172
C. H. Pyeon
fission events. Capture reaction rates of
237 Np and
197 Au were deduced by the saturated radioactivity [8] obtained from two signals of the γ-ray emission of the
237 Np
test foil in the BTB chamber and the
197 Au reference one that set at the location
of (15, O) of the Al sheath (special void element), with the use of a germanium
detector. From the two signals of test and reference foils, the fission reaction rate
ratio was experimentally acquired by
237 Np/
235 U or
241 Am/
235 U, and the capture one
by
237 Np/
197 Au, and finally, validated by comparison with previous experimental
results [1] at a critical state.
6.2.2 Demonstration of Nuclear Transmutation
Fission reaction rates were experimentally obtained by the pulsed-height distributions (voltage) of
237 Np and
241 Am fission events, as shown in Figs. 6.19a, b, respectively, demonstrating original electric signals of test and reference foils. As shown in
Fig. 6.19a, the fission events of two
237 Np and
235 U foils were clearly observed over
entire pulsed heights. Moreover, for
241 Am and
235 U shown in Fig. 6.19b, discrimination between the signals of fission fragments and α-ray induced by
241 Am was
made at 1.2 V, determining the small fission events by
241 Am over 1.2 V and the same
fission events by
235 U over the entire pulsed heights, as confirmed in the critical irradiation [1]. Meanwhile, the difference between pulsed-height distributions of
235 U
shown in Figs. 6.19a, b was mainly attributable to reproducibility of the gain in the
BTB fission chamber when changing the
235 U sample installed. The fission reaction
rate ratio determined by the experimental results was found to be a notable 0.048
± 0.001 and 0.035 ± 0.003 for
237 Np/
235 U and
241 Am/
235 U, respectively, the same
as at critical irradiation shown in Table 6.7, although no data of
237 Np/
235 U were
obtained at critical irradiation due to invalid data acquisition of two electric signals
(
237 Np and
235 U) actuated in the BTB fission chamber.
The capture reaction rate ratio was deduced by the saturated radioactivity on the
basis of the γ-ray emission of
237 Np and
197 Au capture reactions (Fig. 6.20 and
Table 6.8) was found to be a remarkable 1.88 ± 0.28, almost the same as at critical
irradiation shown in Table 6.9.
From the results of fission and capture reaction rate ratios shown in Tables 6.7
and 6.9, respectively, fission and capture reaction events by ADS were successfully
confirmed, and as a conclusion, nuclear transmutation of
237 Np and
241 Am by ADS
was experimentally achieved and demonstrated in the KUCA core.
6.3 Conclusion
The integral experiments on irradiation of
237 Np and
241 Am in cores at critical conditions were carried out in the KUCA A-core with a neutron hard spectrum. The fission
reaction rate ratios (
237 Np/
235 U and
241 Am/
235 U) and the capture reaction rate ratio
C. H. Pyeon
fission events. Capture reaction rates of
237 Np and
197 Au were deduced by the saturated radioactivity [8] obtained from two signals of the γ-ray emission of the
237 Np
test foil in the BTB chamber and the
197 Au reference one that set at the location
of (15, O) of the Al sheath (special void element), with the use of a germanium
detector. From the two signals of test and reference foils, the fission reaction rate
ratio was experimentally acquired by
237 Np/
235 U or
241 Am/
235 U, and the capture one
by
237 Np/
197 Au, and finally, validated by comparison with previous experimental
results [1] at a critical state.
6.2.2 Demonstration of Nuclear Transmutation
Fission reaction rates were experimentally obtained by the pulsed-height distributions (voltage) of
237 Np and
241 Am fission events, as shown in Figs. 6.19a, b, respectively, demonstrating original electric signals of test and reference foils. As shown in
Fig. 6.19a, the fission events of two
237 Np and
235 U foils were clearly observed over
entire pulsed heights. Moreover, for
241 Am and
235 U shown in Fig. 6.19b, discrimination between the signals of fission fragments and α-ray induced by
241 Am was
made at 1.2 V, determining the small fission events by
241 Am over 1.2 V and the same
fission events by
235 U over the entire pulsed heights, as confirmed in the critical irradiation [1]. Meanwhile, the difference between pulsed-height distributions of
235 U
shown in Figs. 6.19a, b was mainly attributable to reproducibility of the gain in the
BTB fission chamber when changing the
235 U sample installed. The fission reaction
rate ratio determined by the experimental results was found to be a notable 0.048
± 0.001 and 0.035 ± 0.003 for
237 Np/
235 U and
241 Am/
235 U, respectively, the same
as at critical irradiation shown in Table 6.7, although no data of
237 Np/
235 U were
obtained at critical irradiation due to invalid data acquisition of two electric signals
(
237 Np and
235 U) actuated in the BTB fission chamber.
The capture reaction rate ratio was deduced by the saturated radioactivity on the
basis of the γ-ray emission of
237 Np and
197 Au capture reactions (Fig. 6.20 and
Table 6.8) was found to be a remarkable 1.88 ± 0.28, almost the same as at critical
irradiation shown in Table 6.9.
From the results of fission and capture reaction rate ratios shown in Tables 6.7
and 6.9, respectively, fission and capture reaction events by ADS were successfully
confirmed, and as a conclusion, nuclear transmutation of
237 Np and
241 Am by ADS
was experimentally achieved and demonstrated in the KUCA core.
6.3 Conclusion
The integral experiments on irradiation of
237 Np and
241 Am in cores at critical conditions were carried out in the KUCA A-core with a neutron hard spectrum. The fission
reaction rate ratios (
237 Np/
235 U and
241 Am/
235 U) and the capture reaction rate ratio