3 Reactor Kinetics
79
future studies, the modeling of the space-state equation has to be modified on the
basis of S eff and detection efficiency.
3.4 Conclusion
Kinetic experiments on ADS with 14 MeV neutrons were conducted at KUCA. The
kinetic experimental and numerical analyses revealed the following: Measurement
and calculation methods proven reliable for the evaluation of subcriticality effects
down to 6 %k/k. Anticipating an ADS subcriticality level around 3 %k/k, the
measurement methodology and the calculation precision were considered convenient for the study of ADS at KUCA. Moreover, optical fiber detectors were considered promising in the evaluation of the subcriticality and the prompt neutron decay
constant evaluation at KUCA, although detector position dependency was observed
in kinetic measurements by using the optical fiber detection system.
In the ADS experiments with spallation neutrons, the measurement of kinetics
parameters was conducted by both the PNS and Feynman-α methods with the use
of optical fiber detectors, under subcriticality ranging between 1160 and 11556
pcm. The results confirmed the validity of the prompt neutron decay constant and
the subcriticality in dollar units through the deduction of kinetics parameters. The
detector position dependency, neutron spectrum, and subcriticality measurement
methods still remained, however, in these ADS experiments.
Transient experiments were carried out to evaluate the performance of subcriticality monitoring by the EKF technique in the presence of an external neutron
source. To ensure the conditions in EKF, a basic transient experiment was conducted
by dropping the control rod at the critical state. In a comparison of the subcriticality
by the inverse kinetic method and the EKF technique, the advantage of EKF was
indicated over the robustness of the estimate with good accuracy even at low counts.
Additionally, the initial condition used in the filtering technique was confirmed as
valid through comparison with measured subcriticality by the rod drop method in
the basic transient experiment. In the transient experiments in the presence of an
external neutron source, the EKF technique was applied to subcriticality monitoring
(time resolution: 1 s), with the use of the initial condition in the basic experiments. The
EKF technique significantly indicated a significant advantage in reducing fluctuation
and estimating more accurately compared with the inverse method, demonstrating
the applicability to the subcriticality monitor.
References
1. Pyeon CH, Hirano Y, Misawa T et al (2007) Preliminary experiments on accelerator-driven
subcritical reactor with pulsed neutron generator in Kyoto University Critical Assembly. J Nucl
Sci Technol 44:1368
79
future studies, the modeling of the space-state equation has to be modified on the
basis of S eff and detection efficiency.
3.4 Conclusion
Kinetic experiments on ADS with 14 MeV neutrons were conducted at KUCA. The
kinetic experimental and numerical analyses revealed the following: Measurement
and calculation methods proven reliable for the evaluation of subcriticality effects
down to 6 %k/k. Anticipating an ADS subcriticality level around 3 %k/k, the
measurement methodology and the calculation precision were considered convenient for the study of ADS at KUCA. Moreover, optical fiber detectors were considered promising in the evaluation of the subcriticality and the prompt neutron decay
constant evaluation at KUCA, although detector position dependency was observed
in kinetic measurements by using the optical fiber detection system.
In the ADS experiments with spallation neutrons, the measurement of kinetics
parameters was conducted by both the PNS and Feynman-α methods with the use
of optical fiber detectors, under subcriticality ranging between 1160 and 11556
pcm. The results confirmed the validity of the prompt neutron decay constant and
the subcriticality in dollar units through the deduction of kinetics parameters. The
detector position dependency, neutron spectrum, and subcriticality measurement
methods still remained, however, in these ADS experiments.
Transient experiments were carried out to evaluate the performance of subcriticality monitoring by the EKF technique in the presence of an external neutron
source. To ensure the conditions in EKF, a basic transient experiment was conducted
by dropping the control rod at the critical state. In a comparison of the subcriticality
by the inverse kinetic method and the EKF technique, the advantage of EKF was
indicated over the robustness of the estimate with good accuracy even at low counts.
Additionally, the initial condition used in the filtering technique was confirmed as
valid through comparison with measured subcriticality by the rod drop method in
the basic transient experiment. In the transient experiments in the presence of an
external neutron source, the EKF technique was applied to subcriticality monitoring
(time resolution: 1 s), with the use of the initial condition in the basic experiments. The
EKF technique significantly indicated a significant advantage in reducing fluctuation
and estimating more accurately compared with the inverse method, demonstrating
the applicability to the subcriticality monitor.
References
1. Pyeon CH, Hirano Y, Misawa T et al (2007) Preliminary experiments on accelerator-driven
subcritical reactor with pulsed neutron generator in Kyoto University Critical Assembly. J Nucl
Sci Technol 44:1368