Reactor physics verification of the MCNP6 unstructured mesh capability by Burke, T. P. (Department of Nuclear Engineering and Radiological Sciences, University
of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109 (United States)); Kiedrowski,
B. C.; Martz, R. L. (X-Computational Physics Division, Monte Carlo Codes Group, Los
Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 (United States));
Martin, W. R. (Department of Nuclear Engineering and Radiological Sciences, University
of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109 (United States)) fromProceedings of the 2013 International Conference on Mathematics and Computational
Methods Applied to Nuclear Science and Engineering - M and C 2013 Read MoreCollapse
[en]
The Monte Carlo software package MCNP6 has the ability to transport particles on unstructured
meshes generated from the Computed-Aided Engineering software Abaqus. Verification
is performed using benchmarks with features relevant to reactor physics - Big Ten
and the C5G7 computational benchmark. Various meshing strategies are tested and results
are compared to reference solutions. Computational performance results are also given.
The conclusions show MCNP6 is capable of producing accurate calculations for reactor
physics geometries and the computational requirements for small lattice benchmarks
are reasonable on modern computing platforms. (authors)$$$$
A method for reducing the largest relative errors in Monte Carlo iterated-fission-source
calculations by Hunter, J. L. (Department of Nuclear Science and Engineering, Massachusetts Institute
of Technology, 77 Massachusetts Ave., 24-107, Cambridge, MA 02139 (United States));
Sutton, T. M. (Knolls Atomic Power Laboratory, Bechtel Marine Propulsion Corporation,
P. O. Box 1072, Schenectady, NY 12301-1072 (United States)) fromProceedings of the 2013 International Conference on Mathematics and Computational
Methods Applied to Nuclear Science and Engineering - M and C 2013 Read MoreCollapse
[en]
In Monte Carlo iterated-fission-source calculations relative uncertainties on local
tallies tend to be larger in lower-power regions and smaller in higher-power regions.
Reducing the largest uncertainties to an acceptable level simply by running a larger
number of neutron histories is often prohibitively expensive. The uniform fission
site method has been developed to yield a more spatially-uniform distribution of relative
uncertainties. This is accomplished by biasing the density of fission neutron source
sites while not biasing the solution. The method is integrated into the source iteration
process, and does not require any auxiliary forward or adjoint calculations. For a
given amount of computational effort, the use of the method results in a reduction
of the largest uncertainties relative to the standard algorithm. Two variants of the
method have been implemented and tested. Both have been shown to be effective. (authors)$$$$
The mathematical formulation of numerous physical problems a results in differential
equations actually partial or ordinary differential equations.In our study we are
interested in solutions of partial differential equations.The aim of this work is
to calculate the concentrations of the pollution, by solving the atmospheric diffusion
equation(ADE) using different mathematical methods of solution. It is difficult to
solve the general form of ADE analytically, so we use some assumptions to get its
solution.The solutions of it depend on the eddy diffusivity profiles(k) and the wind
speed u. We use some physical assumptions to simplify its formula and solve it. In
the present work, we solve the ADE analytically in three dimensions using Green's
function method, Laplace transform method, normal mode method and these separation
of variables method. Also, we use ADM as a numerical method. Finally, comparisons
are made with the results predicted by the previous methods and the observed data.$$$$
One-dimensional families of projections http://dx.doi.org/10.1088/0951-7715/21/3/005 by Järvenpää, E; Järvenpää, M; Leikas, M (Department of Mathematics and Statistics, PO
Box 35, FIN-40014 University of Jyväskylä (Finland)); Ledrappier, F (University of
Notre Dame, Department of Mathematics, 255 Hurley Hall, Notre Dame, IN 46556-4618
(United States)), E-mail: esaj@maths.jyu.fi, E-mail: amj@maths.jyu.fi, E-mail: fledrapp@nd.edu,
E-mail: mileikas@maths.jyu.fi Read MoreCollapse
[en]
Let m and n be integers with 0 < m < n. We consider the question of how much the Hausdorff
dimension of a measure may decrease under typical orthogonal projections from R^{n}
onto m-planes provided that the dimension of the parameter space is one. We verify
the best possible lower bound for the dimension drop and illustrate the sharpness
of our results by examples. The question stems naturally from the study of measures
which are invariant under the geodesic flow$$$$
The objective of this procedure is to help the user to prepare an COMPSIS report on
an event so that important lessons learned are most efficiently transferred to the
database. This procedure focuses on the content of the information to be provided
in the report rather than on its format. The established procedure follows to large
extend the procedure chosen by the IRS incident reporting system. However this database
is built for I and C equipment with the purpose of the event report database to collect
and disseminate information on events of significance involving Computer-Based Systems
important to safety in nuclear power plants, and feedback conclusions and lessons
learnt from such events. For events where human performance is dominant to draw lessons,
more detailed guidance on the specific information that should be supplied is spelled
out in the present procedure. This guidance differs somewhat from that for the provision
of technical information, and takes into account that the engineering world is usually
less familiar with human behavioural analysis than with technical analysis. The events
to be reported to the COMPSIS database should be based on the national reporting criteria
in the participating member countries. The aim is that all reports including computer
based systems that meet each country reporting criteria should be reported. The database
should give a broad picture of events/incidents occurring in operation with computer
control systems. As soon as an event has been identified, the insights and lessons
learnt to be conveyed to the international nuclear community shall be clearly identified.
