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Two-Dimensional Cell Calculations for Critical Assembly Analysis

Description: A pseudo two-dimensional collision probability method for calculating plate and pin cell flux distributions has been developed, tested against Monte Carlo calculations, and has been found to yield collision probabilities which are in error less than 2%. In both the plate and pin cell cases, the pseudo 2-D collision probability methods have been shown to be as accurate as direct collision probability methods for the geometries of interest in ZPPR critical assembly analysis. The computational efficiency of the pseudo 2-D method is approximately the same as standard 1-D methods.
Date: 1984~
Creator: Smith, K. S.
Partner: UNT Libraries Government Documents Department

Reckoning THOR

Description: Theoretical computation of the Los Alamos National Laboratory's critical assembly THOR (a thorium-reflected plutonium sphere) yields a high eigenvalue when compared to the experimentally measured eigenvalue. Several calculational improvements are investigated in an effort to reduce the discrepancy. Finally, the experimental procedure of reducing the raw configuration to clean specifications is reviewed.
Date: May 1, 1981
Creator: Kidman, R.B.
Partner: UNT Libraries Government Documents Department

Criticality design evaluation of the White Sands reactor building storage vault

Description: This report describes the conceptual design and criticality evaluation of a storage vault for components of the fast pulse reactor at White Sands Missile Range. Criticality calculations were performed with the KENO-IV Monte Carlo code for various storage configurations in order to investigate the coupling between the portable reactor and storage arrays of spare reactor rings or other fissile components of similar mass. Abnormal conditions corresponding to pseudo--random arrays of the fuel components, as well as a number of flooded configurations, were also evaluated to assess criticality potential for highly unlikely situations. In a normal, dry configuration, the neutron self-multiplication factor, k/sub eff/, of the fully loaded 3 x 8 planar array plus the reactor is less than 0.87. A completely flooded vault was found to produce self-multiplication factors in excess of 1.2.
Date: March 1, 1979
Creator: Philbin, J.S. & Nelson, W.E.
Partner: UNT Libraries Government Documents Department

Operation of a nuclear test gage at low multiplications

Description: The Nuclear Test Gage (NTG) at the Savannah River Plant is a subcritical multiplying facility (low k) with H/sub 2/O moderator and 2.54-cm-diameter fuel slugs of 5 wt percent /sup 235/U in aluminum alloy at a 4.285-cm triangular pitch. The core of the facility is 61-cm long with a normal diameter of 27 cm. The NTG is used for quality control of reactor components, such as /sup 235/U-Al fuel tubes, Li--Al target tubes, control and safety rods, and miscellaneous special irradiation elements. A component is tested by passing it through an axial test port 11.63 cm in diameter. The ion chamber response from the resultant change in neutron source multiplication is then compared with corresponding responses from known standards.
Date: January 1, 1977
Creator: Baumann, N.P.
Partner: UNT Libraries Government Documents Department

Design guide for category V reactors transient reactors

Description: The purpose of this Design Guide is to provide additional guidance to aid the DOE facility contractor in meeting the requirement that the siting, design, construction, modification, operation, maintenance, and decommissioning of DOE-owned reactors be in accordance with generally uniform standards, guides, and codes which are comparable to those applied to similar reactors licensed by the Nuclear Regulatory Commission (NRC). This Design Guide deals principally with the design and functional requirements of Category V reactor structures, components, and systems.
Date: March 1, 1979
Creator: Brynda, W J; Karol, R C; Lobner, P R; Powell, R W & Straker, E A
Partner: UNT Libraries Government Documents Department

Neutron and gamma-ray measurements on the LANL Little Boy Comet Assembly

Description: We measured the neutron and gamma-ray dose rates at various distances from the Little Boy Comet Assembly at Los Alamos National Laboratory (LANL), Los Alamos, New Mexico on April 28 and 29, 1983. The distances selected varied from 350 ft to 1860 ft from the assembly, with the latter point being located at the edge of the mesa overlooking Pajarito Canyon. We varied the power levels for the various runs but we have normalized all of them to a single power-level. We also made corrections for the variations in the power-level indicators of the assembly using data provided by LANL.
Date: September 1, 1983
Creator: Hankins, D.E.
Partner: UNT Libraries Government Documents Department

Rossi Alpha Method

Description: The Rossi Alpha Method has proved to be valuable for the determination of prompt neutron lifetimes in fissile assemblies having known reproduction numbers at or near delayed critical. This workshop report emphasizes the pioneering applications of the method by Dr. John D. Orndoff to fast-neutron critical assemblies at Los Alamos. The value of the method appears to disappear for subcritical systems where the Rossi-..alpha.. is no longer an ..alpha..-eigenvalue.
Date: January 1, 1985
Creator: Hansen, G.E.
Partner: UNT Libraries Government Documents Department

