In the pursuit of sustainable and low-carbon energy sources, nuclear energy has emerged as a viable and reliable option. However, the economic aspect of nuclear energy remains concerning. Efforts in research and technological innovation are currently being made to address these economic issues while ensuring the highest safety standards. The focus lies on two primary areas with the utilization of new fuel designs: to reduce costs while maintaining the same power output, or the extension of fuel cycles to increase capacity factors.

A fuel design utilizing a novel approach is employed to generate comparable or greater energy output, necessitating fewer natural resources and enhancing waste management, all while maintaining safety. Among the commonly employed burnable absorbers in light water reactors, gadolinium oxide is recognized for its functionality. Nevertheless, its drawbacks impede fuel efficiency. In light of this, a novel fuel design, achieved by enriching gadolinium oxide with the most effective absorber isotopes of gadolinium, offers a solution to eliminate these drawbacks and yield economic advantages without compromising safety.

Moreover, the nuclear power industry has identified the capacity factor of nuclear power plants as an aspect that can be enhanced. This factor gauges the actual output of a plant within a specific timeframe in relation to its hypothetical maximum output if it could continuously function at full capacity. A method to increase the capacity factor is through longer fuel cycles. Nevertheless, extending the duration of these cycles necessitates the inclusion of more fissile material, which presents difficulties in maintaining reactivity control. Consequently, the development of a new design for burnable absorbers becomes imperative to address this challenge.

In this study, an examination is undertaken to explore the potential consequences of incorporating enriched gadolinium oxide, specifically enriched with gadolinium-157, into fuel compositions. Initially, a 2D neutronic analysis is conducted employing the Monte Carlo particle transport method to compare the reactivity properties of natural gadolinium oxide and the enriched variant. The depletion behaviour of the primary neutron-absorbing isotopes and the breeding behaviour of plutonium-239 are also investigated. Subsequently, the study expands to encompass a comprehensive 3D fuel cycle analysis spanning an 18-month cycle. During this phase, the impact of transitioning from utilizing natural gadolinium oxide to employing enriched gadolinium oxide on various factors such as peaking factors, reactivity feedback parameters, shutdown margin, and power profile is thoroughly analysed. Furthermore, the study delves into the economic implications associated with this transition.

Adopting an unconventional approach, this research also explores an innovative solution to overcome the reactivity control challenge that arises from the adoption of high-assay low-enriched uranium in 36-month fuel cycles. The study focuses on the introduction of new designs, namely the Discrete Burnable Absorber Pin and Moderated Discrete Burnable Absorber Pin designs, utilizing zirconium diboride or uranium diboride as burnable absorbers. To evaluate the reactivity characteristics of these novel designs, as well as investigate the depletion behaviour of neutron-absorbing isotopes and the breeding behaviour of plutonium-239, a 2D neutronic analysis is conducted employing the Monte Carlo particle transport method. Additionally, a comprehensive 3D fuel cycle analysis is carried out to examine the transition from an 18-month cycle to a 36-month cycle using high-assay low-enriched uranium. This analysis encompasses an assessment of peaking factors, reactivity feedback parameters, shutdow margin, power profile, and the potential economic advantages that these designs may offer. The study also discusses future research directions to be pursued, thus paving the way for further research in this field.