On the basis of the description of the event, the event shall be analyzed in detail
under the aspect of direct and potential impact to plant safety functions. The first
part should show the common involvement of operation and safety systems and the second
part should show the special aspects of I and C functions, hardware and software$$$$
Reports are on: - Measurement of Cross-Sections for Neutron Induced Reactions at 14
MeV. - Level Schemes and Gamma Ray Angular Distribution Measurements in ^{28}Si,
^{46}Ti, and ^{53}Mn. - A Study of Neutron-Induced Reaction ''1''2C
(n.n')3α at E_{n} =17.4 MeV. - A Study on Nuclear Evaporation in Nuclear Emulsion
Exposed to 3.0 GeV/c Mesons. - Spectroscopy of ^{64}Cu using the (^{3}He,p)
Reaction at 18 MeV.$$$$
Sampling from a polytope and hard-disk Monte Carlo http://dx.doi.org/10.1088/1742-6596/454/1/012031 by Kapfer, Sebastian C; Krauth, Werner (Laboratoire de Physique Statistique, Ecole Normale
Supérieure, UPMC, CNRS 24 rue Lhomond, 75231 Paris Cedex 05 (France)), E-mail: sebastian.kapfer@ens.fr,
E-mail: werner.krauth@ens.fr Read MoreCollapse
[en]
The hard-disk problem, the statics and the dynamics of equal two-dimensional hard
spheres in a periodic box, has had a profound influence on statistical and computational
physics. Markov-chain Monte Carlo and molecular dynamics were first discussed for
this model. Here we reformulate hard-disk Monte Carlo algorithms in terms of another
classic problem, namely the sampling from a polytope. Local Markov-chain Monte Carlo,
as proposed by Metropolis et al. in 1953, appears as a sequence of random walks in
high-dimensional polytopes, while the moves of the more powerful event-chain algorithm
correspond to molecular dynamics evolution. We determine the convergence properties
of Monte Carlo methods in a special invariant polytope associated with hard-disk configurations,
and the implications for convergence of hard-disk sampling. Finally, we discuss parallelization
strategies for event-chain Monte Carlo and present results for a multicore implementation$$$$
Controlling chaos based on an adaptive nonlinear compensator mechanism http://dx.doi.org/10.1088/1674-1056/17/2/028 by Tian Lingling; Sun Xianfang (School of Automation Science and Electrical Engineering,
Beijing University of Aeronautics and Astronautics, Beijing 100083 (China)); Li Donghai
(Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China)),
E-mail: zibotll@asee.buaa.edu.cn Read MoreCollapse
[en]
The control problems of chaotic systems are investigated in the presence of parametric
uncertainty and persistent external disturbances based on nonlinear control theory.
By using a designed nonlinear compensator mechanism, the system deterministic nonlinearity,
parametric uncertainty and disturbance effect can be compensated effectively. The
renowned chaotic Lorenz system subjected to parametric variations and external disturbances
is studied as an illustrative example. From the Lyapunov stability theory, sufficient
conditions for choosing control parameters to guarantee chaos control are derived.
Several experiments are carried out, including parameter change experiments, set-point
change experiments and disturbance experiments. Simulation results indicate that the
chaotic motion can be regulated not only to steady states but also to any desired
periodic orbits with great immunity to parametric variations and external disturbances$$$$
The mathematical and computer modeling of required operation modes of multipurpose
isochronous cyclotrons is presented. The considered procedure is based on the calculation
of currents in trim coils of correction of the main magnetic field (I_{i},
i = 1, 2...z) at a certain level of current in the main coil (I_{main}). A
series of numerical and physical experiments on modeling of the main operation mode
of the mutipurpose isochronous cyclotron AIC144 (INP PAS, Krakow): accelerated particles
are protons (p), extracted proton energy is E_{out} ∼ 60.3/60.7 MeV, RF-generator
frequency is F_{rf} = 26.155/26.25 MHz, confirmed both the necessity of including
the evaluation of solution stability into the calculation, and the possibility of
successful accelerating of the protons in the whole range of working radii with the
allowable phase losses of accelerated protons in the isochronization range of required
magnetic field (with decreasing beam current less than 50%) without stopping the cyclotron
for performing the additional magnetic measurements$$$$
RTP must have sufficient excess reactivity to compensate the negative reactivity feedback
effects such as those caused by the fuel temperature and power defects of reactivity,
fuel burn-up and to allow full power operation for predetermined period of time. To
compensate this excess reactivity, it is necessary to introduce an amount of negative
reactivity by adjusting or controlling the control rods at will. Control rod worth
depends largely upon the value of the neutron flux at the location of the rod and
reflected by a polynomial curve. Purpose of this paper is to rule out the polynomial
curve fitting using least square numerical techniques via MATLAB compatible language.
(author)$$$$