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Errors associated with standard nodal diffusion methods as applied to mixed oxide fuel problems

Description: The evaluation of the disposition of plutonium using light water reactors is receiving increased attention. However, mixed-oxide (MOX) fuel assemblies possess much higher absorption and fission cross- sections when compared to standard UO2 assemblies. Those properties yield very high thermal flux gradients at the interfaces between MOX and UO2 assemblies. It has already been reported that standard flux reconstruction methods (that recover the homogeneous intranodal flux shape using the converged nodal solution) yield large errors in the presence of MOX assemblies. In an accompanying paper, we compare diffusion and simplified PN calculations of a mixed-oxide benchmark problem to a reference transport calculation. In this paper, we examine the errors associated with standard nodal diffusion methods when applied to the same benchmark problem. Our results show that a large portion of the error is associated with the quadratic leakage approximation (QLA) that is commonly used in the standard nodal codes.
Date: July 24, 1998
Creator: Brantley, P. S., LLNL
Partner: UNT Libraries Government Documents Department

New concept of small power reactor without on-site refueling for non-proliferation

Description: Energy demand in developing countries is increasing to support growing populations and economies. This demand is expected to continue growing at a rapid pace well into the next century. Because current power sources, including fossil, renewable, and nuclear, cannot meet energy demands, many developing countries are interested in building a new generation of small reactor systems to help meet their needs. The U.S. recognizes the need for energy in the developing countries. In its 1998 Comprehensive Energy Strategy, the Department of Energy calls for research into low-cost, proliferation- resistant, nuclear reactor technologies to ensure that this demand can be met in a manner consistent with U.S. non-proliferation goals and policies. This research has two primary thrusts: first, the development of a small proliferation-resistant nuclear system (i.e., a technology focus); second, the continuation of open communication with the international community through early engagement and cooperation on small reactor development. A system that meets developing country requirements must: (1) achieve reliably safe operation with a minimum of maintenance and supporting infrastructure; (2) offer economic competitiveness with alternative energy sources available to the candidate sites; and (3) demonstrate significant improvements in proliferation resistance relative to existing reactor systems. These challenges are the most significant driving forces behind the LLNL proposed program for development of a new, small nuclear reactor system. This report describes a technical approach for developing small nuclear power systems for use in developing countries. The approach being proposed will establish a preliminary set of requirements that, if met, will cause new innovative approaches to system design to be used. The proposed approach will borrow from experience gained over the past forty years with four types of nuclear reactor technologies (LWR, LMR, HTGR, and MSR) to develop four or more pre-conceptual designs. The pre-conceptual designs will be used to confirm the ...
Date: July 13, 1998
Creator: Brown, N.W., LLNL
Partner: UNT Libraries Government Documents Department

Analysis of Hydrogen Depletion Using a Scaled Passive Autocatalytic Recombiner

Description: Hydrogen depletion tests of a scaled passive autocatalytic recombine (pAR) were performed in the Surtsey test vessel at Sandia National Laboratories (SNL). The experiments were used to determine the hydrogen depletion rate of a PAR in the presence of steam and also to evaluate the effect of scale (number of cartridges) on the PAR performance at both low and high hydrogen concentrations.
Date: October 28, 1998
Creator: Blanchat, T.K. & Malliakos, A.
Partner: UNT Libraries Government Documents Department

Design Parameters for a Natural Uranium UO{sub 3} or U{sub 3}O{sub 8} Fueled Nuclear Reactor

Description: A recent Oak Ridge National Laboratory report provided preliminary analyses to propose alternative design parameters for a nuclear reactor that could be fueled with natural UO{sub 3} or U{sub 3}O{sub 8} and moderated with either heavy water or reactor-grade graphite. This report provides more specific reactor design and operating parameters for a heavy water-moderated reactor only. The basic assumptions and analytical approach are discussed together with the results of the analysis.
Date: November 15, 2002
Creator: Hopper, C.M.
Partner: UNT Libraries Government Documents Department

Nuclear energy and materials in the 21st century

Description: The Global Nuclear Vision Project at the Los Alamos National Laboratory is examining a range of long-term nuclear energy futures as well as exploring and assessing optimal nuclear fuel-cycle and material strategies. An established global energy, economics, environmental (E{sup 3}) model has been adopted and modified with a simplified, but comprehensive and multi-regional, nuclear energy module. Consistent nuclear energy scenarios are constructed, where future demands for nuclear power are projected in price competition with other energy sources under a wide range of long-term ({approx}2100) demographic, economic, policy, and technological drivers. A spectrum of futures is examined at two levels in a hierarchy of scenario attributes in which drivers are either external or internal to nuclear energy. The result reported examine departures from a basis scenario and are presented in the following order of increasing specificity: (a) definition and parametric variations of the basis scenario; (b) comparison of the basis scenario with other recent studies; (c) parametric studies that vary upper-level hierarchical scenario attributes (external drivers); and (d) variations of the lower-level scenario attributes (internal drivers). Impacts of a range of nuclear fuel-cycle scenarios are reflected back to the higher-level scenario attributes that characterize particular nuclear energy scenarios. Special attention is given to the role of nuclear materials inventories (in magnitude, location, and form) and their contribution to the long-term sustainability of nuclear energy, the future competitiveness of both conventional and advanced nuclear reactors, and proliferation risk.
Date: May 1, 1997
Creator: Krakowski, R.A.; Davidson, J.W. & Bathke, C.G.
Partner: UNT Libraries Government Documents Department

