Program - Brookhaven National Laboratory

incident energies.
[1] Yu. Malyshkin et al., ”Modeling spallation reactions in tungsten and uranium targets with the Geant4
toolkit”, Proc. Third International Workshop on Compound Nuclear Reactions and Related Topics, vol.
21 of EPJ Web of Conferences, p. 10006 (2012) [2] Yu. Malyshkin et al., ”Neutron production and energy
deposition in fissile spallation targets studied with Geant4 toolkit” (to be submitted) [3] J. Apostolakis
et al. (Geant4 Collaboration), ”Geometry and physics of the Geant4 toolkit for high and medium energy
applications”, Radiat. Phys. Chem., 78, p. 859 (2009)
PR 81
A New Formulation for the Doppler Broadening Function Relaxing the Approximations of
Beth-Plackzec
Daniel A. P. Palma, Comissão Nacional de Energia Nuclear - CNEN. Felipe C. Paiva, Fernando C. Silva,
Aquilino S. Martinez, Programa de Engenharia Nuclear - COPPE/UFRJ.
In all nuclear reactors some neutrons can be absorbed in the resonance region and, in the design of these
reactors, an accurate treatment of the resonant absorptions is essential. Apart from that, the resonant
absorption varies with fuel temperature, due to the Doppler broadening of the resonances. The thermal
agitation movement of the reactor core is adequately represented in microscopic cross-section of the
neutron-core interaction through the Doppler broadening function. This function is calculated numerically
in modern systems for the calculation of macro-group constants, necessary to determine the power distribution
of a nuclear reactor. It can also be applied to the calculation of self-shielding factors to correct the
measurements of the microscopic cross-sections through the activation technique and used for the approximate
calculations of the resonance integrals in heterogeneous fuel cells. In these types of application we
can point the need to develop precise analytical approximations for the Doppler broadening function to be
used in the calculation codes that calculates the values of this function. However, the Doppler broadening
function is based on a series of approximations proposed by Beth-Plackzec. In this work a relaxation of
these approximations is proposed, generating an additional term in the form of an integral. Analytical
solutions of this additional term are discussed. The results obtained showed that the new term is important
for high temperatures, typical in the centreline of fuel rods operating in nuclear power plants.
PR 82
Reaction Data Assimilation Phase 1: Model Based Files and Parameter Covariances
A. Palumbo, S. Hoblit, M. Herman, G. P. A. Nobre,, National Nuclear Data Center, Brookhaven National
Laboratory. M. Sin, Dept. of Atomic and Nuclear Physics, University of Bucharest. R. Capote, IAEA. G.
Palmiotti, M. Salvatores, INL.
Assimilation is a refinement of the usual data adjustment procedure. It links results of integral experiments
to the parameters of nuclear reaction theory, so that it is the reaction model parameters that are
adjusted rather than energy-averaged group cross sections. This novel approach should make adjustment
independent from the target application and should account for the physics constraints imposed by the
nuclear reaction models, differential, and integral measurements. The resulting covariances should reflect
our cumulative knowledge leading to the reduction of the uncertainty margins in the final data. Cross
sections and covariances for the model parameters for 239,242Pu, and 235,238U nuclei fully based on the
EMPIRE-3.1 code [1] calculations were produced (starting with values from the RIPL database [2]). The
Kalman filter technique was used for adjusting selected input model parameters to reproduce differential
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