NEUTRON-INDUCED FISSION OF ²³³U, ²³⁸U, ²³²Th, ²³⁹Pu, ²³⁷Np, ^natPb AND ²⁰⁹Bi RELATIVE TO ²³⁵U IN THE ENERGY RANGE 1-200 MeV

Study of 232 Th(n,γ) and 232 Th(n,f) reaction rates in a graphite moderated spallation neutron field produced by 1.6 GeV deuterons on lead target

“…Further 232 Th(n,f) reaction cross section data above 60 MeV were retrieved from the EXFOR database. Experimental data up to 200 MeV have been measured by Shcherbakov et al [37] which agrees extremely well with the ENDF/B-VII.0 data below 60 MeV. Above 200 MeV, the only experimental data involves highly scattered data points [38].…”

“…Above 200 MeV, the only experimental data involves highly scattered data points [38]. Therefore, the region 200-1000 MeV was least-squares fitted with a 2nd order polynomial and normalised to the 200 MeV data point of Shcherbakov et al [37] (Fig. 6(b)) as described in Borger et al [28].…”

“…The statistical uncertainties in the Monte Carlo simulations were kept below 3% in all cases (most were 1-2%). Uncertainty in the 232 Th(n,f) cross section above 60 MeV was inferred from the uncertainty of the experimental measurements [37,38]. An additional 3% was attributed to the uncertainty in the experimentally measured beam position and shape whereby the FWHM x value (4.5 AE 0.7 cm, Table 1) is quite large and it is expected that some of the incident deuterons will miss the lead target.…”

“…Evaluated data is the ENDF/B-VII.0 evaluation and experimental data obtained from Shcherbakov et al[37] and Paradela et al[38].…”

Fission track chemical etching kinetic model

“…The cross sections are 586, 275 (resonance integral), 0.123 and 0.496 b. These nominal values are averaged data presented by Watanabe et al (1987), Khattab (2007), Shcherbakov et al (2001Shcherbakov et al ( , 2007, Muir and Vesser (1971) and Lapenas et al (1975). Adopting an isotopic concentration of C U-235 ¼ 0.72% and C U-238 ¼ 99.28%, the isotopic concentration of 232 Th is 100% and the Th/U ratio is 14.8 (see Table 1), tracks from 232 Th fissions were 2.6%, 96.8% from 235 U (thermal and epithermal) and 0.7% from 238 U.…”