Thermal-neutron capture cross-section measurement of Tantalum-181 using graphite thermal column at KUR

ABSTRACT

Using an activation method with a well-thermalized neutron field, it is principally possible to drive a thermal-neutron capture cross-section without considering an epithermal neutron component. We demonstrated neutron capture cross-section measurements using the graphite thermal column (TC-Pn) of the Kyoto University Research Reactor. First, in order to confirm that the graphite thermal column was a well-thermalized neutron field, neutron irradiation was performed with neutron flux monitors: ¹⁹⁷Au, ⁵⁹Co, ⁴⁵Sc, ⁶³Cu, and ⁹⁸Mo. The TC-Pn was confirmed to be extremely thermalized on the basis of Westcott’s convention, because the thermal-neutron flux component took a constant value regardless of the sensitivity of each flux monitor to epithermal neutrons. Next, as a demonstration, the thermal-neutron capture cross-section of ¹⁸¹Ta(n,γ)^182m+gTa reaction was measured using the graphite thermal column, and then derived to be 20.5 ± 0.4 barn, which supported the evaluated value of 20.4 ± 0.3 barn. The ¹⁸¹Ta nuclide could be useful as a flux monitor that complements the sensitivity between ¹⁹⁷Au and ⁹⁸Mo monitors.

KEYWORDS:

• Tantalum-181
• thermal-neutron capture cross-section
• flux monitor
• activation method
• Westcott’s convention
• TC-Pn
• Kyoto University research reactor

Acknowledgments

This work has been performed under the Visiting Researcher’s Program of the Institute for Integrated Radiation and Nuclear Science, Kyoto University. The authors would like to appreciate the staff of Kyoto University for their support: Dr. Yuichi OKI, Messrs Daisuke MAKI, Ryo OKUMURA, Yuto IINUMA and Hisao YOSHINAGA. One of the authors (S.N.) would also like to express my gratitude to Dr. Osamu IWAMOTO and Dr. Hideo HARADA of JAEA for their constructive comments.

Disclosure statement

No potential conflict of interest was reported by the author(s).