Remote Maintenance Topic Summary

Transcription

1 UKAEA - RACE Remote Maintenance Topic Summary Oliver Crofts 5 th IAEA DEMO Programme Workshop Daejeon, Korea 7 th to 10 th May 2018

2 Tokamak architecture RM Strategies must be defined early to drive the tokamak architecture and then influence the component design to minimise risk of redesign Design must satisfy regulations for a nuclear facility Radiation, containment and safety Selection of tokamak architecture options Horizontal maintenance not feasible All DEMO concepts now use vertical maintenance Magnet and overall vessel size difficult and high cost Assess availability requirements and costs Plant requirement document Define maintenance duration Assessment of RM Strategies against requirements Cross-system investigations into strategies: magnets, plasma control, vessel, blankets, divertor Estimate maintenance duration Assess costs, technical risks and recoverability Consider all plant trade-offs together Robust systems engineering approach Maintenance through small ports Better if possible but there are real limits Develop and test handling systems, particularly control system development to understand limits of precision 2 Slim CS JA DEMO EU blanket kinematics

3 Tokamak architecture CFETR study into a more maintenance oriented layout Significant improvement faster and more robust Reliable and rapid crane based lift and transfer to hot cells Further work on umbilical management and rescue Other maintenance or plant risk factors Inspection requirements allow sufficient space in tokamak Increasing maintenance burden during the design Safety and investment protection constraints Life of components Robust rescue options for all credible failure events Cross-system working groups to understand risks and plan mitigation Demountable superconducting coils might be practicable Being considered to improve magnet manufacture and maintenance This would open up potentially huge benefits to maintenance Considerable time and effort required to assess full benefits Standard tools, interfaces and deployment systems CFETR blanket handling Used wherever possible throughout DEMO Reduces variety of pipe connections, tools, mechanical interfaces, deployment systems and tools Reduces cost of design, testing, manufacture and spares Design and test standard systems during DEMO concept design Informs plant layout and component design allowing suitable space for access and operation 3

4 Service joining technology Do we have the service joining technology required for DEMO? Rapid reliable service joining is required to achieve maintenance requirements Drives the layout of blankets, divertors, ports and pipes so feasibility needs to be established ITER and industry are not considering the full range of DEMO requirements Weld tool trials in the EU and JA has produce acceptable laser welds at small wall thickness Development work for ITER and CFETR and from industry will also provide supporting data Further development and testing required Data needed to chose the best weld technology: in-bore/orbital, laser/tig, filler or autogenous Work required to consider: reliability, speed, life of the weld head control of cracks, weld sagging, suppression of fumes and need for backing gas, alignment, gaps, fit tolerance, space required, radiation tolerance Establish feasibility of cutting and welding thick walled pipe up to 30 mm EU DEMO Pipe bore laser welding tool QST pipe weld misalignment test 4

5 Service joining technology Do we have the service joining technology required for DEMO? Further development and testing required NDT is a significant risk with no clear technology for volumetric inspection of welds in DEMO False positives may reject many acceptable joints Anticipate regulatory requirements Ultrasonic inspection (including phased array) and EMAT may be suitable Further development of visual inspection, computer vision and viewing during welding is needed to find a technology that can achieve the requirements considering the environment and the consequence of error Pipe alignment Deploying and aligning the pipes also needs to be understood so that it can inform the design of the plasma facing component interfaces The pipe deployment approach may need to be different for each DEMO concept 5 QST viewing during weld process EU DEMO pipe cuff for alignment and backing gas EU DEMO pipe layout

6 Maintenance support facility Control the cost of supporting maintenance Initial layout and cost estimation for the EU DEMO facility shows it to be a big cost driver Maintenance strategy and component design must minimise the burden on support facility The scale and extent of the cells required to meet the through-put exceed existing hot cell technology Design of diagnostic and other components to be maintained need to consider maintenance Waste management The cost of waste management must be minimised through the sympathetic design of components Waste segregation and size reduction must be conducted in the facility Recycling is vital to reduce waste generation, either in the facility or in a special active facility off-site Further work identified Safety considerations Decontamination options and efficacy Viewing (synthetic / VR)for windowless hot-cells Identification of radiation tolerant electronics Compilation of a radiation tolerance (database) Automation that can accommodate unknowns Standardisation of plant, equipment and operations Development of an end-to-end waste management strategy including waste management and remote recycling 6 EU DEMO Maintenance facility

7 The impact of safety on maintenance What impact can safety have on technologies and strategies? Safety implications can have a large impact on the maintenance strategy and some may be challenging for a regulator, particular issues are: Lifting large components significant distances above containment structures Managing contamination hazard (dust / tritium) Moving confinement barriers for maintenance Impact between components during accidents Investment protection Potential for significant damage to Tokamak during the maintenance phase asset damage, lost availability Investment protection requirements can exceed safety Regulator involvement No regulator involvement until the design is mature Anticipate what could be approved Consider stakeholder requirements Develop a regulatory compliance strategy Limit the risk of significant redesign DEMO designs have broadly similar key safety issues Safety requirements for control systems Robust systems engineering process 7

8 The impact of safety on maintenance What impact can safety have on technologies and strategies? Experience from fusion Benefit from large knowledge base Experience from fission Benefit from large knowledge base Drawback from current fission centred standards and regulators There is a need to develop fusion specific guidance and standards Consider what is required to gain regulator approval 8

9 Intelligent maintenance What benefits may be achieved with automated control techniques? DEMO remote maintenance has a unique conjunction of control challenges Rapid and precise handling of components throughout the complex trajectory Uncertainty in models and measurements - degradation of the payload Limited sensor availability Heavy and flexible payloads Benefits of automated control Not clear what benefits are likely to be realised Has the potential to greatly speed up operations Task optimisation and efficiency multitasking Smart to adapt to changing conditions Work is required to understand what could be achieved and its impact on the DEMO design Work can also be started to develop the technologies, particularly where industry is unlikely to help Development and realisation strategy Understand gaps and uncertainties and what will be developed by industry? How to implement real-time, secure, and reliable interoperability of heterogeneous nodes through the various network technologies How to achieve real-time, secure and reliable interconnection and integration among different networks Establish a simulation platform consisting of heterogeneous simulation systems such as structure, radiation, decay heat, neutron deformation, and heat 9

10 Conclusion Strong requirements driver for availability Remote Maintenance interfaces with other plant systems Complex plant with many conflicting requirements Robust systems engineering process Converge on optimum solution Integration Talking, sharing information Defining traceable requirements Balancing conflicting requirements Rigorous optioneering process Defining and agreeing interfaces 10