Program - Brookhaven National Laboratory

the MONTEBURNS(1.0)-MCNP5-ORIGEN(2.1) [2,3,4] combinational package. The methods in the ORI-
GEN(2.1) code initially oriented for uranium-based fuel have been upgraded to include the larger number
of actinides and fission products from minor actinides [5]. Influence of nuclear data on discrepancies of
nuclei inventory calculation is briefly discussed.
Corresponding author: A.I. Blokhin
[1] N.Kodochigov, Yu.Sukharev, E.Marova et al. Neutronic features of the GT-MHR reactor. J., Nucl.Eng.&
Des., v.222 (2003), p.161-171. [2] D.I. Poston, H.R. Trellue ”User’s Manual, Version 2.0 for MONTE-
BURNS, Version 1.0”, LA- UR-99-4999 (September 1999) [3] X-5 Monte Carlo Team, ”MCNP - A General
Monte Carlo N-Particle Transport Code”, version 5, April 2003, CCC-710. [4] A.G. Croff ”A User’s Manual
for ORIGEN2 Computer Code”, Oak Ridge National Laboratory document ORNL/TM-7175 (July 1980).
[5] Mitenkova Ye.F., Novikov N.V. “The technology of precision neutronic calculations for nuclear reactor
physics”, Izvestia of Russian Academy of Science (in Russian), v2, pp.72-86, (2004)
PR 10
Joint Neutron Noise Measurements on Metallic Reactor Caliban
Amaury Chapelle, Nicolas Authier, Pierre Casoli, Benoit Richard, CEA and LANL.
Caliban is a benchmarked, bare metallic reactor. It is operated by the Criticality, Neutron Science and
Measurement Department, located on the French CEA Research center of Valduc. This reactor is a cylindre
with a 19.5 cm diameter and a 25 cm height, composed of two blocks, a fixed one and a mobile one, with
three control rods and one excursion rod. The four rods and the two blocks are composed from the same
alloy of molybdenum and high enriched uranium. Its reactivity is controlled by moving the control rods
and the mobile block, also called safety block. This parameter can vary from -20 $ below delayed criticality
to 1.1 $ above delayed criticality. A central cylindrical cavity can be used to place samples or an external
neutron source. This reactor is used to perform neutron noise measurements, that is to say to estimate
the kinetic parameters of the reactor, such as reactivity or delayed neutron fraction, and the associated
uncertainties, from Rossi or Feynman formalisms. The aim is to compare the measured parameters to the
simulated ones, and to determine the relative contribution of uncertainties to the final result. Thus, these
experiments improve the safety task of reactivity control far from criticality, with static methods, and the
knowledge of the behaviour of a subcritical reactor. The uncertainties can be separated in three classes : -
Some uncertainties are due to the knowledge of the experimental configuration, that is the reactivity of the
reactor, or its description. The keff of a configuration can be checked by rod-drop dynamics experiment. -
Other uncertainties are linked to the detection process. The neutron noise methods need to know precisely
the detectors characteristics, their efficiencies (which vary with the distance between the reactor and the
detector), their dead times or their decreasing time constants. - Final uncertainties are due to the analysis
process, and the method to evaluate the uncertainties propagation. To maximize the knowledge of these
uncertainties effect, a joint week of experiments was performed in June 2012 with a French team from
the CEA, and an American team from the Los Alamos National Laboratory (LANL). The reactivity was
varying from the lowest subcriticality to a few percents above delayed criticality. The same configurations
were observed twice, using detectors of each team and switching them. The second class of uncertainties
are thus reduced. Moreover, a joint week of analysis will take place in november 2012 in Los Alamos, to
compare the analysis process. Each team will work with the data of the detectors of the other team, to
reduce the third category of uncertainties. The results will then be use for calculation code qualification.
This work is a part of a PHD work, begun in 2010 by the first author.
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