NSTX

FAILURE MODES AND EFFECTS ANALYSIS

(FMEA)

> Prepared By: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ C Neumeyer (NSTX Project
> Engineer)
>
> Reviewed By: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ J Chrzanowski (WBS 1)

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ R Wilson (WBS 2)

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ T Stevenson (NBI Project)

> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ L Dudek (WBS 3)
>
> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ R Kaita (WBS 4)
>
> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ S Ramakrishnan (WBS 5)
>
> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ G Oliaro (WBS 6)
>
> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ J Levine (Safety Engineer)

TABLE OF CONTENTS

PREFACE 5

SCOPE 5

SAFETY IMPLICATIONS 6

LIST OF ACRONYMS 8

WBS Element: 1.1 Plasma Facing Components 9

Component: Graphite & Carbon Fiber Composite Tiles 9

Component: Passive Plates 10

Component: Inboard & Outboard Divertors 11

Component: NBI Protective Plates 12

WBS Element: 1.2 Vacuum Vessel & Support Structures 14

Component: Vacuum Vessel 14

Component: Support Structures 15

WBS Element: 1.3 Magnets 17

Component: Outer PF Coils (WBS 1.3.1) 17

Component: Outer TF Coils (WBS 1.3.2) 19

Component: TF Inner Leg Bundle (WBS 1.3.3.1) 21

Component: OH Solenoid (WBS 1.3.3.2) 23

Component: Shaping Coils (PF1a & PF1b) (WBS 1.3.3.3) 26

Component: Center Stack Casing (WBS 1.3.3.4) 28

Component: Water Cooled Flexible Cable Leads 30

WBS Element: 2.1 High Harmonic Fast Wave (HHFW) Radio Frequency (RF)
System 31

WBS Element: 2.2 Coaxial Helicity Injection (CHI ) System 34

WBS Element: 2.3 Electron Cyclotron Heating (ECH) System 36

WBS Element: 2.4 Neutral Beam Injection (NBI) System 38

Component: NBI Duct 39

Component: NBI Vacuum Vessel 41

Component: Beam Line Acceleration System 42

Component: Cryopumping System 44

Component: NBI PLC Local Controller 46

WBS Element: 3.1 Vacuum Pumping System 47

Component: Main Pumping Duct 47

Component: Turbomolecular Pumps (TMP) 49

Component: Roughing Pump Skid 51

Component: Backing Pump Skid 52

Component: N2 Vent Valves 53

Component: Vacuum Pumping System Local I&C 54

Component: Residual Gas Analyzer (RGA) 55

WBS Element: 3.2 Cooling Water System 56

Component: Water Distribution in Test Cell 56

Component: Pumps & Automatic Valves 59

Component: Auxiliary Components 50

Component: Cooling Water Local I&C 61

WBS Element: 3.3 Bakeout System 62

WBS Element: 3.4 Gas Delivery System (GDS) 64

WBS Element: 3.5 Glow Discharge Cleaning (GDC) System 66

WBS Element: 4X Diagnostics 67

Component: Flux Loops 68

Component: Thermocouples 69

WBS Element: 5X Power Systems 70

Component: AC Power Systems (WBS 5.1) 70

Component: AC/DC Power Supply Converters 73

Component: Safety Disconnect Switches 76

Component: DC Current Transducers 80

Component: Rochester Instrument System (RIS) Fault Detector 81

Component: Analog Coil Protection (ACP) 82

Component: Ground Fault Detection 83

Component: Power Supply Real Time Controller 84

Component: Hardwired Control System 86

WBS Element: 6X Central I&C 87

Component: EPICS Process Control System 87

Component: MDS+ Data Acquisition System 88

Component: Safety System 89

WBS Element: Operations 92

#   {#section .unnumbered}

# PREFACE

# 

### SCOPE

This revision of the NSTX FMEA is intended to reflect the configuration
of the NSTX device and facility prior to day 2 (summer 2000) plasma
operations. The FMEAs of certain systems which will not be operated at
the time of day 2 plasma are not detailed herein. The systems
specifically included/excluded from day 2 plasma operations are as
follows:

WBS 11: PFCs -- no exclusions

WBS 12: Vacuum Vessel -- no exclusions

WBS 13: Magnets -- no exclusions

WBS 21: High Harmonic Fast Wave RF System: no exclusions

WBS 22: Coaxial Helicity Injection (CHI) - no exclusions

WBS 23: Electron Cyclotron Heating (ECH) - no exclusions

WBS 24: Neutral Beam Injection (NBI) -- no exclusions

WBS 31: Vacuum Pumping System -- no exclusions

WBS 32: Water Cooling Systems -- no exclusions

WBS 33: Bakeout System -- will be operated up to 150C using water only

WBS 34: Gas Delivery System -- no exclusions

WBS 35: Glow Discharge Cleaning (GDC) - no exclusions

WBS 4X: Diagnostics -- magnetic and thermocouple diagnostics are
included; others are excluded (non-essential)

WBS 5X: Power Systems -- no exclusions

WBS 6X: Central I&C -- no exclusions

NSTX will utilize the auxiliary systems of D-site. The TFTR FSAR
includes FMEAs for these systems, including effects of failures on the
auxiliary systems themselves. For NSTX this document only addresses
failures which impact the NSTX device. Effects of failures on the
auxiliary systems themselves are covered by the TFTR FSAR.

In general, single failure modes are addressed. In some cases, for
failures which would have severe consequences in terms of damage to
hardware or risk to personnel safety, multiple failures are addressed.

### SAFETY IMPLICATIONS

Certain failures can increase the risk of injury to personnel. For any
particular failure, the level of risk of injury to personnel depends on
several factors including:

1\) the nature of the failure

2\) the presence or absence of features which mitigate the effect of the
failure (e.g. redundancy, energy isolating barriers, etc.)

3\) the presence or absence of personnel in the area where the failure
has occurred

4\) the level of training of the personnel

This FMEA addresses 1) and 2) above. Items 3) and 4) relate mainly to
administrative procedures which aim to prevent access to hazardous areas
or to limit access to personnel trained to conduct themselves safely in
potentially hazardous areas. This FMEA *does not* address administrative
procedures.

This FMEA addresses new systems which will exist in the NSTX Test Cell,
as well as other D-site systems whose failure could damage the NSTX
device, or which have been significantly modified for use on NSTX, or
which relate to safe access to the NSTX Test Cell.

This FMEA *does not* address safety issues related to the conduct of
operations throughout the balance of the D-site facility. Considering
that the safety of operations of TFTR was documented and approved via
the TFTR FSAR, and demonstrated to be effective for more than a decade,
it would not add to the safety of NSTX operations to repeat that
analysis herein.

Considering its role in establishing safe access to the NSTX Test Cell,
the Safety Lockout Device (SLD), along with the interface between the
SLD and the power supply system Safety Disconnect Switches (SDS), and
the supervision of operation of the power supply system by the Hardwired
Interlock System (HIS), *these safety related systems have been
addressed herein, even though they have not been changed for NSTX in any
substantial way.* *The SLD and SDS interface remain absolutely
unchanged. The HIS has been modified to reflect the simpler requirements
for NSTX but the TFTR concepts (redundancy, etc.) and actual components
have been fully retained.*

Hot Access is a special mode which allows for the presence of a limited
number of personnel in the NSTX Test Cell during coil energization in
order that they can observe first hand any unexpected behavior. These
persons will each have in their possession a key which locks the HIS in
the Hot Access Mode, preventing simultaneous TF and PF energization (and
the possibility of plasma formation) *using exactly the TFTR HIS
interlocking mechanism*. Compared to an observer outside of the NSTX
Test Cell, these persons will unavoidably be exposed to a higher level
of risk of injury. However, via design of protective shields as well as
administrative procedures to ensure their use, all reasonable measures
will be taken to minimize this risk. *The design of these shields and
the administrative procedures is outside of the scope of this FMEA.
However, it is expected that the design of these shields will be similar
to the design used for TFTR, and it is noted that the ability of NSTX to
emit projectile is considerably less than TFTR, owing to its much lower
magnetic fields.*

#### RECOVERY FROM FAILURES

Associated with each failure is a recovery time and cost. Features of
NSTX which serve to facilitate recovery are as follows:

\- sufficient spare OH coil conductor was purchased such that a new coil
can be wound, if required, while avoiding the 3-4 month delay to obtain
new custom extruded conductor

\- the NSTX PF coil design has inherent modularity (PF2, 3, 4, and 5
consist of "a" and "b" parts, either of which could be disconnected in
case of failure, while energizing the remaining part)

\- the NSTX PF4 coil could serve as a back-up for PF5, in case of a
failure of the latter, without a dramatic impact on the program (the
"dimple" would be present in the plasma shape until such time that the
failed coil was replaced)

\- a limited number (one quadrant) of TF inner legs were purchased such
that the fabrication of a new TF inner leg bundle could begin while
conductors for the remaining quadrants were being extruded, thereby
reducing the recovery time

\- the design of the TF outer legs is such that, in case of failure, new
conductors can be formed from standard bar stock with a slot milled in
the edge.

\- spare parts for one ceramic insulator assembly are in possession;
beyond this the options exist for removing assemblies from TFTR (e.g.
pump or NBI ducts), or having entirely new assemblies fabricated

\- in general, NSTX makes use of a subset of the TFTR equipment (e.g.
power supplies) such that the remaining unused components can serve as
spares or as sources of spare parts

#  

# 

# LIST OF ACRONYMS

  -------- ----------------------------- ------- -----------------------------
  ACP      Analog Coil Protection system NSTX    National Spherical Torus
                                                 Experiment

  B        magnetic field                NTC     NSTX Test Cell

  CHI      Coaxial Helicity Injection    OH      Ohmic Heating

  COE      Chief Operating Engineer      PAUX    Permissive relay for
                                                 Auxiliary Systems

  DCCT     DC Current Transducer         PC Link Power Conversion (power
                                                 supply command data ) Link

  DCPT     DC Potential (voltage)        PF      Poloidal Field
           Transducer                            

  E-stop   Emergency Stop                PFC     Plasma Facing Component

  ECH      Electron Cyclotron Heating    PLC     Programmable Logic Controller

  EIC      (FCPC) Engineer In Charge     PPPL    Princeton Plasma Physics Lab

  EPICS    Experimental Physics          PSRTC   Power Supply Real Time
           Instrumentation & Control             Controller
           System                                

  FCPC     Field Coil Power Conversion   RF      Radio Frequency

  FMEA     Failure Modes & Effects       RGA     Residual Gas Analyzer
           Analysis                              

  HCS      Hardwired Control System (in  RIS     Rochester Instrument System
           FCPC)                                 (fault detector)

  HHFW     High Harmonic Fast Wave       rms     root mean square

  HIS      Hardwired Interlock System    SDS     Safety Disconnect Switch

  HSC      Halmar Signal Conditioner     SLD     Safety Lockout Device

  HVAC     Heating/Ventilating/Air       SOL     Scrape Off Layer
           Conditioning                          

  I        current                       TF      Toroidal Field

  I&C      Instrumentation & Control     TFTR    Tokamak Fusion Test Reactor

  I/O      Input/Output                  TMB     Trimethylboron

  IR       Infra Red                     TMP     Turbo Molecular Pump

  LEC      Liquid Effluent Collection    UPS     Uninterruptable Power System
           tank                                  

  MGD      Master Gate Driver            VPS     Vacuum Pumping System

  NBI      Neutral Beam Injection        WBS     Work Breakdown Structure
  -------- ----------------------------- ------- -----------------------------

#  WBS Element: 1.1 Plasma Facing Components 

## Component: Graphite & Carbon Fiber Composite Tiles 

Function: The PFC (Inner Wall, Inboard Divertor, Outboard Divertor, and
Passive Plate) Tiles comprise the surface which interacts with the
plasma and forms the plasma boundary

  ------------------- ----------------- ----------------- -----------------
  Failure Mode        Effect            Detection         Recovery

  Tile overheating    Impurity influx   Visible camera,   Control plasma
  due to              into plasma,      Infra Red (IR)    shape and Scrape
  misalignment, or    reduced           camera, Residual  Off Layer (SOL)
  plasma misoperation performance       Gas Analyzer      to avoid
  (control system                       (RGA)             localized
  failure, CHI                                            heating, repair
  misoperation, etc.)                                     tile when vacuum
                                                          vessel
                                                          accessible.

  Partial (cracked    Loose tile piece  Visible camera,   Repair tile,
  tile) or complete   will fall down in IR camera         remove broken
  tile detachment     vacuum vessel,    (depending on     piece(s) when
  from mounting       could bridge      effect).          vacuum vessel
  surface/backplate   isolating gap                       accessible.
  due to thermal      (e.g. ceramic                       
  shock and/or eddy   insulator,                          
  currents and        passive plate                       
  electromagnetic     toroidal gap,                       
  forces.             etc.), leading to                   
                      localized                           
                      diversion of                        
                      plasma.                             

  Tile support rail   Loose metallic    Visible camera,   Shutdown, vent
  or T-bar or other   piece will fall   IR camera         vacuum vessel,
  mounting hardware   down in vacuum    (depending on     repair
  detachment from     vessel, could     effect).          
  mounting            bridge isolating                    
  surface/backplate   gap (e.g. ceramic                   
  due to thermal      insulator,                          
  shock and/or eddy   passive plate                       
  currents and        toroidal gap,                       
  electromagnetic     etc.), leading to                   
  forces.             localized                           
                      diversion of                        
                      plasma.                             
  ------------------- ----------------- ----------------- -----------------

# WBS Element: 1.1 Plasma Facing Components 

## Component: Passive Plates 

Function: The Passive Plates provide transient stabilization of the
plasma vertical position, and determine the plasma outboard boundary.

  --------------------- ----------------- ----------------- -----------------
  Failure Mode          Effect            Detection         Recovery

  Loose connections     Electrical arcs,  Visible camera,   Repair when
  leading to excessive  local copper      Infra Red (IR)    vacuum vessel
  contact electrical    melting,          camera, Residual  accessible
  resistance on         excessive         Gas Analyzer      
  toroidal or poloidal  resistance and    (RGA), magnetic   
  segment-to-segment    reduction in      diagnostics       
  jumpers, or saddle    current flow,                       
  jumpers               impurity influx                     
                        into plasma,                        
                        reduced                             
                        performance                         

  Loose connections     Increased thermal Thermocouples, IR Repair when
  leading to excessive  resistance,       camera.           vacuum vessel
  contact thermal       higher plate                        accessible
  resistance on         temperatures                        
  toroidal              during                              
  segment-to-segment    operations, lower                   
  jumpers.              plate                               
                        temperatures                        
                        during bakeout.,                    
                        higher thermal                      
                        gradients, higher                   
                        stresses, reduced                   
                        performance                         

  Mechanical            Misalignment      Visible camera    Shutdown, vent
  deformation/failure   and/or                              vacuum vessel,
  of supports due to    dislocation of                      repair
  eddy currents and     plate structures                    
  electromagnetic       into plasma                         
  forces.               envelope, loss of                   
                        machine                             
                        operability                         

  Cooling circuit leak  Release of heat   Residual Gas      Shutdown, vent
                        exchanger fluid   Analyzer (RGA)    vacuum vessel,
                        into vacuum                         repair, bakeout
                        vessel                              

  See PFC Tile FMEA                                         
  --------------------- ----------------- ----------------- -----------------

#  WBS Element: 1.1 Plasma Facing Components 

## Component: Inboard & Outboard Divertors 

Function: The Inboard & Outboard Divertors provide Scrape Off Layer
(SOL) heat flux and impurity targets for diverted (X-point) plasmas. The
Lower Inboard & Outboard Divertors provide the sink and source for the
CHI current drive.

  --------------------- ----------------- ----------------- -----------------
  Failure Mode          Effect            Detection         Recovery

  Outboard Divertor,    Electrical arcs,  Visible camera,   Repair when
  Loose connections     local copper      Infra Red (IR)    vacuum vessel
  leading to excessive  melting, impurity camera, Residual  accessible
  contact electrical    influx into       Gas Analyzer      
  resistance on         plasma, reduced   (RGA), magnetic   
  plate-to-ring         performance       diagnostics       
  connections.                                              

  Outboard Divertor,    Misalignment      Visible camera    Shutdown, vent
  Mechanical            and/or                              vacuum vessel,
  deformation/failure   dislocation of                      repair
  of supports due to    plate structures                    
  eddy currents and     into plasma                         
  electromagnetic       envelope, loss of                   
  forces.               machine                             
                        operability                         

  Outboard Divertor,    Release of heat   Residual Gas      Shutdown, vent
  Cooling circuit leak  exchanger fluid   Analyzer (RGA)    vacuum vessel,
                        into vacuum                         repair, bakeout
                        vessel                              

  See PFC Tile FMEA                                         
  --------------------- ----------------- ----------------- -----------------

# WBS Element: 1.1 Plasma Facing Components 

# Component: NBI Protective Plates

Function: The Protective Plates consist of an array of graphite tiles
mounted on a structure inside the NSTX vacuum vessel centered about the
midplane at bays H & I. The system is designed to absorb neutral beam
energy that is not absorbed by the plasma.

  ------------------- ----------------- ----------------- -----------------
  Failure Mode        Effect            Detection         Recovery

  Tile overheating    Impurity influx   Visible camera,   Terminate beam
  due to misalignment into plasma,      Infra Red (IR)    operation.
  or non-conventional reduced           camera, Residual  
  beam strike         performance       Gas Analyzer      
                                        (RGA) & Thermal   
                                        couples           

  Partial (cracked    Loose tile piece  Visible camera,   Vent machine &
  tile) or complete   will fall down in IR camera         Repair tile,
  tile detachment     vacuum vessel,    (depending on     remove broken
  from mounting       could bridge      effect).          piece(s) when
  surface/backplate   isolating gap                       vacuum vessel
  due to thermal      (e.g. ceramic                       accessible.
  shock and/or eddy   insulator,                          Consider
  currents and        passive plate                       limitation of
  electromagnetic     toroidal gap,                       beam operation.
  forces.             etc.), leading to                   
                      localized                           
                      diversion of                        
                      plasma.                             

  Tile support rail   Loose metallic    Visible camera,   Shutdown, vent
  or T-bar or other   piece will fall   IR camera         vacuum vessel,
  mounting hardware   down in vacuum    (depending on     repair
  detachment from     vessel, could     effect).          
  mounting            bridge isolating                    
  surface/backplate   gap (e.g. ceramic                   
  due to thermal      insulator,                          
  shock and/or eddy   passive plate                       
  currents and        toroidal gap,                       
  electromagnetic     etc.), leading to                   
  forces.             localized                           
                      diversion of                        
                      plasma.                             

