Program - Brookhaven National Laboratory

PR 113
Modelling of Spallation Source for the Myrrha Reactor Using the MCNPX and Geant4
Codes for Sensitivity Analysis of Reactivity
Mauricio Q. Antolin, Aquilino S. Martinez, COPPE/UFRJ. Daniel A. P. Palma, CNEN. Franciole C.
Marinho, IF/UFRJ.
In an accelerator driven nuclear reactor (ADS) neutrons are produced from spallation reactions providing an
external source to the core and sustaining its operation. Although there are different approaches to describe
the kinetic behaviour of these reactors, the complete picture of its functioning still need to be addressed
as there is no commercial ADS reactor in operation. In order to provide a better understanding on this
matter one can take advantage of Monte Carlo techniques which allow to simulate the whole system in three
dimensions considering time dependence and with realistic details of the complicated geometries involved.
In this work a simulation of the time evolution for the MYRRHA conceptual reactor was developed. The
SERPENT code was used allowing to simulate the nuclear fuel depletion. The spallation source which
drives the system was simulated using both MCNPX and GEANT4 codes. These two packages can run
assuming a number of models to describe hadronic interactions. The obtained results for the neutron energy
spectrum from the spallation are coherent with each other and were used as input for the SERPENT code
which simulated the constant power operation regime and also a linear variation of power. The obtained
results show that the criticality of the system is sensitive to the model employed, but keeping relative small
deviations with respect to the results obtained from the inverse kinetic model which comes from the point
kinetic equations proposed by Gandini.
Corresponding author: Daniel A. P. Palma
PR 114
Nuclear Level Density within Extended Superfluid Model with Collective State
Enhancement
V.A. Plujko, O.M. Gorbachenko, B.M. Bondar, E.P. Rovenskykh, M.M. Zolko, Nuclear Physics
Department, Taras Shevchenko National University, Kyiv, Ukraine.
For nuclear level densities, a new variant of extended superfluid model [1,2] with collective state enhancement
factor [3,4] is proposed and tested. An effect of collective states on the temperature of the intrinsic
states is taken into account [3,4]. The ready-to-use table of the asymptotic values of level density parameter
a and addition shift to excitation energy are prepared by the chi-square fit of the theoretical values of
neutron resonance spacing and cumulative number of low-energy levels to experimental values. The systematic
expressions for these parameters as a function of neutron excess are obtained too. The collective
state effect on gamma-ray spectra and cross sections of neutron-induced nuclear reactions is investigated
by the use of EMPIRE code[5] with modified level density parameters. The best expressions for collective
state enhancement factor of nuclear level density are recommended.
[1] R.Capote, M.Herman, P.Oblozinsky et al., Nucl.Data Sheets 110, 3107 (2009),
http://www-nds.iaea.org/RIPL-3/ [2] M.I.Svirin, Fiz.El.Chas.At.Yad (Particles and Nucleus), Dubna
37, 901 (2006) [3] V.A.Plujko, O.M.Gorbachenko, Phys. Atom. Nucl. 70, 1643 (2007) [4] V.A.Plujko,
O.M.Gorbachenko, I.M.Kadenko, Int.J.of Mod.Phys.E 16, 570 (2007) [5] M.Herman, R.Capote, B.V.Carlson
et al., Nucl.Data Sheets 108, 2655 (2007)
PR 115
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