Reactivity and parameter measurements in a coaxial uranium fuel--D/sub 2/O moderated critical lattice

Description: Reactivity and reaction rate parameters were measured for a 7-inch triangular pitch lattice of coaxial uranium fuel in a critical, D/sub 2/O-moderated reactor. The results were compared with RAHABR computations using ENDF/B-IV cross sections and with an earlier subcritical exponential measurement of the same lattice. Measured and calculated reactivity are in good agreement, however, the calculated ratio of epicadmium /sup 238/U captures to subcadmium /sup 238/U captures (rho/sup 28//sub 28/) was 10% lower than measured. Indirect verification of the rho/sup 28/ measurement was obtained by measurement of a new conversion ratio parameter (C/sup +/) defined as the ratio of /sup 238/U captures to total fissions. Agreement between measured and calculated inner-to-outer fuel activation ratios suggests that the discrepancy is caused by underprediction of epicadmium captures in /sup 238/U or by erroneously high measured values of rho/sup 28/ and C/sup +/. However, any adjustment of /sup 238/U captures to match the measured rho/sup 28/ will cause the calculated reactivity to be underpredicted. An unresolved concern is that the experimental results do not satisfy an internal consistency criterion based on the two group neutron balance equation even though all known systematic errors have been accounted for and well known experimental techniques are used. Reaction rate parameters from the critical experiment agree with the exponential measurements indicating that the neutron spectra in the measurement regions were closely identical. The measured buckling in the critical facility is 0.52 m/sup -2/ lower than in the exponential. Other studies have shown systematic differences in reactivity between D/sub 2/O critical and exponential measurements.
Date: January 1, 1978
Creator: Pellarin, D.J.; Ahlfeld, C.E. & Baumann, N.P.
Partner: UNT Libraries Government Documents Department

Design Guide for Category I reactors critical facilities

Description: The purpose of this Design Guide is to provide additional guidance to aid the DOE facility contractor in meeting the requirement that the siting, design, construction, modification, operation, maintenance, and decommissioning of DOE-owned critical facilities be in accordance with generally uniform standards, guides, and codes which are comparable to those applied to similar reactors licensed by the Nuclear Regulatory Commission.
Date: August 1, 1978
Creator: Brynda, W J & Powell, R W
Partner: UNT Libraries Government Documents Department

A Pilot Plant: The Fastest Path to Commercial Fusion Energy

Description: Considerable effort has been dedicated to determining the possible properties of a magneticconfinement fusion power plant, particularly in the U.S.1, Europe2 and Japan3. There has also been some effort to detail the development path to fusion energy, particularly in the U.S.4 Only limited attention has been given, in Japan5 and in China6, to the options for a specific device to form the bridge from the International Thermonuclear Experimental Reactor, ITER, to commercial fusion energy. Nor has much attention been paid, since 2003, to the synergies between magnetic and inertial fusion energy development. Here we consider, at a very high level, the possibility of a Qeng ≥ 1 Pilot Plant, with linear dimensions ~ 2/3 the linear dimensions of a commercial fusion power plant, as the needed bridge. As we examine the R&D needs for such a system we find significant synergies between the needs for the development of magnetic and inertial fusion energy.
Date: March 3, 2010
Creator: Goldston, Robert J.
Partner: UNT Libraries Government Documents Department

Construction Safety Forecast for ITER

Description: The International Thermonuclear Experimental Reactor (ITER) project is poised to begin its construction activity. This paper gives an estimate of construction safety as if the experiment was being built in the United States. This estimate of construction injuries and potential fatalities serves as a useful forecast of what can be expected for construction of such a major facility in any country. These data should be considered by the ITER International Team as it plans for safety during the construction phase. Based on average U.S. construction rates, ITER may expect a lost workday case rate of < 4.0 and a fatality count of 0.5 to 0.9 persons per year.
Date: November 1, 2006
Creator: cadwallader, lee charles
Partner: UNT Libraries Government Documents Department

Prioritization of VHTR system modeling needs based on phenomena identification, ranking and sensitivity studies.

