Since early times people were searching for different sources of energy to provide support for their daily life (protection, lighting, cooking). At first, they mainly depended

on the Sun in providing heat and light during the day. Later on fire was discovered accidentally, providing an artificial yet dependable source of heat and light, especially at night. In the  19th century wood was the main source of fuel for heating, cooking and producing steam for powering engines. After that, alternative sources were discovered mainly water, wind, coal, natural gas and finally nuclear energy.
The  utilization of  nuclear energy is by  using  the energy produced from nuclear reactions to generate heat, which  in turn is used in steam turbines to produce electricity.
From the beginning of nuclear energy   commercialization in the 1970s, nuclear power had been considered as the safest source of power because it prevented about 1.84 million air pollution related deaths, and emission of about 64 billion tons of carbon dioxide equivalent that would have otherwise resulted from the burning of fossil fuels in thermal power stations. Now in 2018 around 11% of the world's electricity is generated by about 450 nuclear power reactors, about 60 more reactors are under construction, equivalent to 16% of existing capacity.
Despite the huge success of nuclear reactors in generating electricity, there are some challenges that face nuclear power, most importantly the potential health hazards and the need for safe use of nuclear reactors, especially after the 1979 accident at the Three Miles Island and the 1986 Chernobyl disaster. Both incidents played a part in stopping construction in many countries, because nuclear reactors accidents might result in releasing many chemical compounds into the air, that have fatal effects on humans and the environment. Subsequently, many countries found safer means to use Nuclear Power, also an international organization promoting safety awareness and professional development on operators in nuclear facilities was created and named World Association of Nuclear Operators (WANO), but that also didn’t stop accidents, for instance, on 11th of March 2011, the world witnessed one of the largest earthquakes ever recorded, this was followed by a tsunami at the coast of Japan. These natural disasters affected Fukushima Daiichi Nuclear power plant. This incident made many countries re-examine their nuclear safety and energy policies. It was not until 2015, when the International Atomic Energy Agency (IAEA) declared nuclear energy as a promising alternative source of energy and that could hugely limit the greenhouse gas emission phenomenon. Furthermore, the agency had noted that the prospects for nuclear energy remain positive in the medium to long term plans, and despite the negative impact in some countries, it is still the second largest source worldwide of low-carbon emission.
Despite the progress made in recent years and the establishment of more than 100 nuclear facilities World Wide (both nuclear reactors and research reactors) another great threat appeared, which is falling of nuclear material or radioactive material  into the wrong hands, and because of that the International Atomic Energy Agency (IAEA), was established to maintain secure use and to prevent, detect and respond to theft, sabotage, unauthorized access, illegal transfers or other malicious acts involving nuclear material, other radioactive material substance or their associated facilities.
The safe use of the nuclear energy is a responsibility for every country utilizing it, therefore all countries should work together to make the best use of that energy as well as protect people and the environment.

Treatment and conditioning of nuclear waste?

Treatment and conditioning are used to convert a wide variety of radioactive waste materials into forms that are suitable for their subsequent management, including transportation ,storage and final disposable. The aims are to:
* Minimize the volume of waste requiring management via treatment process.
* Reduce the potential hazard of the waste by conditioning it into a stable solid form that immobilizes it and provides containment  

How to eliminate radioactive waste?

Firstly, it's important to note that, despite the fact that the use of nuclear energy is only 70 years old, but still the radioactive material will stay dangerous for environment and human health for at least 100 years, after that it will naturally decays to safe chemical compounds, so radioactive waste has to be isolated and confined in appropriate disposal facilities for the sufficient period until it no longer poses a threat, and every radioactive waste must be stored depends on its type.