The effect of graphite thermal column around the newly designed large irradiation channel of GHARR-1 on neutron flux distribution

Abstract

Monte Carlo N-Particle code (MCNP-5) was employed to simulate the neutron flux profile in a newly designed irradiation site surrounded by a graphite thermal column for Large Sample Neutron Activation Analysis, in the Ghana Research Reactor-1. The results shows that the average thermal neutron flux in the irradiation channel surrounded with 6 cm thick graphite was 5.45 × 10 10 n cm -2 s -1 as compared with 1.74 × 10 10 n cm -2 s -1 when there is no graphite around the irradiation channel. This shows an increase in the thermal neutron flux in the irradiation channel by a factor of 3.13. The thermal neutron flux gradient decreased at 7.0 × 10 9 n cm -2 s -1 per cm to 3.90 × 10 7 n cm -2 s -1 per cm when the channel is surrounded by 6 cm thick graphite which makes it very suitable for Large Sample Neutron Activation Analysis. The simulation agrees very well with the experimental k eff of 1.00400 as compared with the final k eff of 1.00390 recorded by this simulation. © 2011 Elsevier Ltd. All rights reserved.