The joint evaluated fission and fusion nuclear data library 3.3 is described. New evaluations for neutroninduced interactions with the major actinides 235 U, 238 U and 239 Pu, on 241 Am and 23 Na, 59 Ni, Cr, Cu, Zr, Cd, Hf, W, Au, Pb and Bi are presented. It includes new fission yields, prompt fission neutron spectra and average number of neutrons per fission. In addition, new data for radioactive decay, thermal neutron scattering, gamma-ray emission, neutron activation, delayed neutrons and displacement damage are presented. JEFF-3.3 was complemented by files from the TENDL project. The libraries for photon, proton, deuteron, triton, helion and alpha-particle induced reactions are from TENDL-2017. The demands for uncertainty quantification in modeling led to many new covariance data for the evaluations. A comparison between results from model calculations using the JEFF-3.3 library and those from benchmark experiments for criticality, delayed neutron yields, shielding and decay heat, reveals that JEFF-3.3 performes very well for a wide range of nuclear technology applications, in particular nuclear energy.

The JET 2019-2020 scientific and technological programme exploited the results of years of concerted scientific and engineering work, including the ITER-like wall (ILW: Be wall and W divertor) installed in 2010, improved diagnostic capabilities now fully available, a major Neutral Beam Injection (NBI) upgrade providing record power in 2019-2020, and tested the technical & procedural preparation for safe operation with tritium. Research along three complementary axes yielded a wealth of new results. Firstly, the JET plasma programme delivered scenarios suitable for high fusion power and alpha particle physics in the coming D-T campaign (DTE2), with record sustained neutron rates, as well as plasmas for clarifying the impact of isotope mass on plasma core, edge and plasma-wall interactions, and for ITER pre-fusion power operation. The efficacy of the newly installed Shattered Pellet Injector for mitigating disruption forces and runaway electrons was demonstrated. Secondly, research on the consequences of long-term exposure to JET-ILW plasma was completed, with emphasis on wall damage and fuel retention, and with analyses of wall materials and dust particles that will help validate assumptions and codes for design & operation of ITER and DEMO. Thirdly, the nuclear technology programme aiming to deliver maximum technological return from operations in D, T and D-T benefited from the highest D-D neutron yield in years, securing results for validating radiation transport and activation codes, and nuclear data for ITER.

Tritium breeding requirements• Tritium self-sufficiency must be guaranteed for DEMO:Net Tritium Breeding Ratio (TBR) ≥ 1.0 mandatory  Global TBR with margin in excess of unity required to account for Tritium losses and uncertainties: TBR ≥ 1.0 +  Uncertainties to be considered/to be accounted for:• Nuclear data uncertainties: 1-2 % for liquid metal blankets utilizing Pb-Li , 5 -10 % for solid breeder blankets with Beryllium • Blanket mock-up experiments: Measured Tritium production perfectly reproduced for HCLL, and underestimated by 5 to 10 % for HCPB blanket mock-up.  No need for TBR margin related to nuclear data uncertainties• Statistical uncertainties of Monte Carlo calculations: negligible • Uncertainties due to modelling assumptions: depend on expert judgement and can be reduced to insignificant level ≤ 0.5 % • Uncertainties due to specific engineering design assumptions: margin of 2 to 3% assumed; not mandatory -might be neglected if one can be sure the design is technically mature. • Effect of 6 Li burn-up on TBR: negligible for Pb-Li based blankets; 1 to 2 % TBR reduction for HCPB type blankets @ assumed DEMO blanket lifetime (2 to 5 fpy) and 6 Li enrichment (30 to 60%).• Effect of blanket ports on TBR: very important and significant, larger for Pb-Li than for HCPB type solid breeder/Be blankets.• Tritium losses in fuel cycle: dominated by Tritium decay (5%/year).TBR design target: TBR = 1.10 calculated by 3D Monte Carlo calculation not considering blanket ports and burn-up. Rationale (pragmatic approach): Assume a conservative margin of 5% for Tritium losses in fuel cycle, neglect nuclear data uncertainties and burn-up, assign 5% margin for port effect (limits the total port area to around 3 %). Context Objective• Specification of neutronic requirements for DEMO.• Assessment of TBR uncertainties, specification of design margins and definition of TBR design target (mandatory).• Radiation shielding requirements: tolerable radiation induced damage to vessel, limitation to the gas production in steel, and the radiation loads to the super-conducting magnets.• Performance of current DEMO models based on HCPB ("helium cooled pebble bed", HCLL ("helium cooled lithium lead") and WCLL ("water cooled lithium lead") blanket concepts.• European Power Plant Physics and Technology (PPPT) programme • Launched initially by EFDA , now conducted within the EUROfusion Consortium organisation. • Conceptual design of DEMO power plant within "Horizon 2020" and the embedded roadmap to fusion.• Key neutronics requirements must be fulfilled for DEMO to operate reliable and safe.• Sufficient Tritium breeding and shielding performance to assured. Void portsPlugged (steel) Port surface area 16 x 1 m x 2 m = 32 m 2 % of first wall area 2.95 TBR reduction HCPB DEMO 10% 4 % HCLL DEMO 15% 6% Shielding requirements• Sufficient protection of the super-conducting magnets from radiation penetrating the blanket/vessel/shield system  Limits for the radiation loads on the Toroidal Field Coils (TFC) to prevent degradation of the supercon...

Alpha particles with energies on the order of megaelectronvolts will be the main source of plasma heating in future magnetic confinement fusion reactors. Instead of heating fuel ions, most of the energy of alpha particles is transferred to electrons in the plasma. Furthermore, alpha particles can also excite Alfvénic instabilities, which were previously considered to be detrimental to the performance of the fusion device. Here we report improved thermal ion confinement in the presence of megaelectronvolts ions and strong fast ion-driven Alfvénic instabilities in recent experiments on the Joint European Torus. Detailed transport analysis of these experiments reveals turbulence suppression through a complex multi-scale mechanism that generates large-scale zonal flows. This holds promise for more economical operation of fusion reactors with dominant alpha particle heating and ultimately cheaper fusion electricity.

No abstract