ºÚÁÏÉçapp

Last week, the ºÚÁÏÉçapp Council Science and Technology Advisory Committee (STAC) met at ºÚÁÏÉçapp Headquarters to review the new plans for construction and operation proposed by the ºÚÁÏÉçapp and Member's Domestic Agencies. This was the first in-person STAC meeting after a hiatus of almost four years caused by the pandemic. These new plans reviewed by STAC have been elaborated to minimize the impact of the repairs of the vacuum vessel and thermal shields on nuclear operation as well as to provide a more robust path to ºÚÁÏÉçapp licencing and to the routine demonstration of the Q=10 goal. In this new approach, ºÚÁÏÉçapp operation is proposed to be divided into three main phases:Augmented First Plasma (AFP): In this phase ºÚÁÏÉçapp will be equipped with inertially cooled plasma facing components in the critical areas of the first wall, which will allow demonstration of 15 MA operation and the commissioning of all required systems, including the disruption mitigation system with low operational risks. Deuterium plasmas with high confinement (H-mode) will also be demonstrated.DT-1: In this phase ºÚÁÏÉçapp will be equipped with a fully water cooled first wall and additional heating power of 33 MW neutral beam heating, 67 MW of electron cyclotron heating (ECH) and 10-20 MW of ion cyclotron heating (ICH). This phase will explore high confinement plasmas at high levels of plasma current in deuterium and deuterium-tritium plasmas culminating in the demonstration of reproducible operation of Q=10 burning plasmas within an accumulated neutron fluence of  ~ 1% compared to the final ºÚÁÏÉçapp project goal. DT-2: In this phase ºÚÁÏÉçapp will be in its final configuration with the objective of demonstrating Q=5 long-pulse and steady-state scenarios and routine operation at high Q with high fluence neutron production. This will allow the study of physics scenarios and technological choices for future electricity-producing fusion reactors.To support these operational phases the configuration of the ºÚÁÏÉçapp device and its ancillaries will be modified. These modifications include a change of first wall material from beryllium to tungsten, which is foreseen to reduce the retention of tritium inside ºÚÁÏÉçapp's vessel and the production of dust, and to increase the resilience of in-vessel components to disruptions. Since a change from beryllium to tungsten can increase the cooling of the plasmas and decrease fusion power production, this change is accompanied by risk-mitigation technical modifications to ºÚÁÏÉçapp ancillary systems. These include the introduction of systems to deposit films of boron to maintain good vacuum conditions and to cover tungsten components, if needed, and an increase of the power available to heat the plasmas with a change of proportion between ECH and ICH radiofrequency heating from that assumed in the 2016 ºÚÁÏÉçapp Baseline. Last week's STAC meeting was the first in-person reunion after a hiatus of almost four years caused by the pandemic. The STAC reviewed the proposed modifications and supported the risk mitigation measure proposed by the ºÚÁÏÉçapp in the context of the change of wall material and the new operational plan with the AFP, DT-1 and DT-2 phases. In particular, STAC supported the inclusion of a boronization system based on glow discharge cleaning and recommended the development of the technology for a boron dropper as ultimate risk mitigation in ºÚÁÏÉçapp. STAC also endorsed the plan for 40 MW ECH power in AFP with a further upgrade to 67 MW in DT-1. For ICH, STAC recommended to install 10 MW for AFP with a further increase to 20 MW in DT-1, after its effectiveness in an all-tungsten ºÚÁÏÉçapp has been confirmed during AFP.With regards to the AFP/DT-1/DT-2 outline operational plan, STAC found the plan compelling and recommended that this outline plan be adopted for the further articulation of the new ºÚÁÏÉçapp Research Plan to be elaborated by the ºÚÁÏÉçapp and Members' experts. STAC also noted the new approach to a staged licencing of ºÚÁÏÉçapp through the three operational phases above, and endorsed this new licencing strategy and the principles upon which it is based. STAC also reviewed progress and the strategy for the construction of the ºÚÁÏÉçapp Tokamak including the repair of vacuum vessel sectors and thermal shields. STAC found the proposal to perform cold testing of the magnets to be important to mitigating technical risks and recommended that, if possible, all the toroidal field coils and poloidal field coil # 1 be tested.In the words of ºÚÁÏÉçapp's Deputy Director-General for Science and Technology Yutaka Kamada, "The ºÚÁÏÉçapp is now fully confident that the New Baseline represents a robust approach to completing ºÚÁÏÉçapp construction and its licencing as well as for its scientific exploitation to demonstrate the project's fusion goals. The ºÚÁÏÉçapp deeply appreciates the advice of the STAC members, who represent the world's fusion science and technology expertise, for their strong support to ºÚÁÏÉçapp and their productive suggestions for improving the New Baseline." In the coming weeks, the ºÚÁÏÉçapp Council Management Advisory Committee (MAC) and the ºÚÁÏÉçapp Council itself will have the opportunity to review and comment on the ºÚÁÏÉçapp's new plans for ºÚÁÏÉçapp construction and operation with the objective of submitting a final version of these plans for review and approval by the ºÚÁÏÉçapp Council in 2024.

The cryopumps that will create and maintain extremely demanding vacuum conditions inside the ºÚÁÏÉçapp machine are marvels of technology that have been in development for over 15 years in Europe. The first production unit is expected at ºÚÁÏÉçapp before the end of the year. Vacuum pumping is required prior to starting the fusion reaction to eliminate all sources of organic molecules that would otherwise be broken up in the hot plasma. Vacuum pumping is also required to create low density—about one million times lower than the density of air. Mechanical pumps alone cannot achieve the vacuum quality that is indispensable to producing the ºÚÁÏÉçapp plasmas. Once mechanical pumps have evacuated most of the air molecules and impurities from inside the vacuum vessel, six torus cryopumps will finalize the job and trap the remaining particles. Two other cryopumps in the cryostat will maintain the low pressure required for the operation of the superconducting magnets. These complex pumps have been in design for years to meet the very specific applications and requirements at ºÚÁÏÉçapp. All are based on cryopanels, cooled with supercritical helium and coated with activated charcoal as sorbent material for imprisoning particles. Under the terms of a Procurement Arrangement signed with the ºÚÁÏÉçapp in 2018, the European Domestic Agency (Fusion for Energy) is procuring the eight cryopumps based on a design developed through the close collaboration of experts at ºÚÁÏÉçapp and Fusion for Energy and the participation of European industry. The first production pump is expected at ºÚÁÏÉçapp before the end of the year.

Last week the International Atomic Energy Agency (IAEA) held its annual General Conference, with delegates representing more than 130 countries and many international organizations including ºÚÁÏÉçapp. The conference highlights a broad range of nuclear technologies and policies—from safeguards against weapons proliferation, to technical cooperation on nuclear and radioisotopic techniques benefiting agriculture, groundwater management, and medicine. This year, the global surge in fusion energy R&D was also in the spotlight.