{sup 16}O neutron cross section evaluation

Description: This work has resulted from a need to compute more accurately the neutron scattering cross sections and angular distributions for {sup 16}O. Several oxygen evaluations have been performed in the past with R-Matrix theory, including ENDF/B-V and ENDF/B-VI. ENDF/B-VI is an improvement over ENDF/B-V, but still underpredicts in general the forward scattering of neutrons below 2.5 MeV. R-Matrix theory is used in describing cross sections at and near the resonance energies; but may not always be adequate in describing cross sections between resonances, especially when they are widely spaced. The optical (potential well) model of the nucleus is very good in representing cross sections that vary smoothly with energy, but not at describing all of the detailed resonance cross sections. A combination of the potential well model and R-Matrix theory was used for this work to represent cross sections with isolated resonances with large spacings between them. The total neutron cross section of oxygen-16 below 3.0 MeV has widely separated resonances and a dip in the cross section at 2.35 MeV. In the vicinity of resonances, where cross sections vary rapidly with energy, R-Matrix theory has been successful in fitting experimental data. In the region between resonances, an analytical procedure with physical basis is needed that agrees with data over a wide range of energies bracketing regions where experimental measurements are lacking.
Date: June 1, 1998
Creator: Caro, E.
Partner: UNT Libraries Government Documents Department

Uncertainties in the analysis of plutonium fueled light water moderated assemblies

Description: A theoretical analysis of UO/sub 2/-- PuO/sub 2/ fueled, light-water- moderated lattice experiments has been performed to aid in establishing technical bases and design criteria for the utilization of plutonium bearing fuel in thermal power reactors. Results for UO/sub 2/ and Al-- Pu lattices are included in order to understand the effects due to uranium and plutonium separately. The problems involved in calculating high leakage critical experiments are discussed. Estimates of the effects of various approximations inherent in the theoretical methods and/or analysis procedures are included along with the consequence on the results of the correlation. Uncertainties in the measurements and the neutron crosssection data are related to uncertainties in the calculated values K/sub eff/ .The results of other studies which bear on evaluating the calculational methods are summarized. Areas which should be investigated in future analyses are also identified. (111 references) (auth)
Date: May 1, 1973
Creator: Liikala, R.C.; Uotinen, V.O. & Jenquin, U.P.
Partner: UNT Libraries Government Documents Department

HELIOS: applications at the Los Alamos National Laboratory

Description: The Los Alamos National Laboratory (LANL) is involved in the analysis of many different types of nuclear systems. The nuclear systems that we have analyzed have included subcritical accelerator driven systems for the transmutation of waste, fusion systems, critical experiment systems, and space propulsion and power systems. We have also analyzed special purpose reactors such as the LANL Omega West reactor, production reactors, and conventional commercial light- and heavy-water reactors. Thus the systems that we analyze and the type of results desired, often vary considerably from those of a power company normally analyzing their PWR or BWR for fissile fuel burnup and production. The reactor geometries that we model are often quite complicated such as those of an RBMK or Savannah River Production Reactor. Rather than fissile fuel production and burnup, the goal of a calculation could be the production rate of some obscure isotope which has medical applications.
Date: October 1, 1997
Creator: Perry, R.T.; Mosteller, R.D.; Chodak, Paul III; Charlton, W. & Adams, B.T.
Partner: UNT Libraries Government Documents Department

Studies of alternative nuclear technologies

Description: This report is a summary of tasks performed for the U.S. Arms Control and Disarmament Agency under Contract AC7NC114. The work is directly related to the Agency effort to examine potential alternative fuel cycles that might enhance uranium resource utilization, minimize plutonium production, and reduce the weapons proliferation risk from spent fuel reprocessing or early introduction of fast breeder reactors. Reported herein are summaries of various inter-related task assignments, including: fuel utilization in current light water reactors operating with the uranium fuel cycle; alternate fuel cycles, including the use of denatured fuel in LWRs and of the spectral shift concept for reactivity control; fuel utilization in high temperature graphite moderated reactors using the denatured fuel cycle; fuel utilization in heavy water reactors (CANDU type), including the use of enriched fuel, denatured fuel, and recycle of plutonium and U-233; the tandem fuel cycle (recovery of spent fuel and further irradiation in a CANDU type reactor); issues in the utilization of denatured fuel in LWRs; preliminary conceptual evaluation of a heavy water moderated reactor suitable for use in the United States.
Date: April 1, 1978
Creator: Turner, S.E.; Gurley, M.K.; Kirby, K.D.; Mitchell, W. III & Roach, K.E.
Partner: UNT Libraries Government Documents Department