  Loose support       Electrical arcs,  Visible camera,   Repair when
  connections leading local copper      Infra Red (IR)    vacuum vessel
  to excessive        melting,          camera, Residual  accessible
  contact electrical  excessive         Gas Analyzer      
  resistance          resistance and    (RGA),            
                      reduction in                        
                      current flow,                       
                      impurity influx                     
                      into plasma,                        
                      reduced                             
                      performance                         
  ------------------- ----------------- ----------------- -----------------

# WBS Element: 1.1 Plasma Facing Components Component: NBI Protective Plates (con't)

  --------------------- ----------------- ----------------- -----------------
  Failure Mode          Effect            Detection         Recovery

  Loose tile            Increased thermal Thermocouples, IR Repair when
  connections leading   resistance,       camera & thermal  vacuum vessel
  to poor thermal       higher plate      couples           accessible
  contact.              temperatures                        
                        during                              
                        operations, lower                   
                        plate                               
                        temperatures                        
                        during bakeout.,                    
                        higher thermal                      
                        gradients, higher                   
                        stresses, reduced                   
                        performance                         

  Mechanical            Misalignment      Visible camera    Shutdown, vent
  deformation/failure   and/or                              vacuum vessel,
  of supports due to    dislocation of                      repair
  eddy currents and     plate structures                    
  electromagnetic       into plasma                         
  forces.               envelope, loss of                   
                        machine                             
                        operability                         

  Cooling circuit leak  Release of heat   Residual Gas      Shutdown, vent
                        exchanger fluid   Analyzer (RGA)    vacuum vessel,
                        into vacuum                         repair, bakeout
                        vessel                              
  --------------------- ----------------- ----------------- -----------------

# WBS Element: 1.2 Vacuum Vessel & Support Structures 

## Component: Vacuum Vessel 

Function: The vacuum vessel provides the high vacuum environment for
plasma operations.

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Excessive         Misalignment of   Visible Camera,   Shutdown, vent
  deformation of    components (e.g.  Infrared (IR)     vacuum vessel,
  structural        PFCs, RF antenna) camera, magnetic  repair
  materials         mounted on vacuum diagnostics       
                    vessel                              

  Failure of        Leak              Residual Gas      Shutdown, vent
  structural                          Analyzer (RGA),   vacuum vessel,
  materials or                        and Vacuum        repair
  welds                               Pumping System    
                                      pressure gauges   

  Failure of port   "                 "                 Provide temporary
  flange vacuum                                         repair in situ if
  seal connections                                      possible,
                                                        otherwise
                                                        shutdown, vent
                                                        vacuum vessel,
                                                        repair
  ----------------- ----------------- ----------------- -----------------

# WBS Element: 1.2 Vacuum Vessel & Support Structures 

## Component: Support Structures 

Function: The coil support structures provide mechanical support for the
outer PF coils and outer TF coil legs, and provide dielectric breaks
where required (PF5). The vacuum vessel legs support the vacuum vessel
and provide dielectric breaks.

  ------------------ ----------------- ----------------- -----------------
  Failure Mode       Effect            Detection         Recovery

  Failure of coil    Misalignment,     Maintenance       Shutdown, vent
  support structural movement, or      inspection,       vacuum vessel,
  materials or welds dislocation of    magnetic          repair
  due to             outer PF coils or diagnostics,      
  electromagnetic,   outer TF coil     power supply      
  vacuum and/or      legs,             system ground     
  thermal loads      perturbation of   fault detector.   
                     magnetic field                      
                     topology,                           
                     possible                            
                     mechanical damage                   
                     to coil leading                     
                     to coil                             
                     electrical damage                   
                     (ground fault or                    
                     turn to turn                        
                     fault).                             

  Failure of sliding Misalignment      Maintenance       Shutdown, vent
  joint in outer PF  and/or            inspection,       vacuum vessel,
  coil supports      deformation of    magnetic          repair
  (excessive         outer PF coils,   diagnostics,      
  resistance to      perturbation of   power supply      
  sliding motion).   magnetic field    system ground     
                     topology,         fault detector.   
                     possible                            
                     mechanical damage                   
                     to coil leading                     
                     to coil                             
                     electrical damage                   
                     (ground fault or                    
                     turn to turn                        
                     fault).                             
  ------------------ ----------------- ----------------- -----------------

WBS Element: 1.2 Vacuum Vessel & Support Structures Component: Support
Structures (con't)

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Failure of        Excessive stress  Maintenance       Shutdown and
  sliding joint of  in umbrella and   inspection,       repair
  umbrella          vacuum vessel     magnetic          
  structure         during bakeout,   diagnostics.      
  (excessive        possible                            
  resistance to     structural                          
  sliding motion).  deformations,                       
                    failure of welds,                   
                    weakening of                        
                    structure                           

  Failure of        Excessive stress  Monitoring of     Shutdown and
  sliding joint of  in leg and        displacement of   repair
  vacuum vessel leg structure during  vacuum vessel.    
  support           bakeout, possible Maintenance       
  (excessive        structural        inspection.       
  resistance to     deformations,                       
  sliding motion).  failure of welds,                   
                    weakening of                        
                    structure,                          
                    possible                            
                    dislocation of                      
                    vacuum vessel,                      
                    loss of vacuum                      
                    integrity                           

  Failure of        During non-CHI    Maintenance       Shutdown and
  dielectric        operations,       inspection &      repair
  joint(s)          conducting        test, magnetic    
  associated with   electrical loops, diagnostics,      
  outer PF coils    perturbation of   power supply      
  supports or       magnetic field.   system ground and 
  vacuum vessel leg During CHI        overcurrent fault 
  supports          operations, fault detection.        
                    on CHI power                        
                    supply, arcing,                     
                    burning, melting.                   
  ----------------- ----------------- ----------------- -----------------

# WBS Element: 1.3 Magnets 

## Component: Outer PF Coils (WBS 1.3.1) 

Function: The Outer PF Coils contribute the magnetic field topology
required for plasma position and shape control.

  ------------------------ ------------------------ ---------------- -------------
  Failure Mode             Effect                   Detection        Recovery

  Blockage of cooling      Reduction in cooling     Flow switches    Shutdown and
  water circuit            water flow, reduction in which are        flush/clear
                           rate of cooling between  interlocked to   coolant
                           pulses[^1].              prevent power    passage.
                                                    supply operation 

  Leak in cooling water    Depending on extent of   Flow             Shutdown and
  circuit                  leak, reduction in       switches[^2],    repair.
                           cooling water flow,      power supply     
                           possible ground fault    system ground    
                                                    fault detection, 
                                                    visual           
                                                    inspection       

  Delamination/debonding   Possible motion of       None             None
  of turn-to-turn          conductors under load,                    
  insulation               abrasion, eventual                        
                           electrical failure                        

  Electrical failure of    If non-CHI operations,   Power supply     Shutdown,
  groundwall insulation at or CHI operations and    system ground    repair if
  single location[^3]      outer vacuum vessel      fault detector.  possible, or
                           grounded, small leakage                   replace.
                           current to ground                         
                           (limited by high                          
                           resistance grounding),                    
                           and redistribution of                     
                           voltage to ground. If                     
                           CHI operations and outer                  
                           vacuum vessel energized                   
                           by CHI power supply,                      
                           small leakage current                     
                           between CHI and affected                  
                           PF circuit.                               
  ------------------------ ------------------------ ---------------- -------------

WBS Element: 1.3 Magnets Component: Outer PF Coils (con't)

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Electrical        Fault current     Magnetic          Shutdown, repair
  failure of        flow in shorted   diagnostics,      if possible, or
  turn-to-turn      turns, opposite   unusual           replace.
  insulation        to direction of   electrical        
                    normal current    impedance and     
                    flow to oppose    response to power 
                    flux produced by  supply            
                    non-shorted       excitation.       
                    turns, large                        
                    internal                            
                    repulsive forces                    
                    between shorted                     
                    and non-shorted                     
                    turns, arcing,                      
                    burning, and                        
                    melting in region                   
                    of failure,                         
                    possible                            
                    destruction of                      
                    coil.                               

  Loss of contact   Excess joint      Maintenance (bolt Shutdown, repair
  pressure leading  resistance and    torque),          if possible, or
  to excess         heating, arcing,  inspection        replace.
  electrical        melting, if       (temperature      
  contact           lead(s) become    stickers), test   
  resistance and    physically        (joint resistance 
  /or open circuit  disconnected,     measurement);     
  condition under   could be          Magnetic          
  load at coil      displaced from    diagnostics,      
  terminals or coil normal point of   unusual           
  leads             connection,       electrical        
                    possible          impedance and     
                    diversion of      response to power 
                    current into      supply            
                    other metallic    excitation.       
                    path(s), possible                   
                    destruction of                      
                    coil[^4].                           
  ----------------- ----------------- ----------------- -----------------

WBS Element: 1.3 Magnets

## Component: Outer TF Coils (WBS 1.3.2) 

Function: The Outer TF Coils provide the return path for the Inner Leg
TF Bundle

  ------------------------ ------------------------ ---------------- -------------
  Failure Mode             Effect                   Detection        Recovery

  Blockage of cooling      Reduction in cooling     Flow switches    Shutdown and
  water circuit            water flow, reduction in which are        flush/clear
                           rate of cooling between  interlocked to   coolant
                           pulses[^5].              prevent power    passage.
                                                    supply operation 

  Leak in cooling water    Depending on extent of   Flow             Shutdown and
  circuit                  leak, reduction in       switches[^6],    repair.
                           cooling water flow,      power supply     
                           possible ground fault    system ground    
                                                    fault detection, 
                                                    visual           
                                                    inspection       

  Delamination/debonding   Possible motion of       None             None
  of turn-to-turn          conductors under load,                    
  insulation               abrasion, eventual                        
                           electrical failure                        

  Electrical failure of    If non-CHI operations,   Power supply     Shutdown,
  groundwall               or CHI operations and    system ground    repair if
  insulation[^7]           outer vacuum vessel      fault detector.  possible, or
                           grounded, small leakage                   replace.
                           current to ground                         
                           (limited by high                          
                           resistance grounding)                     
                           and redistribution of                     
                           voltage to ground. If                     
                           CHI operations and outer                  
                           vacuum vessel energized                   
                           by CHI power supply,                      
                           small leakage current                     
                           between CHI and TF                        
  ------------------------ ------------------------ ---------------- -------------

WBS Element: 1.3 Magnets Component: Outer TF Coils (con't)

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Electrical        Fault current     Magnetic          Shutdown, repair
  failure of        flow in shorted   diagnostics,      if possible, or
  turn-to-turn      turns, opposite   unusual           replace.
  insulation        to direction of   electrical        
                    normal current    impedance and     
                    flow to oppose    response to power 
                    flux produced by  supply            
                    non-shorted       excitation.       
                    turns, large                        
                    internal                            
                    repulsive forces                    
                    between shorted                     
                    and non-shorted                     
                    turns, arcing,                      
                    burning, and                        
                    melting in region                   
                    of failure,                         
                    possible                            
                    destruction of                      
                    coil.                               

  Loss of contact   Excess joint      Maintenance (bolt Shutdown, repair
  pressure leading  resistance and    torque),          if possible, or
  to excess         heating, arcing,  inspection        replace.
  electrical        melting, if       (temperature      
  contact           lead(s) become    stickers), test   
  resistance and    physically        (joint resistance 
  /or open circuit  disconnected,     measurement);     
  condition under   could be          Magnetic          
  load at coil      displaced from    diagnostics,      
  terminals or coil normal point of   unusual           
  leads             connection,       electrical        
                    possible          impedance and     
                    diversion of      response to power 
                    current into      supply            
                    other metallic    excitation.       
                    path(s), possible                   
                    destruction of                      
                    coil[^8].                           
  ----------------- ----------------- ----------------- -----------------

WBS Element: 1.3 Magnets

## Component: TF Inner Leg Bundle (WBS 1.3.3.1) 

Function: The TF Inner Leg Bundle current forms the toroidal field for
plasma confinement.

  ------------------------ ------------------------- ---------------- -------------
  Failure Mode             Effect                    Detection        Recovery

  Blockage of cooling      Reduction in cooling      Flow switches    Shutdown and
  water circuit            water flow in blocked     which are        flush/clear
                           paths, differential       interlocked to   coolant
                           temperature between turns prevent power    passage
                           in bundle, reduction in   supply operation 
                           rate of cooling between                    
                           pulses[^9].                                

  Leak in cooling water    Depending on extent of    Flow             Shutdown and
  circuit                  leak, reduction in        switches[^10],   repair
                           cooling water flow,       power supply     
                           possible ground fault     system ground    
                                                     fault detection, 
                                                     visual           
                                                     inspection       

  Delamination/debonding   Possible motion of        None             None
  of turn-to-turn          conductors under load,                     
  insulation               abrasion, eventual                         
                           electrical failure                         

  Electrical failure of    Small leakage current to  Power supply     Shutdown,
  groundwall               ground (limited by high   system ground    repair if
  insulation[^11]          resistance grounding),    fault detector   possible, or
                           and redistribution of                      replace
                           voltage to ground.                         

  Electrical failure of    Fault current flow in     Magnetic         Shutdown,
  turn-to-turn insulation  shorted turns, opposing   diagnostics,     repair if
                           current flow and flux     unusual          possible, or
                           produced by non-shorted   electrical       replace
                           turns, large internal     impedance and    
                           repulsive forces between  response to      
                           shorted and non-shorted   power supply     
                           turns, arcing, burning,   excitation.      
                           and melting in region of                   
                           failure, possible                          
                           destruction of coil                        
  ------------------------ ------------------------- ---------------- -------------

WBS Element: 1.3 Magnets Component: TF Inner Leg Bundle (con't)

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Loss of           Excess joint      Maintenance (bolt Shutdown and
  structural        resistance and    torque),          repair
  integrity of hub  heating, possible inspection        
  assembly and/or   contact surface   (temperature      
  contact pressure  melting, arcing,  stickers), test   
  on radial flags   could lead to     (joint resistance 
  connecting inner  open circuit      measurement)      
  legs to flexible  condition                           
  connectors                                            

  Loss of contact   Excess joint      Maintenance (bolt Shutdown and
  pressure on       resistance and    torque),          repair
  flexible joints   heating, possible inspection        
  connecting radial contact surface   (temperature      
  flags to outer    melting, arcing,  stickers), test   
  legs              could lead to     (joint resistance 
                    open circuit      measurement)      
                    condition                           
  ----------------- ----------------- ----------------- -----------------

WBS Element: 1.3 Magnets

## Component: OH Solenoid (WBS 1.3.3.2)

Function: The OH Solenoid provides loop voltage for plasma initiation
and flux swing for inductive generation of plasma current

+-----------+-----------------+-----------------+---------------------+
| Failure   | Effect          | Detection       | # Recovery          |
| Mode      |                 |                 |                     |
+-----------+-----------------+-----------------+---------------------+
| Blockage  | Reduction in    | Flow switches   | Monitor cooling     |
| of        | coolant flow    | which are       | water flows and     |
| cooling   | and heat        | interlocked to  | temperatures, and   |
| water     | removal rate    | remove power    | OH coil groundwall  |
| circuit   | between         | supply          | temperatures,       |
| during    | pulses[^14],    | permissive via  | continue operations |
| normal    | reduced         | PAUX relay      | at reduced          |
| ope       | performance     |                 | repetition rate or  |
| rations[^ | (reduced pulse  |                 | discontinue.        |
| 12],[^13] | repetition      |                 | Flush/clear coolant |
|           | rate)           |                 | passage after       |
|           |                 |                 | shutdown.           |
+-----------+-----------------+-----------------+---------------------+
| Blockage  | Reduction in    | Flow switches   | Discontinue heat    |
| of        | coolant flow    | and             | input and/or switch |
| cooling   | and heat        | thermocouples   | to cooling, monitor |
| water     | removal rate,   | measuring       | cooling water flows |
| circuit   | interruption of | temperature of  | and temperatures,   |
| during    | bakeout or      | water returning | and OH coil         |
| bakeout   | reduction in    | to outlet       | groundwall          |
|           | allowable       | manifold,       | temperatures,       |
|           | bakeout         | thermocouples   | continue bakeout at |
|           | temperature     | measuring       | reduced temperature |
|           |                 | temperature of  | or discontinue.     |
|           |                 | OH groundwall   | Flush/clear coolant |
|           |                 | insulation.     | passage after       |
|           |                 |                 | bakeout shutdown.   |
+-----------+-----------------+-----------------+---------------------+
| Leak in   | Depending on    | Flow            | Shutdown and        |
| cooling   | extent of leak, | switches[^15],  | repair.             |
| water     | reduction in    | power supply    |                     |
| circuit   | cooling water   | system ground   |                     |
|           | flow, possible  | fault           |                     |
|           | ground fault    | detection,      |                     |
|           |                 | visual          |                     |
|           |                 | inspection      |                     |
+-----------+-----------------+-----------------+---------------------+

WBS Element: 1.3 Magnets Component: OH Solenoid (con't)

+------------+-----------------+-----------------+-------------------+
| Failure    | Effect          | Detection       | # Recovery        |
| Mode       |                 |                 |                   |
+------------+-----------------+-----------------+-------------------+
| De         | Possible motion | None            | None              |
| lamination | of conductors   |                 |                   |
| /debonding | under load,     |                 |                   |
| of         | abrasion,       |                 |                   |
| tu         | eventual        |                 |                   |
| rn-to-turn | electrical      |                 |                   |
| insulation | failure         |                 |                   |
+------------+-----------------+-----------------+-------------------+
| Electrical | Small leakage   | Power supply    | Shutdown, repair  |
| failure of | current to      | system ground   | if possible, or   |
| groundwall | ground (limited | fault detector. | replace.          |
| insul      | by high         |                 |                   |
| ation[^16] | resistance      |                 |                   |
|            | grounding), and |                 |                   |
|            | redistribution  |                 |                   |
|            | of voltage to   |                 |                   |
|            | ground.         |                 |                   |
+------------+-----------------+-----------------+-------------------+
| Electrical | Fault current   | Magnetic        | Shutdown, repair  |
| failure of | flow in shorted | diagnostics.    | if possible, or   |
| tu         | turns, opposite |                 | replace.          |
| rn-to-turn | to direction of |                 |                   |
| insulation | normal current  |                 |                   |
|            | flow to oppose  |                 |                   |
|            | flux produced   |                 |                   |
|            | by non-shorted  |                 |                   |
|            | turns, large    |                 |                   |
|            | internal        |                 |                   |
|            | repulsive       |                 |                   |
|            | forces between  |                 |                   |
|            | shorted and     |                 |                   |
|            | non-shorted     |                 |                   |
|            | turns, arcing,  |                 |                   |
|            | burning, and    |                 |                   |
|            | melting in      |                 |                   |
|            | region of       |                 |                   |
|            | failure,        |                 |                   |
|            | possible        |                 |                   |
|            | destruction of  |                 |                   |
|            | coil.           |                 |                   |
+------------+-----------------+-----------------+-------------------+

WBS Element: 1.3 Magnets Component: OH Solenoid (con't)

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Mechanical        High resistance,  Excessive coil    Shutdown, remove
  failure of        overheating,      impedance         center stack and
  in-line           arcs, burning,                      OH coil, repair
  conductor[^17] or melting                             if possible, or
  conductor joint                                       replace

  Loss of contact   Excess joint      Maintenance (bolt Shutdown, repair
  pressure leading  resistance and    torque),          if possible, or
  to excess         heating, arcing,  inspection        replace.
  electrical        melting, if       (temperature      
  contact           lead(s) become    stickers), test   
  resistance and    physically        (joint resistance 
  /or open circuit  disconnected,     measurement);     
  condition under   could be          Magnetic          
  load at coil      displaced from    diagnostics,      
  terminals or coil normal point of   unusual           
  leads             connection,       electrical        
                    possible          impedance and     
                    diversion of      response to power 
                    current into      supply            
                    other metallic    excitation.       
                    path(s), possible                   
                    destruction of                      
                    coil[^18].                          
  ----------------- ----------------- ----------------- -----------------

WBS Element: 1.3 Magnets

## Component: Shaping Coils (PF1a & PF1b) (WBS 1.3.3.3) 

Function: PF1a provides plasma shaping. PF1b provides control of the
shape of the X-point for CHI and provides a means for plasma current
Rogowski Loop calibration.

