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Idaho Falls, ID, United States

The Idaho Military Department consists of the Idaho Army National Guard, the Idaho Air National Guard, and the Idaho Bureau of Homeland Security.Its headquarters are located in Boise. Wikipedia.

Williamson R.L.,Idaho National Laboratory
Journal of Nuclear Materials | Year: 2011

A powerful multidimensional fuels performance analysis capability, applicable to both steady and transient fuel behavior, is developed based on enhancements to the commercially available ABAQUS general-purpose thermomechanics code. Enhanced capabilities are described, including: UO 2 temperature and burnup dependent thermal properties, solid and gaseous fission product swelling, fuel densification, fission gas release, cladding thermal and irradiation creep, cladding irradiation growth, gap heat transfer, and gap/plenum gas behavior during irradiation. This new capability is demonstrated using a 2D axisymmetric analysis of the upper section of a simplified multipellet fuel rod, during both steady and transient operation. Comparisons are made between discrete and smeared-pellet simulations. Computational results demonstrate the importance of a multidimensional, multipellet, fully-coupled thermomechanical approach. Interestingly, many of the inherent deficiencies in existing fuel performance codes (e.g., 1D thermomechanics, loose thermomechanical coupling, separate steady and transient analysis, cumbersome pre- and post-processing) are, in fact, ABAQUS strengths. © 2011 Elsevier B.V. All rights reserved. Source

We introduce a new method of solution for the convective heat transfer under forced laminar flow that is confined by two parallel plates with a distance of 2a or by a circular tube with a radius of a. The advection-conduction equation is first mapped onto the boundary. The original problem of solving the unknown field T (x, r, t) is reduced to seek the solutions of T at the boundary (r = a or r = 0, r is the distance from the centerline shown in Fig. 1), i.e., the boundary functions T a(x, t) ≡ T(x, r = a, t) and/or T 0(x, t) ≡ T(x, r = 0, t). In this manner, the original problem is significantly simplified by reducing the problem dimensionality from 3 to 2. The unknown field T (x, r, t) can be eventually solved in terms of these boundary functions. The method is applied to the convective heat transfer with uniform wall temperature boundary condition and with heat exchange between flowing fluids and its surroundings that is relevant to the geothermal applications. Analytical solutions are presented and validated for the steady-state problem using the proposed method. © 2012 American Society of Mechanical Engineers. Source

Derr K.,Idaho National Laboratory | Manic M.,University of Idaho
IEEE Transactions on Industrial Informatics | Year: 2013

This is the second of a two-part investigation of the generation of wireless sensor network (WSN) configurations that: 1) maximize coverage of irregular shaped polygonal areas and 2) maintain a high degree of node connectivity. The first-part of the investigation presented centralized algorithms for the generation of mesh (wireless sensor) network configurations that maximize coverage and connectivity. In this second part, we present a decentralized and distributed approach using an Extended Virtual Spring Mesh (EVSM)-Adaptive Coverage Algorithm and Protocol (ACAP) algorithm. The EVSM-ACAP algorithm represents an extension of EVSM algorithm with the newly developed ACAP. ACAP provides adaptive coverage and configuration of the mesh network by dynamically adjusting the sensing range of sensor nodes. EVSM-ACAP is compared to centralized mesh generation algorithms (described in the part one of the investigation), as well as other decentralized algorithms from artificial physics, for the control of large numbers of physical agents in sensor networks. EVSM-ACAP is shown to produce a sensor network deployment with an average sensor spacing within 1.6% of the desired spacing, versus 5.75% for the best centralized algorithmic approach. To the best of our knowledge, this is the first time that these centralized mesh network configuration algorithms have been contrasted with the scalable, robust, decentralized algorithms of artificial physics and EVSM. © 2005-2012 IEEE. Source

Hansen G.,Idaho National Laboratory
Journal of Computational Physics | Year: 2011

Multibody contact problems are common within the field of multiphysics simulation. Applications involving thermomechanical contact scenarios are also quite prevalent. Such problems can be challenging to solve due to the likelihood of thermal expansion affecting contact geometry which, in turn, can change the thermal behavior of the components being analyzed. This paper explores a simple model of a light water reactor nuclear fuel rod, which consists of cylindrical pellets of uranium dioxide (UO2) fuel sealed within a Zircalloy cladding tube. The tube is initially filled with helium gas, which fills the gap between the pellets and cladding tube. The accurate modeling of heat transfer across the gap between fuel pellets and the protective cladding is essential to understanding fuel performance, including cladding stress and behavior under irradiated conditions, which are factors that affect the lifetime of the fuel. The thermomechanical contact approach developed here is based on the mortar finite element method, where Lagrange multipliers are used to enforce weak continuity constraints at participating interfaces. In this formulation, the heat equation couples to linear mechanics through a thermal expansion term. Lagrange multipliers are used to formulate the continuity constraints for both heat flux and interface traction at contact interfaces. The resulting system of nonlinear algebraic equations are cast in residual form for solution of the transient problem. A Jacobian-free Newton Krylov method is used to provide for fully-coupled solution of the coupled thermal contact and heat equations. © 2011 Elsevier Inc. Source

Tumuluru J.S.,Idaho National Laboratory
Biosystems Engineering | Year: 2014

A flat die pellet mill was used to understand the effect of high levels of feedstock moisture content in the range of 28-38% (w.b.), with die rotational speeds of 40-60Hz, and preheating temperatures of 30-110°C on the pelleting characteristics of 4.8mm screen size ground corn stover using an 8mm pellet die. The physical properties of the pelletised biomass studied are: (a) pellet moisture content, (b) unit, bulk and tapped density, and (c) durability. Pelletisation experiments were conducted based on central composite design. Analysis of variance (ANOVA) indicated that feedstock moisture content influenced all of the physical properties at P<0.001. Pellet moisture content decreased with increase in preheating temperature to about 110°C and decreasing the feedstock moisture content to about 28% (w.b.). Response surface models developed for quality attributes with respect to process variables has adequately described the process with coefficient of determination (R2) values of >0.88. The other pellet quality attributes such as unit, bulk, tapped density, were maximised at feedstock moisture content of 30-33% (w.b.), die speeds of >50Hz and preheating temperature of >90°C. In case of durability a medium moisture content of 33-34% (w.b.) and preheating temperatures of >70°C and higher die speeds >50Hz resulted in high durable pellets. It can be concluded from the present study that feedstock moisture content, followed by preheating, and die rotational speed are the interacting process variables influencing pellet moisture content, unit, bulk and tapped density and durability. © 2013 The Author. Source

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