Observations of the boiling process from a downward-facing torispherical surface: Confirmatory testing of the heavy water new production reactor flooded cavity design

Description: Reactor-scale ex-vessel boiling experiments were performed in the CYBL facility at Sandia National Laboratories. The boiling flow pattern outside the RPV bottom head shows a center pulsating region and an outer steady two-phase boundary layer region. The local heat transfer data can be correlated in terms of a modified Rohsenow correlation.
Date: June 1, 1995
Creator: Chu, T.Y.; Bentz, J.H. & Simpson, R.B.
Partner: UNT Libraries Government Documents Department

Neutronic performance of high-density LEU fuels in water-moderated and water-reflected research reactors

Description: At the Reduced Enrichment for Research and Test Reactors (RERTR) meeting in September 1994, Durand reported that the maximum uranium loading attainable with U{sub 3}Si{sub 2} fuel is about 6.0 g U/cm{sup 3}. The French Commissariat a l`Energie Atomique (CEA) plan to perform irradiation tests with 5 plates at this loading. Compagnie pour L`Etude et La Realisation de Combustibles Atomiques (CERCA) has also fabricated a few uranium nitride (UN) plates with a uranium density in the fuel meat of 7.0 g/cm{sup 3} and found that UN is compatible with the aluminum matrix at temperatures below 500 C. High density dispersion fuels proposed for development include U-Zr(4 wt%)-Nb(2 wt%), U-Mo(5 wt%), and U-Mo(9 wt%). The purpose of this note is to examine the relative neutronic behavior of these high density fuels in a typical light water-reflected and water-moderated MTR-type research reactor. The results show that a dispersion of the U-Zr-Nb alloy has the most favorable neutronic properties and offers the potential for uranium densities greater than 8.0 g/cm{sup 3}. On the other hand, UN is the least reactive fuel because of the relatively large {sup 14}N(n,p) cross section. For a fixed value of k{sub eff}, the required {sup 235}U loading per fuel element is least for the U-Zr-Nb fuel and steadily increases for the U-Mo(5%), U-Mo(9%), and UN fuels. Because of volume fraction limitations, the UO{sub 2} dispersions are only useful for uranium densities below 5.0 g/cm{sup 3}. In this density range, however, UO{sub 2} is more reactive than U{sub 3}Si{sub 2}.
Date: September 1, 1996
Creator: Bretscher, M.M. & Matos, J.E.
Partner: UNT Libraries Government Documents Department

India's baseline plan for nuclear energy self-sufficiency.

Description: India's nuclear energy strategy has traditionally strived for energy self-sufficiency, driven largely by necessity following trade restrictions imposed by the Nuclear Suppliers Group (NSG) following India's 'peaceful nuclear explosion' of 1974. On September 6, 2008, the NSG agreed to create an exception opening nuclear trade with India, which may create opportunities for India to modify its baseline strategy. The purpose of this document is to describe India's 'baseline plan,' which was developed under constrained trade conditions, as a basis for understanding changes in India's path as a result of the opening of nuclear commerce. Note that this treatise is based upon publicly available information. No attempt is made to judge whether India can meet specified goals either in scope or schedule. In fact, the reader is warned a priori that India's delivery of stated goals has often fallen short or taken a significantly longer period to accomplish. It has been evident since the early days of nuclear power that India's natural resources would determine the direction of its civil nuclear power program. It's modest uranium but vast thorium reserves dictated that the country's primary objective would be thorium utilization. Estimates of India's natural deposits vary appreciably, but its uranium reserves are known to be extremely limited, totaling approximately 80,000 tons, on the order of 1% of the world's deposits; and nominally one-third of this ore is of very low uranium concentration. However, India's roughly 300,000 tons of thorium reserves account for approximately 30% of the world's total. Confronted with this reality, the future of India's nuclear power industry is strongly dependent on the development of a thorium-based nuclear fuel cycle as the only way to insure a stable, sustainable, and autonomous program. The path to India's nuclear energy self-sufficiency was first outlined in a seminal paper by Drs. H. J. ...
Date: January 1, 2009
Creator: Bucher, R .G. & Division, Nuclear Engineering
Partner: UNT Libraries Government Documents Department