Description: Quantification of uncertainty is a key requirement for the design of a nuclear power plant and the assurance of its safety. Historically the procedure has been to perform the required uncertainty assessment through comparison of the analytical predictions with experimental simulations. The issue with this historical approach has always been that the simulations through experiments could not be at full scale for the practical reasons of cost and scheduling. Invariably, only parts of the system were tested separately or if integral testing was performed for the complete system, the size or scale of the experimental apparatus was significantly smaller than the actual plant configuration.
Date: April 30, 2006
Creator: Vilim, R. B.; Pointer, W. D. & Wei, T. Y. C.
Partner: UNT Libraries Government Documents Department

Plasma-material Interactions in Current Tokamaks and their Implications for Next-step Fusion Reactors

Description: The major increase in discharge duration and plasma energy in a next-step DT [deuterium-tritium] fusion reactor will give rise to important plasma-material effects that will critically influence its operation, safety, and performance. Erosion will increase to a scale of several centimeters from being barely measurable at a micron scale in today's tokamaks. Tritium co-deposited with carbon will strongly affect the operation of machines with carbon plasma-facing components. Controlling plasma wall interactions is critical to achieving high performance in present-day tokamaks and this is likely to continue to be the case in the approach to practical fusion reactors. Recognition of the important consequences of these phenomena has stimulated an internationally coordinated effort in the field of plasma-surface interactions supporting the Engineering Design Activities of the International Thermonuclear Experimental Reactor (ITER) project and significant progress has been made in better under standing these issues. This paper reviews the underlying physical processes and the existing experimental database of plasma-material interactions both in tokamaks and laboratory simulation facilities for conditions of direct relevance to next-step fusion reactors. Two main topical groups of interactions are considered: (i) erosion/redeposition from plasma sputtering and disruptions, including dust and flake generation, (ii) tritium retention and removal. The use of modeling tools to interpret the experimental results and make projections for conditions expected in future devices is explained. Outstanding technical issues and specific recommendations on potential R and D [Research and Development] avenues for their resolution are presented.
Date: January 10, 2001
Creator: Federici, G.; Skinner, C.H.; Brooks, J.N.; Coad, J.P. & Grisolia, C.
Partner: UNT Libraries Government Documents Department

ANL pre analysis of the SHEBA/CERES experiments.

Description: The French and British nuclear programs have prepared a series of natural uranium oxide fuel samples spiked with small amounts of the individual fission products which makeup a large fraction of the total neutron absorption by fission products in spent nuclear fuel. Both programs have utilized these samples in experimental reactors and have inferred the worth of the individual fission products. These results have been used to validate the cross sections used in criticality safety calculations. These measurements constitute a major element in support of spent fuel burnup credit in these countries.
Date: May 5, 2000
Creator: Palmiotti, G.; Smith, M.; Klann, R.; Fujita, E. & Imel, G.
Partner: UNT Libraries Government Documents Department

Chemical Reaction Mechanisms for Modeling the Fluorocarbon Plasma Etch of Silicon Oxide and Related Materials

Description: As part of a project with SEMATECH, detailed chemical reaction mechanisms have been developed that describe the gas-phase and surface chemistry occurring during the fluorocarbon plasma etching of silicon dioxide and related materials. The fluorocarbons examined are C{sub 2}F{sub 6}, CHF{sub 3} and C{sub 4}F{sub 8}, while the materials studied are silicon dioxide, silicon, photoresist, and silica-based low-k dielectrics. These systems were examined at different levels, ranging from in-depth treatment of C{sub 2}F{sub 6} plasma etch of oxide, to a fairly cursory examination of C{sub 4}F{sub 8} etch of the low-k dielectric. Simulations using these reaction mechanisms and AURORA, a zero-dimensional model, compare favorably with etch rates measured in three different experimental reactors, plus extensive diagnostic absolute density measurements of electron and negative ions, relative density measurements of CF, CF{sub 2}, SiF and SiF{sub 2} radicals, ion current densities, and mass spectrometric measurements of relative ion densities.
Date: May 1, 2001
Partner: UNT Libraries Government Documents Department


Description: OAK-B135 Under DOE Contracts DE-AC03-89ER51114 and DE-AC03-99ER54463 to General Atomics (GA), three ''capital project'' upgrade projects were accomplished on DIII-D from FY93 to FY03 at a total GA cost of $27.2M. These projects included the Fast Wave Current Drive (FWCD) Upgrade ($8.2M), the Radiative Divertor Upgrade ($7.2M) and the Electron Cyclotron Heating (ECH) Upgrade ($11.8M). The ECH and FWCD upgrades provided DIII-D rf and microwave power for electron heating, driving plasma current, controlling the plasma current profile, controlling tearing mode instabilities, and modulated transport studies.The divertor provided adequate density and impurity control for high triangularity single null plasmas in the Advanced Tokamak (AT) Program and information for International Thermonuclear Experimental Reactor (ITER) divertor design. These upgrades provide the power and density control required to initiate the active control of advanced tokamak discharges, which is the key element in the DIII-D program.
Date: June 1, 2003
Partner: UNT Libraries Government Documents Department

