University of Science and Technology of China (USTC) Hefei, China May 2015

Transcription

1 Limited Distribution INTERNATIONAL ATOMIC ENERGY AGENCY WORKING MATERIAL Report of the 3 rd IAEA DEMO Programme Workshop University of Science and Technology of China (USTC) Hefei, China May 2015 Reproduced by the IAEA Vienna, Austria, September 2015 NOTE The Material in this document has been supplied by the authors and has not been edited by the IAEA. The views expressed remain the responsibility of the named authors and do not necessarily reflect those of the government(s) of the designating Member State(s). In particular, neither the IAEA nor any other organization or body sponsoring this meeting can be held responsible for any material reproduced in this document. 1

2 Executive Summary The third IAEA DEMO Programme Workshop was held May 2015 on the campus of the University of Science and Technology of China (USTC), Hefei, China. The Technical Programme Committee was chaired by Prof. Takeo Muroga of the National Institute for Fusion Science in Japan, and the local arrangements were made by the Institute of Plasma Physics of the Chinese Academy of Sciences (ASIPP), under the leadership of Prof. Xiang Gao. This workshop, like the previous workshops in this series, was organized around three topics. The overall aim is to understand the required programmes and facilities needed to resolve scientific and technical issues leading to fusion energy demonstration, and to identify opportunities to make greater progress through international collaboration. Under Topic 1, Contribution of Integrated Fusion Devices to Closing the Gaps, participants discussed ITER and a set of planned integrated devices intended to take significant steps beyond ITER in fusion nuclear science and technology. The expected accomplishments of ITER are well understood internationally and its contributions to DEMO physics, technology, and programme planning were clearly presented. Next-step machines currently being studied by several ITER partners would clearly make important advances going well beyond ITER, but the degree to which they would close gaps toward DEMO readiness will need to be quantified as these plans mature. These machines themselves have readiness gaps, especially for their later phases, for which R&D is necessary in the near term. Plans for closing these gaps need to be clarified. Under Topic 2, In-Vessel Systems and Engineering, the discussion focused on the heart of the fusion reactor, the in-vessel systems. More so than in present facilities, high availability is a prominent consideration in the design of fusion machines, requiring careful strategic decisionmaking in the early phases of plant configuration development. Reliability requires having a materials properties data base for relevant conditions, and designing with ample margin to be robust against damage and synergistic effects in the harsh fusion in-vessel environment. Remote maintenance is a key design driver of tokamak architecture requiring care to, for example, ensure adequate space for in-vessel piping, decouple primary functional requirements, and be able to access auxiliary systems without dismantling. Participants found that the step beyond ITER will require innovation in the plasma scenario and in-vessel systems, including the divertor hardware configuration, and the materials and technology of plasma facing components. Under Topic 3, ITER-TBM and Blanket Programmes toward DEMO, participants considered the relationship between the ITER Test Blanket Module (TBM) projects and long-term blanket development needs for DEMO. The ITER TBM programme provides a unique opportunity for blanket development to take advantage of the, as of today, single facility with environmental conditions and constraints closest to those of DEMO to be available in the near future. Yet, it is equally clear that very large extrapolations are required for many significant design parameters, for example tritium breeding rate, neutron dose, coolant and liquid mass flow, and extracted heat. Blanket designs must necessarily evolve so the main contribution of the ITER TBM experiments will be to generate a data base that can be used as a benchmark for the validation of modelling tools needed for DEMO design. The ITER TBMs will produce data on important aspects such as MHD effects, neutronics, tritium generation and transport, and electromagnetic forces. In order to derive benefit from these results, however, it is essential to develop modelling tools that can be used with similar confidence both at ITER TBM and DEMO conditions. While a significant 2

