Program - Brookhaven National Laboratory

PR 40
Sensitivity and System Response of Pin Power Peaking in VVER-1000 Fuel Assembly
Using TSUNAMI-2D
Jan Frybort, Department of Nuclear Reactors, Czech Technical University in Prague, V Holesovickach 2,
18000, Prague, Czech Republic.
Computational determination of pin power peaking must be done during designing of fuel assemblies and
preparation of fuel batches. Large expertise was accumulated in this field, but modern calculational tools
offer more sophisticated approach. For safety reasons the fuel in nuclear reactors must be prepared in
such a away that fission power distribution must be flat among the assemblies in the reactor core and fuel
pins in all assemblies. System TSUNAMI [1] developed in Oak Ridge National Laboratory can be used for
sensitivity and uncertainty analysis of various systems and their responses. In this case, TSUNAMI-2D
was applied to calculation of fission power distribution in a fuel assembly of VVER-1000 reactor. Results
from these calculations can be used to determination of sensitivity of fission power in selected pins to
fissile material concentration in other fuel pins. Alternatively, it can help to determine the best position
of a burnable absorber (Gd203) containing fuel pins for suppression of excessive fission power in some fuel
pins (close to the assembly periphery). Several cases were analysed. They differ in number and position
of gadolinium fuel pins. The sensitivity of pin power peaking is important also during reactor operation,
therefore the calculations were repeated for several fuel compositions obtained by fuel burnup calculation.
This work was supported by Technology Agency of the Czech Republic (project TA02020840).
[1] Rearden, B. T. and Mueller, D. E. and Bowman, S. M. and Busch, R. D. and Emerson, S. J. ”TSUNAMI
Primer: A Primer for Sensitivity/Uncertainty Calculations with SCALE”, Oak Ridge National Laboratory,
Oak Ridge, Tenn., 2009.
PR 41
Reactor g-ray Heating Studies at EXOGAM@ILL: Prompt g-ray Emission in U and Pu
C. Guerrero, E. Berthoumieux, CERN, Geneva (Switzerland). D. Cano-Ott, T. Martinez, E. Mendoza,
CIEMAT, Madrid (Spain). A. Algora, C. Domingo-Pardo, J. L. Tain, CSIC-IFIC, Valencia (Spain). M.
Cortes-Giraldo, J. Praena, J. M. Quesada, Universidad de Sevilla (Spain). O. Litaize, D. Regnier, O.
Serot, CEA, Cadarache (France).
Nuclear energy plays a key role in the production of energy in the world, contributing nowadays to one third
to the electricity consumption in the European Union. Although the present technology is well established,
there is still an interest for improving the knowledge in some areas that would allow a safer and more efficient
use of the existing reactors. In particular, the g-ray heating in the core of nuclear reactors is one of the
main concerns for the safety during operation and also the decommissioning of nuclear reactors. Since the
characteristics of g-ray emission (multiplicity, total energy and spectrum shape) [1] produced by capture
(20% of prompt heat) and inelastic scattering (10% of prompt heat) is considered to be fairly known, the
g-rays from the fission process become the major source of uncertainty in the prediction of prompt g-ray
heating. It is estimated that the maximum uncertainty acceptable in the estimates for heat in innovative
fast nuclear reactors is 7.5% [2], and a similar requirement is considered for the Jules Horowitz Reactor at
Cadarache [3]. However, when the state-of-the-art calculations, based in experimental data from 70s, are
compared to integral measurements in MINERVE the difference found in the C/E values amounts to 30%,
a large discrepancy which arises from the lack of knowledge on g-ray emission [3]. For this reason, the
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