  ------------------------ ------------------------- ---------------- -------------
  Failure Mode             Effect                    Detection        Recovery

  Blockage of cooling      Reduction in cooling      Flow switches    Shutdown and
  water circuit            water flow, reduction in  which are        flush/clear
                           rate of cooling between   interlocked to   coolant
                           pulses[^19].              prevent power    passage.
                                                     supply operation 

  Leak in cooling water    Depending on extent of    Flow             Shutdown and
  circuit                  leak, reduction in        switches[^20],   repair.
                           cooling water flow,       power supply     
                           possible ground fault     system ground    
                                                     fault detection, 
                                                     visual           
                                                     inspection       

  Delamination/debonding   Possible motion of        None             None
  of turn-to-turn          conductors under load,                     
  insulation               abrasion, eventual                         
                           electrical failure                         

  Electrical failure of    Small leakage current to  Power supply     Shutdown,
  groundwall               ground (limited by high   system ground    repair if
  insulation[^21]          resistance grounding),    fault detector.  possible, or
                           and redistribution of                      replace.
                           voltage to ground.                         

  Electrical failure of    Fault current flow in     Magnetic         Shutdown,
  turn-to-turn insulation  shorted turns, opposite   diagnostics.     repair if
                           to direction of normal                     possible, or
                           current flow to oppose                     replace.
                           flux produced by                           
                           non-shorted turns, large                   
                           internal repulsive forces                  
                           between shorted and                        
                           non-shorted turns,                         
                           arcing, burning, and                       
                           melting in region of                       
                           failure, possible                          
                           destruction of coil.                       
  ------------------------ ------------------------- ---------------- -------------

WBS Element: 1.3 Magnets Component: Shaping Coils (PF1a & PF1b) (con't)

  ----------------- ----------------------- --------------- ---------------
  Failure Mode      Effect                  Detection       Recovery

  Loss of contact   Excess joint resistance Maintenance     Shutdown,
  pressure leading  and heating, arcing,    (bolt torque),  repair if
  to excess         melting, if lead(s)     inspection      possible, or
  electrical        become physically       (temperature    replace.
  contact           disconnected, could be  stickers), test 
  resistance and    displaced from normal   (joint          
  /or open circuit  point of connection,    resistance      
  condition under   possible diversion of   measurement);   
  load at coil      current into other      Magnetic        
  terminals or coil metallic path(s),       diagnostics,    
  leads             possible destruction of unusual         
                    coil[^22].              electrical      
                                            impedance and   
                                            response to     
                                            power supply    
                                            excitation.     
  ----------------- ----------------------- --------------- ---------------

WBS Element: 1.3 Magnets

## Component: Center Stack Casing (WBS 1.3.3.4) 

Function: The Center Stack Casing provides the inner vacuum boundary,
and is physically connected to the vacuum vessel but electrically
isolated via ceramic insulator assemblies. The Inner Wall PFCs are
attached to and supported by the Center Stack Casing. Thermal Insulation
within the Center Stack Casing bore serves to thermally isolate the OH
coil from the casing. Pedestal mounted to test cell floor provides
support and dielectric breaks.

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Excessive         Misalignment of   Visible Camera,   Shutdown, vent
  deformation of    PFC components.   Infrared (IR)     vacuum vessel,
  structural                          camera, magnetic  repair
  materials                           diagnostics       

  Failure of        Leak              Residual Gas      Shutdown, vent
  structural                          Analyzer (RGA),   vacuum vessel,
  materials or                        and Vacuum        repair
  welds                               Pumping System    
                                      pressure gauges   

  Failure of vacuum "                 "                 Provide temporary
  seal connections                                      repair in situ if
                                                        possible,
                                                        otherwise
                                                        shutdown, vent
                                                        vacuum vessel,
                                                        repair

  Electrical        During non-CHI    Power supply      Shutdown, vent
  breakdown of      operations,       overcurrent and   vacuum vessel,
  ceramic insulator conducting        ground fault      repair if
                    electrical loops, detection,        possible or
                    perturbation of   Visible Camera,   replace
                    magnetic field.   Infrared (IR)     
                    During CHI        camera, magnetic  
                    operations, fault diagnostics,      
                    on CHI power      Residual Gas      
                    supply, arcing,   Analyzer (RGA),   
                    burning, melting, and Vacuum        
                    possible loss of  Pumping System    
                    vacuum conditions pressure gauges.  
  ----------------- ----------------- ----------------- -----------------

WBS Element: 1.3 Magnets Component: Center Stack Casing (con't)

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Electrical        If during CHI     OH and CHI power  Shutdown, remove
  breakdown of      operations with   systems ground    center stack
  thermal           center stack      fault detection   assembly and OH
  insulation        casing energized, systems.          coil, repair if
                    fault current                       possible or
                    flow through OH                     replace.
                    coil ground plane                   
                    and                                 
                    instrumentation                     
                    mounted thereon,                    
                    arcing, burning,                    
                    melting, possible                   
                    OH ground fault                     
                    and possible                        
                    destruction of OH                   
                    coil.                               

  Degradation of    Low thermal       Thermocouples on  Shutdown, remove
  thermal           resistance        OH and PF1a coil  center stack
  insulation due    between center    ground planes.    assembly and
  abrasion, heat,   stack casing and                    repair
  or coolant leak   OH/PF1a, excess                     
  from coil system  temperature rise                    
  etc.              on OH/PF1a coil                     
                    ground plane,                       
                    reduced                             
                    performance                         
                    (reduced                            
                    repetition rate                     
                    and bakeout                         
                    temperature).                       
  ----------------- ----------------- ----------------- -----------------

WBS Element: 1.3 Magnets

## Component: Water Cooled Flexible Cable Leads 

Function: The Water Cooled Flexible Cable Leads provide the electrical
connection between the terminals of the WBS 5 air cooled bus and the
magnet coil terminals.

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Water leak        Water on floor,   Depending on      Repair or replace
                    depending on      extent of leak,   
                    extent of leak,   flow switch drop  
                    possibly draining out, ground fault 
                    to Liquid         indication on     
                    Effluent          power supply      
                    Collection (LEC)  system ground     
                    tank, possible    fault detector    
                    ground fault,                       
                    small leakage                       
                    current to ground                   
                    limited by high                     
                    impedance                           
                    grounding                           
                    resistors                           

  Electrical        Likely to occur   Water leak and/or Repair or replace
  breakdown of      on one conductor  electrical        
  dielectric        first,            leakage to        
                    accompanied by a  ground, depending 
                    water leak,       on extent of      
                    possible ground   water leak,       
                    fault, small      possible flow     
                    leakage current   switch drop out,  
                    to ground limited possible ground   
                    by high impedance fault indication  
                    grounding         on power supply   
                    resistors, prior  system ground     
                    to developing     fault detector    
                    unnoticed into a                    
                    line-line fault                     
  ----------------- ----------------- ----------------- -----------------

# WBS Element: 2.1 High Harmonic Fast Wave (HHFW) Radio Frequency (RF) System 

Component:

Function: High Harmonic Fast Wave (HHFW) Radio Frequency (RF) System
provides plasma heating and current drive.

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Plasma strike on  Could impress     Plasma TV         Plasma striking
  HHFW antenna      high voltage on                     the antenna loops
  loops             antenna loops                       is prevented by
                                                        Faraday shields

  Faraday shield    Could impress     Plasma TV         In the unlikely
  HHFW antenna loop high voltage on                     event of a
  ablated by severe antenna loops                       Faraday shield
  plasma strike                                         failure, current
                                                        flowing on the
                                                        transmission line
                                                        inner conductor
                                                        is prevented from
                                                        getting out of
                                                        the Test Cell
                                                        area by the
                                                        antenna\'s DC
                                                        breaks

  HHFW antenna\'s   Could impress     Ground fault      Shunted via
  inner conductor   high voltage on   detector, routine chokes between
  DC breaks short   transmission      vacuum vessel     the inner and
  out               line(s) center    Hi-pot            outer conductors
                    conductor(s)                        in the antenna\'s
                                                        Tuning and
                                                        Matching
                                                        components

  HHFW antenna\'s   Could impress     Ground fault      Shunted via
  outer conductor   high voltage on   detector, routine grounding cables
  DC breaks short   transmission      vacuum vessel     connecting
  out               line(s) outer     Hi-pot            transmission
                    conductor(s)                        lines outer
                                                        conductors to
                                                        building steel
                                                        and grounding
                                                        mats along
                                                        lines\' entire
                                                        path

  HHFW RF power     Could direct RF   NSTX Hardwired    HIS monitors the
  transfer switch   power into the    Interlock System  positions of all
  atop the RF       Test Cell         (HIS)             D-Site RF
  Enclosure in the                                      transfer switches
  MockUp Building                                       and imposes RF
  in ENABLED                                            global E-STOP
  (unsafe) position                                     should any switch
  while personnel                                       be in the ENABLED
  are in the Test                                       position during
  Cell                                                  access to the
                                                        NSTX Test Cell.
  ----------------- ----------------- ----------------- -----------------

WBS Element: 2.1 High Harmonic Fast Wave (HHFW) Radio Frequency (RF)
System (con't)

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Mechanical damage Possible RF       Pressure switches The HHFW
  punctures outer   radiation         in transmission   hardwired control
  conductor of HHFW exposure of       lines             system monitors
  transmission line personnel in                        gas pressure in
                    vicinity of                         the transmission
                    puncture                            line. It
                                                        automatically
                                                        prohibits rf
                                                        pulsing should
                                                        the pressure in
                                                        any line drop
                                                        below its set
                                                        point

  HHFW transmission Possible RF       Standard test     RF radiation
  line flange not   radiation         procedure         survey is
  tightened after   exposure of                         performed
  servicing         personnel in                        whenever the
                    vicinity of loose                   transmission
                    flange                              lines are
                                                        serviced. The
                                                        survey is also
                                                        performed
                                                        annually. Any
                                                        leaks are
                                                        immediately
                                                        repaired

  Anode DC-blocking Could impress     High Voltage      Shunted via
  capacitor in HHFW high voltage on   Power Supply      chokes between
  high power        transmission line (HVPS)            the inner and
  amplifier shorts  center conductor  over-current      outer conductors
  out                                 interlocks        in the
                                                        amplifiers\'
                                                        output
                                                        transmission
                                                        lines

  Lightning strike  Could impress     None              In the event that
  or other          high voltage on                     an appreciable
  phenomena that    Control wiring                      difference in
  may cause         from D-Site to                      potential occurs
  difference in     C-Site                              between the
  potential between                                     building steel at
  D-Site and C-Site                                     each Site,
  building steel                                        gas-filled spark
                                                        gaps limit
                                                        \"touch\"
                                                        potential to
                                                        \< 15 volts at
                                                        either end of the
                                                        control wiring.
  ----------------- ----------------- ----------------- -----------------

WBS Element: 2.1 High Harmonic Fast Wave (HHFW) Radio Frequency (RF)
System (con't)

  ----------------- ----------------- ----------------- -------------------
  Failure Mode      Effect            Detection         Recovery

  Unplanned loss of Possible loss of  NSTX Hardwired    A loss of AC power
  AC power at       coordination      Interlock system  at D-Site causes a
  D‑Site            between D-Site RF (HIS) and HHFW    loss in the \"NOT
                    transfer switches local control     E-STOP\" Hardwired
                    and NSTX Test     system            Interlock System
                    Cell access state                   signal to the HHFW
                                                        System. This
                                                        automatically
                                                        precipitates an
                                                        Emergency Stop to
                                                        the HHFW System,
                                                        opening
                                                        [all]{.underline}
                                                        of its high voltage
                                                        power supply
                                                        circuit breakers

  Unplanned loss of Possible thermal  RF PLC            Loss of water in
  water to NTC HHFW stress or failure                   NTC causes RF
  Antenna           to HHFW antenna                     controls to inhibit
                                                        high power RF
                                                        pulsing
  ----------------- ----------------- ----------------- -------------------

# WBS Element: 2.2 Coaxial Helicity Injection (CHI ) System 

Component:

Function: The Coaxial Helicity Injection (CHI) Current Drive System
provides non-inductive plasma current drive by providing a potential
difference between the center stack casing and the outer vacuum and
injecting a current. Components involved are the CHI buswork, the lower
inboard and outboard PFCs (which act as electrodes, see WBS 1.1), the
CHI power supply (see WBS 5) and the lower dome gas injection systems
(see WBS 3.4). Only the buswork is covered in this section. The buswork
is also used to carry current during ohmic heating of the center stack
casing during bakeout operations.

  ----------------- ------------------------ ---------------- ------------
  Failure Mode      Effect                   Detection        Recovery

  Blockage or       Reduction in cooling     Flow switches    Shutdown
  leakage of        water flow in water      which are        normal
  cooling water     circuit involving CHI    interlocked to   operations
  circuit during    and other water cooled   prevent power    and restore
  normal operations cable conductors in same supply           integrity of
                    water circuit, reduction operation,       coolant
                    in rate of cooling,      ground fault     passage.
                    possible ground fault    detection        

  Blockage or       Reduction in cooling     Flow switches    Shutdown
  leakage of        water flow in water      which are        bakeout
  cooling water     circuit involving CHI    interlocked to   operations
  circuit during    and other water cooled   prevent power    and restore
  bakeout           cable conductors in same supply           integrity of
                    water circuit, reduction operation,       coolant
                    in rate of cooling,      visual           passage.
                    possible overheating of  inspection       
                    bus due to latent heat                    
                    from center stack casing                  
  ----------------- ------------------------ ---------------- ------------

#  

# WBS Element: 2.2 Coaxial Helicity Injection (CHI ) System (con't)

# 

  ----------------- ------------------------ ---------------- -----------
  Failure Mode      Effect                   Detection        Recovery

  Electrical        If line to line, CHI     Power supply     Shutdown,
  failure of        power supply short       system           repair if
  insulation        circuit, overcurrent,    overcurrent and  possible,
                    large forces, heating,   ground fault     or replace.
                    arcing, burning; if line detection.       
                    to ground, CHI ground                     
                    fault, small fault                        
                    current, limited heating                  
                    and burning of                            
                    insulation.                               

  Failure of        Possible open circuit,   Improper circuit Shutdown,
  structural        joint resistance         electrical       repair if
  support due to    heating, arcing,         function and/or  possible,
  electromagnetic   melting, possible ground ground fault,    or replace.
  loads during      fault, possible          visual           
  normal operation  diversion of current     inspection of    
                    into other metallic      impending        
                    path(s).                 condition during 
                                             maintenance      
  ----------------- ------------------------ ---------------- -----------

#  

# WBS Element: 2.3 Electron Cyclotron Heating (ECH) System 

Component:

Function: The ECH System provides pre-ionization of the plasma fuel gas
to facilitate avalanche breakdown and inductive current drive by the OH
loop voltage. The ECH power supply and all waveguide/launcher components
are located in the NSTX Test Cell. The input 480V AC circuit breaker is
interlocked with the Hardwired Interlock System and Test Cell access
control.

  ----------------- ------------------- ----------------- -----------------
  Failure Mode      Effect              Detection         Recovery

  Fail to deliver   Loss of             Transient         Troubleshoot and
  RF power on       preionization       digitizer         repair
  receipt of        function, reduced   analysis          
  trigger signal    plasma performance                    
  from central                                            
  control system                                          

  Delivery of RF    If during pulse,    Transient         Troubleshoot and
  power outside     minor deviation     digitizer         repair
  time window of    from expected       analysis, RGA     
  trigger signal    auxiliary heating   analysis          
                    profiles, if                          
                    outside pulse                         
                    window (in vacuum)                    
                    possible                              
                    overheating of                        
                    internal vacuum                       
                    vessel wiring or                      
                    damage to sensitive                   
                    diagnostics                           

  Electrical        If CHI operations   If CHI operations Repair if
  breakdown of DC   with outer vacuum   , power supply    possible or
  break             vessel energized,   ground fault      replace
                    ground fault for    detection.        
                    CHI power supply,   Otherwise,        
                    small fault current detected at time  
                    flow through        of next vacuum    
                    waveguide, arcing,  vessel hipot.     
                    burning, melting.                     
                    Otherwise, ground                     
                    loop eddy currents                    
                    and very minor                        
                    magnetic field                        
                    perturbation.                         
  ----------------- ------------------- ----------------- -----------------

WBS Element: 2.3 Electron Cyclotron Heating (ECH) System (con't)

  ----------------- ------------------- ------------------ ---------------------
  Failure Mode      Effect              Detection          Recovery

  Launcher/window   Depending on leak,  Pressure           Depending on leak
  vacuum leakage    possible            instrumentation,   rate, shutdown, vent
                    interruption of     rate of rise       vacuum vessel, repair
                    operations          measurements       or replace

  RF leakage from   RF energy outside   Periodic RF        Repair
  power supply      waveguide in test   surveys            waveguide/shielding
  enclosure or      cell[^23], possible                    
  waveguide         malfunction of                         
                    nearby electrical                      
                    equipment                              

  Unplanned loss of Possible thermal    RF PLC             Loss of water in NTC
  water to ECH      stress or failure                      causes RF controls to
  source equipment  of ECH klystrons                       remove high voltage
                                                           from ECH klystrons

  Attempted         Possible RF         NSTX Hardwired     HIS monitors status
  energization of   radiation exposure  Interlock System   of the ECH PI 480VAC
  ECH during        of personnel in     (HIS)              and imposes an RF
  personnel access  Test Cell                              global E-STOP should
  in the Test Cell                                         it be ENABLED during
                                                           general personnel
                                                           access in the NSTX
                                                           Test Cell.