3 effort will be required in order to develop these, the activities for development and benchmarking is an area in which international collaboration can be very useful. In addition six Special Topics presentations were carried out on updates of roadmap planning, next-step facility designs and R&D in some nations, and special investigations on DEMO-related issues. They are (1) status of Chinese next generation facility CFETR, (2) DEMO conceptual design approach in EU, (3) New Japanese DEMO strategy report, (4) IFMIF-EVEDA and the vision of neutron source, (5) Fusion safety with consideration of fission regulations, and (6) Nonproliferation compliance. The workshop s focus on DEMO science and technology highlighted some strategy issues in view of the emerging world DEMO programme. The multiple plans for next step tokamak reactors appear to be very similar in what they would contribute to the basis for future steps. All might have the potential to demonstrate net electricity at some stage, but would not necessarily go far enough in physics and technology to close readiness gaps for commercial power plants. Supporting facilities focussing on narrower sets of issues, which might reduce technical risks for next integration steps, are less prominent in the planning. It is not clear whether the emerging programme is the optimum one in terms of number and diversity of planned facilities. These circumstances prompted discussion of a possible international strategy to improve coverage of DEMO needs that are currently under-addressed, to reduce duplication, and to be more robust against setbacks. Given the costs of fusion next steps, there could be significant advantages in an international strategy for planning and coordination of work. Discussions at this and previous workshops have raised awareness of non-proliferation as an issue that must be taken into account in fusion planning. Further dialog with experts is necessary to understand what technical measures, e.g. monitoring of neutron radiation, gamma radiation, or fission products, would be most effective. Prof. W. Biel (Kfz-Juelich, Germany) was appointed as a point of contact (POC) in order to maintain the communication with non-proliferation specialists and arrange for a progress report at the next workshop. The Technical Programme Committee (TPC) met during the workshop to discuss plans for the 4th IAEA DEMO Programme Workshop (DPW-4), the next in the series. That workshop will be held during November 2016 in Karlsruhe, Germany, maintaining a spacing of about 1.5 years between meetings. Dr. Elizabeth Surrey of the UK s Culham Centre for Fusion Energy (CCFE) will chair the Technical Programme Committee. It was decided to maintain a strong technical focus in the topic choice, and accordingly the following topics were suggested for consideration by the TPC for DWP-4: 1. Tritium issues: plant-wide, including ex-vessel systems 2. Towards a DEMO Physics Basis 3. DEMO Heating and Current Drive Physics and Technology The TPC will be responsible for developing more specific discussion questions for each topic and to work closely with contributors in ensuring that their contributions are responsive to the questions. The tradition of scheduling several stand-alone special topic presentations will be continued. In planning the next workshop, the committee intends to increase the emphasis on technical discussion leading to conclusions, with the presentations providing targeted input. 3

4 1. Introduction The evolving worldwide magnetic fusion programmes are increasingly focused on developing plans to demonstrate the production of electricity. The ITER project, which is being carried out as a partnership among nations with large fusion research programmes- Europe, Japan, India, China, Russia, South Korea, and the United States, is the first large step in this phase of the fusion programme. ITER, now well into construction, will advance the physics and technology of a power plant-scale burning plasma. Even as the partners tackle the formidable challenges of ITER, the need to understand the scientific and technical issues for going beyond ITER, and the need to start addressing them now, is widely appreciated. Collectively the activities to develop solutions for harnessing fusion energy comprise a world DEMO Programme, even though there is currently no single or coordinated view of the roadmap to DEMO. Against this backdrop, the IAEA decided in 2012 to establish a series of annual DEMO Programme Workshops (DPW) to facilitate international cooperation on defining and coordinating DEMO programme activities. The first workshop in the series was held at the University of California at Los Angeles (UCLA), U.S.A., in October 2012; the second was held at IAEA Headquarters in Vienna, Austria, in December Here we report on the third workshop (DPW-3), which was held May 2015 on the campus of the University of Science and Technology of China (USTC) in Hefei, China. The objective of this workshop was to discuss a subset of key DEMO scientific, technical, and programmatic issues with the aim of defining the facilities and programme activities that can lead to their resolution. A related aim was to identify opportunities to make greater progress through international collaboration. In order to promote continuity in the workshop series, topics for the next workshop (DPW-4) were determined (see Section 3 of this report). The workshop, like the previous workshops in this series, was organized around three topics for focussed discussion and future action, as well as a number of special topic presentations. The three topics for this workshop were: 1. Contribution of Integrated Fusion Devices to Closing the Gaps 2. In-Vessel Systems and Engineering 3. ITER-TBM and Blanket Programmes toward DEMO The main agenda was structured with presentations and discussion on these topics, with a daylong session of oral presentations devoted to each topic. Each session was organized in advance by a topic chair, who then led the discussion and summarized the session in a meeting of the Technical Programme Committee. Poster presentations addressed these as well as other topics relevant to DEMO preparation and planning. The special topic presentations focussed on new developments including updates of DEMO roadmap activities and planning in various parties. Some 76 participants from 14 countries and 2 international organizations attended the workshop. Excellent facilities and meeting support were provided by USTC. 2. Summary of Discussions The presentations and discussions were helpful in clarifying the scientific and technical issues within the main workshop topics and illuminated possible paths to their resolution. Here we briefly summarize the outcomes from the discussions at this workshop. 4

