NSTX‐U Recovery Project
Review, Status and Plans
R. J. Hawryluk
Presented at FESACFebruary 1, 2017

Outline• Background• Machine Disassembly• Extent of Condition Review• Plans

FESAC 2017

NSTX-U Recovery Project2NSTX‐U will Access New Physics
with 2 Major New Tools:
1. New Central Magnet

2. Tangential 2nd Neutral Beam

Full non-inductive current drive
Higher T, low * from low to high  Not obtained in high-T low-* ST
 Unique regime, study new
essential for any future steady-state ST
transport and stability physics
FESAC 2017

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NSTX‐U Science and Engineering
Accomplishments• Achieved H‐mode on 8th day of 10 weeks of operation• Surpassed magnetic field and pulse‐duration of NSTX
• Identified and corrected dominant error fields• Matched best NSTX H‐mode performance at ~1MA
• Commissioned all magnetic and kinetic profile diagnostics• Initiated turbulent transport studies using BES in L‐mode• New 2nd NBI suppresses Global Alfven Eigenmodes (GAE)• Evidence of hollow fast‐ion profiles from off‐axis NBI• Implemented techniques for controlled plasma shut down,disruption detection, commissioned new tools formitigation• Run ended prematurely due to divertor field coil failure
FESAC 2017

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Prior Issues• NSTX‐U has experienced a series of problems• OH “Arc Flash” incident – April 2015
• Unable to bake inboard divertor PFCs at 350C – Sept 2015
• PF1A Upper Bus Bar incident – May 2016
• Center Stack Passive Structure Issues– May 2016
• Failure of PF1A Upper coil – June 2016

• Each event can be attributed to a variety of Technical andProcedural Causes• PPPL is conducting a broad investigation• Extent of Condition• Extent of CauseFESAC 2017

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Region Where Problems Have Occurred
OH Grounding

PF1B

PF1C

PF1A

Copper Tubes
Horizontal Inboard Divertor
FESAC 2017

NSTX-U Recovery Project6Removal of PF1A Upper CoilPF1AUpperCoil

Centerstack Removed thenCasing Separated from TF bundle

FESAC 2017

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Lower Ceramic Break Removed
Machinedisassemblycompletedenabling
detailed
inspection andrepair

FESAC 2017

NSTX-U Recovery Project9PF1AU Forensic Analysis Overview• Identify locations with issues• Section the coil in ways that do not destroy regions of interest• Do visual, electrical, pressure, and vacuum testing on thesections.
• Followed by inspection of the turn‐to‐turn fault

FESAC 2017

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Coil Was Sectioned Using a Milling Machine
Section Planes Chosen to Avoid
Any Regions of Interest

Detail of an Initial Cut
FESAC 2017

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A Battery of Tests Was Performed on theThree Sections
Electrical Tests

Also vacuum &pressure testingof individualchannels

FESAC 2017

NSTX-U Recovery Project12Videoscope Shows Breach in Cooling ChannelShortedTurns Turns
Regionof Shorted

Section A-B, Layer 3, Row 9 Void Anomaly
Large Voidon ThisTurn13• Dry glass found – not impregnatedFESAC 2017

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Coil Section with Fault Was Split
Between Layers

Concave Side

Convex SideFESAC 2017

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Failure of PF1A Upper Coil• Technical Cause• Turn‐to‐Turn fault, most likely due to poor Vacuum PressureImpregnation (VPI) plus other quality factors leading to turn‐to‐turn insulation breakdown• Procedural Issues• Manufacturability of coil design• Inadequate QA and QC surveillance of manufacturing
process at factory• On‐going investigations currently under way:
• Reviewing VPI with experts in the field• Checking integrity of the conductor
FESAC 2017

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Design Verification & Validation Review
System Design Description (SDD) is Key Element••

DVVR looks for potential gaps in design basis or as‐built configuration
Corrective Action Plan (CAP), derived from the DVVRs, determines path forward

Design Verification and Validation Reviews
Have Started
SystemCentral I&C
Integrated Project Design
Heating Systems:
HHFWNBIMagnets
VV & Int. Hdwe.
Cooling
Power Systems
Test Cell
Vacuum & Fueling
Diagnostics
Bakeout
Realtime Control & Protection

Date
18-Jan24-Jan30-Jan31-Jan7-Feb
14-Febweek of 20-Feb
week of 27-Feb
week of 13-Mar
week of 20-Mar
week of 27-Mar
week of 3-Apr
week of 10-Apr• Dates are preliminary and dependent on reviewer availability

Develop Corrective Action Plan Based on theIssues Identified in DVVR for the Components• The Corrective Action Plan will be reviewed by the external Extentof Condition Committee.

Extent of Condition Review Committee to ReviewCorrective Action PlanFirst Extent of Condition Review in March• First Extent of Condition Review will occur during theweek of March 6th, depending on revieweravailability• Include the results from the magnet and vacuum vessel andinternal hardware DVVRs as well as Integrated Project
Design, Central I&C and Heating Systems.

• Interim report will be submitted to FES end of March• Second Extent of Condition Review upon completionof the DVVRs and Corrective Action PlanRedesign of Failed Coil is Underway• The design of the PF1‐A coil is nearing completion.
• PDR within the next two months• FDR within the next three months• Evaluating different options for coil manufacturing:• PPPL• Industry• Other national laboratory• Evaluating whether other coils should also be rebuilt.

NSTX‐U Recovery is Moving Forward• To ensure reliable and predictable operation in thefuture:• Addressing the issues comprehensively• Taking a deep dive into all systems• Applying a rigorous systems engineering approach• Developing the corrective action plan to define the scopeof the recovery project is the immediate priority.
• Interim report March 31• Final report September 30• Plan will enable reliable and predictable operations!
FESAC 2017

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