the European Sustainable Nuclear Energy Technology Platform The Vision of the European Sustainable Nuclear Energy Technology Platform Strategic Research Agenda on the Safety R&D for GEN-IV Reactors G.B. Bruna, IRSN - 18/11/2018 1

The Sustainable Nuclear Energy Strategic Research Agenda - SRA Technology Platform SNE-TP Strategic Research Agenda - SRA C.F.LWR GEN-IV FRS HTR Ad. F.C. Materials Codes & Standards C-C. A Modelling Fuel Safety R. Infr. Educ.–Tr. SFR LFR GFR ADS - 18/11/2018 2

Strategic Research Agenda Safety Objective ● This presentation is aimed at summarizing the content of the SRA Sub-Chapter “Safety”, mainly focusing on GEN-IV aspects. - 18/11/2018 3

Strategic Research Agenda Safety Context Very effective collaboration among Contributors (35 from 8 countries and 20 organizations), Many Contributors have participated in some selected parts only, In general, Contributors for Current and Advanced and Innovative Fission Reactors are different. - 18/11/2018 4

Strategic Research Agenda Summary of the SRA Safety Sub-Chapter ● Forewords ● Uncertainty analysis and “safety margins”: two cross-cutting topics for safety research ● Current Reactors ● Advanced and Innovative Fission Reactors - 18/11/2018 5

Strategic Research Agenda Safety The connection between safety research and regulation is mandatory in the nuclear technology. Safety research has to accompany nuclear installations throughout all phases of their life, from concept definition, through design, licensing, construction and operation, up to decommissioning. Even if the excellent performance record of existing installations might suggest that a high safety level can be achieved without new huge research efforts, consciousness of research needs should be maintained, ● focusing on new trends, ● supporting public information and training. - 18/11/2018 6

Strategic Research Agenda Safety Anticipatory research should look ahead to safety questions that may arise in the future, due to changes in the design and operating-mode, and the appearance of new concepts, such as the GEN-IV; The role of the future research should foster in an improved international cooperation to promote achieving common understanding of the safety and its standards, mainly when dealing with the advanced and innovative concepts which are intended to: • intrinsically eliminating severe accidents from occurring, • reducing either their probability or the level of their expected consequences. This is done by design, not necessarily by addition of safety systems, which requires integrating since the beginning of the conceptual phase, the deterministic and the probabilistic approaches. - 18/11/2018 7

Strategic Research Agenda Safety (Current Reactors) Priority topics for action (short-term within the FP7) [issues to be either implemented or reinforced] Current Reactors 1/3 Reactor Physics and Dynamics Thermal-Hydraulics Criticality Nuclear Fuel - Human and Organisational Factors - I&C and Electrical Systems - 18/11/2018 8

Strategic Research Agenda Safety (Current Reactors) Priority topics for action (short-term within the FP7) [issues to be either implemented or reinforced] Current Reactors 2/3 - Aggression and Hazards In recent years, new threats are coming up forcing to focus not only on internal hazards, but also on the destructive action of external agents including the time. When assessing the safe behavior of a system, a component or an equipment, its robustness and resistance to the aging-related phenomena and to all kind of external aggressions is to be demonstrated, including ◊ Flooding, ◊ Extreme whether condition, ◊ Seism, ◊ Fire - 18/11/2018 9

Strategic Research Agenda Safety (Current Reactors) Priority topics for action (short-term within the FP7) [issues to be either implemented or reinforced] Current Reactors 3/3 Plant Simulation Severe Accidents Emergency Management . - 18/11/2018 10

Strategic Research Agenda Safety (Advanced and Innovative Reactors) Advanced and innovative reactors encompass a variety of different designs and operating modes. They span a very large set of configurations, including small and large size cores, fast-neutron and moderated spectra, gas, water and liquid metal cooling, each one matching more or less completely and comprehensively the objectives of the GEN-IV roadmap (GIF). - 18/11/2018 11

Participants in the G.I.F. People’s Republic of China Russian Federation •Economy: - Natural Resources, - Fuel cycle; •Safety; •Operability; •Environmental impact: - Severe Accidents, Emergency - Crisis, Wastes. - 18/11/2018 12

The Generation IV System Family HTR/VHTR SFR GFR LFR MSR SCWR SFR GFR LFR MSR HTR/VHTR SCWR - 18/11/2018 13

The Sustainable Nuclear Energy Technology Platform SRA MSR SCWR included in LWR Chapter, as an evolutionary concept HTGR – VHTGR accounted for as a multi-energy system Fast Neutrons Reactors : - LFR, - GCR, - SFR, - ADS not part in the GIF - 18/11/2018 14

Strategic Research Agenda Safety (Advanced and Innovative Reactors) Natural resource optimization and waste minimization are goals more likely affordable for systems with fast neutron flux, such as SFR - Sodium Fast Reactor -, GFR - Gas Fast Reactor - and LFR - Lead Fast Reactor -. Graphite moderated, gas cooled high temperature reactors such as the Very High Temperature Reactor (V/HTR) are more likely to be inherently safe; they also have the best potential for a diversified energy production (electricity, but also industrial heat and hydrogen). - 18/11/2018 15

Strategic Research Agenda Safety (Advanced and Innovative Reactors) Operating experience should contribute to identify crucial needs for Advanced and Innovative Systems research, All the modifications adopted for Current Reactors and the associated safety assessments should entail research, including code development and experimental activity. - 18/11/2018 16

Strategic Research Agenda Safety (Advanced and Innovative Reactors) Nuclear Reactors are presently facing a very open landscape as regards the industrial maturity of concepts. That is very challenging from the safety point of view, because the safety assessment is strictly tied to design features, the details of which are hardly disclosed and remain widely unknown for the most concepts at the present stage of development. - 18/11/2018 17

