a gap-graded soil. The computational inferences were supported with experimental results using an internally stable soil, which was subjected to one-dimensional flow stimulating desired hydraulic loadings: a hydraulic gradient lower than the critical gradient applied as a multi-staged loading pattern. The 35th percentile size of the flow-dependent CSD (Dc35) for both internally stable and unstable gap-graded soils becomes approximately equal to Dc35 at steady-state. However, a greater variation of larger constrictions persists for the unstable soils. This pilot study has shown the applicability of the proposed method to estimate flow-dependent CSD for a wide range of experimentally observed K values.

Minimizing Power Peaking Factor of BEAVRS-based Reactor Using Polar Bear Optimization Algorithms

Fuel loading pattern optimization is a complex problem because there are so many possibilities for combinatorial solutions, and it will take time to try it one by one. Therefore, the Polar Bear Optimization Algorithm was applied to find an optimum PWR loading pattern based on BEAVRS. The desired new fuel loading pattern is the one that has the minimum Power Peaking Factor (PPF) value without compromising the operating time. Operating time is proportional to the multiplication factor (k eff ). These parameters are usually contradictive with each other and will make it hard to find the optimum solution. The reactor was modelled with the Standard Reactor Analysis Code (SRAC) 2006. Fuel pins and fuel assemblies are modelled with the PIJ module for cell calculations. One-fourth symmetry was used with the CITATION X-Y module for core calculations. The optimization was done with 200 populations and 50 iterations. The PPF value for the selected solution should never exceed 2.0 in every burn-up step. Out of 28 solutions, the best optimal fuel loading pattern had a maximum value PPF of 1.458 and a k eff of 0.916 at day 760 of calculated time (corresponding to a cycle length of 479 days). Therefore, the maximum PPF value was 27.1% lower than the safety factor, and the same operating time as the standard loading pattern has been achieved.

Optimization of the loading pattern of the PWR core using genetic algorithms and multi-purpose fitness function

The study demonstrates an application of genetic algorithms (GAs) in the optimization of the first core loading pattern. The Massachusetts Institute of Technology (MIT) BEAVRS pressurized water reactor (PWR) model was applied with PARCS nodal-diffusion core simulator coupled with GA numerical tool to perform pattern selection. In principle, GAs have been successfully used in many nuclear engineering problems such as core geometry optimization and fuel configuration. In many cases, however, these analyses focused on optimizing only a single parameter, such as the effective neutron multiplication factor (k eff), and often limited to the simplified core model. On the contrary, the GAs developed in this work are equipped with multiple-purpose fitness function (FF) and allow the optimization of more than one parameter at the same time, and these were applied to a realistic full-core problem. The main parameters of interest in this study were the total power peaking factor (PPF) and the length of the fuel cycle. The basic purpose of this study was to improve the economics by finding longer fuel cycle with more uniform power/flux distribution. Proper FFs were developed, tested, and implemented and their results were compared with the reference BEAVRS first fuel cycle. In the two analysed test scenarios, it was possible to extend the first fuel cycle while maintaining lower or similar PPF, in comparison with the BEAVRS core, but for the price of increased initial reactivity.

Experimental Study of the Effect of Cavities on the Load Capacity of Two-Way Reinforced Concrete Plates on Fixed Concrete Thickness

The study aims to determine the effect of cavities on the load capacity of reinforced concrete slabs when compared to massive reinforced concrete slabs that have the same thickness, with the hope of reducing the structure’s weight and the use of concrete materials. The modified PVC pipes, as cavity formers, will be placed in the tensile area without reducing the flexural strength that is caused by the weak nature of concrete against tensile strength. The test is carried out on a full scale against 14 cm thick solid plates (PP-1), and hollow plates, which use modified PVC pipes (PB-2), with a cavity diameter of 7.6 cm that has the same thickness. The test uses joint supports on all four sides and the loading pattern is evenly distributed. All slabs are made, on the spot, of cast concrete with the same size and distance between the reinforcement. PVC hollow plate (PB-2) has the same effective thickness as solid plate but has 14% less concrete volume. The maximum load capacity on the solid plate (PP-1) is 522.66 kN and on the hollow plate (PB-2) is 444.33 kN. The melting capacity on the solid plate (PP-1) is 373,515 kN and on the hollow plate (PB-2) is 325,935 kN. Initial crack load capacity on the solid plate (PP-1) is 19.5 kN and on the hollow plate (PB-2) is 16.75 kN

A study on the core loading pattern of the VVER-1200/V491

The VVER-1200/V491 was a selected candidate for the Ninh Thuan I Nuclear Power Plant.However, in the Feasibility Study Safety Analysis Report (FS-SAR) of the VVER-1200/V491, the core loading pattern of this reactor was not provided. To assess the safety features of the VVER- 1200/V491, finding the core loading patterns and verifying their safety characteristics are necessary. In this study, two core loading patterns of the VVER-1200/V491 were suggested. The first loading pattern was applied from the VVER-1000/V446 and the second was searched by core loading optimization program LPO-V. The calculations for power distribution, the effective multiplication factor (k-eff), and fuel burn-up were then calculated by SRAC code. To verify several safety parameters of loading patterns of the VVER-1200/V491, the neutron delayed fraction (DNF), fuel andmoderator temperature feedbacks (FTC and MTC) were investigated and compared with the safety standards in the VVER-1200/V491 FS-SAR or the VVER-1000/V392 ISAR.

Effect of Hallux Valgus Correction with Kinesiology Taping on Hindfoot Position. Pilot Study

Background. Hallux valgus is the most common deformity of the forefoot. It has a multifactorial aetiology, with hindfoot valgus considered one of its causes. The aim of this study was to evaluate hindfoot position and loading pattern after a treatment of Kinesiology Taping (KT) for the mechanical correction of hallux valgus. Material and methods. The study involved 25 feet with hallux valgus deformity and hindfoot valgus. The hallux valgus angle (HVA) and hindfoot angle were assessed with a 3D scanner. Hindfoot loading pattern was examined with a baropodometric platform while standing and during gait. Measurements were taken on the following three occasions: before and immediately after KT placement as well as after a month of taping. Results. The KT treatment had a significant influence on the hindfoot angle (p<0.001) and HVA (p<0.001) measured while standing and on lateral heel loading in dynamic conditions during gait (p<0.01). Conclusions. 1. KT decreased HVA and improved hindfoot position while standing in the pilot study participants. 2. KT exerted a corrective influence on the foot loading pattern in patients with hallux valgus and hindfoot pronation. 3. The foot position correction and normalisation of foot loading achieved in the pilot study provide a basis for further research on KT effectiveness in patients with hallux valgus and hindfoot pronation.

Application of Evolutionary Simulated Annealing Method to Design a Small 200 MWt Reactor Core

This paper presents the application of an evolutionary simulated annealing (ESA) method to design a small 200 MWt reactor core. The core design is based on a reference ACPR50 reactor deployed in a floating nuclear power plant. The core consists of 37 typical 17x17 PWR fuel assemblies with three different U-235 enrichments of 4.45, 3.40 and 2.35 wt%. Core loading pattern (LP) has been optimized for obtaining the cycle length of 900 effective full power days, while minimizing the average U-235 enrichment and the radial power peaking factor. The optimization process was performed by coupling the ESA method with the COREBN module of the SRAC2006 system code.