5 2.1. Contribution of Integrated Fusion Devices to Closing the Gaps H. Neilson, E. Surrey A number of integrated fusion devices are now being studied throughout the world, an indication of serious planning for fusion development steps beyond ITER. Here, we are referring to a class of fusion facilities generally characterized by steady-state or long-pulse deuterium-tritium burning plasmas, reactor-relevant neutron wall loads, tritium breeding, and possibly electricity generation. The aim of this session was to consider what these machines, as well as ITER, will contribute to closing gaps in the scientific and technical basis for fusion power plants. Contributions of ITER to Closing DEMO Gaps The technical basis and expected accomplishments of ITER have been developed and scrutinized by a broad-based international community for over two decades and are broadly understood. ITER s main contribution to the fusion programme will be to advance the physics understanding of a burning plasma, where alpha heating equals or exceeds external heating. In addition, ITER will make significant progress on challenging plasma stability and control issues, including prediction and avoidance or mitigation of disruptions and control of edge-localized modes (ELMs). It will take a major step toward understanding the conditions for effective plasma heat exhaust and its compatibility with high core performance. In terms of fusion technology, as the first machine in which the consequences of using the fusion reaction impact upon the engineering, ITER s design and construction activities are already making major contributions to the design of next-step integrated machines. Regarding superconducting magnets, ITER s structural design codes and the project s response to issues that have arisen, e.g., in quench protection and in the treatment of transient heat excursions, provide a valuable legacy for the future. In power exhaust technology, ITER will help establish the effects of long term exposure of plasma facing components to plasma, such as ion damage to first-wall and divertor materials. To the extent that DEMO uses heating and current drive systems similar to ITER s, ITER will provide direct demonstrations of technical feasibility for several key components. Finally ITER will contribute to blanket technology through the Test Blanket Module (TBM) programme, as discussed in Section 2.3. Programmatically, ITER provides valuable and broadly applicable experience in the approach to engaging with the regulatory body. The experience shows that the technical design and integration analysis should be as detailed as possible and all validation and qualifications should be established before issuing the Preliminary Safety Analysis to the regulator. ITER will provide a comprehensive physics and technology data base for DEMO designers to use that will support the analysis required to satisfy the need for detail in the Preliminary Safety Analysis. Contribution of Next-Step Integrated Fusion Devices to Closing DEMO Gaps Several parties now have under way design and R&D efforts toward integrated devices intended to take significant steps beyond ITER in fusion science and technology. In contrast to ITER, these studies are national and are currently only at a pre-conceptual stage of design. Their contributions to closing DEMO gaps can be discussed broadly but not at the level of specificity that is possible for ITER. Information on four such devices was presented at this meeting, EU DEMO (Europe), JAEA DEMO (Japan), K-DEMO (S. Korea), and CFETR (China). There are both similarities and differences in mission and design among the devices. All are tokamaks targeting long-pulse or steady state operation of a deuterium-tritium plasma and tritium 5

6 self-sufficiency. All are designed with low-temperature superconducting magnets and breeding blankets using reduced activation ferritic-martensitic (RAFM) structural materials, at least in their first phases. All incorporate provisions for efficient maintenance of in-vessel systems by remote handling. The designs vary in major radius from about 1 to 1.5 times that of ITER and from 200 to 2,000 MW of fusion power. Some plans envision a two-phase mission in which the second phase would take advantage, following a complete upgrade of in-vessel systems, of anticipated advances in plasma performance and fusion technology to increase plant performance. In terms of expected contributions it is reasonable to expect that all, if carried out as planned, would make large advances beyond ITER in the technology of tritium breeding, including blankets and tritium extraction and recirculation. All would make advances toward DEMO availability requirements through performance of large-scale remote handling operations such as blanket changeouts, performance of unscheduled repairs, and accumulation of reliability data on critical components. All would make advances in plasma control, power exhaust, and plasma heating and current drive as well. These plans thus hold the potential for impressive strides toward a fusion DEMO by mid-century, but quantitative measures of expected progress against a complete set of DEMO readiness metrics are needed to assess the gaps that might remain even if all these projects were successfully carried out. Readiness for Next-Step Integrated Fusion Machines The next-step machines currently under consideration themselves require significant advances beyond current knowledge and expected ITER outcomes. There are general readiness gaps for these machines, especially their later phases, for which R&D is necessary in the near term. Open questions exist in some key readiness issues, for example: Readiness of burning plasma physics and control: What is needed to establish a basis for steady-state operation? Readiness of materials and component technologies: What are the prerequisite testing requirements for safety case and licensing? What additional facilities, for tasks such as material irradiation and component development, are necessary? Availability: While all studies are addressing maintenance turnaround times through design, what are the requirements, for example margins and ex-tokamak testing, for high component reliability in a fusion machine? Magnetic configuration options: tokamak, stellarator: Is the near-term readiness being weighed against the long-term potential? With many issues in common, especially technology, how can we advance both most effectively? 2.2. In-Vessel Systems and Engineering. C. Waldon, T. Muroga Providing energy from fusion is widely regarded as the prominent engineering grand challenge of the 21 st century. The difficulty in achieving this objective is illustrated in the hampered progress as the reactor performance moves closer to that of a power plant and more of the complexities are revealed. The problem is a truly integrated one with the competing demands from the reactor s constituent parts, their relational impact on one another, and the effect of uncertainties as they propagate through the incipient Integrated Fusion Machine designs. To this 6

