**1.1 Overview**

The ever-increasing population worldwide has put a toll on the need to produce efficient energy at a very fast pace to meet the demand. It is for this reason that the United Nations (UN), in setting its agenda for sustainability for 2030, included Goal 7, which targets affordable, reliable, and clean energy [1]. Moreover, due to the debilitating effect of climate change, most countries are either moving towards nuclear energy or adding nuclear energy to their energy mix to prevent excessive greenhouse gases from the coal used in powering the country's thermal plants. And this is also geared towards the achievement of the Sustainable Development Goals (SDGs) 7 aforementioned by member countries [1]. According to the International Atomic Energy Agency's Power Reactor Information System (PRIS), as of March 24, 2023, [2]

there were 57 nuclear reactors under construction worldwide. China ranked first with 19 units, followed by India, with eight reactors under construction at the time. In all, about 18 countries were constructing at least one reactor unit.

Moreover, as the demand keeps increasing, the need for reliable materials to sustain the needed energy without any incidents, as happened in the cases of Chernobyl, and Fukushima, is on the rise. This has led to the constant assessment of the existing materials and even the design of new, safer, or reliable materials. The assessment of the behavior of these materials, under different conditions and environments, is because the qualities of engineering materials have hindered the performance of power-generating devices since time immemorial. Several of the materials that were employed in the design either failed through corrosion, embrittlement, creep, radiation damage, or fracture, among others. This has led to the suspension or shutdown of some existing reactors.

The nuclear industry, since its early days, has employed several materials in different areas. These nuclear materials depended mostly on the type of reactor plant being designed. But generally, materials are needed for structural/cladding, moderators and reflectors, control, coolant, and shielding for a better and longer operating period for nuclear power plants. Some of the major materials that have been employed over the past years are aluminum, beryllium, magnesium, zirconium, stainless steel, carbon, graphite, boron, cadmium, hafnium, water, concrete, etc. Generally, these materials that are used in nuclear reactor design can be grouped or classified into four categories. Thus, metals, ceramics, polymers, and advanced materials such as semiconductors.

However, due to the harsh corrosive environmental conditions that exist in the nuclear reactor, coupled with the high radiation dose and high temperature, these materials at some point failed or experienced a lot of defects. The formation, distribution, and interaction of point defects (vacancies and interstitials) and their clusters, such as Frenkel pairs (vacancy-interstitial pairs), interstitial loops, voids, vacancy clusters, inert gas bubbles, and radiation-induced dislocation segments and networks were mostly associated with the nature of the defect in crystalline materials. And since no material can escape from such defects or damages, materials are normally subjected to ion beams of equal radiation doses about that of the nuclear reactor to assess their response. The materials are then modified based on these defects from the ion beams, and this is done over and over again to be able to determine the radiation tolerance which will help in advancing the technology and in the design of reactors even for a higher dose and with a prolonged reactor lifespan.

Most of the time these advanced reactors are only designed after the required material types are achieved. And since such reactor technology is not even at the prototype stage, there would not be any such reactor for testing materials except to utilize the likes of accelerators and some computational tools to bombard these materials and vary their compositions to be fit for application in the design of reactors of such technology. This is exactly the procedure that the current generation, Generation IV energy systems, fusion reactor systems, and even the previous generations of reactors are going through or went through. Currently, no fusion neutron irradiation facility exists for materials testing with a fusion spectrum irradiation and it is not easy studying the neutron irradiation effect even in the current reactor systems. Hence, ion beam experiments have therefore been researched by several researchers and it has been employed by most industry players to assess the irradiation effects on materials already employed in the fission spectrum [3, 4].
