\begin{comment}
Every year there is a growing global demand for energy driven by emerging economies and
developing countries alike. However, with growing concerns about climate change and the
potential harm greenhouse gas emissions have on the environment due to conventional energy
sources such as coal and natural gas, nations around the world have been called to come
up with innovative solutions to address the energy problem in an economic and sustainable
manner.
Nuclear energy is one such solution that, over the years, has had to face harsh criticism due
to the issues it has had in the past in particular with safety and nuclear waste management.
The industry in response has set out to design a new array of reactors, better known as
Gen-IV reactors, who not only address these issues but also improves upon many others aspects
including inherent safety, reliability, scalability, and economics [1]. Accelerator Driven
Systems (ADS) are such designs that look to improve the way nuclear energy is created
and is the basis for the Multi-purpose Hybrid Research Reactor for High-tech Applications
(MYRRHA) design currently in development at the SCK-CEN Research Centre in Belgium.

## IAEA report

At the end of 2021, the world’s total nuclear power capacity was 389.5 gigawatts (electrical)
(GW(e)), generated by 437 operational nuclear power reactors in 32 countries. During
the year, over 5.2 GW(e) of new capacity was connected to the grid, from 4 pressurized
water reactors and 1 pressurized heavy water reactor and 1 high-temperature reactor.
During 2021, 8.7 GW(e) of capacity was retired, with the permanent shutdown of ten
nuclear power reactors. Supplying 2653.1 terawatt-hours of greenhouse gas emission-free
electricity, nuclear power accounted for about 10% of total global electricity generation
and more than a quarter of the world’s low carbon electricity production. At the end of
the year, 58.1 GW(e) of capacity was under construction, comprising 56 reactors, including
10 reactors (8.8 GW(e)) where construction started in 2021.

## WEO

Electricity accounts for about 20% of the world’s total final consumption of energy, but its
share of energy services is higher due to its efficiency. It is central to many aspects of daily
life and becomes more so as electricity spreads to new end‐uses, such as electric vehicles
(EVs) and heat pumps. The electricity sector accounted for 59% of all the coal used globally
in 2021, together with 34% of natural gas, 4% of oil, 52% of all renewables and nearly 100%
of nuclear power. It also accounted for over one‐third of all energy‐related CO2 emissions in
2021.
This chapter mainly draws on two scenarios, the Stated Policies Scenario (STEPS) and the
Announced Pledges Scenario (APS). As described in Chapter 2, the STEPS maps out a
trajectory that reflects current policies, while the APS assumes that all long‐term emissions
and energy access pledges and targets are met on time and in full. This chapter also draws
on the updated Net Zero Emissions by 2050 (NZE) Scenario, which describes a cost‐effective
pathway for the world to achieve net zero emissions by mid‐century in the energy sector that
also limits cumulative emissions in line with a 50% chance of limiting the global average
temperature increase to 1.5 °C by 2100.
\end{comment}
Electricity accounts for about 20\% of the world’s total final consumption of energy according to \cite{INTERNATIONALENERGYAGENCYWorld2022} and the demand is increasing up to 150\% by 2050.
%Increase of final energy consumption of 30\% by 2050.
At the end of 2021, the world’s total nuclear power capacity was 389.5 gigawatts (electrical) (GW(e)) and it accounts for about 10\% of the global electricity production and more than a quarter of the world’s low carbon electricity production \cite{GrossiIAEA2021}.
The current nuclear reactor fleet is old and replacement is necessary to keep providing the same share of energy production in the near future.\\

Climate change is one of the driver to maintain and expand the use of nuclear power since it avoids emission of $CO_2$ in atmosphere which is the main concern regarding to climate change.
Most of the technologies to introduce to reach the net zero emission in 2050 are currently under development and it is particularly true for nuclear power reactors: advanced reactors are under investigation with the aim of providing clean energy at an affordable price, focusing on safety aspects and spent fuel management.\\
In this framework, the R\&D on Generation-IV nuclear reactor technologies is particularly important to ensure the highest level of safety and performance. On this respect, liquid metal cooled reactors \cite{Smith2016Lead-cooledReactor} offer many advantages:
\begin{itemize}
\item low pressure operation thanks to the high melting and boiling point;
\item better fuel utilization and less high-level waste production thanks to the fast neutron spectra;
\item high power density with a low coolant to fuel ratio thanks to more effective coolant than water;
\item high coolant density that promotes natural convection cooling and mitigation of thermal transients;
\item high retention properties of the coolant for some fission products.
\end{itemize}
The feasibility of this technology has to be investigated and MYRRHA research reactor will serve the purpose. It will also play a key role in the nuclear waste treatment, that remains the main environmental concern related to nuclear power since the radioactive waste can remain radioactive and dangerous to human health for thousands of years.
