Measurement of Thermal Neutron Capture Cross Section and Resonance Integral of the ^166mHo(n, γ¹⁶⁷Ho Reaction using a Two-Step Irradiation Technique

Abstract

The thermal neutron capture cross section (a₀) and the resonance integral (I₀) of ^166mHo have been measured as data for the transmutation of nuclear waste. Samples of ^166mHo were made by the neutron irradiation of ¹⁶⁵Ho. Two metallic foils of ¹⁶⁵Ho were irradiated for 2 weeks and two others for 3 weeks at the Kyoto University Reactor. A high purity Ge detector was employed for activity measurement. The samples irradiated were cooled for 3 months to reduce the activity of ^166gHo. One of the samples irradiated for 2 weeks was irradiated again with Cd cover sheets and the other one without a Cd cover sheet. For the samples irradiated for 3 weeks, the same irradiation was performed. The ¹⁶⁷Hon uclei were produced at the second irradiation via the neutron capture of ^166mHo and the double neutron capture of ¹⁶⁵Ho. The amount of ¹⁶⁷Ho via the double capture was estimated from the difference between the data of 2 week irradiation and 3 week irradiation, and corrected. The reaction rate to produce ¹⁶⁷Ho from ^166mHo was analyzed by Westcott's convention. A resonance at 0.274 eV was considered in the analysis. The results obtained were 3.11±0.82kb for the a₀ and 10.0±2.7 kb for the I_a of ^166mHo.

KEYWORDS:

• nuclear transmutation
• radioactive wastes
• fission products
• holmium 166m
• holmium 167
• activation method
• thermal neutron capture cross sections
• resonance integrals
• half-life
• two-step irradiation