7 end the topic 2 session focused on the heart of the reactor, the in-vessel components, highlighting some key requirements and those systems influence on the overall plant configuration. DEMO is understood to lie somewhere between ITER and a "first of a kind" commercial station but there is no clear international consensus on the exact performance. Europe has created a stakeholders working group from the wider representative community as a pseudo client to help formulate and prioritize the top level requirements. These have been rationalized into a set of cardinal missions namely: Safety, Performance, and Economic Viability. Using a system engineering methodology these top level requirements have been assessed outlining their contextual impact on one another and as an initial indication for areas of further study in plant configuration optimization. The focus of the existing international operational tokamak fleet has been largely centered on the plasma performance. The study and validation of DEMO relevant plasma scenarios remains the priority of the immediate next generation machines, however, other influences become prominent as the facilities approach those expected of a power generating plant. Less importance will be placed on the gathering of plasma data and consequently power plants will not need to be equipped with scientific diagnostics other than those fundamental to controlling the plant within a safe working envelope. Experience has shown that some of the power plant relevant essential requirements cannot be easily designed-in retrospectively. Design for high availability and high reliability require deep consideration and strategic decisions in the early phases of developing plant configuration concepts. Indeed the impact of designing for compatibility with the harsh invessel environment and its associated damage and synergistic effects was illustrated in the forecast margins for engineering design data for materials. This adds a dramatic constraint on the design envelope and a decisive factor in the selection of in vessel concepts. With an increasing reliance on in-situ testing supported with modest empirical data the greater the risk of failure and therefore the tokamak designer must care for minimizing the impact of remote maintenance intervention. Remote maintenance is a key design driver of tokamak architecture but this is not a performance derived requirement. A K-DEMO concept was presented showing the strategic design options selected to enhance in-vessel remote maintenance and its impact on the tokamak and building architecture. This included increased space for in-vessel piping systems, decoupling primary functional requirements and removal of auxiliary systems without dismantling. Illustrating the trades and impacts from conflicting requirements and what was needed to steward compromise. During the wrap-up discussion for this session, it was generally accepted that managing the exhaust of DEMO is one of the most challenging aspects of the design and that the successful solution will have implications for the overall engineering (tokamak architecture) and plasma scenario design. It is also shown to be a deeply integrated problem, certainly in determining exhaust management systems that are likely to succeed. The step beyond ITER appears to require innovation in both (a) the divertor plasma and configuration and (b) the plasma facing components materials and technology. Speakers from ASIPP shared some of their recent EAST experience with the upper divertor tungsten upgrade highlighting fabricated features that can give rise to flaws and be life-limiting through reduced material performance raising the importance of functional testing as part of the component qualification. Work continues within China to develop better refractory material and therefore functional performance. Even assuming unrealistic steady state conditions for DEMO, the gap between technology performance and those compatible with the plasma scenario is still significant. The absolute upper limit for real, 7

8 manufacturable solutions is well short of the predicted values expected for a conventional divertor design. Not only must this gap be closed but a significant overlap must be generated to ensure that a resilient reactor design can be delivered. Given the wide ranging impact the power exhaust has on DEMO much of the focus of the international community remains on bridging this gap between the technology and the plasma operating window ITER-TBM and Blanket Programmes toward DEMO A. Ibarra, R. Kurtz The topic of the interlink between the ITER-TBM projects and the Blanket Programmes towards DEMO is identified in this workshop as a very important one, deserving careful analysis in order to better understand the type of information that can be obtained from the experiments to be made in ITER and to be used for the DEMO design. In introducing the session, topic chair A. Ibarra (Spain) emphasized the relevance of the breeding blanket mission in a DEMO reactor and briefly reviewed the different breeding blanket concepts being developed, as well as the different Test Blanket Modules (TBMs) presently under development and should be tested in ITER. The TBM experiments to be carried out in ITER are unique in the sense that ITER is the only facility with environmental conditions (magnetic fields, thermal and magnetic gradients, radiation field, geometrical constrains, ) closest to those of DEMO. With that in mind, the objectives and strategies of all the six TBM designs were analyzed in detail during the workshop. It became clear that all of them are in a very much advanced stage of design and are close to manufacturing. On the other side, it was also clear that the different DEMO designs presently under development will evolve with time and there is a significant probability that they will be different from the ITER TBM designs. Moreover, from comparison of the ITER and DEMO working conditions, it also became clear that large extrapolations (typically two or three orders of magnitude) are required for many significant design parameters, for example tritium breeding rate, neutron dose, He and LiPb mass flow, extracted heat, etc. All these conclusions together clearly show the ITER TBM experiments cannot be conceived as 1:1 prototypes of a DEMO breeding blanket. On the contrary, their main role is to generate experimental data under different working conditions that can be used as a benchmark for the validation of modelling tools that will be used for DEMO designs. This is a very important point that came out from the analysis of the strategy followed by all the involved parties. The different TBM experimental phases foreseen to be tested in ITER are linked to different properties to be validated. The ones presently identify are mainly linked to: 1) MHD effects, 2) Neutronics, 3) Tritium generation and transport, and 4) Electromagnetic forces. Again, this conclusion is very important because it has two significant consequences: 1. In order to fully benefit from the obtained results, it is required to develop modelling tools able to be used with similar confidence both at the TBM conditions as well as in the DEMO ones. These modelling tools are not fully available today and a significant effort will be required in the next few years in order to develop them. They also usually require the use of many numerical values for physical parameters as inputs that, in some cases, are not currently known with enough certainty. 2. If an experiment is going to be run for validation purposes, it must produce a significant amount of experimental data with adequate time and spatial resolution for that purpose. This means that a very significant number of diagnostics with enough precision located at 8

