Program - Brookhaven National Laboratory

ZPR-6/10 cores were applied as comparable core sets with blanket and reflector. The FCA X-1 and X-2
cores were constructed at the Fast Critical Assembly (FCA) facility of JAEA for the mockup experiments
of the Joyo Mk-II core. The FCA X-1 core was surrounded by depleted uranium blanket and the X-2
core by sodium and stainless steel reflector while the compositions of the two cores were identical. The
Joyo Mk-I and Mk-II cores were constructed at the experimental fast reactor Joyo of JAEA. The Joyo
Mk-I core was surrounded by UO2 blanket and the Mk-II core by stainless steel reflector. The ZPR-3/53,
-3/54 and ZPR-6/10 cores were constructed at the Zero Power Reactor (ZPR) critical assembly of ANL.
The ZPR-3/53 was surrounded by depleted uranium blanket and the ZPR-3/54 by iron reflector while the
compositions of the two cores were identical. The ZPR-6/10 was surrounded by stainless steel reflector
and the core composition was different from those of ZPR-3/53 and -3/54. We analyzed reflector effects by
comparing the ratio of calculation to experimental (C/E) values of keff between the cores with reflector and
blanket, e.g. the FCA X-1 and X-2 cores. The keff calculations were performed by using the continuous
energy Monte Carlo code MVP. Sensitivity analyses were also done to specify the source of keff difference
among the nuclear data libraries. Sensitivity coefficients were obtained by diffusion calculations using a
generalized perturbation code, SAGEP. In the benchmark test for the FCA cores by JENDL-4.0, there
are no dependence of the C/E values between the FCA X-1 (depleted uranium blanket) and X-2 (stainless
steel reflector) cores. On the contrary, by ENDF/B-VII.1, there appears a significant underestimation for
the FCA X-2 core with reflector. From the sensitivity analysis, the different behaviors of the C/E values
between JENDL-4.0 and ENDF/B-VII.1 are due to the discrepancies of µ-bar of Cr-52 and Na, the elastic
scattering cross-section of Fe-57, Ni-60 and Al. This paper presents the results of the other cores and
the JEFF-3.1.2. Finally, recommendations to nuclear-data study are summarized on the scattering-related
data evaluation.
PE 2 4:00 PM
Analysis of the Neutronic Properties of the Prototype FBR Monju Based on Several
Evaluated Nuclear Data Libraries
W.F.G. van Rooijen, N. Yamano, Y. Shimazu
Research Institute of Nuclear Engineering, University of Fukui
In a recent study [1] an uncertainty analysis was presented for the criticality of the prototype FBR Monju
using JENDL-4.0. In the course of the research for that paper, a considerable deviation was found for the
reactivity as a function of which set of nuclear data was used. This deviation occurred in the analysis of
Monju as well as in the analysis of benchmark experiments. In some cases, the deviation is larger than the
expected error margins due to uncertainties in the nuclear data. The analyses of the neutronic properties
of Monju published by JAEA were obtained using highly specific code systems using cross sections and
covariance data that are specially adjusted for Monju, so in that sense it is not surprising that calculations
with unadjusted data give different results. However, in general it would be desirable that evaluated nuclear
data is of such a quality that adjustment for a specific application is not necessary. Besides, FBRs that are
being designed for future applications, such as ASTRID (France) and JSFR (Japan) have design features
for which no or very few experimental data are available. This means that a proper data adjustment
is difficult or even impossible, and one may need (expensive) measurement campaigns to obtain enough
experimental information to perform a proper data adjustment. To see how well modern nuclear data is
capable of predicting the neutronic properties of an FBR, we are analyzing the prototype FBR Monju with
the well-established ERANOS software. An automated system to generate cross sections and covariance
data for ERANOS has been created. Monju was operated in 1994 / 1995 and 2010, and the 15-year
shutdown period has caused considerable changes in the fuel composition (increase of Am-241). For the
238