Measurement of the Thermal Neutron Cross Section of the⁹⁰Sr(n, γ)⁹¹Sr Reaction

Abstract

To obtain fundamental data for the research of the transmutation of nuclear waste, the thermal neutron cross section of the reaction 90Sr(n,r)91Sr has been measured by means of a radiochemical method.Strontium chloride targets containing about 2 MBq of 90Sr were irradiated for 10 min with reactor neutrons. Activation detectors of Co/AI and Au/AI alloy wires were irradiated simultaneously to monitor the neutron flux and Westcott's epithermal index ~( T / T O )~/~. The irradiated Sr samples were purified chemically and their r-ray spectra were measured with a high purity Ge detector. Since the targets included %r, a r-ray emitter and a tracer for gOSr, and a ratio of the amount of %r to that of 90Sr was measured in advance, an effective cross section of the goSr(n,r)glSr reaction for a reactor neutron spectrum was determined from the ratio of radioactivities of 91Sr and 86Sr, and neutron flux data. The resonance integral was also measured by a modified Cd-ratio measurement.Considering an upper limit of the resonance integral to be 0.16 b, the thermal neutron cross section (2,200 m/s neutron cross section) of goSr(n, ~)~l S r reaction was found to be 0.0153+:: :::: b.The value obtained is only 1/50 of the value reported by Zeisel (1966), and is in good agreement with the figure reported by McVey et al. (1983).

Measurement of the Thermal Neutron Capture Cross Section and the Resonance Integral of the90Sr(n, γ)91Sr Reaction

“…The σ 0 can be derived from data in Ref. 3) and the present result for s 0 , and estimated to be 11.2±1.2 mb. This value agreed with the present result within the limits of errors.…”

“…The data reported previously 3,[9][10][11] are tabulated in Table 1. There are discrepancies among values of thermal cross sections: Zeisel 9) reported the cross section as 800 mb, McVey et al 10) 14.0 mb, Harada et al 3) 15.3 mb, and Lone et al 9.7 mb. 11) Only one data is reported for the upper limit of the I 0 3) and no exact data for I 0 .…”

“…The present authors have measured the σ 0 and the I 0 of FP [1][2][3][4][5][6][7] with large yields or long half-lives. Strontium-90 is one of the important middle lived fission products (MLFP), with its half-life of 28.8 yr, 8) in the research of the nuclear transmutation, since its fission yield and decay heat is large.…”

“…The authors in Ref. 3) have tried to measure both the σ 0 and the I 0 of the 90 Sr(n, γ ) 91 Sr reaction by an activation method. Figure 1 shows the partial decay scheme of 91 Sr.…”

“…Figure 1 shows the partial decay scheme of 91 Sr. They used a 10) 14.0±2.4 -Lone et al 11) 9.7±0.7 -Harada et al 3) 15.3 polyethylene bottle as an irradiation target container, and the period of irradiation was limited to less than 10 min. Therefore, sufficient yields of 91 Sr were not obtained, and only the upper limit of I 0 was obtained.…”