Kenneth L. Peddicord

Material property correlations for uranium mononitride

Abstract The experimental data for the lattice parameter (a), density (p), and mean linear thermal expansion coefficient (α) of uranium mononitride (UN) have been collected and reviewed. Empirical correlations for these three properties as functions of temperature (T, in K) were developed and are given as: a( A ) = 4.879 + 3.264 × 10 −5 (T) + 6.889 × 10 −9 (T 2 ) , ρ(g/cm3) = 14.42-2.779 × 10−4(T)−4.897 × 10−8(T2), α(K−1) = 7.096 × 10−6 + 1.409 × 10−9(T). The lattice parameter correlation was constructed from experimental data in the range of 298

Heat conduction in spheres packed in an infinite regular cubical array

Abstract Steady-state temperature solutions are sought for an infinite cubical array of spheres. Heat transfer is by conduction and constant properties are assumed. The problem is treated as a unit cube containing a sphere at the center. Due to symmetry the cube is further subdivided into a wedge representing the unit cell. Applying continuity and boundary conditions, the analytical temperature solutions are obtained. For the case in which the sphere is assumed to represent porosity in a solid, a porosity correction to thermal conductivity is obtained in the form: f(p) = e −2,14p 0.0 where p = fractional porosityf(p) = porosity correction factor, f(p) ≤ 1.

Development of a creep rate porosity correction factor

Abstract A general method for constructing a creep rate porosity correction factor for any porous material has been developed. The creep rate of a porous material is assumed to be influenced by the effect of porosity on stress, diffusion coefficient and shear modulus. The effect of porosity on stress and diffusion coefficient was derived from simple physical considerations; the effect of porosity on shear modulus was addressed empirically. The resulting general method has been applied to the construction of a porosity correction factor for the creep of UO2, and comparison with experimental results shows good agreement.

Nuclear materials safety management

Foreword K.L. Peddicord. Preface N. Schulte. Opening the Workshop - Welcome and Introductions. Nuclear Materials Safety Management: Framework and Overview. Overview of Plutonium Storage and Transportation Safety Issues. MOX Fabrication and Transportation. Spent Fuel Storage Issues and Other Nuclear Materials Safety Topics. Meeting of the Nuclear Group on the Amarillo National Resource Center for Plutonium. Strategy for the Nuclear Materials Safety Management Initiative. Ongoing Programs. Planning for the Nuclear Materials Safety Management Initiative. Appendix. Author and Subject Index.

Fault-tolerant adaptive control for load-following in static space nuclear power systems

The possible use of a dual-loop model-based adaptive control system for load following in static space nuclear power systems is investigated. The proposed approach has thus far been applied only to a thermoelectric space nuclear power system but is equally applicable to other static space nuclear power systems such as thermionic systems.

Heat conduction in eccentric annuli

Abstract Under the assumption of constant properties and negligible axial effects, heat conduction in the radial direction through concentric annuli is a straightforward, 1-dim. problem. However, when the annular region is shifted from the centerline, the analysis must be made in two dimensions. A theoretical, experimental, and numerical study has been made of the 2-dim. temperature distributions for a system of eccentric annuli. Two boundary conditions are examined. The first is an angular temperature function on the outer boundary. The second is a convective boundary condition with a constant heat transfer coefficient and a constant ambient temperature. The general solutions are described which are valid for any size annular region and any degree of eccentricity. The evaluation of the analytical solutions are verified by an appropriate experiment. Several numerical approximations are examined for their suitability in handling the eccentric problem.

H2-MHR Pre-Conceptual Design Report: SI-Based Plant; HTE-Based Plant

Hydrogen and electricity are expected to dominate the world energy system in the long term. The world currently consumes about 50 million metric tons of hydrogen per year, with the bulk of it being consumed by the chemical and refining industries. The demand for hydrogen is expected to increase, especially if the U.S. and other countries shift their energy usage towards a hydrogen economy, with hydrogen consumed as an energy commodity by the transportation, residential, and commercial sectors. However, there is strong motivation to not use fossil fuels in the future as a feedstock for hydrogen production, because the greenhouse gas carbon dioxide is a byproduct and fossil fuel prices are expected to increase significantly. For electricity and hydrogen production, an advanced reactor technology receiving considerable international interest is a modular, passively-safe version of the high-temperature, gas-cooled reactor (HTGR), known in the U.S. as the Modular Helium Reactor (MHR), which operates at a power level of 600 MW(t). For electricity production, the MHR operates with an outlet helium temperature of 850 C to drive a direct, Brayton-cycle power-conversion system (PCS) with a thermal-to-electrical conversion efficiency of 48 percent. This concept is referred to as the Gas Turbine MHR (GT-MHR). For hydrogen production, the process heat from the MHR is used to produce hydrogen. This concept is referred to as the H2-MHR.

Re-Assessment of Nitride Fuel Potential in the Current Context of the Nuclear Industry

In recent years, there has been a renewal of interest in nitride fuels throughout the international community. The new challenges met by the nuclear industry, which include greater safety margin and the question of the waste management, have resulted in active research programs in next generation fast spectrum reactors and waste transmutation systems. Through these programs, nitride fuel has emerged as one of the most promising advanced fuels, thanks to their numerous favorable properties.Copyright

Utilization of Plutonium and Higher Actinides in the HTGR as Possibility to Maintain Long-Term Operation on One Fuel Loading

Promising existing nuclear reactor concepts together with new ideas are being discussed worldwide. Many new studies are underway in order to identify prototypes that will be analyzed and developed further as systems for Generation IV. The focus is on designs demonstrating full inherent safety, competitive economics and proliferation resistance. The work discussed here is centered on a modularized small-size High Temperature Gas-cooled Reactor (HTGR) concept. This paper discusses the possibility of maintaining long-term operation on one fuel loading through utilization of plutonium and higher actinides in the small-size pebble-bed reactor (PBR). Acknowledging the well-known flexibility of the PBR design with respect to fuel composition, the principal limitations of the long-term burning of plutonium and higher actinides are considered. The technological challenges and further research are outlined. The results allow the identification of physical features of the PBR that significantly influence flexibility of the design and its applications.Copyright

Gain‐Scheduled Controller Design for Load‐Following in Static Space Nuclear Power Systems

The possible use of a model‐based adaptive control system for load‐following in static space nuclear power systems is investigated. The objective of the control system is to deliver the demanded electric power at the desired voltage level by appropriately manipulating the neutron power through the control drums; the validated load voltage reading is assumed to be the only sensor available for feedback. Even though the proposed approach has thus far been applied only to a thermoelectric space nuclear power system, it is equally applicable to other static space nuclear power systems, such as thermionic systems. The proposed adaptive controller is for use in combination with the currently considered shunt regulators, or as a back‐up controller when other passive means of power system control, including some of the sensors, fail. The results of this systematic controller design attempt appear very encouraging, however, they are only preliminary in nature and they have been restricted to computer simulations. ...