9 very different positions of the TBM are required. This is a significant challenge due to space limitations and due to the reliability issues. It was identified that the activities for development of the modelling tools, and benchmarking with different experimental facilities, is an area in which international collaboration can be very useful. Another important aspect that came out during the workshop discussions is related to the very significant technology expertise that has been developed for the manufacturing of the TBM systems and will be required for DEMO. This expertise has been developed for many different areas, for example the methodology for integration of new materials and fabrication techniques in the Codes and Standards, implementation of regulatory rules (e.g. waste disposal, national regulatory documents such as France s ESPN, ) and its consequences in the design, availability analysis, etc. This development clearly shows that the selection/ranking among different breeding blankets alternatives cannot be made only using conceptual studies and basic R&D results but it should also take into account other technology-related issues Special topics There were six Special Topics presentations covering updates of roadmap planning, next-step facility designs and R&D in some parties, and special investigations on DEMO-related issues. Highlights of these presentations are as follows. 1) Present status of CFETR (Y.X. Wan) The key milestones of the Chinese roadmap are: 1) start to construct the China Fusion Engineering Test Reactor (CFETR) in 2020, complete the construction by 2030 (P fus ~ 200 MW and test of steady-state operation and tritium self-sufficiency) and upgrade it (P fus ~1 GW, Q eng > 1) at around It is hoped that a Prototype Fusion Power Plant (PFPP) (~1 GWe, Power Plant Validation) can be completed around The key step in the roadmap is to design and construct CFETR. Some progress in the CFETR effort has been achieved: 1) the conceptual design of CFETR has been completed; 2) R&D activities of CFETR via ITER CN PA and China domestic programme are underway and are already making progress. Further working plan of CFETR is : 1) start the engineering design of CFETR as soon as possible; 2) the proposal for more key R&D items and the construction of CFETR should be approved by the Chinese government before It is hoped that CFETR construction can be completed around ) Integrated DEMO conceptual design approach in the EU (G. Federici) The focus of the DEMO design activity in EU is on a systems engineering and design integration approach, which is recognized to be essential from an early stage to identify and address the engineering and operational challenges, and the requirements for technology and physics R&D. There are some preliminary design choices/sensitivity studies to explore and narrow down the design space and identify/select attractive design points. In the presentation, the results of a process engaging key technology stakeholders and experts (e.g., industry, utilities, grids, safety, licensing, etc.), initiated to establish realistic high level requirements for the DEMO plant to embark on a self-consistent conceptual design approach, was also discussed. Finally, some initial results of work being executed in the EUROfusion Consortium by a geographically distributed Project Team involving many EU laboratories, universities and industries in Europe were described. 9

10 3) Japanese Joint Core Team report for the establishment of technology bases required for the development of a demonstration fusion reactor (R. Kasada) The joint-core team has progressed with examinations of planning for the development of DEMO since the team s formation in July The present report introduces a chart which iluustrates development of all of the related programmes in a timeline and provides an overview picture of all related processes. It is expected that the fusion-related community of industry, education and research, and government will closely examine this chart, and share recognition of perspectives on issues and future direction in common, which will lead to joint activity and accomplishment throughout Japan. In particular, definition of the roadmap of the development of DEMO, planning of research and development programmes after the Broader Approach (BA) activities which will end in 2017, and reinforcement of joint usage and collaborating research systems and role-sharing with NIFS and universities are anticipated as a consequence. In order to define the roadmap of development of DEMO in future, there remain two important tasks which the joint-team has not completed. These are socio-economic examination of fusion energy and review of alternative approaches of helical magnetic fusion system and laser fusion system. 4) Vision of neutron source for the post BA activities (S. O hira) In the IFMIF / EVEDA project, realization of a stable lithium flow in the EVEDA lithium test loop has been achieved and commissioning of the Injector of the Linear IFMIF Prototype Accelerator (LIPAc) has been started. EU and Japan started, in early 2014, to consider the collaboration on the post BA activity as areas of possible current cooperation, development or enhancement of existing BA activities have been studied. In this discussion, evaluation and discussion of the necessity to provide a new high-flux fusion neutron source, named DONES or A-FNS, with an effective use of resources in IFMIF/EVEDA, were carried out. In Japan, additional purposes of utilizing neutrons, e.g., irradiation of blanket test modules, medical (boron neutron capture therapy- BNCT, production of short lifetime radioisotopes), etc. are studied. However, it is necessary to carry out additional engineering tests for Li target/test facility (Li purification, remote handling tools, etc.). In the presentation, the current status and results of the IFMIF/EVEDA project for the accelerator, target facilities individually and study of the new neutron source in Japan and Europe were presented. 5) Aspects of fusion safety considering fission regulations (R. Stieglitz) Fusion safety concepts rely on state-of-the-art safety concepts for nuclear installations containing radioactive environment and are based on DiD (Defense in Depth) concept. There are similarities and differences between safety concepts of fusion and fission. The main reasons for differences are radioactive inventories in plants and relevant potential release paths. Plant-internal events do not result in conditions requiring off-site evacuation. Systematic assignment of measures & installations to the different levels of defence (as required by international fission regulations) has to be performed once an adequately detailed design level of a FPP is attained. Safety function cooling demands detailed design of in-vessel components (blanket and others) and necessitates demonstration of safe decay (passive) heat removal. Thus development of validated tools is mandatory. External hazards must be included in the future safety analysis. Numerous issues, including waste management, remain open and requires adequate attention. 6) Implications of MFE compliance with non-proliferation (M. Englert) There are several challenges that fusion technology will face with regard to its proliferation resistance while it matures from experiment to a full-fledged energy option. Pure fusion facilities do not require nuclear materials such as uranium under normal operating procedures, yet due to 10