  480V AC main      Unable to operate   EPICs Process      De-energize AC input
  input circuit     ECH                 Control            power at higher
  breaker failure                                          level, access NTC,
  to close                                                 troubleshoot and
                                                           repair

  480V AC main      Indication to       HIS "unsafe"       De-energize AC input
  input circuit     Hardwired Interlock indication         power at higher
  breaker failure   System (HIS)                           level, access NTC,
  to open           preventing normal                      troubleshoot and
                    means of access to                     repair
                    NSTX Test Cell                         
                    (NTC)                                  

  Leakage of        Fluid contained in  Maintenance        Repair leak and/or
  Dielectric        collection tray     inspection, or     electrical components
  Fluid[^24] from   with                functional failure 
  HV Tank           hose-connection to  if significant     
                    drum below,         quantity lost      
                    possible electrical                    
                    breakdown if                           
                    significant                            
                    quantity lost                          
  ----------------- ------------------- ------------------ ---------------------

#  

# WBS Element: 2.4 Neutral Beam Injection (NBI) System Component: General

Function: The NBI System provides plasma heating via one TFTR beam line,
consisting of three ion sources, injecting 80keV neutral particles at
5MW, for pulses of 5 second duration, into the NSTX plasma. In addition,
brief (50mS) conditioning pulses are performed between NSTX machine
discharges, without plasma, with the NBI power being deposited on the
protective plates..

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Misoperation of   One or more ion   Physics waveforms Troubleshoot and
  Accel Power       sources fails to                    repair. Depending
  System, or        deliver intended                    on cause of
  Auxiliary Power   power vs. time to                   fault, could
  System, Ion       plasma.                             require access to
  Sources, Beam                                         NTC.
  Line Accelerating                                     
  Systems, or                                           
  Control System,                                       
  *NBI power                                            
  waveform does not                                     
  conform to                                            
  pre-programmed                                        
  request.*                                             

  Misoperation of   Unintended NBI    Physics waveforms Troubleshoot and
  Control System,   power is                            repair.
  *NBI power is     deposited on                        
  injected outside  protective                          
  of normal         plates, possible                    
  intended time     overheating.                        
  interval.*                                            

  Failure of plasma Unintended NBI    Physics waveforms Troubleshoot and
  permissive        power is                            repair.
  interlock, *NBI   deposited on                        
  occurs in absence protective                          
  of plasma.*       plates.[^25]                        
  ----------------- ----------------- ----------------- -----------------

# WBS Element: 2.4 Neutral Beam Injection (NBI) System Component: NBI Duct

Function: The NBI Duct provides a means for connection to the NSTX
vacuum vessel. Equipment consists of the flange connections to vacuum
vessel, bellows assemblies and flanges, Torus Isolation Gate Valve
(TIV), ceramic insulator assembly and flanges (on NSTX side of TIV), and
protective scraper plates to protect the duct wall and TIV from beam
divergence. The TIV provides a vacuum seal for the NBI at atmosphere
with NSTX at vacuum, or vice-versa. Actuation time from open to closed
position, or vice-versa, is 30 seconds.

  ----------------- ----------------- ------------------ -----------------
  Failure Mode      Effect            Detection          Recovery

  Excessive         Depending on      Pressure           Provide temporary
  deformation of    extent, could     instrumentation,   repair in situ if
  structural        involve buckling  rate of rise       possible,
  materials         of duct, and/or   measurements       otherwise
                    vacuum leak,                         shutdown, vent
                    possible                             vacuum vessel,
                    interruption of                      repair
                    operations; in                       
                    case of major                        
                    vacuum leak, will                    
                    result in                            
                    automatic closure                    
                    of TIV.                              

  Failure of        "                 "                  Provide temporary
  structural                                             repair in situ if
  materials or                                           possible,
  welds                                                  otherwise
                                                         shutdown, vent
                                                         vacuum vessel,
                                                         repair

  Failure of vacuum Vacuum leak,      "                  Provide temporary
  seal connections  possible                             repair in situ if
                    interruption of                      possible,
                    operations                           otherwise
                                                         shutdown, vent
                                                         vacuum vessel,
                                                         repair

  Electrical        If CHI            If CHI operations  Depending on
  breakdown of      operations,       , power supply     leakage
  ceramic insulator ground fault for  ground fault       resistance, and
                    CHI power supply, detection.         need to operate
                    small fault       Otherwise,         CHI, shutdown,
                    current, arcing,  detected at time   vent NSTX,
                    burning.          of vacuum vessel   repair.
                    Otherwise, ground hipot.             
                    loop eddy                            
                    currents and very                    
                    minor magnetic                       
                    field                                
                    perturbation.                        
  ----------------- ----------------- ------------------ -----------------

# WBS Element: 2.4 Neutral Beam Injection (NBI) System Component: NBI Duct (con't)

+-----------------+-----------------+-----------------+-----------------+
| Failure Mode    | Effect          | Detection       | Recovery        |
+-----------------+-----------------+-----------------+-----------------+
| TIV Failure to  | Beam pathway to | No "beam ready  | Troubleshoot    |
| Fully Open      | torus is        | to arm"         | and repair,     |
|                 | partially or    |                 | depending on    |
|                 | totally blocked | indication      | failure, could  |
|                 | preventing NBI  |                 | require venting |
|                 | operations.     |                 | NSTX.           |
+-----------------+-----------------+-----------------+-----------------+
| TIV Failure to  | Inability to    | Ion gauges read | Troubleshoot    |
| Fully Close     | seal NB duct    | pressures from  | and repair,     |
|                 | and beam line   | vessel activity | depending on    |
|                 | from NSTX       |                 | failure, could  |
|                 | vacuum vessel.  |                 | require venting |
|                 |                 |                 | NSTX.           |
+-----------------+-----------------+-----------------+-----------------+
| TIV Excess      | "               | Ion gauges read | Troubleshoot    |
| leakage across  |                 | pressures from  | and repair,     |
| valve           |                 | vessel activity | depending on    |
|                 |                 |                 | failure, could  |
|                 |                 |                 | continue        |
|                 |                 |                 | operations via  |
|                 |                 |                 | vacuum pumping  |
|                 |                 |                 | and cryopumping |
|                 |                 |                 | on NBI side of  |
|                 |                 |                 | valve, could    |
|                 |                 |                 | require venting |
|                 |                 |                 | NSTX.           |
+-----------------+-----------------+-----------------+-----------------+
| TIV Excessive   | Very small      | Ion gauges      | Halt TMB        |
| leakage across  | amounts of TMB  | reading         | procedure.      |
| valve during    | may be pumped   | increase during | Cycle/repair    |
| TMB operation   | on cryopanels   | He pre-glow     | valve or        |
|                 | if GDC          | period in TMB   | suspend TMB     |
|                 | extinguishes    | procedure.      | operation.      |
+-----------------+-----------------+-----------------+-----------------+

# WBS Element: 2.4 Neutral Beam Injection (NBI) System Component: NBI Vacuum Vessel

Function: The NBI Vacuum Vessel provides the main vacuum envelope for
the NBI Beam Line Accelerating Systems, and the NBI Cryopumping systems.

  ----------------- ----------------- ------------------ -----------------
  Failure Mode      Effect            Detection          Recovery

  Excessive         Depending on      Pressure           Provide temporary
  deformation of    extent, could     instrumentation,   repair in situ if
  structural        involve buckling  rate of rise       possible,
  materials         of duct, and/or   measurements       otherwise
                    vacuum leak,                         shutdown, vent
                    possible                             vacuum vessel,
                    interruption of                      repair
                    operations; in                       
                    case of major                        
                    vacuum leak, will                    
                    result in                            
                    automatic closure                    
                    of TIV, possible                     
                    fast regeneration                    
                    of cryopumping                       
                    system (see FMEA                     
                    entry for NBI                        
                    Cryopumping                          
                    System).                             

  Failure of        "                 "                  Provide temporary
  structural                                             repair in situ if
  materials or                                           possible,
  welds                                                  otherwise
                                                         shutdown, vent
                                                         vacuum vessel,
                                                         repair

  Failure of vacuum Vacuum leak,      "                  Provide temporary
  seal connections  possible                             repair in situ if
                    interruption of                      possible,
                    operations,                          otherwise
                    possible fast                        shutdown, vent
                    regeneration of                      vacuum vessel,
                    cryopumping                          repair
                    system (see FMEA                     
                    entry for NBI                        
                    Cryopumping                          
                    System).                             
  ----------------- ----------------- ------------------ -----------------

# WBS Element: 2.4 Neutral Beam Injection (NBI) System Component: Beam Line Acceleration System

Function: The Beam Line Accel System consists of the Ion Sources,
Neutralizers, Deflection Magnets, Ion Dumps, Beam Scrapers, and the
Calorimeter, and the associated water cooling system.

  ----------------- ---------------------- -------------- -----------------
  Failure Mode      Effect                 Detection      Recovery

  Incorrect aiming  Impingement of         Thermocouple   Steering
  of beamline       beamline onto duct     monitoring     alignment
  and/or abnormal   scrapers and/or                       
  divergence.       protective plates in                  
                    duct, local                           
                    melting/sputtering of                 
                    metallic surfaces.                    

  Ion Source        Reduced generation of  Source         Troubleshoot and
  filament, arc, or beam current; affected waveforms      repair; if source
  accel grid        power supply shutdown,                hardware failure
  misoperation.     but continued                         involved, repair
                    operation of other ion                or replace
                    sources.                              affected source
                                                          during
                                                          maintenance
                                                          period.

  Neutralizer       Reduced                Ion gauge      Reset bending
  misoperation      neutralization, excess waveform       magnet, repair
                    ion current, mismatch  abnormal, loss beamline if
                    with deflection magnet of beam ready  required
                    current, ions are not  to arm due to  
                    efficiently deflected  magnet power   
                    onto the ion dump but  supply         
                    are sprayed on to the  controller     
                    beam scrapers in the                  
                    beam box and duct,                    
                    local                                 
                    melting/sputtering of                 
                    metallic surfaces.                    

  Ion deflection    Ions are not           Ion gauge      Reset bending
  magnet            efficiently deflected  waveform       magnet, repair
  misoperation      onto the ion dump but  abnormal, loss beamline if
                    are sprayed on to the  of beam ready  required
                    beam scrapers in the   to arm due to  
                    beam box and duct,     magnet power   
                    local                  supply         
                    melting/sputtering of  controller     
                    metallic surfaces.                    

  Loss of water     Low flow and/or high   Flow and       Troubleshoot and
  cooling system to water exit temperature temperature    repair; if beam
  one or more beam  to affected component, interlocks.    line hardware
  line components   NBI shutdown via                      failure involved,
                    interlocks, possible                  repair or replace
                    freezing of water                     affected
                    lines, possible leak                  components during
                    (see next FMEA                        maintenance
                    entry)[^26].                          period.
  ----------------- ---------------------- -------------- -----------------

# WBS Element: 2.4 Neutral Beam Injection (NBI) System Component: Beam Line Accel System (con't)

  ----------------- -------------------- ------------------ -----------------
  Failure Mode      Effect               Detection          Recovery

  Water leak from   Depending on size of Pressure           Repair or replace
  ion source, ion   leak, vacuum vessel  instrumentation,   component(s)
  dump,             pressure rise;       rate of rise       during
  calorimeter, beam shutdown of water    measurements       maintenance
  scraper,          system;, water                          period.
  neutralizer, or   condensation on                         
  deflection        cryopanels;                             
  magnet.           cryopumping system                      
                    shutdown; possible                      
                    fast regeneration of                    
                    cryopumping system                      
                    (see FMEA entry for                     
                    NBI Cryopumping                         
                    System);possible                        
                    closure of TIV,                         
                    possible opening of                     
                    pressure relief                         
                    valve; discharge of                     
                    water into local                        
                    containers.                             

  SF~6~ leak in NTC SF6 detectors sound  SF6 detectors      Shutdown NBI
  or NBI Power      alarm and close                         operations and
  Conversion        valves on SF6 supply                    repair leak.
  Building[^27]     skid, small quantity                    
                    of SF6 released.                        

  SF~6~ leak into   Ion source           Poor base          Repair or replace
  ion source.       misoperation and     pressure, rate of  affected ion
                    shutdown; possible   rise in source     source during
                    closing of source    during regens,     maintenance
                    isolation valve. If  poor source        period
                    valve remains open,  performance        
                    SF~6~ is trapped on                     
                    cryopanels and                          
                    subsequently pumped                     
                    from machine when                       
                    panels are                              
                    regenerated. If                         
                    valve closes, gas is                    
                    pumped out via                          
                    source roughing                         
                    system.                                 

  Calorimeter       Beam pathway to      No ready to arm,   Troubleshoot and
  failure to raise  torus is partially   no beam            repair; if
                    or totally blocked                      necessary repair
                    preventing NBI                          or replace
                    operations.                             affected assembly
                                                            during
                                                            maintenance
                                                            period via
                                                            venting of NBI
                                                            vacuum vessel.
  ----------------- -------------------- ------------------ -----------------

#  WBS Element: 2.4 Neutral Beam Injection (NBI) System Component: Beam Line Accel System (con't)

  ----------------- -------------------- -------------- -----------------
  Failure Mode      Effect               Detection      Recovery

  Calorimeter       Inability to perform No ready to    Troubleshoot and
  failure to lower  beam power           arm, no beam   repair; if
                    calibration shots.                  necessary repair
                                                        or replace
                                                        affected assembly
                                                        during
                                                        maintenance
                                                        period via
                                                        venting of NBI
                                                        vacuum vessel.
  ----------------- -------------------- -------------- -----------------

# WBS Element: 2.4 Neutral Beam Injection (NBI) System Component: Cryopumping System

Function: The cryopumping system assists the active pumping systems to
maintain high vacuum in the NBI vacuum vessel and duct, and the NSTX
vacuum vessel, via cryocondensation on to liquid helium (LHe) cooled
panels guarded by liquid nitrogen (LN~2~) cooled panels. System consists
of the LHe and LN refrigeration systems, piping systems, and cryopanels
in the NBI vacuum vessel.

  ------------------ ---------------------- -------------- ---------------
  Failure Mode       Effect                 Detection      Recovery

  Cryopumping        Depending on           Operator       Operator
  system, cryogen    nature/extent of       annunciated    adjustments,
  supply low flow or reduction in supply,   fault          repair
  high inlet         reduction in           condition by   refrigerator.
  temperature.       cryopumping            PLC, security, 
                     effectiveness;         and procedural 
                     possible NBI shutdown; phone calls to 
                     possible regeneration  cog engineer   
                     (boil off) of absorbed                
                     gases (exhausted by                   
                     vacuum pumping                        
                     systems); possible                    
                     fast regeneration of                  
                     cryopumping system                    
                     (see FMEA below).                     

  Fast regeneration  Rupture of pressure    Operator       Operator
  of Cryopumping     relief (burst) disks   annunciated    adjustments,
  System.            external to NBI vacuum fault          repair
                     vessel box, inside     condition by   refrigerator.
                     NTC; cryogen supply    PLC, security, 
                     valves will close;     and procedural 
                     cryogenic vapors will  phone calls to 
                     be released into NTC;  cog engineer   
                     boil-off of condensed                 
                     gases from cryopanels,                
                     will be released to                   
                     vacuum vessel and                     
                     exhausted by vacuum                   
                     pumping system; NBI                   
                     TIV will close.                       
  ------------------ ---------------------- -------------- ---------------

#  

# WBS Element: 2.4 Neutral Beam Injection (NBI) System Component: Cryopumping System (con't)

  ------------------ ---------------------- --------------- ---------------
  Failure Mode       Effect                 Detection       Recovery

  High H             Potential explosion    Vacuum gauge    Pump out lines
  concentration in   hazard[^28]            reading during  
  pumping exhaust                           regenerations   
  during                                                    
  regeneration                                              

  Cryogenic line     Potential explosion    Loss of thermal Pump out lines
  inward leakage to  hazard.                resistance of   
  vacuum jacketed                           jacket, excess  
  supply lines and                          temperature     
  condensation of                           rise of         
  oxygen[^29]                               cryogens.       

  Cryogenic line     Release of cryogenic   Plumes          Repair lines
  rupture external   fluid and vapor into                   
  to NBI vacuum      NTC, cryogen supply                    
  vessel.            valves will close, NBI                 
                     TIV will close, fast                   
                     regeneration will                      
                     occur (see prior FMEA                  
                     entry).                                

  Cryogenic line     Release of cryogenic   Ion gauge       Vent beamline,
  rupture internal   fluid and vapor into                   repair leak, or
  to NBI vacuum      NBI vacuum vessel,                     replace
  vessel.            cryogen supply valves                  beamline cryo
                     will close, NBI TIV                    panels
                     will close, fast                       
                     regeneration will                      
                     occur (see prior FMEA                  
                     entry).                                
  ------------------ ---------------------- --------------- ---------------

WBS Element: 2.4 Neutral Beam Injection (NBI) System Component: Local
PLC Controller

###### Function: Provides PLC based operator interface and interlocks for NBI equipment protection

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Loss of PLC       Shutdown of NBI,  Status signals to Troubleshoot and
  functionality     all power supply  EPICS Process     repair
                    systems, valves   Control System    
                    and pumps revert  and PLC monitor   
                    to safe state,                      
                    interruption of                     
                    machine                             
                    operations                          

  PLC I/O failure   Loss of           PLC logic         Troubleshoot and
                    action/reaction                     repair
                    confirmation, PLC                   
                    alarm condition                     
  ----------------- ----------------- ----------------- -----------------

# 

#  

# 

# WBS Element: 3.1 Vacuum Pumping System 

## Component: Main Pumping Duct 

Function: The main pumping duct, consisting of flange connection to
vacuum vessel, bellows assembly and flanges, ceramic insulator assembly
and flanges, as well as tee ducts and flanges for connections to TMP and
Roughing isolation valve assemblies, provides the physical means for
connection of the pumping system to the vacuum vessel, as well as
provision for interface of diagnostics and vacuum pumping I&C (including
the Residual Gas Analyzer (RGA)).

