TITLE:
MCNP Simulation of Multi-Capsule Irradiation Protocol for a K0-Based INAA Using the GHARR-1 MNSR
AUTHORS:
George Adu-Okyere, Vincent Yao Agbodemegbe, Isaac Kwasi Baidoo, Henry Cecil Odoi, Edward Shitsi
KEYWORDS:
Neutron Spectrum Parameters, K0-Method, MCNP Simulation, Bottom, Middle and Top Irradiation Column, Flux Monitor
JOURNAL NAME:
World Journal of Engineering and Technology,
Vol.13 No.3,
August
22,
2025
ABSTRACT: The GHARR-1 MCNP5 input deck was successfully modified to simulate the multi capsule irradiation protocol adopted in the present work to experimentally characterise the neutron flux in the inner irradiation channel of the GHARR-1 LEU core. The inner irradiation site was modified by discretising its 17cm active length into spatial demarcations to enable Bottom, Middle and Top irradiation other than the single capsule irradiation which is the normal protocol in the conduct of neutron activation analysis at the GHARR-1. Flux characterization and analytical measurement of sample were carried out in the three (3) irradiation capsules introduced into the inner irradiation channels at the bottom (normal), middle and top positions using the scheme developed in the experimental work for validation of the MCNP simulations. Flux monitors were used for irradiation and k0-method was adopted for the experimental flux characterization analysis. Neutron spectrum parameters such as Cadmium ratios, a measure of the deviation of epithermal neutrons from the ideal 1/E distribution (α) and thermal-epithermal flux ratio (f) were determined for the three capsules as well as the thermal, epithermal and fast neutron fluxes, and the MCNP simulation results were compared with these experimental results. Results obtained from the MCNP simulations agree fairly with experimental results. However, relatively high thermal, epithermal and fast neutron fluxes were obtained from the MNCP simulations than what was determined experimentally. This increase could be attributed to the treatment of the core as a fresh core for the MCNP simulation rather than a core that has been in operation for five years with anticipated core depletion which may have impacted the experimental results. The present work could further be improved by incorporating results from burn up studies into the MCNP input deck so as to more appropriately capture and simulate the actual state of the GHARR-1 LEU core which has been in operation for almost 5 years.