JAEA-Conf 2011-002 - 日本原子力研究開発機構

JAEA-Conf 2011-002
Sensitivity Analysis for Curium Isotope Concentrations
of Light Water Reactor Mixed-Oxide Burned Fuel
Go CHIBA and Makoto ISHIKAWA
Research Group for Reactor Physics, Japan Atomic Energy Agency
Tokai-mura, Naka-gun, Ibaraki-ken 319-1195
e-mail: chiba.go@jaea.go.jp
With a help of the depletion perturbation theory, sensitivities of curium isotope concentrations
to nuclear data are calculated for a light water reactor mixed-oxide burned fuel. Through the
sensitivity analysis, phenomenon of the curium isotope generations during a reactor operation is
well understood. In addition, important nuclear data for accurate prediction of the curium
isotope concentrations are successfully specified. These information are helpful to investigate a
cause of discrepancy between experimental and calculation values for the curium isotope
concentrations.
1. Introduction
In order to validate prediction calculation methods for fuel depletion of light water reactors,
some experimental programs focusing on fuel depletion, such as the MALIBU program [1], have
been conducted, and the experimental data obtained through these programs have been analyzed
by calculation methods used for core design of light water reactors. As shown in Ref. [2], there
are still some discrepancies between experimental and calculation values even if modern nuclear
data files are employed, and some differences are observed among results obtained with different
nuclear data files.
A sensitivity analysis, which is performed with sensitivity coefficients of nuclide
concentrations (number densities) to nuclear data, is quite a useful technique to investigate causes
of the discrepancies and the differences between different nuclear data files. Moreover,
sensitivity coefficients can be utilized also to quantify uncertainties associated with nuclear data if
uncertainty data for the nuclear data are available.
Sensitivity coefficients of nuclide concentrations to nuclear data can be easily calculated by the
depletion perturbation theory. The depletion perturbation theory for the zero-dimensional
nuclide field equation has been initially proposed by Gandini [3], and has been extended to the
nuclide/neutron coupled field by Williams [4]. Application of the depletion perturbation theory
can be found in some literatures. For example, we can see some examples of the application of
this theory to sensitivity studies for fission product concentrations [5][6].
In a light water reactor mixed-oxide fuel, curium isotopes are generated and are accumulated
through a reactor operation. The accurate prediction for the curium isotope concentrations after
burn-up is not easy since the many ancestor nuclides contribute to the curium isotope generations.
In the present study, we perform a sensitivity analysis focusing on curium isotope concentrations
of a light water reactor mixed-oxide burned fuel with the depletion perturbation theory.