+-----------------+-----------------+-----------------+-----------------+
| Failure Mode    | Effect          | Detection       | #               |
|                 |                 |                 | ###### Recovery |
+-----------------+-----------------+-----------------+-----------------+
| Excessive       | Depending on    | Pressure        | Provide         |
| deformation of  | extent, could   | i               | temporary       |
| structural      | involve         | nstrumentation, | repair in situ  |
| materials       | buckling of     | rate of rise    | if possible,    |
|                 | duct, and/or    | measurements    | otherwise       |
|                 | vacuum leak,    |                 | shutdown, vent  |
|                 | possible        |                 | vacuum vessel,  |
|                 | interruption of |                 | repair          |
|                 | operations      |                 |                 |
+-----------------+-----------------+-----------------+-----------------+
| Failure of      | "               | "               | Provide         |
| structural      |                 |                 | temporary       |
| materials or    |                 |                 | repair in situ  |
| welds           |                 |                 | if possible,    |
|                 |                 |                 | otherwise       |
|                 |                 |                 | shutdown, vent  |
|                 |                 |                 | vacuum vessel,  |
|                 |                 |                 | repair          |
+-----------------+-----------------+-----------------+-----------------+
| Failure of      | Vacuum leak,    | "               | Provide         |
| vacuum seal     | possible        |                 | temporary       |
| connections     | interruption of |                 | repair in situ  |
|                 | operations      |                 | if possible,    |
|                 |                 |                 | otherwise       |
|                 |                 |                 | shutdown, vent  |
|                 |                 |                 | vacuum vessel,  |
|                 |                 |                 | repair          |
+-----------------+-----------------+-----------------+-----------------+
| Electrical      | If CHI          | If CHI          | Shutdown, vent  |
| breakdown of    | operations with | operations ,    | vacuum vessel,  |
| ceramic         | outer vacuum    | power supply    | repair if       |
| insulator       | vessel, ground  | ground fault    | possible or     |
|                 | fault for CHI   | detection.      | replace         |
|                 | power supply,   | Otherwise,      |                 |
|                 | small fault     | detected at     |                 |
|                 | current,        | time of next    |                 |
|                 | arcing,         | vacuum vessel   |                 |
|                 | burning.        | hipot.          |                 |
|                 | Otherwise,      |                 |                 |
|                 | ground loop     |                 |                 |
|                 | eddy currents   |                 |                 |
|                 | and very minor  |                 |                 |
|                 | magnetic field  |                 |                 |
|                 | perturbation.   |                 |                 |
+-----------------+-----------------+-----------------+-----------------+

WBS Element: 3.1 Vacuum Pumping System

## Component: Turbomolecular Pumps (TMP) 

Function: The Turbomolecular Pumps (TMP) and associated duct, bellows,
isolation valve, backing valve, and flange which connects to the main
pumping duct provide the high vacuum pumping of the vacuum vessel.

  ----------------- ----------------- ------------------ -----------------
  Failure Mode      Effect            Detection          Recovery

  Vacuum leak on    Vacuum leak,      Pressure           Provide temporary
  duct side of      possible          instrumentation,   repair in situ if
  isolation valve   interruption of   rate of rise       possible,
                    operations        measurements       otherwise
                                                         shutdown, vent
                                                         vacuum vessel,
                                                         repair

  Vacuum leak on    Vacuum leak,      "                  Close valve,
  pump side of      possible                             repair leak
  isolation valve   interruption of                      
                    operations, or                       
                    reduced pumping                      
                    speed                                

  Isolation valve   Depending on leak Pressure           Depending on leak
  closed, vacuum    rate and state of instrumentation    rate, back fill
  leak across       TMP, possible                        TMP volume with
  isolation valve   interruption of                      He, or shutdown,
  seat              operations                           vent vacuum
                                                         vessel, repair

  Isolation valve   No immediate      PLC logic          Troubleshoot and
  fail to close     effect                               repair in situ if
                                                         possible,
                                                         otherwise
                                                         shutdown, vent
                                                         vacuum vessel,
                                                         repair

  Isolation valve   Reduction in      PLC logic          Troubleshoot and
  fail to open      pumping                              repair in situ if
                    capability,                          possible,
                    reduced                              otherwise
                    performance                          shutdown, vent
                                                         vacuum vessel,
                                                         repair
  ----------------- ----------------- ------------------ -----------------

WBS Element: 3.1 Vacuum Pumping System Component: Turbomolecular Pumps
(con't)

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  TMP failure (fail Reduction in      TMP               Close isolation
  to start, or      pumping           instrumentation   valve, backfill
  trip)             capability,       and/or PLC logic  TMP volume with
                    reduced                             N2, repair
                    performance                         

  TMP foreline      Loss of TMP and   PLC logic         Close all TMP
  valve fail to     reduced pumping                     isolation and
  open              speed and                           backing valves,
                    possible                            repair
                    interruption of                     
                    machine                             
                    operations                          
  ----------------- ----------------- ----------------- -----------------

WBS Element: 3.1 Vacuum Pumping System

## Component: Roughing Pump Skid 

Function: Roughing Pump Skid and associated duct, bellows, isolation
valve, nitrogen vent valve, and flange connect to the main pumping duct
to provide rough pumping of the vacuum vessel. Note: The roughing pump
skid is shared with the NBI system, and is controlled by the NBI PLC.

  ----------------- ----------------- ------------------ -----------------
  Failure Mode      Effect            Detection          Recovery

  Vacuum leak on    Vacuum leak,      Pressure           Provide temporary
  duct side of      possible          instrumentation,   repair in situ if
  isolation valve   interruption of   rate of rise       possible,
                    operations        measurements       otherwise
                                                         shutdown, vent
                                                         vacuum vessel,
                                                         repair

  Vacuum leak on    "                 "                  Close valve,
  pump side of                                           repair leak
  isolation valve                                        

  Isolation valve   Depending on leak Pressure           Depending on leak
  closed, vacuum    , possible        instrumentation    rate, back fill
  leak across       interruption of                      TMP volume with
  isolation valve   operations                           He, or shutdown,
  seat                                                   vent vacuum
                                                         vessel, repair

  Isolation valve   Rough pumping not PLC logic          Troubleshoot and
  fail to open      available, pump                      repair
                    down and machine                     
                    operations                           
                    precluded                            

  Isolation valve   Transition from   PLC logic          Troubleshoot and
  fail to close     rough pumping to                     repair
                    high vacuum                          
                    pumping not                          
                    possible, machine                    
                    operations                           
                    precluded                            
  ----------------- ----------------- ------------------ -----------------

WBS Element: 3.1 Vacuum Pumping System

## Component: Backing Pump Skid 

Function: Backing Pumps and associated duct, nitrogen vent valve, and
flange connect to the TMPs backing isolation valve to provide low
pressure conditions on back side of TMPs.

  ----------------- ----------------- ------------------ -----------------
  Failure Mode      Effect            Detection          Recovery

  Vacuum leak in    Possible          Pressure           Close TMP backing
  foreline          interruption of   instrumentation,   isolation valve
                    operations        rate of rise       and TMP foreline
                                      measurements       valves, backfill
                                                         TMPs with N2,
                                                         repair leak

  Pump failure      High vacuum       Pressure           Close isolation
  (fail to start,   pumping           instrumentation    valve, backfill
  or trip)          precluded,        and/or PLC logic   TMP volume with
                    interruption of                      N2, repair
                    operations                           

  Backing skid      TMP operations    Pressure           Backfill TMP with
  valve fails to    precluded,        instrumentation    N2 and repair
  open              interruption of   and/or PLC logic   
                    NSTX operations                      
  ----------------- ----------------- ------------------ -----------------

WBS Element: 3.1 Vacuum Pumping System

## Component: N2 Vent Valves 

Function: Provide connections to N2 source for backfilling TMP, Backing,
and Roughing volumes

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  N2 Vent Valve of  Automatic         Pressure          Troubleshoot and
  TMP system leaks  isolation of      instrumentation   repair
  or fails to stay  effected system,  and PLC monitor   
  closed            possible                            
                    interruption of                     
                    operations                          

  N2 Vent Valve of  Automatic         Pressure          Troubleshoot and
  Backing system    isolation of      instrumentation   repair
  leaks or fails to effected system,  and PLC monitor   
  stay closed       possible                            
                    interruption of                     
                    operations                          

  N2 Vent Valve of  Automatic         Pressure          Troubleshoot and
  Roughing system   isolation of      instrumentation   repair
  leaks or fails to effected system,  and PLC monitor   
  stay closed       possible                            
                    interruption of                     
                    operations                          
  ----------------- ----------------- ----------------- -----------------

WBS Element: 3.1 Vacuum Pumping System

## Component: Vacuum Pumping System Local I&C 

Function: Provides PLC based operator interface and interlocks for VPS
equipment protection

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Loss of PLC       Shutdown of VPS,  Status signals to Troubleshoot and
  functionality     all valves and    EPICS Process     repair
                    pumps revert to   Control System    
                    safe state,       and PLC monitor   
                    interruption of                     
                    machine                             
                    operations                          

  PLC I/O failure   Loss of           PLC logic         Troubleshoot and
                    action/reaction                     repair
                    confirmation, PLC                   
                    alarm condition                     
  ----------------- ----------------- ----------------- -----------------

WBS Element: 3.1 Vacuum Pumping System

## Component: Residual Gas Analyzer (RGA) 

Function: Analysis of content of residual gasses.

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Measurement head  Temporary loss of Loss of signal    Revert to
  failure           RGA functionality and status from   installed spare
                                      RGA monitor       measuring head

  RGA monitor       Loss of RGA       Loss of signal    Troubleshoot and
  failure           functionality,    and status from   repair
                    loss of           RGA monitor       
                    information to                      
                    machine operators                   
  ----------------- ----------------- ----------------- -----------------

# WBS Element: 3.2 Cooling Water System 

## Component: Water Distribution in Test Cell 

Function: Distributes water from main manifolds to NSTX coils, coil
leads, and detects loss of flow

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Coil water        Reduction/loss of Depending on      Shutdown and
  circuit leak,     flow to coil;     extent of leak,   repair
  supply side hose  large leak would  flow switch       
                    result in flow    dropout[^30], or  
                    into floor drain  low tank level,   
                    system,           and PLC logic     
                    eventually to     response (loss of 
                    TFTR Liquid       flow removes PAUX 
                    Effluent          permissive from   
                    Collection (LEC)  power supply      
                    tank              system, low tank  
                                      level causes      
                                      operator alarm)   

  Coil water        Large leak would  Depending on      Shutdown and
  circuit leak,     result in flow    extent of leak,   repair
  return side       into floor drain  flow switch       
  hose[^31]         system,           dropout[^32], or  
                    eventually to     low tank level,   
                    TFTR Liquid       and PLC logic     
                    Effluent          response (loss of 
                    Collection (LEC)  flow removes PAUX 
                    tank              permissive from   
                                      power supply      
                                      system, low tank  
                                      level causes      
                                      operator alarm)   

  Coil connection   Small leakage     Depending on      Troubleshoot and
  hose electrical   current to ground failure,          repair
  breakdown         (limited by high  maintenance       
                    resistance        inspection & test 
                    grounding)        (Megger/hipot),   
                                      ground fault      
                                      detected by power 
                                      supply system     
                                      ground fault      
                                      detector          
  ----------------- ----------------- ----------------- -----------------

WBS Element: 3.2 Cooling Water System Component: Water Distribution
(con't)

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Piping water leak Water dripping on Maintenance       Shutdown and
                    floor, possible   inspection, or    repair
                    reduction/loss of low flow switch   
                    flow; large leak  flow, or low tank 
                    would result in   level, and PLC    
                    significant flow  logic response    
                    into floor drain  (loss of flow     
                    system and rapid  removes PAUX      
                    reduction in tank permissive from   
                    level             power supply      
                                      system, low tank  
                                      level causes      
                                      operator alarm)   

  Venturi sensor    Venturi pressure  PLC logic checks  Troubleshoot and
  tubing leak, low  independent of    that all flow     repair
  pressure side     flow, false       switches are      
                    indication of     dropped out prior 
                    flow              to energizing     
                                      pumps (not        
                                      detected until    
                                      pumps are         
                                      de-energized)     

  Venturi sensor    Venturi pressure  PLC logic         Troubleshoot and
  tubing leak, high independent of    response as if    repair
  pressure side     flow, false       low flow (remove  
                    indication of low PAUX permissive   
                    flow              from power supply 
                                      system)           
  ----------------- ----------------- ----------------- -----------------

WBS Element: 3.2 Cooling Water System Component: Water Distribution
(con't)

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Flow switch stuck False indication  PLC logic         Troubleshoot and
  open              of low flow       response (removes repair
                                      PAUX permissive   
                                      from power supply 
                                      system)           

  Flow switch stuck False indication  PLC logic checks  Troubleshoot and
  closed            of adequate flow  that all flow     repair
                                      switches are      
                                      dropped out prior 
                                      to energizing     
                                      pumps (not        
                                      detected until    
                                      pumps are         
                                      de-energized)     
  ----------------- ----------------- ----------------- -----------------

WBS Element: 3.2 Cooling Water System

## Component: Pumps & Automatic Valves 

Function: The Low Pressure Pump provides cooling water flow, the High
Pressure Pump (and redundant back-up unit) boosts the pressure for the
OH coil. The Automatic Supply and Return Valves control the overall
supply of cooling water to the NTC.

+------------+---------------------+---------------+------------------+
| Failure    | # Effect            | Detection     | Recovery         |
| Mode       |                     |               |                  |
+------------+---------------------+---------------+------------------+
| Low        | Loss of coolant     | Flow switch   | Shutdown and     |
| Pressure   | flow to NTC         | measurements, | repair or        |
| Pump       |                     | de-energize   | replace          |
| failure    |                     | PAUX relay to |                  |
|            |                     | power supply  |                  |
|            |                     | system        |                  |
|            |                     | permissives   |                  |
+------------+---------------------+---------------+------------------+
| High       | Loss of OH          | Flow switch   | Switch to        |
| Pressure   | pressure, reduction | measurements, | back-up unit     |
| Pump       | of OH coolant flow  | de-energize   |                  |
| failure    |                     | PAUX relay to |                  |
|            |                     | power supply  |                  |
|            |                     | system        |                  |
|            |                     | permissives   |                  |
+------------+---------------------+---------------+------------------+
| Automatic  | Delivery of coolant | PLC logic     | Troubleshoot and |
| Supply     | to NTC precluded,   |               | repair or        |
| Valve      | PLC logic prevents  |               | shutdown and     |
| failure to | starting of pumps   |               | replace          |
| open       |                     |               |                  |
+------------+---------------------+---------------+------------------+
| Automatic  | Loss of ability to  | PLC logic     | Close manually,  |
| Supply     | isolate NTC water   |               | troubleshoot and |
| Valve      | circuits from pump  |               | repair or        |
| failure to | room, PLC logic     |               | shutdown and     |
| close      | prevents closing of |               | replace          |
|            | Automatic Return    |               |                  |
|            | Valve               |               |                  |
+------------+---------------------+---------------+------------------+
| Automatic  | Delivery of coolant | PLC logic     | Troubleshoot and |
| Return     | to NTC precluded,   |               | repair or        |
| Valve      | PLC logic prevents  |               | shutdown and     |
| failure to | opening of          |               | replace          |
| open       | Automatic Supply    |               |                  |
|            | Valve               |               |                  |
+------------+---------------------+---------------+------------------+
| Automatic  | Loss of ability to  | PLC logic     | Close manually,  |
| Return     | isolate NTC water   |               | troubleshoot and |
| Valve      | circuits from pump  |               | repair or        |
| failure to | room                |               | shutdown and     |
| close      |                     |               | replace          |
+------------+---------------------+---------------+------------------+

WBS Element: 3.2 Cooling Water System

## Component: Auxiliary Components 

Function: The D-site HVAC cooling system provides chilled water for
removing heat from the coil cooling water and the Vacuum Pumping skids.
The Deionizing System maintains high coil cooling water resistivity.
Filters remove particulate from the coil cooling water system. Dew Point
Detection System prevents operation of coils below dew point
temperature.

  ------------- ------------------------- ------------------ --------------
  Failure Mode  Effect                    Detection          Recovery

  D-site HVAC   Loss of chilled water,    Vacuum Pumping     Shutdown and
  cooling       loss of cooling of Vacuum System PLC loss of repair
  system        Pumping System,           cooling water flow 
  failure       interruption of           alarms, Cooling    
                operations                water PLC high     
                                          temperature alarm, 
                                          interlocked with   
                                          PAUX relay to      
                                          power supply       
                                          system permissives 

  De-ionizing   Gradual decrease in       Daily hipot of     Troubleshoot
  System        cooling water             coils prior to     and repair
  failure       resistivity, possibly     energization,      
                leading to ground fault,  power supply       
                small leakage current to  system ground      
                ground                    fault detection    

  Blockage in   Reduced coolant flow,     Pressure drop      Perform
  filters       possibly leading to drop  across filters is  maintenance
                out of flow switches,     monitored by water 
                interruption of           system operators   
                operations                                   

  Dew Point     Inaccurate dew point      PLC logic          Troubleshoot
  Detection     indication, possible      indicating input   and repair
  System        condensation on coils,    out of normal      
  failure       possible ground fault,    range, power       
                small leakage current     supply system      
                (limited by high          ground fault       
                resistance grounding),    detection          
                redistribution of voltage                    
                to ground, Level 1 power                     
                supply fault                                 
                (suppress/bypass)                            
  ------------- ------------------------- ------------------ --------------

WBS Element: 3.2 Cooling Water System

## Component: Cooling Water Local I&C 

Function: PLC system monitors flow switches, valve positions,
temperatures, etc., provides interlocks to ensure proper sequence of
operations and configuration, and provides interlock to Power Supply
System PAUX relay which is required to issue power supply permissive to
energize the coils.

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  Loss of PLC       Interruption of   Status signals to Manually position
  functionality     machine           EPICS Process     all valves and
                    operations, PAUX  Control System    pumps set to safe
                    relay drops out   and drop out of   state,
                    due to loss of    PAUX relay to     troubleshoot and
                    "keep             power supply      repair
                    alive"[^33].      permissive        
                    State of water    interlock         
                    system components                   
                    depends on                          
                    failure scenario,                   
                    all components                      
                    could stay in                       
                    last commanded                      
                    state                               

  PLC I/O failure   Loss of           PLC logic         Troubleshoot and
                    action/reaction                     repair
                    confirmation, PLC                   
                    alarm condition                     
  ----------------- ----------------- ----------------- -----------------

# WBS Element: 3.3 Bakeout System 

Component:

Function: The Bakeout system heats the plasma facing components (PFCs)
and vacuum vessel (VV) to elevated temperatures (350oC and 150oC
respectively) for cleaning, and provides heating and cooling during
operations. The use of the bakeout system for day 2 operations will be
limited to 150C max, with water as the heat exchange fluid.

