Four societal and industrial goals were defined for Generation-IV nuclear fission systems, planned to enter in service around 2030, namely: (1) sustainability; (2) safety & reliability; (3) socio-economics; and (4) proliferation resistance. These four high-level goals aim at responding to a number of requirements of the 21st century and therefore are shared by many countries world-wide (more than, strictly speaking, the 10 Members of the Generation-IV International Forum (GIF)). These four goals are also at the heart of any improvement of the current Generations II and III. They are naturally aligned with the main objectives of the general EU policy for energy: European strategy for sustainable, competitive and secure energy and EU Energy Roadmap 2050.

Experts with skills in science (e.g. physics, energy, environment and socio-economic sciences) and engineering (e.g. breakthrough developments in Structures, Systems and Components (SSC), materials and control systems) are necessary to develop these new nuclear fission systems, taking into account the long time horizon of nuclear power plants (NPP) which is circa 100 years. The Euratom programme in nuclear fission (Horizon-2020) aims at improving the scientific expertise requested in all Member States concerned. This is made possible through joint actions at EU level, devoted to research and innovation with a focus on Generations II, III and IV, as well as education and training with a focus on lifelong learning and cross-border mobility.

1 - Sustainability (two questions: S-Q1 and S-Q2)

• S-Q1: How to minimise the volume, heat and toxicity of radioactive waste?
• S-Q2: Is plutonium (Pu) an asset or a liability? Is depleted uranium (U) a recyclable material or waste?

The response to question S-Q1 determines national strategy regarding the back-end of the fuel cycle. In other words, what are the pros and cons of recycling (in particular, of Pu) versus a once-through approach? Currently, most countries world-wide consider spent and used nuclear fuel as waste, and have therefore opted for direct disposal or long-term storage of spent fuel. The response to question S-Q2 is related to partitioning and transmutation processes for Pu and minor actinides (Np, Am, Cm), aimed at reducing the amount and/or hazard of waste for disposal.

The Generation-IV approach fosters fast neutron spectrum reactors, aiming at breeding fissile Pu-239 fuel from non-fissionable but fertile U-238, thereby making Pu an asset and U a recyclable material. As a result of the actinide burning capacities of fast reactors, the U-238 resource will be optimally exploited and there will be plenty of fuel for reactors.

It should be noted that that, in the EU, a "European Industrial Initiatives" was launched in 2010, dedicated to Generation-IV systems, namely: the “European Sustainable Nuclear Energy Industrial Initiative”. ESNII has set up priorities in the research and development of fast neutron spectrum reactors (namely: sodium, lead and gas cooled reactors), as a complement to the current Generations II and III of nuclear power plants, based on slow (thermal) neutrons.

2 - Safety & Reliability (two questions: SR-Q1 and SR-Q2)

• SR-Q1: How safe is safe enough?
• SR-Q2: What is the impact of managerial and human factors on safety performance (safety culture)?

As far as question SR-Q1 is concerned, nuclear reactor designers use two methods to demonstrate that high levels of safety have been achieved: deterministic and probabilistic. The aim of the deterministic approach is to define and apply a set of conservative rules and requirements for the design and operation of a nuclear facility. If these rules and requirements are met, they are expected to provide a high degree of confidence that the level of risk to workers and the public at large from operation of the nuclear facility will be acceptably low. A second way of looking at the problem is to use the probability of failure as a guide. Probabilistic safety assessment (PSA) methods are usually developed at 3 levels:

• in Level 1 PSA, the Core Damage Frequency (CDF) is estimated.
• in Level 2 PSA, the Large Early Release Frequency (LERF) is estimated.
• In Level 3 PSA, public health and other societal consequences are estimated.

The Generation-IV approach fosters probabilistic safety targets more stringent than those of Generation-III (e.g. EPR 1600 NPP in Finland), i.e. CDF < 10^-5 per reactor year and LERF (100 TBq Cs-137) < 10^-7 per reactor year.

As far as question SR-Q2 is concerned, the focus is on the continuous development of a common nuclear safety culture, based on the highest achievable standards (for all generations of NPPs), as this is also one of the main lessons learnt from the "stress tests" conducted in all 131 NPPs in the EU following the Fukushima Daiichi accident (11 March 2011).

3 - Socio-economics (two questions: SE-Q1 and SE-Q2)

• SE-Q1: How to evaluate the total social costs (private + external) of energy technologies?
• SE-Q2: How to improve public engagement in decision-making (energy governance)?

As far as question SE-Q1 is concerned, major studies are being conducted to audit the costs of the nuclear sector and to estimate, in particular, the total social costs (private + external) in comparison with renewable and fossil energy sources. The target for Generation-IV systems is to be competitive with respect to other primary energy sources and, in particular, with Generation-III reactors, that is: for a first-of-a-kind reactor, approximately 5000 Euro per kWe installed and up to 90 Euro per MWh for electricity generation.

As far as question SE-Q2 is concerned, the focus is on a new type of governance in energy matters (based on improved openness, participation, accountability, effectiveness and coherence) for all high-tech technologies, and, in particular, for all generations of NPPs.

4 - Proliferation resistance (two questions: PR-Q1 and PR-Q2)

• PR-Q1: Is the nuclear proliferation risk over-estimated (weapons of mass destruction, CBRN threats)?
• PR-Q2: How to combat radiological terrorism (related to “small weapons”)?

As far as question PR-Q1 is concerned, the fear of so-called ‘rogue nations’ acquiring nuclear weapons, or terrorist organisations creating outrages by misuse of nuclear materials, clearly remains strong. As a consequence, political and technological experts are working to reduce the risk of dissemination and proliferation of nuclear weapons. Nuclear proliferation, however, should be considered from a broader perspective. Other mass destruction threats do exist: it should be noted that the EU is involved in chemical, biological, radiological and nuclear (CBRN) risk mitigation activities.

The ambition of Generation-IV in this domain focuses on two breakthrough technologies:

(1) new reprocessing techniques (partitioning) where U and Pu are no longer separated as is the case in the traditional PUREX process; and

(2) new fuel fabrication techniques for fast neutron flux reactor systems aiming to use (fertile) uranium-238 to breed (fissionable) plutonium-239, while burning the minor actinides neptunium, americium and curium (transmutation).

As far as question PR-Q2 is concerned, a number of risks exist in relation with nuclear materials and with malevolent or criminal acts related to certain radio-isotopes. Appropriate legal and technological security measures have been developed to combat nuclear criminality for all generations of NPPs.

In conclusion, energy problems should be looked at in the light of the economic, environmental and social requirements of the 21st century, integrating non-technical and technical dimensions. Especially in the nuclear fission domain, a number of inter-disciplinary challenges remain open in order to continuously improve technologies and services to meet the requirements of sustainability, safety & reliability, socio-economics and proliferation resistance, as they are demanded by both society and industry. These concerns are at the heart of EU research and innovation programmes, as demonstrated, for example, in the key document prepared for Euratom Horizon-2020 upon request of the EU Council: "2012 Interdisciplinary Study - Benefits and limitations of nuclear fission for a low carbon economy: Defining priorities for Euratom fission research & training (Horizon 2020)" ¹.

¹2012 Study: Symposium on "Benefits and Limitations of Nuclear Fission for a Low Carbon Economy"