Impact of weight percent gadolinium and the number of its fuel rods on the neutronic and safety parameters

• Main Authors: Uguru, Edwin Humphrey, Sapli, Mohd Faiq Bin Ahmad, Sani, Siti Fairus Abdul, Khandaker, Mayeen Uddin, Rabir, Mohamad Hairie, Karim, Julia Abdul, Bradley, David Andrew
• Format: Article
• Published: Elsevier 2021
• Subjects: QC Physics; QD Chemistry
• Online Access: http://eprints.um.edu.my/28682/
• Institution: Universiti Malaya

Control of neutron multiplication in a nuclear reactor is fundamental in achieving stable reactor power. The present study has sought to determine the impact of gadolinium weight percent (w/o) in respect of the number of fuel rods on the neutronic and safety parameters of (Th, U)O-2 fuel in a Westinghouse small modular reactor. The MCNPX 2.7 integrated with CINDER90 fuel depletion code was used. The results show that the k-infinite and reactivity swing peak decrease with increasing gadolinium weight percent, with the highest and lowest k-infinite recorded in the fuel assembly containing zero (0) and 12 w/o, respectively. The largest and lowest reactivity swing curve occurs in the fuel assembly with 3.6 and 12 w/o at similar to 15 and similar to 35 GWd/THM, respectively. It shows that the impact of gadolinium w/o and the number of fuel rods on k-infinite follow similar trend. Conversely, the reactivity swing curve is observed to flatten with increasing gadolinium w/o but increases with increase in the number of gadolinium burnable absorber fuel rods. These phenomenological variations suggest that flat reactivity swing and power control can be achieved within 9.2-12 w/o gadolinium although not without economic penalty on fuel utilisation.