  ----------------- ----------------- ------------------ -----------------
  Failure Mode      Effect            Detection          Recovery

  Loss of Heater    Loss of heat      Thermocouples on   Troubleshoot and
  Power             input to VV and   NSTX machine       repair
                    PFCs                                 

  Failure of Pump   Loss of heat      Over-temperature   Troubleshoot and
  in High           input to VV and   switch trips off   repair
  Temperature Loop  PFCs              heater             

  Failure of Pump   Loss of heat      Thermocouples on   Shutdown all heat
  in Low            removal from VV   NSTX machine       inputs,
  Temperature Loop  and PFCs                             troubleshoot and
                                                         repair

  Leak in Pipeline  Heat exchange     Residual Gas       Vent VV and
  inside Vacuum     fluid released    Analyzer           repair leak
  Vessel            into VV                              

  Leak in Pipeline  Heat exchange     Expansion tank     Repair leak
  outside Vacuum    fluid released    level detection    
  Vessel            into NSTX Test                       
                    Cell, possible                       
                    injury to                            
                    personnel if in                      
                    contact with hot                     
                    liquid[^34]                          

  Blockage in       Uneven heating    Thermcouples on    If inside, vent
  Pipeline          and/or cooling    NSTX machine and   VV and remove
                                      IR Camera          blockage, if
                                                         outside, remove
                                                         blockage

  Loss of Nitrogen  Expansion Tank    Expansion tank     Repair leak and
  blanket in        level rises       level detection    restore blanket
  Expansion Tank                                         

  Reduction of HVAC Reduction in      Bakeout Skid       Shutdown all heat
  cooling water     cooling           control panel      inputs and
  flow and/or       capability        logic,             restore HVAC
  excess cooling                      Thermocouples on   cooling water
  water temperature                   NSTX machine       supply
  ----------------- ----------------- ------------------ -----------------

# WBS Element: 3.3 Bakeout System (con't)

# 

  ----------------- ------------------ ------------------ -----------------
  Failure Mode      Effect             Detection          Recovery

  Failure of        Temperature not    Over-temperature   Troubleshoot and
  Temperature       per setpoint, if   switch trips off   repair
  Controller        overtemperature,   heater             
                    possible boiling                      
                    of heat exchanger                     
                    fluid, possible                       
                    opening of                            
                    pressure relief                       
                    valve                                 

  Contamination of  Loss of electrical Hipot leakage      Clean
  Dielectric Break  isolation of outer measurements       
  in manifolding    VV                                    

  Electrical        If CHI operations  If CHI operation,  Repair if
  breakdown of      with outer vacuum  power supply       possible or
  Dielectric Break  vessel energized,  ground fault       replace
  in manifolding    ground fault for   detection.         
                    CHI power supply,                     
                    small fault                           
                    current flow                          
                    through                               
                    manifolding to                        
                    ground. Otherwise,                    
                    small ground loop                     
                    eddy currents and                     
                    resultant magnetic                    
                    field                                 
                    perturbation.                         
  ----------------- ------------------ ------------------ -----------------

#  WBS Element: 3.4 Gas Delivery System (GDS) 

Component:

Function: The Gas Delivery System provides storage of gases and delivers
prescribed quantities of same at prescribed rates in pulses which are
synchronized with the NSTX facility clock system. In addition the system
provides vacuum pumping to remove and exhaust residual gases from gas
delivery lines. Control is via the Vacuum Pumping System PLC

  ----------------- ----------------- ----------------- -----------------
  Failure Mode      Effect            Detection         Recovery

  TIV fails to      Inability to      Valve status      Possible need to
  close             isolate pulse     indication on PLC pump out and
                    valve from vacuum                   backfill volume.
                    vessel                              Troubleshoot and
                                                        repair.

  TIV fails to open Inability to      Valve status      Troubleshoot and
                    utilize injector  indication on PLC repair.

  Piezoelectric     Gas delivery from Injection volume  Troubleshoot and
  injection valve   failed valve      and vacuum vessel repair if
  failure to open   precluded,        pressure          possible, or
                    reduced           instrumentation   replace during
                    performance       monitored via PLC vacuum opening

  Piezoelectric     Leakage of gas    Injection volume  Troubleshoot and
  injection valve   from injection    and vacuum vessel repair if
  failure to close, volume into       pressure          possible, or
  or leakage across vacuum vessel,    instrumentation   isolate and
  valve             gas delivery from monitored via PLC evacuate
                    failed valve                        injection volume
                    precluded,                          and replace
                    reduced                             during vacuum
                    performance                         opening
  ----------------- ----------------- ----------------- -----------------

WBS Element: 3.4 Gas Delivery System (con't)

Component:

  ----------------- ----------------- ----------------- -----------------------
  Failure Mode      Effect            Detection         Recovery

  Vacuum pump       Inability to      Vacuum pump       Troubleshoot and repair
  failure           remove residual   status            
                    gases from        indication, line  
                    portions of the   pressure          
                    GDS or gas        instrumentation   
                    injection         monitored by PLC  
                    assembly                            

  Failure of GDS    Inability to      Vacuum pump       Troubleshoot and
  pumpout valve     remove residual   status            repair.
                    gases from        indication, line  
                    portions of the   pressure          
                    GDS or gas        instrumentation   
                    injection         monitored by PLC  
                    assembly                            

  Leakage in GDS    Inability to      Pressure          Troubleshoot and repair
  due to faulty     achieve required  instrumentation   
  welds or leaky    vacuum in gas     monitored via PLC 
  fittings          delivery system                     

  TMB leakage due   TMB leaking into  With handheld gas Close all remotely
  to faulty welds   NTC where TMB     leak detector or  actuated valves.
  or leaky fittings pressure \> atm.  thermal imager,   Attempt to isolate
                    pressure (typ. to or inability to   leak. If safe, wearing
                    Piezoelectric     hold pressure in  SCBA close TMB cylinder
                    valves)           system.           valve.

  Gas cylinder or   Release of gas    Loss of gas       Repair or replace
  supply piping     into NTC[^35]     pressure          
  leak, due to                        monitored via PLC 
  faulty valve or                                       
  fittings                                              

  TMB Gas cylinder  TMB leaking into  With handheld gas Close all remotely
  or supply piping  NTC where TMB     leak detector or  actuated valves.
  leaking due to    pressure \> atm.  thermal imager or Attempt to isolate
  faulty valve or   pressure          inability to hold leak. If safe, wearing
  fittings                            pressure in       SCBA close TMB cylinder
                                      system.           valve.

  Lower Dome Gas    Electrical        Pressure          Repair/replace/adjust
  Injection System, breakdown across  instrumentation   malfunctioning
  excess gas        ceramic, arcing,  monitored via PLC components
  pressure in       burning, melting  and interlocked   
  forelines                           with CHI power    
  involving ceramic                   supply permissive 
  insulator break                                       
  between center                                        
  stack casing and                                      
  ground                                                
  ----------------- ----------------- ----------------- -----------------------

WBS Element: 3.4 Gas Delivery System (con't)

Component:

  ----------------- ----------------- ------------------- -----------------------
  Lower Dome Gas    If not detected,  Pressure            Repair/replace/adjust
  Injection System, excess gas would  instrumentation     malfunctioning
  excess gas        be admitted to    monitored via PLC   components
  prefill pressure  vacuum vessel     and interlocked     
  in injection      leading to        with CHI power      
  reservoir         reduced           supply permissive   
                    dielectric                            
                    strength across                       
                    various ceramic                       
                    insulator gaps                        

  Failure of        Unable to detect  Unable to           Suspend TMB injection.
  Portable Gas Leak TMB in the NTC    calibrate, either   Close all remotely
  Detector for TMB  atmosphere        manually or via     actuated GDS valves.
                                      self-calibration.   Trouble shoot and
                                                          repair. If repair
                                                          infeasible, terminate
                                                          TMB injection.

  Vent stack        Lack of nitrogen  Lack of flow in     Halt NBI or TMB
  nitrogen purge    flow in vent      vent stack          operation as
  fails             stack will lead                       appropriate. Trouble
                    to presence of                        shoot system. Once on
                    air in vent                           line- resume normal
                    stack.                                operation.
                    Possibility of                        
                    fire or explosion                     
                    during TMB                            
                    injection if GDC                      
                    is lost..                             
  ----------------- ----------------- ------------------- -----------------------

#  

# WBS Element: 3.5 Glow Discharge Cleaning (GDC) System 

Component:

Function: GDC provides conditioning of the vacuum vessel and PFCs via
bombardment by particles from a diffuse plasma in helium. Vacuum vessel
and center stack casing will be grounded. The GDC system for 1st plasma
will consist of a retractable probe attached to a portable power supply.

  ------------- ---------------------- ------------------ -----------------
  Failure Mode  Effect                 Detection          Recovery

  Short circuit GDC power supply will  Loss of GDC        Troubleshoot and
  between probe trip on overcurrent.   current as         repair
  and vacuum    No measurable          indicated by GDC   
  vessel        potential rise of      power supply       
                grounded vacuum vessel instrumentation    
                will occur due to                         
                limited current                           
                delivery of GDC power                     
                supply.                                   

  Failure of    GDC power supply will  Loss of GDC        Troubleshoot and
  GDC power     trip on overcurrent.   current as         repair
  supply        No measurable          indicated by GDC   
  current       potential rise of      power supply       
  limiting      grounded vacuum vessel instrumentation    
  resistor      will occur due to                         
                limited current                           
                delivery of GDC power                     
                supply.                                   

  Incorrect     GDC current could      Visible arcing     Increase pressure
  helium        become concentrated                       to reduce arcing
  pressure      and sputter metallic                      and achieve
                impurities onto PFCs                      uniform GDC
                leading to loss of                        
                conditioning                              

  GDC probe     If stuck in retracted  Local probe        Remove actuator,
  stuck         position, unable to    position           bellows
                perform GDC, if in     indication         enclosure,
                extended position,                        withdraw probe,
                unable to resume                          and repair.
                normal NSTX operations                    

  GDC probe     Depending on leak,     Pressure           Withdraw probe,
  vacuum leak   possible interruption  instrumentation,   close torus
                of operations          rate of rise       interface gate
                                       measurements       valve, remove
                                                          probe and repair
  ------------- ---------------------- ------------------ -----------------

#  WBS Element: 3.5 Glow Discharge Cleaning (GDC) System (con't) 

Component:

  ------------- ---------------------- ----------------- -----------------
  Glow stops    TMB does not break     PLC observes low  Restart GDC with
  during TMB    down and deposit on    GDC current and   He and return to
  injection.    surfaces. TMB pumps    automatically     operation. If
                through NSTX vacuum    shuts down TMB    repeated failure
                system. Vent stack     injection.        of system to
                purged with nitrogen,                    maintain GDC,
                so no possibility of                     trouble shoot
                combustion in vent                       system up to and
                stack.                                   including
                                                         aborting TMB
                                                         operation.

  ------------- ---------------------- ----------------- -----------------

#  WBS Element: 4X Diagnostics

Component: Plasma Current Rogowski Coils See Footnote[^36]

Function: Two (2) Plasma Current Rogowski Coils provide redundant
measurements of plasma current

  ------------- ----------------------- ----------------- -----------------
  Failure Mode  Effect                  Detection         Recovery

  Shorted turns Reduced voltage per     Difference        Adjust scaling,
                unit of plasma current  between redundant replace coil if
                derivative              measurements      and when NSTX
                                                          center stack
                                                          removed and
                                                          disassembled

  Open circuit  Loss of signal          Difference        Revert to single
                                        between redundant measurement,
                                        measurements      replace coil if
                                                          and when NSTX
                                                          center stack
                                                          removed and
                                                          disassembled

  Groundwall    Common mode voltage     Noisy signal      Revert to single
  insulation    electrically coupled                      measurement,
  failure to OH into integrator                           replace coil if
  ground plane  circuitry                                 and when NSTX
                                                          center stack
                                                          removed and
                                                          disassembled

  Groundwall    If non-CHI operations   If non-CHI        Revert to single
  insulation    or CHI operations with  operations or CHI measurement,
  failure to    center stack casing     operations with   replace coil if
  center stack  grounded, common mode   center stack      and when NSTX
  casing[^37]   voltage electrically    casing grounded,  center stack
                coupled into integrator noisy signal. If  removed and
                circuitry. If CHI       CHI operations    disassembled
                operations with center  with center stack 
                stack casing energized, casing energized, 
                fault path for CHI      CHI power supply  
                power system, possible  system ground     
                destruction of coil,    fault and/or      
                arcing, burning,        overcurrent       
                melting of leads to     detection         
                integrator rack and/or                    
                integrator circuit                        
                board                                     

  Integrator    Signal error            Difference        Troubleshoot and
  failure                               between redundant repair/replace
                                        measurements      
  ------------- ----------------------- ----------------- -----------------

WBS Element: 4X Diagnostics

## Component: Flux Loops 

Function: Single turn flux loops (redundant pairs, each loop wired to
instrument rack, one instrumented) installed at approx. 50 locations
inside/outside vacuum vessel. Used for plasma control (shape
reconstruction) and calculation of eddy currents in conducting passive
structures.

  ----------------- --------------------- ---------------- -----------------
  Failure Mode      Effect                Detection        Recovery

  Open circuit      Loss of signal        Abnormal         Revert to spare
                                          magnetic         loop, replace
                                          reconstruction   failed loop when
                                                           accessible

  Groundwall        Small common mode     Noisy signal     Revert to spare
  insulation        voltage electrically                   loop, replace
  failure to        coupled into                           failed loop when
  structure at same integrator circuitry                   accessible
  circuit common as                                        
  instrumentation                                          

  Center stack flux If non-CHI operations If non-CHI       Diagnose extent
  loop (around OH   or CHI operations     operations or    of failure and
  coil ground       with center stack     CHI operations   damage, repair
  plane) groundwall casing grounded,      with center      and replace as
  insulation        small common mode     stack casing     required.
  failure to center voltage electrically  grounded, noisy  
  stack casing[^38] coupled into          signal. If CHI   
                    integrator circuitry. operations with  
                    If CHI operations     center stack     
                    with center stack     casing           
                    casing energized,     energized, CHI   
                    fault path for CHI    power supply     
                    power system,         system ground    
                    possible destruction  fault and/or     
                    of loop, arcing,      overcurrent      
                    burning, melting of   detection        
                    leads to integrator                    
                    rack and/or                            
                    integrator circuit                     
                    board                                  

  Integrator        Signal error          Abnormal         Troubleshoot and
  failure                                 magnetic         repair/replace
                                          reconstruction   
  ----------------- --------------------- ---------------- -----------------

WBS Element: 4X Diagnostics

## Component: Thermocouples 

Function: Thermocouples (approx. 50 in vessel, 20 ex-vessel) installed
on PFC backplates, vacuum vessel, center stack casing, and OH groundwall
insulation. In general, toroidal redundancy is provided (for each
poloidal location, several toroidal locations are instrumented).

  ----------------- ----------------------- --------------- -----------------
  Failure Mode      Effect                  Detection       Recovery

  Open circuit or   Loss of signal          Signal outside  Use nearby
  short circuit                             normal range,   thermocouples or
                                            alarm via EPICS others in same
                                            Process Control poloidal location

  Groundwall        Small common mode       Noisy signal    Ignore noisy
  insulation        voltage electrically    during pulse    signal during
  failure to        coupled into monitoring                 pulse
  structure at same circuitry, signal noisy                 
  circuit common as during pulse                            
  instrumentation                                           

  Center stack      If non-CHI operations   If non-CHI      Ignore noisy
  thermocouple      or CHI operations with  operations or   signal during
  (around OH coil   center stack casing     CHI operations  pulse. If
  ground plane)     grounded, small common  with center     failure, diagnose
  groundwall        mode voltage            stack casing    extent of failure
  insulation        electrically coupled    grounded, noisy and damage,
  failure to center into monitoring         signal. If CHI  repair and
  stack casing[^39] circuitry. If CHI       operations with replace as
                    operations with center  center stack    required.
                    stack casing energized, casing          
                    fault path for CHI      energized, CHI  
                    power system, possible  power supply    
                    destruction of          system ground   
                    thermocouple, arcing,   fault and/or    
                    burning, melting of     overcurrent     
                    leads to instrument     detection       
                    rack and/or monitoring                  
                    circuitry board                         

  Monitoring        Signal error            Signal outside  Troubleshoot and
  electronics                               normal range,   repair/replace
  failure                                   alarm via EPICS 
                                            Process Control 
  ----------------- ----------------------- --------------- -----------------

#  WBS Element: 5X Power Systems 

## Component: AC Power Systems (WBS 5.1) 

Function: AC Power Systems receives power from the 138kV utility grid
and supplies all electrical power to the NTSX experiment This includes
Auxiliary (House) AC Power and Experimental AC Power.

+----------------+-----------------------+---------------+------------+
| Failure Mode   | Effect                | Detection     | # Recovery |
+----------------+-----------------------+---------------+------------+
| Loss of 138kV  | Interruption of NSTX  | Various       | Await      |
| AC power to    | operations, Vital     |               | r          |
| PPPL           | loads supplied        |               | estoration |
|                | immediately by UPS    |               | of power   |
|                | power:                |               |            |
|                |                       |               |            |
|                | \- NTC Fire           |               |            |
|                | Protection Panel      |               |            |
|                |                       |               |            |
|                | \- NTC Emergency      |               |            |
|                | Lighting              |               |            |
|                |                       |               |            |
|                | \- HIS                |               |            |
|                |                       |               |            |
|                | Critical loads        |               |            |
|                | supplied by Standby   |               |            |
|                | Diesel Generator      |               |            |
|                | after start up delay  |               |            |
|                | of approximately 10   |               |            |
|                | seconds:              |               |            |
|                |                       |               |            |
|                | \- NTC Cooling Water  |               |            |
|                | Skids & PLC           |               |            |
|                |                       |               |            |
|                | \- NTC Vacuum Pumping |               |            |
|                | Skids & PLC           |               |            |
|                |                       |               |            |
|                | \- NTC Lighting       |               |            |
|                |                       |               |            |
|                | -   NSTX Control Room |               |            |
|                |                       |               |            |
|                | -   NBI Helium        |               |            |
|                |     Refrigeration and |               |            |
|                |     Water Systems     |               |            |
+----------------+-----------------------+---------------+------------+
| Loss of AC     | If pumps, cooling     | PLC and EPICS | Await      |
| power to       | water flow ceases; if | Process       | r          |
| any/all        | automatic valves,     | Control       | estoration |
| components of  | valves remain in last |               | of power   |
| Cooling Water  | position, all valves  |               |            |
| System         | remain manually       |               |            |
|                | operable              |               |            |
+----------------+-----------------------+---------------+------------+

WBS Element: 5X Power Systems Component: AC Power Systems (con't)

+----------------+--------------------+------------------+------------+
| Failure Mode   | Effect             | Detection        | # Recovery |
+----------------+--------------------+------------------+------------+
| Loss of AC     | All components     | PLC and EPICs    | Await      |
| power to       | revert to safe     | Process Control  | r          |
| any/all        | state              |                  | estoration |
| components of  |                    |                  | of power   |
| Vacuum Pumping |                    |                  |            |
| System and Gas |                    |                  |            |
| Delivery       |                    |                  |            |
| System         |                    |                  |            |
+----------------+--------------------+------------------+------------+
| Standby Diesel | All components     | Loss of power    | Await      |
| Generator      | revert to safe     |                  | r          |
| failure during | state. If bakeout  |                  | estoration |
| 138kV utility  | underway[^40],     |                  | of power   |
| outage         | revert to          |                  |            |
|                | alternate 26kV     |                  |            |
|                | line to PPPL or,   |                  |            |
|                | if 26kV not        |                  |            |
|                | available,         |                  |            |
|                | configure cooling  |                  |            |
|                | water system       |                  |            |
|                | valves to          |                  |            |
|                | circulate          |                  |            |
|                | municipal water    |                  |            |
|                | supply through OH  |                  |            |
|                | coil. Loss of      |                  |            |
|                | power to Helium    |                  |            |
|                | Refrigeration      |                  |            |
|                | System;            |                  |            |
|                | regeneration of    |                  |            |
|                | cryopanels,        |                  |            |
|                | possible rupture   |                  |            |
|                | of burst disks,    |                  |            |
|                | possible freezing  |                  |            |
|                | of water cooling   |                  |            |
|                | lines (see NBI     |                  |            |
|                | FMEA).             |                  |            |
+----------------+--------------------+------------------+------------+

WBS Element: 5X Power Systems

## Component: AC/DC Power Supply Converters 

Function: The AC/DC Power Supply Converters (a.k.a. Transrex power
supplies) convert AC power to controlled DC power in the TF, PF, OH, and
CHI circuits.