11 their very hard and very intense neutron spectrum they hold out the potential for producing significant amounts of weapons-grade plutonium in a shorter period of time and with less source material than with fission reactors. Also tritium is handled in amounts much larger than in a modern nuclear warhead. Research should be conducted on the verification of absence of nuclear material in fresh fusion blankets, during operation and after exposure; on the practicality of source material being mixed with coolant or purge flow; on the possibility to replace pure-fusion test blanket modules in a fusion power plant with blanket modules designed to breed special fissionable material and on the possibility to misuse other internal components exposed to high neutron fluence. It is important to address questions about the proliferation resistance of fusion facilities as early as possible as adequate answers to open question will be needed in the future. It is very important to meet the concerns of all stakeholders in a constructive and respectful dialogue DEMO Programme Strategy Issues The plans for ITER and proposed next-step integrated fusion machines represent a portfolio that could form the basis for a world programme to achieve the goal of a fusion power plant. Viewed from that perspective, there are important strategic questions that confront the community. It is generally recognized that no single machine is likely to resolve all DEMO issues simultaneously but at the same time it is not clear how many machines are needed, nor how diverse a portfolio is optimum. There are multiple plans for tokamak reactors that, despite spanning a range in size and fusion output, are very similar in their physics and technology bases and in what they would contribute to the basis for future steps. All might have the potential to demonstrate net electricity at some stage, but would not necessarily go far enough in physics and technology to close commercial power plant readiness gaps. Supporting facilities focussing on narrower sets of issues, such as component test facilities, fusion materials irradiation facilities, and dedicated divertor test tokamak facilities, which might reduce technical risks for next integration steps, have been dropped or downgraded in some of the plans. Instead, it is generally envisioned that the integrated facilities will assume these missions. The risk management choices being considered, e.g. acceptance of technical risk in order to minimize the time to net electricity demonstration, are important ones for the fusion community. These circumstances, along with the delays in the ITER schedule, prompted discussion of a possible international strategy to improve coverage of DEMO needs that are currently underaddressed, to reduce duplication, and to be more robust against technical setbacks and delays. For example, a response to ITER delays might be to unload ITER of some responsibilities that do not require its unique conditions, and seek alternative ways of addressing them. The workarounds to mitigate the impact of delays on the overall timeline and make the best use of available time and resources could benefit from coordinated planning approach by the whole community. Given the costs and time spans for fusion next steps, there could be significant advantages in an international strategy for planning and coordination of work Non-proliferation and fusion The presentation by Prof. Englert on non-proliferation considerations was informative, raising awareness of an issue that must be taken into account in fusion planning. The Technical Programme Committee concluded that further dialog with experts in this area is necessary to understand what technical measures, e.g. monitoring of neutron radiation, gamma radiation, or 11

