Design of a large irradiation channel at MNSR facility in Ghana

In the design of new slant tube for large sample irradiation in the Ghana Research Reactor-1 facility, Monte Carlo N-Particle Code version 5 (MCNP-5) was employed to simulate the neutron flux profile of the new design. The results show that the neutron flux peaks at different points, at an average thermal neutron flux of (1.1406 ± 0.0046) × 10¹¹, (1.1849 ± 0.0047) × 10¹¹ and (1.0580 ± 0.0044) × 10¹¹n cm^-2 s^-1 around the reactor vessel. The first two peaks happened to coincide with pneumatic transfer pipes in the pool, but the third peak happened to be in line with the slant tube position. It was observed that as the diameter of the tube varies from 3.90 cm to 23.40 cm, the average thermal neutron flux decreased exponentially from (1.1849 ± 0.0047)10¹¹ n cm^-2 s^-1 to (3.3241 ± 0.0100) × 10¹⁰ n cm^-2 s^-1. The average thermal neutron flux decreases exponentially along the diameter of the designed slant tube from (1.0366 ± 0.0042) × 10¹¹ n cm ^-2 s^-1 to (9.7396 ± 0.0136) × 10⁹ n cm^-2 s^-1. From the results, it is evident that a slant tube of diameter 15.00 cm can be installed at the original slant tube position for large sample irradiation.