+----------------+--------------------+------------------+------------+
| Failure Mode   | Effect             | Detection        | # Recovery |
+----------------+--------------------+------------------+------------+
| Thyristors     | Voltage applied to | Power supply     | Tr         |
| failure to     | output terminals,  | fault detector   | oubleshoot |
| block voltage  | unintended flow of | will detect loss | and repair |
| when system    | current in the     | of permissive    |            |
| has been       | coils if SDS line  | during pulse,    |            |
| disarmed       | switches closed    | (internal power  |            |
| (requires that | and SDS ground     | supply Level 1   |            |
| ≥ 2 Master     | switches open.     | faults), and     |            |
| Gate Drivers   | Will result in     | failure to       |            |
| suffer         | Level 1 fault,     | suppress firing  |            |
| spurious       | followed by Level  | (Level 2 fault   |            |
| missfire, or   | 2 fault and AC     | and AC circuit   |            |
| ≥ 4 thyristors | breaker trip       | breaker trip).   |            |
| suffer         |                    |                  |            |
| spurious       |                    |                  |            |
| missfire       |                    |                  |            |
| without MGD    |                    |                  |            |
| pulse). Note:  |                    |                  |            |
| since the      |                    |                  |            |
| permissive     |                    |                  |            |
| relay contacts |                    |                  |            |
| directly       |                    |                  |            |
| disable the    |                    |                  |            |
| MGD optodriver |                    |                  |            |
| boards,        |                    |                  |            |
| control        |                    |                  |            |
| failures       |                    |                  |            |
| (firing        |                    |                  |            |
| generator,     |                    |                  |            |
| Central I&C,   |                    |                  |            |
| etc.) cannot   |                    |                  |            |
| cause this     |                    |                  |            |
| fault.         |                    |                  |            |
+----------------+--------------------+------------------+------------+

WBS Element: 5X Power Systems Component: AC/DC Power Supply Converters
(con't)

+----------------+--------------------+------------------+------------+
| Failure Mode   | Effect             | Detection        | # Recovery |
+----------------+--------------------+------------------+------------+
| Loss of normal | Output voltage     | PSRTC software   | Tr         |
| thyristor gate | waveform not in    | branch and/or    | oubleshoot |
| pulse control  | accordance with    | load overcurrent | and repair |
| due to:        | PSRTC software     | detection, Power | or swap    |
|                | command, load      | supply fault     | power      |
| \-             | (coil) current not | detector         | supplies   |
| miscellaneous  | controllable,      | including        | if spare   |
| power supply   | possible           | section          | available  |
| internal fault | overcurrent or     | overcurrent,     |            |
| conditions     | excessive duration | module           |            |
| detected by    | of current. After  | overcurrent, and |            |
| power supply   | detection of       | overtime         |            |
| fault detector | fault, shutdown by | detection        |            |
|                | suppress, bypass   | (internal power  |            |
| \- firing      | action with        | supply Level 1   |            |
| generator      | delivery of        | faults), Analog  |            |
| malfunction    | additional         | Coil Protection  |            |
|                | volt-seconds to    | over             |            |
| \- master gate | load depending on  | current/overtime |            |
| driver         | AC sine wave phase | detection,       |            |
| malfunction    | angle at time of   | Rochester        |            |
|                | fault initiation,  | Instrument       |            |
| \- loss of     | possible AC feeder | System           |            |
| incoming       | breaker trip.      | (RIS)[^42]       |            |
| 13.8kV         | Current waveform   | overcurrent and  |            |
|                | after fault        | ∫i2(t)dt         |            |
| \- loss of     | depends on time    | detection        |            |
| 120V control   | delay to           | (external        |            |
| power          | suppress/bypass,   | Hardwired        |            |
|                | phase angle at     | Control System   |            |
|                | time of            | (HCS) Level 1    |            |
|                | suppress/bypass    | faults) , AC     |            |
|                | initiation, and    | feeder breaker   |            |
|                | load inductance,   | overcurrent and  |            |
|                | as well as         | overtime         |            |
|                | shutdown sequence  | detection        |            |
|                | of mutually        |                  |            |
|                | coupled            |                  |            |
|                | circuits[^41]      |                  |            |
+----------------+--------------------+------------------+------------+

WBS Element: 5X Power Systems Component: AC/DC Power Supply Converters
(con't)

+-----------------+-----------------+-----------------+-----------------+
| Failure Mode    | Effect          | Detection       | # Recovery      |
+-----------------+-----------------+-----------------+-----------------+
| Failure to      | Continued flow  | Power supply    | Troubleshoot    |
| suppress/bypass | of current in   | fault detector  | and repair or   |
| after internal  | converter       | Level 2 fault   | swap power      |
| Level 1 fault   | transformer and | detection and   | supplies if     |
|                 | application of  | AC feeder       | spare available |
|                 | voltage to load | breaker         |                 |
|                 | following       | overcurrent and |                 |
|                 | initial fault   | overtime        |                 |
|                 | detection,      | detection       |                 |
|                 | transition to   |                 |                 |
|                 | power supply    |                 |                 |
|                 | internal Level  |                 |                 |
|                 | 2 fault state,  |                 |                 |
|                 | command to trip |                 |                 |
|                 | AC feeder       |                 |                 |
|                 | breaker, AC     |                 |                 |
|                 | feeder breaker  |                 |                 |
|                 | trip            |                 |                 |
+-----------------+-----------------+-----------------+-----------------+
| Ground fault    | Shift in        | Power supply    | Troubleshoot    |
|                 | voltage to      | system ground   | and repair or   |
|                 | ground around   | fault detection | swap power      |
|                 | circuit, small  |                 | supplies if     |
|                 | leakage current |                 | spare available |
|                 | to ground       |                 |                 |
|                 | (limited by     |                 |                 |
|                 | high resistance |                 |                 |
|                 | grounding),     |                 |                 |
|                 | suppress/bypass |                 |                 |
|                 | per HCS Level 1 |                 |                 |
|                 | fault           |                 |                 |
+-----------------+-----------------+-----------------+-----------------+
| CHI power       | None; Master    | Absence of TF   | Diagnose and    |
| supply delivers | Gate Drivers    | current above   | troubleshoot    |
| current without | (MGDs) of CHI   | threshold and   |                 |
| Btf \>          | power supplies  | of correct      |                 |
| threshold due   | are blocked     | polarity        |                 |
| to control      | unless RIS      |                 |                 |
| failure         | indicates Itf   |                 |                 |
|                 | \> threshold    |                 |                 |
+-----------------+-----------------+-----------------+-----------------+

WBS Element: 5X Power Systems

## Component: Safety Disconnect Switches 

Function: The Safety Disconnect Switches (SDS) provide two pole no load
line disconnect switches and two pole grounding switches which connect
the power supply system to the load. They serve to isolate the NTC from
electrical hazards due to the power supply system during access to the
NTC via interlocks in the Safety Lockout Device (SLD). They include
spark gaps and non-linear resistors (surge arrestors) connected to
ground.

  --------------- --------------------- ---------------- -----------------
  Failure Mode    Effect                Detection        Recovery

  Line switch     Unable to effect      Limit switch     Provide alternate
  fail to open    normal isolation of   detectors        means of
                  power supply system   monitored by     isolating energy
                  from load, unable to  EPICS Process    source (e.g. rack
                  place SLD in \"safe\" Control, HCS,    out AC feeder
                  state, unable to      SLD, and HIS     breakers),
                  access NTC                             troubleshoot and
                                                         repair

  Line switch     Unable to connect     Limit switch     Troubleshoot and
  fail to close   power supply system   detectors        repair
                  to load               monitored by     
                                        EPICS Process    
                                        Control, HCS,    
                                        SLD, and HIS     

  Ground switch   Unable to effect      Limit switch     Provide alternate
  fail to close   normal grounding of   detectors        means of
                  power supply system,  monitored by     isolating energy
                  unable to place SLD   EPICS Process    source (e.g. rack
                  in \"safe\" state,    Control, HCS,    out AC feeder
                  unable to access NTC  SLD, and HIS     breakers),
                                                         troubleshoot and
                                                         repair

  Ground switch   Unable to place power Limit switch     Troubleshoot and
  fail to open    supply system in      detectors        repair
                  operating             monitored by     
                  configuration (unable EPICS Process    
                  to \"arm\")           Control, HCS,    
                                        SLD, and HIS     
  --------------- --------------------- ---------------- -----------------

WBS Element: 5X Power Systems Component: Safety Disconnect Switches
(con't)

  --------------- ------------------------------ -------------- --------------
  Failure Mode    Effect                         Detection      Recovery

  Line switch     Disparity between status of    Limit switch   Troubleshoot
  limit switch    the two limit switches mounted detectors are  and repair
  failure, or     on the two line switch poles   monitored by   
  short or open   actuated by common pneumatic   EPICS Process  
  in wiring       mechanism; if line switches    Control and    
                  are open and failed limit      SLD            
                  switch indicates closed,                      
                  unable to place SLD in safe                   
                  state, and data highlighted as                
                  erroneous on EPICs display. If                
                  line switches are closed and                  
                  failed limit switch indicates                 
                  open, data highlighted as                     
                  erroneous on EPICs display.                   

  Ground switch   Error in status reported by    If fail to     Troubleshoot
  limit switch    the single limit switch        indicate open, and repair
  failure         mounted on the common          would close    
                  pneumatic mechanism which      (audible event 
                  actuates the two ground switch in FCPC        
                  poles; if ground switches are  building) upon 
                  open and failed limit switch   venting SLD.   
                  indicates closed, SLD          If fail to     
                  electrical interlock would not indicate       
                  block transition to the safe   closed, ground 
                  state with switches open[^43]. fault and      
                  If ground switches are closed  overcurrent    
                  and failed limit switch        detection, HCS 
                  indicates open, could close    Level 1 fault  
                  line switches and arm power                   
                  supplies with ground and short                
                  circuit on system, possible                   
                  ground and overcurrent                        
                  condition                                     
  --------------- ------------------------------ -------------- --------------

WBS Element: 5X Power Systems Component: Safety Disconnect Switches
(con't)

  --------------- ------------------------------ -------------- --------------
  Failure Mode    Effect                         Detection      Recovery

  Pressure switch Error in status reported by    If pressure    Troubleshoot
  failure, or     pressure switch on the         switch status  and repair
  short or open   pneumatic reservoir; if        stuck          
  in wiring       reservoir is vented and failed indicating     
                  switch indicates pressure,     vented         
                  unable to place SLD in safe    condition,     
                  state. If reservoir is not     would report   
                  vented and failed switch       erroneous data 
                  indicates vented, SLD could    when           
                  transition to safe state with  pressurized    
                  pressure remaining in          (would be      
                  reservoir. If ground or line   noticed on     
                  switches changed state as a    EPICs mimic    
                  result of this pressure being  display if     
                  available, electrical          failure        
                  interlocks in SLD would issue  affected EPICs 
                  an E-Stop condition, all       signal). If    
                  ground switches would close,   pressure       
                  all line switches would open,  switch status  
                  and all AC feeder circuit      stuck          
                  breakers would open.           indicating     
                                                 pressurized    
                                                 condition,     
                                                 unable to      
                                                 place SLD into 
                                                 safe state.    
  --------------- ------------------------------ -------------- --------------

WBS Element: 5X Power Systems Component: Safety Disconnect Switches
(con't)

  ---------------- ----------------------- --------------- ----------------
  Failure Mode     Effect                  Detection       Recovery

  Ground switch    Unable to place power   Limit switch    Troubleshoot and
  fail to open     supply system in        detectors       repair
                   operating configuration monitored by    
                   (unable to \"arm\")     EPICS Process   
                                           Control, HCS,   
                                           SLD, and HIS    

  Loss of contact  High contact electrical Maintenance     Troubleshoot and
  pressure on line resistance, possible    (mechanical     repair
  switch blades    arcing, melting,        adjustment and  
                   burning                 joint           
                                           resistance      
                                           measurement)    
                                           and inspection  
                                           (temperature    
                                           stickers)       

  Spark gap        Ground fault, small     Power supply    Troubleshoot and
  electrical       leakage current         system ground   re-adjust
  breakdown[^44]   (limited by high        fault detection 
                   resistance grounding),                  
                   redistribution of                       
                   voltage to ground,                      
                   Level 1 (power supply                   
                   suppress/bypass)                        
                   shutdown                                

  Surge arrestor   Arcing and burning      Depending on    Replace
  electrical       within SDS metal        cause, Power    
  breakdown (due   enclosed cabinet (or,   supply system   
  to energy        in case of CHI, within  ground fault    
  overload)        metal enclosure         detection       
                   containing additional   and/or power    
                   protection unit located supply          
                   in NSTX Test Cell)      overcurrent     
                                           condition       

  DC Potential     Error in measurement of Abnormal signal Troubleshoot and
  Transducer       voltage to ground                       repair
  (DCPT) failure   (information only                       
                   signal: not used for                    
                   control or                              
                   interlocking)                           
  ---------------- ----------------------- --------------- ----------------

WBS Element: 5X Power Systems

## Component: DC Current Transducers 

Function: The DC Current Transducers (DCCTs) measure the branch currents
in the power supply system, which sum to the load currents in the NSTX
coils and CHI circuit. They consist of, in most cases "Halmar" zero flux
non-contact transducers, and in some cases "shunts" (current viewing
resistors) whose voltage drop is transmitted to ground potential using a
fiber optic v/f-f/v link. The signals are received by a "Halmar Signal
Conditioner" which provides buffering and fan out to the various
destinations. Redundant measurements of load current provided in all
cases.

  ---------------- ----------------------- --------------- ----------------
  Failure Mode     Effect                  Detection       Recovery

  Excessive drift  Measurement error,      Comparison with Troubleshoot and
  or failure of    possible current        redundant       repair
  electronics      control error (control  measurement in  
                   in PSRTC shifts to      PSRTC software  
                   signal with largest     (alarm) and in  
                   magnitude),             RIS[^45] (HCS   
                   interruption of pulse   Level 1 fault)  
                   via PSRTC or HCS Level                  
                   1 suppress/bypass                       
                   shutdown                                

  Loss of AC power "                       "               "
  ---------------- ----------------------- --------------- ----------------

WBS Element: 5X Power Systems

## Component: Rochester Instrument System (RIS) Fault Detector 

Function: The RIS receives the output of redundant DCCTs from the TF,
OH, PF2L, and PF3U&L circuits. It compares redundant signals and
performs single time constant exponential ∫i2(t)dt simulation (heating
and cooling) to detect current/time overloads, and detects overcurrents.
In addition it produces a signal when \|Itf\| exceeds a setpoint, for
interlocking CHI operation.

+--------------+-----------------------+---------------+--------------+
| Failure Mode | Effect                | Detection     | # Recovery   |
+--------------+-----------------------+---------------+--------------+
| Fail to      | None, detected in     | Operational   | Troubleshoot |
| detect DCCT  | PSRTC                 | diagnosis of  | and repair   |
| discrepancy  |                       | system fault  |              |
|              |                       | response or   |              |
|              |                       | mai           |              |
|              |                       | ntenance/test |              |
+--------------+-----------------------+---------------+--------------+
| Fail to      | None, overcurrent     | Operational   | Troubleshoot |
| detect       | detected in PSRTC,    | diagnosis of  | and repair   |
| overcurrent  | ACP, power supply     | system fault  |              |
|              | fault detectors, AC   | response or   |              |
|              | feeder protective     | mai           |              |
|              | relaying              | ntenance/test |              |
+--------------+-----------------------+---------------+--------------+
| Fail to      | None, detected in     | Operational   | Troubleshoot |
| detect       | PSRTC, and backed up  | diagnosis of  | and repair   |
| ∫i2(t)dt     | by overtime detection | system fault  |              |
| overload     | in ACP, power supply  | response or   |              |
| during pulse | fault detectors, AC   | mai           |              |
|              | feeder protective     | ntenance/test |              |
|              | relaying              |               |              |
+--------------+-----------------------+---------------+--------------+
| Fail to      | Abnormally high       | EPICS alarms  | Troubleshoot |
| detect       | temperatures before   | on cooling    | and repair   |
| ∫i2(t)dt     | and after pulse       | water outlet  |              |
| overload     |                       | temperatures  |              |
| caused by    |                       | returning to  |              |
| repetition   |                       | collection    |              |
| rate error   |                       | manifolds     |              |
| by operators |                       |               |              |
+--------------+-----------------------+---------------+--------------+

WBS Element: 5X Power Systems

## Component: Analog Coil Protection (ACP) 

Function: The ACP receives outputs from the DCCTs, via the Halmar Signal
Conditioner (HSC), and detects overcurrent and current overtime
conditions.

+--------------+-----------------------+---------------+--------------+
| Failure Mode | Effect                | Detection     | # Recovery   |
+--------------+-----------------------+---------------+--------------+
| Fail to      | None, overcurrent     | Operational   | Troubleshoot |
| detect       | detected in PSRTC,    | diagnosis of  | and repair   |
| overcurrent  | RIS , power supply    | system fault  |              |
|              | fault detectors, AC   | response or   |              |
|              | feeder protective     | mai           |              |
|              | relaying              | ntenance/test |              |
+--------------+-----------------------+---------------+--------------+
| Fail to      | None, detected in     | Operational   | Troubleshoot |
| detect       | PSRTC, ∫i2(t)dt       | diagnosis of  | and repair   |
| overtime     | detection in RIS ,    | system fault  |              |
|              | power supply fault    | response or   |              |
|              | detectors, AC feeder  | mai           |              |
|              | protective relaying   | ntenance/test |              |
+--------------+-----------------------+---------------+--------------+

WBS Element: 5X Power Systems

## Component: Ground Fault Detection 

Function: The Ground Fault Detection system monitors the current through
the high resistance grounding resistors located in the SDS cabinets. The
current is sensed via an electromagnetic relay as well as an electronic
level detector.