12 fission products such as xenon or krypton, would be most effective. After discussion, it was agreed to appoint Prof. W. Biel as a point of contact (POC) because of Kfz-Juelich s contract on non-proliferation issues and Prof. Biel s strong connection to EU s DEMO diagnostics activity. The POC will maintain communication with Prof. Englert and arrange for a progress report at the next workshop. 3. Plans for the 4th IAEA DEMO Programme Workshop Following the workshop, the Technical Programme Committee (TPC) met to discuss plans for the 4 th IAEA DEMO Programme Workshop (DPW-4), the next in the series. It was decided to maintain a spacing of about 1.5 years between workshops, so the set dates for DPW-4 are November 2016 in Karlsruhe, Germany. The workshop will continue the tradition of focussing on three topics, with a one-day session devoted to each topic, plus several stand-alone special topic presentations. It is planned that each session will be organized and led by a Topic Chair and Co-chair, at least one of whom shall, for the sake of continuity, be appointed from the standing members of the TPC. All DPW-4 Topic Chairs and Co-chairs shall be included in the TPC for at least DPW-4. In addition, a representative of the European Commission will be appointed to the TPC for DPW-4. Dr. Elizabeth Surrey of the UK s Culham Centre for Fusion Energy (CCFE) was elected to chair the Technical Programme Committee for DPW-4. In considering possible topics for the next workshop, the committee discussed numerous suggestions from members and DPW-3 participants. It was generally agreed to organize around technically focussed topics, emphasizing working level discussions in preference to high-level status reports, and to adhere more closely to objectives than has been achieved to date. It was also agreed that the practice of issuing topic-specific guidance and/or questions to the presenters in each session should be continued. However, more interaction between topic chairs and presenters in advance of the workshop would be valuable to reinforce and encourage close adherence to the guidance, so as to obtain input that is detailed and specific enough to enable indepth discussion and reaching conclusions. It is recognized that such an iterative process would place additional burden on the topic chairs and contributors but could pay dividends in enhancing the quality of the discussions. The Programme Committee may wish to consider this suggestion for future meetings. Preliminary descriptions of the selected topics for DPW-4 are provided here, but going forward it will be up to the TPC to develop more specific discussion questions for each topic and to work closely with presenters in ensuring that their contributions are responsive to the questions. The DPW-4 topics are: 1. Tritium issues: plant-wide, including ex-vessel systems Fusion systems based on the deuterium-tritium (DT) reaction face a wide set of issues associated with the tritium fuel cycle. Tritium self-sufficiency requires that the large quantities consumed (~60 kg per full-power year per gigawatt of fusion power), plus radioactive decay and other losses, must be equaled by production in the breeding blankets. Tritium is extracted from the breeder material outside the fusion core, and recirculated back to the plasma via various fueling systems. Since the plasma is estimated to consume only a few per cent of the tritium introduced into the plasma chamber, the rate of tritium circulation in the fuel cycle can be more than 10 times the rate at which it is being consumed. Safety considerations place rigorous limits on the 12

13 overall plant inventory as well as losses. Because tritium can easily migrate into and through solid materials, highly precise behavior prediction and accounting is required for safe operation and to determine the global breeding ratio needed to ensure self sufficiency. Present estimates of TBR appear marginal against a tritium loss greater than 1-2%. Understanding the behavior of tritium, and controlling its movement with specific material choices, barriers, operating conditions, and extraction is critical. The aim of this session is to identify priorities in tritiumrelated science and technology, considering both issues and research activities to resolve them. 2. Towards a DEMO Physics Basis Plasma physics considerations are fundamental to the design of any DEMO device, affecting such basic choices as machine dimensions, magnetic field strength, plasma heating and sustainment methods, and materials selection. Mechanical and thermal loads to structures and plasma-facing components are derived from design-basis plasma scenarios for both normal operation and transients. The physics basis for DEMO can make use of much of what has been developed for ITER, but the more demanding requirements for fusion energy demonstration will require physics advances beyond ITER. A DEMO will require high-performance plasma scenarios compatible with feasible material solutions and capable of near-continuous operation for many years with minimum interruption. The harsh environment and competition for space with breeding blankets will greatly limit the possibilities for plasma control compared to ITER and present-day machines. The aim of this session will be to identify the main physics advances needed to establish a basis for DEMO, and the research programmes, including ITER itself, needed to realize those advances. 3. DEMO Heating and Current Drive Physics and Technology DEMO plasma control requirements place stringent demands on plasma heating and current drive systems, which must operate continuously and at a higher level of energy efficiency than is currently achieved. The neutron environment and plasma access limitations imposed by breeding and shielding requirements make the task especially challenging. Solutions that have worked well in present-day experiments may not be optimum for DEMO conditions, so there is substantial scope for innovation, of which high-field-side-launch lower hybrid, top-launch electron cyclotron, and helicon waves are examples. Substantial advances in both the technology and physics of heating and current drive are needed and close coupling to physics basis development is essential. The aim of this session will be to identify the main advances needed to establish heating and current drive solutions for DEMO, the research programmes, including ITER and other facilities needed to realize those advances. 4. Special topics The special topics category has been very useful for keeping participants up to date with important developments in DEMO programme planning, and in identifying topics in need of more in-depth treatment in subsequent workshops. Special topics presentations for DPW-4 will be selected in the future by the TPC, however several possibilities discussed at DPW-3 may be considered: Materials design codes and standards (e.g. ASME) and interaction with design activities. This is hampered by a lack of materials irradiation data. Where possible the ITER codes could be considered where the safety classification of DEMO components is comparable to that in ITER. A review of the cyclic softening and brittle materials rules is required. This 13

