Chapter 17
Method Development for Calculating Minor
Actinide Transmutation in a Fast Reactor
Toshikazu Takeda, Koji Fujimura, and Ryota Yamada
Abstract To effectively transmute minor actinides (MAs), which have long-lived
radioactivity and high decay heat, fast reactors are very promising because many
minor actinides can be loaded and transmutation rates are high compared to light
water reactors. With the increase of loaded minor actinides, the neutron spectrum
becomes hard and core safety parameters will deteriorate. Especially, the sodium
void reactivity increases with MA addition to cores. To overcome the difficulty, we
propose MA transmutation fast reactors using core concepts with a sodium plenum
and internal blanket region in reactor cores. Therefore, cores become complex, and
calculation accuracy becomes poor. To accurately evaluate the neutronic properties
such as MA transmutation rate and sodium void reactivity, we improved calculation
methods. In this chapter we show new methods for calculating MA transmutation
rates for each MA nuclide, for calculating the uncertainty of MA transmutation
using sensitivities. A new sensitivity is derived that is defined as a relative change
of core parameters relative to infinite-dilution cross sections, not effective cross
sections. To eliminate bias factors in estimating core parameter uncertainties, a new
method is proposed. This method is used to reduce the calculation uncertainty
through the use of adjusted cross sections.
Keywords Calculation methods • Fast reactors • Minor actinide • Sensitivity
• Sodium void reactivity • Transmutation
17.1 Introduction
The importance of nuclear energy, as a realistic option to solve the issues of the
depletion of energy resources and the global environment, has been acknowledged
worldwide. However, acceptance of large-scale contributions would depend on
satisfaction of key drivers to enhance sustainability in terms of economics, safety,
T. Takeda (*) • R. Yamada
Research Institute of Nuclear Engineering, University of Fukui, Fukui, Japan
e-mail: t_takeda@u-fukui.ac.jp
K. Fujimura
Hitachi Works, Hitachi-GE Nuclear Energy, Ltd., Ibaraki, Japan
© The Author(s) 2015
K. Nakajima (ed.), Nuclear Back-end and Transmutation Technology for Waste
Disposal, DOI 10.1007/978-4-431-55111-9_17
179
Method Development for Calculating Minor
Actinide Transmutation in a Fast Reactor
Toshikazu Takeda, Koji Fujimura, and Ryota Yamada
Abstract To effectively transmute minor actinides (MAs), which have long-lived
radioactivity and high decay heat, fast reactors are very promising because many
minor actinides can be loaded and transmutation rates are high compared to light
water reactors. With the increase of loaded minor actinides, the neutron spectrum
becomes hard and core safety parameters will deteriorate. Especially, the sodium
void reactivity increases with MA addition to cores. To overcome the difficulty, we
propose MA transmutation fast reactors using core concepts with a sodium plenum
and internal blanket region in reactor cores. Therefore, cores become complex, and
calculation accuracy becomes poor. To accurately evaluate the neutronic properties
such as MA transmutation rate and sodium void reactivity, we improved calculation
methods. In this chapter we show new methods for calculating MA transmutation
rates for each MA nuclide, for calculating the uncertainty of MA transmutation
using sensitivities. A new sensitivity is derived that is defined as a relative change
of core parameters relative to infinite-dilution cross sections, not effective cross
sections. To eliminate bias factors in estimating core parameter uncertainties, a new
method is proposed. This method is used to reduce the calculation uncertainty
through the use of adjusted cross sections.
Keywords Calculation methods • Fast reactors • Minor actinide • Sensitivity
• Sodium void reactivity • Transmutation
17.1 Introduction
The importance of nuclear energy, as a realistic option to solve the issues of the
depletion of energy resources and the global environment, has been acknowledged
worldwide. However, acceptance of large-scale contributions would depend on
satisfaction of key drivers to enhance sustainability in terms of economics, safety,
T. Takeda (*) • R. Yamada
Research Institute of Nuclear Engineering, University of Fukui, Fukui, Japan
e-mail: t_takeda@u-fukui.ac.jp
K. Fujimura
Hitachi Works, Hitachi-GE Nuclear Energy, Ltd., Ibaraki, Japan
© The Author(s) 2015
K. Nakajima (ed.), Nuclear Back-end and Transmutation Technology for Waste
Disposal, DOI 10.1007/978-4-431-55111-9_17
179