A beam of 1 GeV proton coming from Dubna Nuclotron colliding with a lead target surrounded by 6 cm paraffin produces spallation neutrons. A Th-foil was kept on lead target (neutron spallation source) in a direct stream of neutrons for activation and other samples of ¹⁹⁷Au, ²⁰⁹Bi, ⁵⁹Co, ¹¹⁵In and ¹⁸¹Ta were irradiated by moderated beam of neutrons passing through 6 cm paraffin moderator. The gamma spectra of irradiated samples were analyzed using gamma spectrometry and DEIMOS software to measure the neutron cross-section. For this purpose neutron fluence at the positions of samples is also estimated using PREPRO software. The results of cross-sections for reactions ²³²Th($n, \gamma$), ²³²Th($n, 2n$), ¹⁹⁷Au($n, \gamma$), ¹⁹⁷Au($n, \alpha$), ¹⁹⁷Au($n, xn$), ⁵⁹Co($n, \alpha$), ⁵⁹Co($n, xn$), ¹⁸¹Ta($n, \gamma$) and ¹⁸¹Ta($n, xn$) are given in this paper. Neutronics validation of the Dubna Cascade Code is also done using cross-section data by other experiments.

Dubna Cascade Code (version-2004) has been used for the Monte Carlo simulation of the 1500 MW$_{t}$ accelerator driven sub-critical system (ADS) with ²³³U + ²³²Th fuel using the IAEA benchmark. Neutron spectrum, cross-section of $(n, xn)$ reactions, isotopic yield, heat spectra etc. are simulated. Many of these results that help in understanding the IAEA benchmark are presented. It is revealed that the code predicts the proton beam current required for the 1500 MW$_{t}$ ADS for $K_{\text{eff}} = 0.98$ to be 11.6 mA. Radial distribution of heat is fairly in agreement with other codes like the EA-MC and it needs nearly 1% less enrichment than given by other codes. This may be because the code takes care of the role of larger order of the $(n, xn)$ reactions. It is emphasized that there is a strong need to study $(n, xn)$ reactions both theoretically and experimentally for better design.