NSTX-U Team Meeting

1. NSTX-U Supported by NSTX-U Team Meeting Culham Sci Ctr U St. Andrews York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Hebrew U Ioffe Inst RRC Kurchatov Inst TRINITI NFRI KAIST POSTECH Seoul National U ASIPP ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep Columbia U CompX General Atomics FIU INL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U ORNL PPPL Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Illinois U Maryland U Rochester U Washington U Wisconsin June 5, 2015

2. NSTX-U Team Meeting Agenda Time: 1:30 ~ 3:00, June 5 (Friday), 2015 Place: B318, PPPL • General Items (10 minutes) M.O. • OH event update (30 minutes) • OH event recovery activity (20 minutes) S.R. • Experimental research operation (15 minutes) S.G. • Program Items (15 minutes) J.M.

3. Safely, Safely, Safely • ES&H Issues (J. Levine) • The need to work safely and carefully during the cleanup and recommissioning process and to use the Lab processes including JHAs to plan and execute work. • • NSTX-U operational preparation activity (e.g., diagnostic installation) requires constant vigilance regarding safety! • • Summer vacation season approaching • - Proper protective clothing if working outdoor (e.g., long sleeve shirts and pants) • - Mindful of summer heat and sun / dehydration and sun screen • - Be safe and have fun!

4. Direct Causes of Arc: Summary S. Gerhardt

5. Upper OH Coil Arrangement Inner TF Conductors Water Connections (8) OH Coil Ground Plane Paint L. Dudek

6. Chronology since the arc event PPPL Review Extent cond PPPL Review causes arc May June 4/24 PPPL Advisory committee External review Root cause analysis (for long-term improvements) Assessment, design, reassembly restart S. Prager

7. Review committee memberships On causes: technical, procedural, process (April 30 – May 13) R. Ellis (chair, ME) ,J. Delooper (best practices), J. Hosea (phys.), C. Neumeyer (EE), M. Bell (phys.) On technical extent of condition (May 13 – May 22) J. Hosea (chair, phys), R. Ellis (ME), N. Greenough (EE), D. Mueller (phys) Root cause analysis (May 4 – July) I. Zatz (chair, ME), J. Lacenere (EE), J. Malsbury (QA), M. Mardenfeld (ME) S. Prager

8. NSTX-U Arc Event External Review (May 28, 2015) External Review Committee Report Committee Members Arnie Kellman (Chair), General Atomics Jim Irby, MIT Plasma Fusion Center Brad Merrill, Idaho National Laboratory George Ganetis, Brookhaven National Laboratory General Comments The committee was impressed with the thorough, high quality effort presented by the team and the larger lab personnel to address the fault event. We believe that they are addressing the right issues, both technically and procedurally. We were also impressed by the extent that they are addressing issues beyond the immediate fault and using this opportunity to improve the system. Gave a strong endorsement of internal reviews and a vote of confidence for the team to repair and restart NSTX-U safely. Get the job done correctly and do not squeeze the research plan (MO)

9. Technical cause: Are the causes for the arc correctly identified and understood? Are there any other likely causes that should be more carefully considered. • Findings: • Committee generally agreed with the finding. But suggested an alternative scenario of previous shots causing insulator damages leading to the final arc event (MO). • The path of the arc did not include any ground fault sensors and therefore the shot was not shutdown for 300 ms, as indicated by the ground fault signals. • However, the committee felt that the proximate cause was the motion of the cable and does not require unequivocal identification of which scenario occurred. The procedural and hardware solutions to prevent the reoccurrence of this or similar event is the same for either scenario. • Recommendation • None

10. 2. Procedural and process causes: Are there procedural or process lapses that contributed to the fault understood? Is the Root Cause Analysis process adequate to identify all the contributing causes? • Recommendations: • The procedure for handling off-normal events including ground faults must be completed prior to restart of testing. This must address the control room conduct of operations including required personnel, the amount of discretion that operations personnel have in continuing a given test campaign, i.e. when can protection systems be bypassed. Operations must stop until a serious fault condition is understood before proceeding. • A systematic check of all installation packages for NSTX-U must be performed with the object of identifying any other field installations and then evaluating whether they were installed properly. This review team should include at least the cognizant engineer and installation technician. • A policy for equipment grounding must be developed. • A Root Cause Analysis must be delivered to the ACC prior to approval of restart of high power test operations.