Strategic Research Agenda Safety (Advanced and Innovative Reactors) ● Specific R&D efforts on design features should enable to practically preclude any significant energy release in case of Severe Accident, ● That should be searched for through adoption of optimised core design features such as the geometry of the fuel subassembly, the relative volume fraction of core materials, the density of heavy metal within the fuel and the possible use of light materials to moderate neutrons and increase the Doppler Coefficient. SFR 1/3 - 18/11/2018 18

Strategic Research Agenda Safety (Advanced and Innovative Reactors) ● Other core desirable features for enhanced safety include reducing reactivity swing and increasing temperature margins, ● The mechanical behaviour of the core and specific design options are to be carefully investigated so as to minimise the risk of core compaction, ● Innovation in core instrumentation and surveillance should allow for early detection of abnormal situations. SFR 2/3 - 18/11/2018 19

Strategic Research Agenda Safety (Advanced and Innovative Reactors) ● Sodium technology risk, could be minimized through substituting conventional steam turbine energy conversion systems with gas turbine and Brayton cycle conversion, ● The merit of innovations in the reactor design to enhance safety is to be assessed through normal and accidental operating transient analyses in terms of robustness of the safety approach. SFR 3/3 - 18/11/2018 20

Strategic Research Agenda Safety (Advanced and Innovative Reactors) GFR LFR ● The exclusion approach should be fully discussed and validated and the Risk Informed methodology applied all along the pre-conceptual design phase, ● A list of Design Basis Accidents –DBA list- should be established for safety and margin assessment. ● To cope with any potential danger situation, suitable passive or active systems should be implemented, if needed. - 18/11/2018 21

Strategic Research Agenda Safety (Advanced and Innovative Reactors) ● Industrial heat generation process requirements would be quite different from electricity generation ones, and much more versatile, which will demand a high flexibility of the nuclear heat source; however competitiveness of nuclear energy is usually achieved via standardisation, ● Competitiveness and flexibility requirements will have to be reconciled through a conceptual design phase. V/HTR 1/3 - 18/11/2018 22

Strategic Research Agenda Safety (Advanced and Innovative Reactors) ● Several safety systems, relying on intrinsic properties of materials and system arrangements as well as on active devices, have been already studied during the exploratory phase, such as the core cooling function in tight relationship with the LPA - Loss of Pressure Accident-; the other safety functions should be analyzed in accordance to the DBA list, ● To cope with any potential danger situation, suitable passive or active systems should be implemented. V/HTR 2/3 - 18/11/2018 23

Strategic Research Agenda Safety (Advanced and Innovative Reactors) ● Safety challenges are raised by the coupling with conventional energy-production facilities, which may propagate instability and perturbations to the reactor, through intermediate heat exchangers. ● The demonstration of the feasibility of the coupling of the reactor with process heat applications and cogeneration is actually the main challenge for the short term for reactor-systems such as the V/HTR. V/HTR 3/3 - 18/11/2018 24

Strategic Research Agenda Safety (Advanced and Innovative Reactors) ● Major Safety concerns for GEN-IV • Minimizing the risks attached to the liquid metal coolant (sodium; lead, …), • Practically precluding large energy release in case of severe accident (even hypothetical), • Minimizing the system vulnerability to external events and aggressions, • Assessing the impact of MA -Minor Actinides- bearing fuels, • Diversifying the safety systems (e.g., decay heat removal), • Developing an improved instrumentation for early detection of abnormal situations, • Developing an improved instrumentation and techniques for in service inspection and repair. - 18/11/2018 25

Strategic Research Agenda Safety (Advanced and Innovative Reactors) ● The relevant R&D activity can be grouped in several main fields of endeavour • Core Physics and Simulation, • Residual Heat Removal, • Fuel Integrity, • Fission Product Release, • Reduction of Major Risk of a Broad and Severe Damage of the Core, • In Service Inspection and Repair. - 18/11/2018 26

Strategic Research Agenda Safety (Advanced and Innovative Reactors) Concluding Remarks 1/4 • The need for new experimental and simulation tools, aimed at sustaining safety analyses, should be focused on current reactor needs with GEN-IV as a definitely new perspective in view; • Research hardly accommodates uncertainties and breakthroughs, and must enjoy continuity to maintain its effectiveness and usefulness; - 18/11/2018 27

Strategic Research Agenda Safety (Advanced and Innovative Reactors) Concluding Remarks 2/4 The simulation tools should be conceived and the experimental results should be presented in such a way as: ◊ to be really user friendly, ◊ to support their adoption and, as a consequence, their dissemination among users and countries, ◊ to captivate confidence on the capability to manage nuclear technologies and handle unexpected phenomena and events. - 18/11/2018 28

Strategic Research Agenda Safety (Advanced and Innovative Reactors) Concluding Remarks 3/4 • The need for keeping a suitable experimental capability for safety assessment is to be claimed; • Safety assessment cannot avoid a convenient experimental support, for investigation of physical phenomena, validation of computation chains, training and keeping competence alive; - 18/11/2018 29

Strategic Research Agenda Cross-cutting Activity Safety (Advanced and Innovative Reactors) Concluding Remarks 4/4 • Today, the public acceptance plays a key role and may strongly affect the profitability of an investment in the nuclear field; • The cost of experimental activities calls for participation of partners at the international level; • Extensive information of the public on safety R&D can contribute significantly to increase confidence and acceptance, to attract newcomers to the field, to guarantee the necessary financial support. - 18/11/2018 30