14 activity needs to be extended. Further progress is expected to be made and can be reported at DPW-4. Functional materials and degradation. Impact of degradation on reactor performance, and readiness assessment of critical functional materials. Multiphysics effects in blankets, including MHD. Important theme but difficult to coordinate topical presentations, because the target subjects are wide. Presentations on these issues should probably be considered for inclusion in technology topics rather than special topics. Safety approach to DEMO; technical risk management and uncertainty propagation. We have had some general presentations on these subjects and any future discussions should become more focused and specific. The subject can include failure modes, standards, etc. Safety from many aspects should be considered. Safety-engineering relationship is of interest. Collaboration between fusion designers and safety specialists is essential. For DPW- 4, a special topics presentation on safety in conjunction with remote maintenance should be considered. Technology and plasma facilities. Goals of support facilities and their contribution to solving the issues for present or near-term machines and DEMO should be considered. (This would be analogous to the DPW-3 discussion of ITER TBM contributions to DEMO blanket development.) The assessment of such facilities will be highly dependent on DEMO definition. Careful consideration should be given to how one should select or group ongoing facilities and programmes, and how best to evaluate them. Tokamak simulator projects being carried out by, e.g., Broader Approach (EU-JA), China, Korea. Perhaps include under the DEMO Physics Topic. Possible collaboration may be discussed. Detached divertor study, integrated approach to the power exhaust. While this topic has been covered by the previous workshops, it may be useful to plan a special topics presentation at DPW-4 to provide an update of progress. DEMO Scenario development Logically falls under DEMO Physics Basis topic. Cost and competiveness. An important issue for fusion and a possible subject for future special topics presentation. 14

15 Appendix A. Workshop Organization Programme Chair: T. Muroga (Japan) Local Chair: X. Gao (China) Topics and Topic Co-chairs 1. Contribution of Integrated Fusion Devices to Closing the Gaps H. Neilson (U.S.A.), E. Surrey (U.K.) 2. In-Vessel Systems and Engineering C. Waldon (U.K.), T. Muroga (Japan) 3. ITER-TBM and Blanket Programmes toward DEMO A. Ibarra (Spain), R. Kurtz (U.S.A.) Mohamed Abdou, U.S.A. Wolfgang Biel, Germany Shishir Deshpande, India Gianfranco Federici, EU-EFDA Andrea Garofalo, U.S.A. Richard Kamendje, IAEA Predhiman Kaw, India Keeman Kim, Korea Richard Kurtz, U.S.A. Technical Programme Committee Local Organizing Committee Boris Kuteev, Russian Federation Gyung-Su Lee, Korea Jiangang Li, China Takeo Muroga (Chair), Japan Hutch Neilson, U.S.A. Elizabeth Surrey, United Kingdom Kenji Tobita, Japan Hartmut Zohm, Germany Xiang Gao (Chair), Shaohua Dong, Nan Shi, Yao Yang, Shoubiao Zhang, Guoqiang Li, Damao Yao, Yuntao Song Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) Hefei, China 15

16 Appendix B. Agenda 3 rd IAEA DEMO Programme Workshop 11-14, May 2015 Shuishang Lecture Hall University of Science and Technology of China (No.96, Jinzhai Road Baohe District, Hefei) Programme Monday, 11 May, :00 Departure at the hotel by the conference shuttle bus Opening 08:45-09:00 Welcome and opening address R. Kamendje, J. Li, T. Muroga Special Session 1 Chair : M. Abdou 09:00-09:30 Y.X. Wan Present Status of CFETR 09:30-10:00 G. Federici Integrated DEMO conceptual design approach in the EU 10:00-10:15 Coffee break Topics 2 : In-vessel Systems Design and Engineering (1) Chair : B. Kuteev 10:15-10:30 C. Waldon and T. Muroga Introduction 10:30-11:00 I. Mazul PFC components development from ITER to DEMO 11:00-11:30 A.E. Costley Diagnostic & control requirements: Their possible impact on device design 11:30-12:00 T. Brown 16

17 12:00-13:00 Lunch 13:00-14:00 Poster Design strategies for high availability: Accommodating in-vessel piping services and auxiliary systems Topics 2 : In-vessel Systems Design and Engineering (2) Chair : K. Kim 14:00-14:30 G.N. Luo W divertor technical development towards DEMO 14:30-15:00 M. Shannon and G. Federici In-vessel system integration towards a coherent European DEMO concept 15:00-15:30 M. Mittwollen and A. Loving Remote handling - Impact on DEMO design and availability 15:30-16:00 Coffee 16:00-16:30 Hiroyasu Tanigawa Fusion structural material development in view of DEMO design requirement 16:30-17:30 Session 2 Wrap-up : C. Waldon and T. Muroga 17:30 Adjourn 18:30-20:30 Reception Tuesday, 12 May, :00 Departure at the hotel by the conference shuttle bus Special Session 2 Chair : G. Federici 08:30-09:00 R. Kasada, H. Yamada, A. Ozaki, Y. Sakamoto, R. Sakamoto, H. Takenaga, T. Tanaka, H. Tanigawa, K. Okano, K. Tobita, K. Ushigusa, O. Kaneko Japanese Joint Core Team report for the establishment of technology bases required for the development of a demonstration fusion reactor 09:00-09:30 S. O hira, K. Ochiai, M. Sugimoto, Y. Okumura, T. Nishitani, K. Ushigusa, J. Knaster, A. Ibarra and R. Heidinger 09:30-09:45 Coffee break Vision of the neutron source for the post BA activities 17