11. Extend of condition is understood. Combination of Hosea committee, Root Cause Analysis, and recommendation of this review will be adequate to identify and address design and process weaknesses. • Findings: • Grounding (variety of issues - what to ground, how to ground, inspect, and document) • Water Connection redesign (improved HV design) • OH Coaxial Feed (improved HV design, joint integrity, improved strength) • Electrical connections for TF flex connectors (evaluate electrical/thermal measurements of poor joint resistance, improve quality of connection, G10 spacer failure) • PF1A, 1B, 1C Considerations • Bakeout Constraints • Aquapour/epoxy between TF Inner Bundle and OH center stack • Other areas of interest: • Ground fault/loop detector sensitivity lessened by capacitors installed across HHFW transmission line DC breaks • Adequacy of control room displays and associated computers. • Add cameras for real-time viewing of critical machine components.  3. Extent of condition: Is the extent of condition understood? Is the extent of condition process adequate to identify potential design and process weaknesses?

12. Yes. The committee feels that if the hardware design changes outlined are completed properly, that will avoid a recurrence of a similar hardware fault. Procedural changes have been discussed, but not yet developed. These will need to be completed prior to restart of high power operations. 4. Repair and design solution: Are the conceptual designs, repairs, and corrections identified by the NSTX-U team likely to avoid a recurrence of a similar fault? Are there other approaches that would be superior? • Recommendation: • An Impulse test must be performed to fully qualify the OH coil prior to restart. • Additional ground fault sensors should be added to the new OH ground straps , and the signals made part of a quickly acting ground fault relay. The OH preload stack should be grounded properly and sensors added and their signals recorded. • The signals from all ground fault signals should be digitized and made easily displayable by the operations group. • Install Lexan sheets or a similar insulator at the bottom of the machine to make sure that metal objects are not drawn up by the magnetic field into the bus work and connections • Complete implementation of design changes identified by the team. • Properly insulated the water cooling tubes while maintaining the ability to detect water leaks. • Process changes are needed. These are addressed in recommendations in Charge #2.

13. 5. Overall recovery plan: Are the quality and thoroughness of the recovery plans and recent internal reviews adequate? Do you see any areas of concern that are not being addressed? Design changes are adequate. Procedural changes are needed and these have been identified. Procedures need to be prepared. Comment: • Improvement in instrumentation to aid in identification of causes of off-normal events should be addressed. This is true not only for ground faults, but any signals that provide interlocks for serious machine shutdown conditions. • Careful attention must be paid to the recommissioning of the machine after the recovery effort. It may be best to err on rechecking more systems than less since some things may have been inadvertently affected during disassembly. • Assuming design reviews are properly completed, as per normal PPPL procedure, and installation process is carefully reviewed and inspected, the committee believes that the reassembly of the machine can proceed.

14. • 73 action items suggested by the internal and external reviews • 26 main action items combining similar ones together. • 11 main items before CD-4 and the rest are 15 are after CD-4. • There is a hold point (touch point with OFES) before the TF flex bus installation. • External committee wanted to have the root cause analysis feeds into ACC before CD-4. That is the present plan. • The present schedule shows CD-4 to be end of July. We will try out best to start as soon as possible. But we will take necessary time to get the job done correctly. OH arc recovery action items

15. Plan as of May 15 Pre-CD-4 / research operation activities May 2015 June 2015 July 2015 OH Repair ISTP Bakeout Commissioning Research Plasma Operation CD4 OH Fault Boronization Repair complete Bakeout: June 2011- 367 hours (15 days), February 2010 - 472 hours (20 days) Need 3 days to set-up and 2 days to remove Dummy load testing MPTS R&R NBI 1 & 2 MAPP, Fast Mirnov, X-ray, bolometer, plasma TV, VIPS, etc. Boronization, GDCs, gas Injector-4, LITER, SGI, Divertor inj., MGI, CGI, etc. If the commissioning goes well, research operation could start earlier!

16. Present Plan Pre-CD-4 / research operation activities July 2015 August 2015 September 2015 OH Repair ISTP Bakeout Commissioning Research Plasma Operation CD4 Boronization Repair complete Bakeout: June 2011- 367 hours (15 days), February 2010 - 472 hours (20 days) Need 3 days to set-up and 2 days to remove Dummy load testing MPTS R&R NBI 1 & 2 MAPP, Fast Mirnov, X-ray, bolometer, plasma TV, VIPS, etc. Boronization, GDCs, gas Injector-4, LITER, SGI, Divertor inj., MGI, CGI, etc. The CD-4 plasmas can be used to commission diagnostics if ready! You are encouraged to take regular summer vacation during July – August.