The approach for nuclear reactor technology and safety is developed in two steps. The first step is the next 50 years where the system will be dominated by the present proven system notably LWR’s and to a lesser extent PHWR’s with some evolutionary improvements in technology and safety of the system. The main reasons for this is : the present NPP’s are quite competitive with respect to coal plant, they are cleaner than fossil plants and they have good operational and safety performance.

The evolutionary improvements in the safety and technology must be performed to reach better performance, better economics, better protection for the investors and wider acceptance by the public.

The so-called "advanced reactor", such as ABWR or AP-600, offer improved safety systems features by simplification and introduction of passive safety features. In other point of view, the improvement of man-machine interface in the system is also a good point for these advanced reactors in order to resolve the complexity of the machine and make the operator’s life easier.

In longer term future, despite efforts in conservation and efficiency programs in energy production and use, the tendency of energy demand will keep increasing well into the long term future. This is due to increasing of living standard and the population growth especially in developing countries.

Nuclear energy can have a very important role in energy supply system, if it succeeds in its development and rises to challenges it is facing. If not, the role of nuclear energy will be replaced by coal or gaz.

The challenges that should be resolved are :

• possible weapons proliferation and diversion of nuclear materials

• sabotage against nuclear facilities

• safety concerns

• radioactive wastes and environmental issues

• standardization of future plants

From the challenges mentioned above, the possible requirements for next generation of NPP’s would be in essence based on revolutionary concepts which are among others :

• design NPP’s that provides inherent resistance to sabotage and man-induced events through physical, security, and institutional design and arrangement

• concerns over safety should be eliminated through non catastrophe reactor and fuel design (no core melt accident)

• standardization of future NPP’s is of great development in order to reduce and keep the development cost at reasonable level, on the other hand this will improve the economy of the NPP’s

In this context, the integral reactor concepts provide a remarkable inherent safety features.