**47**: 85

https://doi.org/10.1140/epja/i2011-11085-4

Regular Article - Experimental Physics

## A study of reaction rates of (n, f ) , (n,) and (n, 2n) reactions in ^{nat}U and ^{232}Th by the neutron fluence produced in the graphite set-up (GAMMA-3) irradiated by 2.33 GeV deuteron beam

^{1}
Joint Institute for Nuclear Research, 141980, Dubna (Moscow Region), Russian Federation

^{2}
Czech Academy of Science, Nuclear Physics Institute, 250 68, Řež, Prague, Czech Republic

^{3}
HENP Laboratory (ADS Program), Physics Department, University of Rajasthan, Jaipur, India

^{4}
Institute of Physics of National Academy of Sciences, Minsk, Belarus

^{5}
Kernchemie Institute, Philips-Universität, Marburg, Germany

^{6}
Joint Institute of Power and Nuclear Research, Sosny, Minsk, Belarus

^{7}
University School of Basic and Applied Sciences, GGS IPUniversity, New Delhi, India

^{*} e-mail: vkv1951@gmail.com

Received:
30
November
2010

Accepted:
15
June
2011

Published online:
22
July
2011

Spallation neutrons produced in the collision of a 2.33GeV deuteron beam with a large lead target are moderated by a thick graphite block surrounding the target and used to activate the radioactive samples of ^{nat}U and Th put at three different positions, identified as holes “a”, “b” and “c” in the graphite block. Rates of the (n, f), (n, and (n, 2n) reactions in the two samples are determined using the gamma spectrometry. The ratios of the experimental reaction rates, *R* (n, 2n)/*R* (n, f), for ^{232}Th and ^{nat}U are estimated in order to understand the role of the (n, *x* n) kind of reactions in Accelerator-Driven Sub-critical Systems. For the Th-sample, the ratio is ∼ 54 (10)% in the case of hole “a” and ∼ 95 (57)% in the case of hole “b” compared to 1.73(20)% for hole “a” and 0.710(9)% for hole “b” in the case of the ^{nat}U sample. Also the ratio of fission rates in uranium to thorium, ^{nat}U (n, f)/ ^{232}Th (n, f), is ∼ 11.2 (17) in the case of hole “a” and 26.8(85) in hole “b”. Similarly, the ratio ^{238}U (n, 2n)/ ^{232}Th (n, 2n) is 0.36(4) for hole “a” and 0.20(10) for hole “b” showing that ^{232}Th is more prone to the (n, *x* n) reaction than ^{238}U . All the experimental reaction rates are compared with the simulated ones by generating neutron fluxes at the three holes from MCNPX 2.6c and making use of the LA150 library of cross-sections. The experimental and calculated reaction rates of all the three reactions are in reasonably good agreement. The transmutation power, *P*
_{norm} as well as *P*
_{norm}/*P*
_{beam} of the set-up is estimated using the reaction rates of the (n, and (n, 2n) reactions for both the samples in the three holes and compared with some of the results of the “Energy plus Transmutation” set-up and TARC experiment.

*© SIF, Springer-Verlag Berlin Heidelberg, 2011*