Nuclear Engineering and Design 263 (2013) 70–76 Contents lists available at SciVerse ScienceDirect Nuclear Engineering and Design j ourna l h om epa ge: www.elsevier.com/locate/nucengdes Installation of permanent cadmium-lined channel as a means for increasing epithermal NAA capabilities of miniature neutron source reactors Y.A. Ahmed a,b,∗ , I.B. Mansir a , B.B.M. Dewu a a Centre for Energy Research and Training, Ahmadu Bello University, Zaria, Nigeria b Associates Office 115, Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy h i g h l i g h t s • High demand for epithermal neutrons necessitated the need of a permanent cadmium-line. • We reported the design specifications, preliminary studies done and steps followed. • Reactivity worth of the old channel = 0.12 mk and the new channel = 0.336 mk. • Temperature coefficient = −0.1 mk/ ◦ C and control rod worth coefficient = 0.023 mk/mm. • The work is a useful tool to the MNSR community for upgrading their reactors. a r t i c l e i n f o Article history: Received 3 December 2012 Received in revised form 17 March 2013 Accepted 24 March 2013 a b s t r a c t High demand for epithermal neutrons by the clients of the Nigerian Research Reactor-1 (NIRR-1), a Miniature Neutron Source Reactor (MNSR) has necessitated the need to explore avenues for increasing epithermal Neutron Activation Analysis (NAA) capabilities of the reactor. Safety and flux stability simu- lations were done by our group using Monte Carlo Transport Code MCNP5 for permanent cadmium line inside the irradiation channel of NIRR-1 and compared with the ones reported by other MNSR groups. The results of all these simulations revealed that the effect of cadmium-line on safety and flux stability is very minimal in the outer channel than in the inner channel. We have reported here the design specifica- tions, preliminary studies done, steps followed in installation and measurements done in the pre and post installation of the permanent cadmium-line in outer channel of the reactor. We measured the reactivity worth of the old and new channel and readjusted the reactor’s core excess reactivity after the installation. Results obtained are: reactivity worth of the old channel (0.12 mk), reactivity worth of the new chan- nel = 0.336 mk, temperature coefficient = −0.1 mk/ ◦ C, control rod worth coefficient = 0.023 mk/mm and the core excess reactivity = 3.85 mk. We have also measured the radial and axial flux distribution in the channels of the reactor after the installation. The installation of the permanent cadmium-lined channel reported here will not only boost the sample handling capabilities of NIRR-1 but will also provide useful data to the MNSR community for upgrading their reactors. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The Nigeria Research Reactor-1 (NIRR-1) is a Miniature Neu- tron Source Reactor (MNSR) with a fuel material of highly enriched uranium (90.2%) and light water as moderator and coolant (Zhu, 1990; Balogun, 2003). The reactor’s first criticality was achieved on the 3rd of February 2004 (Balogun et al., 2004) and has since then been operating safely for neutron activation analysis (Jonah et al., 2005; Jonah et al., 2006). The NIRR-1 is primarily designed for neu- tron activation analysis (NAA) and in support of research activities ∗ Corresponding author. Tel.: +234 8036913646; fax: +234 69550737. E-mail addresses: yahmed@ictp.it, yaahmed1@gmail.com (Y.A. Ahmed). (Ahmed et al., 2006; Emmanuel et al., 2011). It is also used for teaching of nuclear engineering and radiation protection courses (Azande et al., 2010, 2011; Ahmed et al., 2010). Detailed descrip- tion of the reactor and its operating parameters were presented in our earlier works (Ahmed et al., 2002; Ahmed et al., 2008, 2011). Epithermal neutron activation analysis (ENAA) method is a technique which is ideally suited for determination of key trace ele- ments in geological, biological and environmental samples which cannot be accomplished by traditional use of thermal neutrons alone (Desorte et al., 1972; Kapsimalis et al., 2009; Ahmed et al., 2010). The ENAA technique is one of the most highly developed techniques in experimental nuclear physics (Landsberger et al., 1990, 1993a; Filby, 1995). The method became popular because gamma ray detection and gamma spectrum determination which 0029-5493/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nucengdes.2013.03.058