Chapter 3
Reactor Kinetics
Cheol Ho Pyeon
Abstract In static and kinetic experimental analyses, the reactivity effect of introducing a neutron guide has been examined with various materials and adjustments of
the beam window. With the objective of improving the KUCA core characteristics,
the implementation of the neutron guide is predicted to increase the fast neutrons in
directing the fuel region. With regard to the kinetic characteristics, the subcriticality
and the prompt neutron decay constant are monitored for several core configurations
and detector positions. The KUCA core is equipped to make locally a hard spectrum core region with the combined use of
235 U fuel, a polyethylene moderator, and
a Pb–Bi reflector for criticality. In this study, the first attempt is made to examine
experimentally the characteristics of kinetics parameters in ADS comprised of
235 Ufueled and Pb–Bi-zoned core, and spallation neutrons generated by an injection of
100 MeV protons onto the solid Pb–Bi target. Online monitoring of reactivity has
been deduced in real time by the inverse kinetic method on the basis of the one-point
kinetic equation with measured neutron signals in the core. Here, measurements by
the one-point kinetic equation are validated through the subcriticality evaluation with
the PNS histogram and the methodology by the inhour equation.
Keywords α-fitting method · Pulsed-neuron source method · Inverse kinetic
method · Kalman filter method
3.1 α-Fitting Method
3.1.1 Experimental Settings
3.1.1.1 Core Configurations
For safety reasons particular to KUCA, the tritium target is located not at the center
of the core but at a peripheral position in the critical assembly. This location is very
C. H. Pyeon (B)
Institute for Integrated Radiation and Nuclear Science, Kyoto University, Osaka, Japan
e-mail: pyeon.cheolho.4z@kyoto-u.ac.jp
© The Author(s) 2021
C. H. Pyeon (ed.), Accelerator-Driven System at Kyoto University Critical Assembly,
https://doi.org/10.1007/978-981-16-0344-0_3
51
Reactor Kinetics
Cheol Ho Pyeon
Abstract In static and kinetic experimental analyses, the reactivity effect of introducing a neutron guide has been examined with various materials and adjustments of
the beam window. With the objective of improving the KUCA core characteristics,
the implementation of the neutron guide is predicted to increase the fast neutrons in
directing the fuel region. With regard to the kinetic characteristics, the subcriticality
and the prompt neutron decay constant are monitored for several core configurations
and detector positions. The KUCA core is equipped to make locally a hard spectrum core region with the combined use of
235 U fuel, a polyethylene moderator, and
a Pb–Bi reflector for criticality. In this study, the first attempt is made to examine
experimentally the characteristics of kinetics parameters in ADS comprised of
235 Ufueled and Pb–Bi-zoned core, and spallation neutrons generated by an injection of
100 MeV protons onto the solid Pb–Bi target. Online monitoring of reactivity has
been deduced in real time by the inverse kinetic method on the basis of the one-point
kinetic equation with measured neutron signals in the core. Here, measurements by
the one-point kinetic equation are validated through the subcriticality evaluation with
the PNS histogram and the methodology by the inhour equation.
Keywords α-fitting method · Pulsed-neuron source method · Inverse kinetic
method · Kalman filter method
3.1 α-Fitting Method
3.1.1 Experimental Settings
3.1.1.1 Core Configurations
For safety reasons particular to KUCA, the tritium target is located not at the center
of the core but at a peripheral position in the critical assembly. This location is very
C. H. Pyeon (B)
Institute for Integrated Radiation and Nuclear Science, Kyoto University, Osaka, Japan
e-mail: pyeon.cheolho.4z@kyoto-u.ac.jp
© The Author(s) 2021
C. H. Pyeon (ed.), Accelerator-Driven System at Kyoto University Critical Assembly,
https://doi.org/10.1007/978-981-16-0344-0_3
51