1 In-Vessel Coil System Interim Design Review – July 2010 IVC Structural Design Criteria I. Zatz, P. Titus, M. Kalish Presented by P. Heitzenroeder Princeton Plasma Physics Laboratory July 26, 2010

In-Vessel Coil System Interim Design Review – July Overview of SDC-IC Last revision in 2004 [ITER_D_222RHC_V2.0] New revision request was written in 2007 [ITER_D_28Q39F - Draft] applicable to: –Blanket System –Divertor –Fuelling –Ion Cyclotron Heating and Current Drive (H & CD) –Electron Cyclotron H & CD –Neutral Beam H & CD –Lower Hybrid H & CD –Diagnostics & Port Mounted Equipment –Test Blankets But, not in-vessel coils…

In-Vessel Coil System Interim Design Review – July In-Vessel Coils (IVC) SDC-IC meeting in February 2009 recognized that criteria document needs to address IVC’s including Edge Localized Mode (ELM) coils, Vertical Stability (VS) coils and Test Blanket Module (TBM) Correction Coils In addition, it was recognized that there are other related conditions and considerations that need to be considered including: –Categorizing loading uncertainties (especially EM loads, including halo currents) –New materials and joining processes (not yet addressed by the ITER project) –How can analyses and assumptions be validated –Components may not be inspectable or serviceable. –Etc.

In-Vessel Coil System Interim Design Review – July How will the IVC Structural Design Criteria fit in with the existing document? The existing SDC-IC is comprised of: –The main section –Appendix A – Material Design Limit Data –Appendix B – Guidelines for Analysis –Appendix C – Rationale or Justification of the Rules Due to the unique characteristics of IVC’s that do not readily conform with the document as presently configured, the IVC SDC will be Appendix D. –This was agreed at a meeting attended by G. Sannazzaro held ~ September, Applicable criteria and definitions in the main body document will be referenced – Appendix D will focus on exceptions to the main body document that apply to IVC’s.

In-Vessel Coil System Interim Design Review – July How will the IVC Structural Design Criteria be formatted? The IVC SDC will be based primarily on the approach used in the structural design criteria for other machines such as NSTX, TPX and NCSX. These criteria have been in use and evolved for nearly 30 years and are based on the cumulative knowledge of experts in research and industry specifically for fusion devices. Particular emphasis was placed on stress analysis, fatigue analysis, crack growth and initial flaw size limitation, and mechanical limits for insulation materials. –Whereas the present IVC SDC focuses on components operating in an extremely high temperature and radiation environment, the new Appendix D engineering basis will be specific to coils operating at lower temperatures and lower radiation levels compared to those addressed in the present IVC SDC. It is also planned to include specific materials data for the mineral insulated conductors which will be used for the In-Vessel Coils. These data will likely be placed in Appendix A, referencing limits defined in Appendix D.

In-Vessel Coil System Interim Design Review – July Outline of Table of Contents for IVC SDC Appendix D Introduction Structural Criteria –Design Loads (with particular emphasis on EM-related events) –Load Combinations similar to those defined in ITER_D_222QGL_v.3.4, but adjusted for the specifics (such as coil currents during events such as disruptions) of the In-Vessel Coil operating conditions. –Stress Terminology (Tresca based) –Metallic Structural Acceptance Criteria Monotonic stress limits (including ductility, creep, welds, and bolts) Fatigue evaluation including crack growth limitation Structural stability

In-Vessel Coil System Interim Design Review – July Outline of Table of Contents for IVC SDC (cont.) Structural Criteria (continued) –Non-Metallic Structural Acceptance Criteria (Insulation Materials). It is expected that the mineral insulated cables will require specialized treatment due to its unique combination of materials and construction. Compressive stress allowable Tensile strain allowable normal to plane Shear stress allowable In-plane strain allowable Coefficient of friction Radiation limits –Specific coil structural acceptance criteria for special situations not covered by the general criteria –Abandoned coils (i.e, coils that are not actively powered or cooled, but that still must be able to withstand nuclear heating). –Deviations from Criteria

In-Vessel Coil System Interim Design Review – July Unique IVC Issues ITER is NOT experimental in the eyes of the ASN. The IVCs should not be considered as pressure vessels as defined by the ESPN since the operating stresses are much higher than the stresses due to water pressure. IVCs must be designed for high reliability – they cannot be easily serviced or replaced - costs would be high and, once activated, RH would have to be used. –Goal: develop a design that can be considered RH Category 3 (replacement not expected). This design aspect puts an especially difficult burden on fatigue reliability. The IVCs will be utilizing mineral insulated cable for which little or no fatigue data exists. A program is being established that qualifies and tests aspects of IVC coils for which material and geometric data is lacking. –R&D tests on mineral insulated cable are currently underway. A new element of the criteria is water erosion issues. In previous devices, it was relatively easy to limit water velocities and operating lifetimes to levels that avoided flow induced erosion as an issue.

In-Vessel Coil System Interim Design Review – July Unique IVC Issues (cont.) Fatigue calculations will use well developed crack growth methodology. –This will be based on the criteria developed for the NSTX Upgrade.

In-Vessel Coil System Interim Design Review – July IVC Issues (cont.) As defined by the ASME, limit analysis is a special case of plastic analysis in which the material is assumed to be ideally plastic (non-strain hardening) - in limit analysis the equilibrium and flow characteristics at the limit state are used to calculate the collapse load – usual limits on stress intensity need not be satisfied at a specific location if it can be shown by limit analysis that the specified loadings do not exceed two thirds of the lower bound collapse load. The yield strength to be used in these calculations is 1.5Sm. Limit analysis is permitted for IVCs. However, Limit analysis applies to monotonic stress criteria, but the analyses of these coils are predominately driven by fatigue.

In-Vessel Coil System Interim Design Review – July Status of Appendix D Large portions of the document are written. Coordination with the updated main document is necessary. Definition of missing data, especially material properties, will be listed and the appropriate testing programs have been initiated. For other criteria under development, including brazed joints, fast fracture and high temperature rules for multi- layer heterogeneous structures, the consensus is to design by experiment via R&D programs since the available data and knowledge is limited.