Safety analysis of the Los Alamos critical experiments facility: burst operation of Skua

Description: A detailed consideration of the Skua burst assembly is presented, thereby supplementing the facility safety analysis report covering the operation of other critical assemblies at Los Alamos. As with these assemblies the small fission-product inventory, ambient pressure, and moderate temperatures in Skua are amenable to straightforward measures to ensure the protection of the public.
Date: May 1, 1979
Creator: Orndoff, J.D.; Paxton, H.C. & Wimett, T.F.
Partner: UNT Libraries Government Documents Department

Neutron radiographic facility at the 3-mw Livermore pool-type reactor

Description: A description is presented of the neutron experimental radiographic facility at the Livermore Pool-Type Reactor. This facility was installed in 1974 to assist Lawrence Livermore Laboratory research programs. Some of the testing techniques used to modify the neutron beam and the present radiographic parameters are also discussed. (auth)
Date: September 10, 1975
Creator: Richards, W.J.; Peterson, R.T. & Prindle, J.A.
Partner: UNT Libraries Government Documents Department

Plasma Simulation Program

Description: Many others in the fusion energy and advanced scientific computing communities participated in the development of this plan. The core planning team is grateful for their important contributions. This summary is meant as a quick overview the Fusion Simulation Program's (FSP's) purpose and intentions. There are several additional documents referenced within this one and all are supplemental or flow down from this Program Plan. The overall science goal of the DOE Office of Fusion Energy Sciences (FES) Fusion Simulation Program (FSP) is to develop predictive simulation capability for magnetically confined fusion plasmas at an unprecedented level of integration and fidelity. This will directly support and enable effective U.S. participation in International Thermonuclear Experimental Reactor (ITER) research and the overall mission of delivering practical fusion energy. The FSP will address a rich set of scientific issues together with experimental programs, producing validated integrated physics results. This is very well aligned with the mission of the ITER Organization to coordinate with its members the integrated modeling and control of fusion plasmas, including benchmarking and validation activities. [1]. Initial FSP research will focus on two critical Integrated Science Application (ISA) areas: ISA1, the plasma edge; and ISA2, whole device modeling (WDM) including disruption avoidance. The first of these problems involves the narrow plasma boundary layer and its complex interactions with the plasma core and the surrounding material wall. The second requires development of a computationally tractable, but comprehensive model that describes all equilibrium and dynamic processes at a sufficient level of detail to provide useful prediction of the temporal evolution of fusion plasma experiments. The initial driver for the whole device model will be prediction and avoidance of discharge-terminating disruptions, especially at high performance, which are a critical impediment to successful operation of machines like ITER. If disruptions prove unable to be avoided, ...
Date: October 4, 2011
Creator: Greenwald, Martin
Partner: UNT Libraries Government Documents Department

Final Report for "Implimentation and Evaluation of Multigrid Linear Solvers into Extended Magnetohydrodynamic Codes for Petascale Computing"

Description: Extended magnetohydrodynamic (MHD) codes are used to model the large, slow-growing instabilities that are projected to limit the performance of International Thermonuclear Experimental Reactor (ITER). The multiscale nature of the extended MHD equations requires an implicit approach. The current linear solvers needed for the implicit algorithm scale poorly because the resultant matrices are so ill-conditioned. A new solver is needed, especially one that scales to the petascale. The most successful scalable parallel processor solvers to date are multigrid solvers. Applying multigrid techniques to a set of equations whose fundamental modes are dispersive waves is a promising solution to CEMM problems. For the Phase 1, we implemented multigrid preconditioners from the HYPRE project of the Center for Applied Scientific Computing at LLNL via PETSc of the DOE SciDAC TOPS for the real matrix systems of the extended MHD code NIMROD which is a one of the primary modeling codes of the OFES-funded Center for Extended Magnetohydrodynamic Modeling (CEMM) SciDAC. We implemented the multigrid solvers on the fusion test problem that allows for real matrix systems with success, and in the process learned about the details of NIMROD data structures and the difficulties of inverting NIMROD operators. The further success of this project will allow for efficient usage of future petascale computers at the National Leadership Facilities: Oak Ridge National Laboratory, Argonne National Laboratory, and National Energy Research Scientific Computing Center. The project will be a collaborative effort between computational plasma physicists and applied mathematicians at Tech-X Corporation, applied mathematicians Front Range Scientific Computations, Inc. (who are collaborators on the HYPRE project), and other computational plasma physicists involved with the CEMM project.
Date: June 19, 2008
Creator: Vadlamani, Srinath; Kruger, Scott & Austin, Travis
Partner: UNT Libraries Government Documents Department