+--------------+-----------------------+---------------+--------------+
| Failure Mode | Effect                | Detection     | # Recovery   |
+--------------+-----------------------+---------------+--------------+
| Ele          | Overall I vs. T       | Maintenance   | Troubleshoot |
| ctromagnetic | limits based on       | testing       | and repair   |
| relay        | electronic level      |               |              |
| malfunction  | detector only         |               |              |
+--------------+-----------------------+---------------+--------------+
| Electronic   | Overall I vs. T       | Maintenance   | Troubleshoot |
| sensor       | limits based on       | testing       | and repair   |
| malfunction  | electromagnetic relay |               |              |
|              | level only            |               |              |
+--------------+-----------------------+---------------+--------------+

WBS Element: 5X Power Systems

## Component: Power Supply Real Time Controller 

Function: The Power Supply Real Time Controller (PSRTC) provides control
of the voltage and current delivered by the power supply system to the
NSTX coils and CHI circuit. It includes the computer processors and I/O
equipment located in and associated with the "Skybolt/DAS" computer
system as well as the "Power Conversion Link" (PC Link) which delivers
the PSRTC commands to the individual AC/DC converters.

+--------------+-----------------------+---------------+--------------+
| Failure Mode | Effect                | Detection     | # Recovery   |
+--------------+-----------------------+---------------+--------------+
| Delivery of  | Overcurrent (level    | RIS[^46],     | Diagnose,    |
| excess       | depends on failure    | ACP, power    | troubleshoot |
| current      | mechanism, circuit in | supply fault  | and repair   |
| magnitude    | question, protection  | detector, AC  | if required  |
| due to,      | settings), HCS Level  | feeder        |              |
| software,    | 1 fault (suppress     | protective    |              |
| computer, or | bypass), possible AC  | relaying      |              |
| I/O failure  | feeder breaker trip   |               |              |
+--------------+-----------------------+---------------+--------------+
| Delivery of  | Excessive temperature | RIS           | Diagnose,    |
| excess       | rise in load (level   | (exponential  | troubleshoot |
| ∫i2(t)dt due | depends on failure    | he            | and repair   |
| to,          | mechanism, circuit in | ating/cooling | if required  |
| software,    | question, protection  | simulation),  |              |
| computer, or | settings), HCS Level  | ACP           |              |
| I/O failure  | 1 fault (suppress     | (overtime),   |              |
|              | bypass), possible AC  | power supply  |              |
|              | feeder breaker trip   | fault         |              |
|              |                       | detector      |              |
|              |                       | (overtime) ,  |              |
|              |                       | AC feeder     |              |
|              |                       | protective    |              |
|              |                       | relaying      |              |
|              |                       | (overtime)    |              |
+--------------+-----------------------+---------------+--------------+
| Delivery of  | Excessive ratcheting  | RIS           | Diagnose,    |
| excess rms   | of load temperature   | (exponential  | troubleshoot |
| current due  | (level depends on     | he            | and repair   |
| to operator  | failure mechanism,    | ating/cooling | if required  |
| error        | circuit in question,  | simulation),  |              |
| (repetition  | protection settings), | (overtime) ,  |              |
| rate too     | HCS Level 1 fault     | AC feeder     |              |
| high)        | (suppress bypass),    | protective    |              |
|              | possible AC feeder    | relaying      |              |
|              | breaker trip          | (thermal      |              |
|              |                       | replica)      |              |
+--------------+-----------------------+---------------+--------------+

WBS Element: 5X Power Systems Component: PSRTC (con't)

+--------------+---------------------+----------------+---------------+
| Failure Mode | Effect              | Detection      | # Recovery    |
+--------------+---------------------+----------------+---------------+
| Delivery of  | None; Special       | Absence of CHI | Diagnose and  |
| command to   | interlock is        | current        | troubleshoot  |
| CHI power    | provided such that  |                |               |
| supply       | Master Gate Drivers |                |               |
| without Btf  | (MGDs) of CHI power |                |               |
| \> threshold | supplies are        |                |               |
| due to       | blocked unless RIS  |                |               |
| operator,    | indicates Itf \>    |                |               |
| software,    | threshold in        |                |               |
| computer, or | appropriate         |                |               |
| I/O failure  | direction           |                |               |
+--------------+---------------------+----------------+---------------+
| Delivery of  | None; Special       | Absence of     | Diagnose and  |
| OH and PF1b  | interlock is        | PF1b current   | troubleshoot  |
| current      | provided such that  |                |               |
| combination  | Master Gate Drivers |                |               |
| producing    | (MGDs) of PF1b      |                |               |
| excess axial | power supplies are  |                |               |
| force in (+) | blocked unless RIS  |                |               |
| z direction  | indicates Ioh \>    |                |               |
| (launching   | threshold in        |                |               |
| load) due to | appropriate         |                |               |
| software or  | direction           |                |               |
| I/O failure  |                     |                |               |
+--------------+---------------------+----------------+---------------+

WBS Element: 5X Power Systems

## Component: Hardwired Control System 

Function: The Hardwired Control System (HCS) provides interlocks which
prevent misoperation/misconfiguration of the power supply systems and
which interface with the overall Hardwired Interlock System (HIS). Two
fault levels (1 and 3) are communicated throughout each system using
both series and parallel loops, referred to as L1S, L1P, L3S, L3P.

+-----------------+-------------------------+----------------+--------+
| Failure Mode    | Effect                  | #              | # Re   |
|                 |                         | #### Detection | covery |
+-----------------+-------------------------+----------------+--------+
| Power Supply    | Possible power supply   | RIS[^47], ACP, | Dia    |
| Arm Permissive  | operation in invalid    | power supply   | gnose, |
| interlock       | configuration or with   | fault          | troubl |
| chain, one or   | equipment status not    | detector,      | eshoot |
| more input      | ready, possible         | ground fault   | and    |
| contact states  | overcurrent or ground   | detector, AC   | repair |
| invalid (do not | fault on power supply   | feeder         | if     |
| reflect true    | system, Level 1 HCS     | protective     | re     |
| equipment       | Fault (suppress/bypass) | relaying       | quired |
| state)          |                         |                |        |
+-----------------+-------------------------+----------------+--------+
| Configure       | Possible SDS operation  | RIS, ACP,      | Dia    |
| Permissive      | in invalid              | power supply   | gnose, |
| interlock       | configuration, possible | fault          | troubl |
| chain, one or   | overcurrent or ground   | detector,      | eshoot |
| more input      | fault on power supply   | ground fault   | and    |
| contact states  | system, Level 1 HCS     | detector, AC   | repair |
| invalid (do not | Fault (suppress/bypass) | feeder         | if     |
| reflect true    |                         | protective     | re     |
| equipment       |                         | relaying       | quired |
| state)          |                         |                |        |
+-----------------+-------------------------+----------------+--------+
| Level 1 or      | None, redundant         | Disagreement   | Dia    |
| Level 3 fault   | parallel lines          | between L1S    | gnose, |
| line, series    |                         | and L1P (or    | troubl |
| loop short      |                         | L3S and L3P)   | eshoot |
| circuit results |                         | states.        | and    |
| in bypass of    |                         |                | repair |
| status from     |                         |                | if     |
| power supplies  |                         |                | re     |
| to HCS          |                         |                | quired |
+-----------------+-------------------------+----------------+--------+
| Level 1 or      | Redundant series lines, | Disagreement   | Dia    |
| Level 3 fault   | but slower fault        | between L1S    | gnose, |
| line, parallel  | response of PS to HCS   | and L1P (or    | troubl |
| loop open       | (approx 50 mS),         | L3S and L3P)   | eshoot |
| circuit results | disconnected power      | states.        | and    |
| in disconnect   | supplies go to fault    |                | repair |
| of status       | state upon open circuit |                | if     |
| to/from power   | and report to HCS via   |                | re     |
| supplies & HCS  | series loop             |                | quired |
+-----------------+-------------------------+----------------+--------+

#  WBS Element: 6X Central I&C 

## Component: EPICS Process Control System 

Function: The Experimental Physics Instrumentation and Control System
(EPICS) Process Control System provides the operator interface for
non-real time control and monitoring of the NSTX device

+----------------+-----------------------+---------------+------------+
| Failure Mode   | Effect                | Detection     | # Recovery |
+----------------+-----------------------+---------------+------------+
| Any failure    | No deleterious effect | Various       | Diagnose,  |
| mode           | on equipment or       |               | tr         |
|                | personnel safety; all |               | oubleshoot |
|                | NSTX systems required |               | and repair |
|                | to be immune to       |               | if         |
|                | failure of Central    |               | required   |
|                | I&C in this regard.   |               |            |
|                | Operations will be    |               |            |
|                | interrupted.          |               |            |
|                | Information regarding |               |            |
|                | status of facility,   |               |            |
|                | beside that reported  |               |            |
|                | via the HIS, may not  |               |            |
|                | be available to the   |               |            |
|                | operators.            |               |            |
+----------------+-----------------------+---------------+------------+

WBS Element: 6X Central I&C

## Component: MDS+ Data Acquisition System 

Function: The Modular Data Systems Plus (MDS+) Data Acquisition System
provides the operator interface for diagnostics control and monitoring
of the NSTX device, and provides facility for archiving experimental
data

+----------------+-----------------------+---------------+------------+
| Failure Mode   | Effect                | Detection     | # Recovery |
+----------------+-----------------------+---------------+------------+
| Any failure    | No deleterious effect | Various       | Diagnose,  |
| mode           | on equipment or       |               | tr         |
|                | personnel safety; all |               | oubleshoot |
|                | NSTX systems required |               | and repair |
|                | to be immune to       |               | if         |
|                | failure of Central    |               | required   |
|                | I&C in this regard.   |               |            |
|                | Operations will be    |               |            |
|                | interrupted.          |               |            |
|                | Information regarding |               |            |
|                | status of facility,   |               |            |
|                | beside that reported  |               |            |
|                | via the HIS, may not  |               |            |
|                | be available to the   |               |            |
|                | operators.            |               |            |
+----------------+-----------------------+---------------+------------+

WBS Element: 6X Central I&C

## Component: Safety System 

Function: The Safety System consists of the Hardwired Interlock System
(HIS) and the Safety Lockout Device (SLD). The HIS provides permissives
to the power supply, RF, and NBI systems which enable them to be
configured and operated. The SLD monitors the status of the power supply
system safety disconnect switches and provides a "Safe" signal only when
all switches are in the safe position and the compressed air supply
(which actuates the switches) has been vented. Two search and secure
loops are provided, one for the NSTX Test Cell and one for the cable
spread room. These loops must be armed in order for permissives to be
issued.

+-----------------+------------------------+----------------+---------+
| Failure Mode    | Effect                 | Detection      | # R     |
|                 |                        |                | ecovery |
+-----------------+------------------------+----------------+---------+
| HIS UPS failure | E-stop condition,      | Loss of        | Troub   |
|                 | permissives to power   | indications on | leshoot |
|                 | supply, RF, and NBI    | HIS control    | and     |
|                 | systems removed,       | panel in NSTX  | repair  |
|                 | search and secure      | control room   |         |
|                 | loops drop out, status |                |         |
|                 | indications in control |                |         |
|                 | room not functional.   |                |         |
+-----------------+------------------------+----------------+---------+
| SLD electrical  | Overall SLD "Safe"     | EPICs Process  | Troub   |
| interlock       | status not achieved,   | Control in     | leshoot |
| failure         | since SDS ground       | combination    | and     |
| indicating SDS  | switches cannot be     | with SLD       | repair  |
| ground switches | open without air       | status         |         |
| in safe         | supply, and SLD"Safe"  | indicator      |         |
| condition when  | status not issued if   | lamps          |         |
| in unsafe state | air supply still       |                |         |
|                 | available              |                |         |
+-----------------+------------------------+----------------+---------+
| SLD electrical  | Unable to achieve      | EPICs Process  | Troub   |
| interlock       | "Safe" status required | Control in     | leshoot |
| failure         | for area access        | combination    | and     |
| indicating SDS  |                        | with SLD       | repair  |
| ground switches |                        | status         |         |
| in an unsafe    |                        | indicator      |         |
| condition when  |                        | lamps          |         |
| in safe state   |                        |                |         |
+-----------------+------------------------+----------------+---------+

#  

WBS Element: 6X Central I&C

Component: Safety System (con't)

+-----------------+---------------------------+--------------+---------+
| Failure Mode    | Effect                    | Detection    | # R     |
|                 |                           |              | ecovery |
+-----------------+---------------------------+--------------+---------+
| SLD electrical  | Loss of one level of      | EPICs        | Troub   |
| interlock       | isolation. However,       | Process      | leshoot |
| failure         | permissive to power       | Control in   | and     |
| indicating SDS  | supply AC/DC converters   | combination  | repair  |
| line switches   | not issued in "Safe"      | with SLD     |         |
| in safe         | state. Even if AC/DC      | status       |         |
| condition when  | converters failed to      | indicator    |         |
| in unsafe state | block, closed ground      | lamps        |         |
|                 | switches would prevent    |              |         |
|                 | high voltage from         |              |         |
|                 | appearing on bus bars in  |              |         |
|                 | NSTX Test Cell            |              |         |
+-----------------+---------------------------+--------------+---------+
| SLD electrical  | Unable to achieve "Safe"  | EPICs        | Troub   |
| interlock       | status required for area  | Process      | leshoot |
| failure         | access                    | Control in   | and     |
| indicating SDS  |                           | combination  | repair  |
| line switches   |                           | with SLD     |         |
| in unsafe       |                           | status       |         |
| condition when  |                           | indicator    |         |
| in safe state   |                           | lamps        |         |
+-----------------+---------------------------+--------------+---------+
| SLD electrical  | Loss of one level of      | EPICs        | Troub   |
| interlock       | prevention of SDS line or | Process      | leshoot |
| failure         | ground switch changing    | Control in   | and     |
| indicating      | state to unsafe position. | combination  | repair  |
| compressed air  | However, electrical       | with SLD     |         |
| vented when     | interlocks still in       | status       |         |
| pressure still  | effect. In case a switch  | indicator    |         |
| present         | changed state, an E-stop  | lamps        |         |
|                 | would result.             |              |         |
+-----------------+---------------------------+--------------+---------+
| SLD electrical  | Unable to achieve "Safe"  | EPICs        | Troub   |
| interlock       | status required for area  | Process      | leshoot |
| failure         | access                    | Control in   | and     |
| indicating      |                           | combination  | repair  |
| compressed air  |                           | with SLD     |         |
| not vented      |                           | status       |         |
| after venting   |                           | indicator    |         |
| has occurred    |                           | lamps        |         |
+-----------------+---------------------------+--------------+---------+

WBS Element: 6X Central I&C

# Component: Safety System (con't) 

# 

+-----------------+---------------------------+--------------+---------+
| Failure Mode    | Effect                    | Detection    | # R     |
|                 |                           |              | ecovery |
+-----------------+---------------------------+--------------+---------+
| HIS interface   | None, receiving end will  | Loss of      | Troub   |
| wiring (e.g.    | revert to safe condition  | expected     | leshoot |
| permissive,     | since all signals are     | 120V AC      | and     |
| status, search  | 120VAC sourced and        | signal       | repair  |
| and secure,     | energized in safe state   |              |         |
| etc.) open      |                           |              |         |
| circuit or      |                           |              |         |
| short circuit   |                           |              |         |
+-----------------+---------------------------+--------------+---------+
| Search and      | Search and secure         | Loop does    | Troub   |
| secure loop     | procedure, which first    | not drop     | leshoot |
| relay stuck in  | drops the loop, will      | when door to | and     |
| armed position  | reveal the deficiency     | area is      | repair  |
|                 |                           | opened.      |         |
+-----------------+---------------------------+--------------+---------+

#  WBS Element: Operations 

Function: Operations personnel (Chief Operations Engineer (COE), Power
Supply Engineering In Charge (EIC), and Field Coil Power Conversion
(FCPC) operators) set the configuration of the power supply system and
program the PSRTC.

+-------------------+---------------------+-------------+------------+
| Failure Mode      | Effect              | Detection   | # Recovery |
+-------------------+---------------------+-------------+------------+
| Programming of    | Fault detected by   | PSRTC       | Correct    |
| input data        | PSRTC,              |             | p          |
| leading to excess | suppress/bypass     |             | rogramming |
| current           | shutdown            |             | error      |
| magnitude,        |                     |             |            |
| ∫i2(t)dt, or      |                     |             |            |
| duration          |                     |             |            |
+-------------------+---------------------+-------------+------------+
| Programming of    | None; Master Gate   | Absence of  | Correct    |
| CHI operation     | Drivers (MGDs) of   | CHI current | p          |
| with incorrect    | CHI power supplies  |             | rogramming |
| Btf magnitude and | are blocked unless  |             | error      |
| polarity          | RIS indicates Itf   |             |            |
|                   | \> threshold        |             |            |
+-------------------+---------------------+-------------+------------+
| Programming of OH | Fault detected by   | PSRTC       | Correct    |
| and PF1b current  | PSRTC,              |             | p          |
| combination       | suppress/bypass     |             | rogramming |
| producing excess  | shutdown            |             | error      |
| axial force in    |                     |             |            |
| (+) z direction   |                     |             |            |
| (launching load)  |                     |             |            |
| due to operator   |                     |             |            |
| error             |                     |             |            |
+-------------------+---------------------+-------------+------------+
| Excess applied    | Safety Disconnect   | Power       | Replace    |
| voltage due to    | Switch (SDS) surge  | supply      | arresters  |
| operator error,   | arrestor voltage    | module and  |            |
| too many power    | limiting, possible  | section     |            |
| supply sections   | surge arrestor      | overcurrent |            |
| connected in      | energy overload and | detection   |            |
| series            | short circuit,      |             |            |
| (administrative   | short circuit on    |             |            |
| procedures not    | power supplies,     |             |            |
| correctly         | overcurrent,        |             |            |
| followed)[^48]    | suppress/bypass per |             |            |
|                   | HCS Level 1 fault   |             |            |
+-------------------+---------------------+-------------+------------+

WBS Element: Operations (con't) Component:

+------------------+---------------------+---------------+------------+
| Failure Mode     | Effect              | Detection     | # Recovery |
+------------------+---------------------+---------------+------------+
| Voltage          | Short circuit       | Power supply  | Re         |
| unbalance in     | current circulating | fault         | configure, |
| parallel or      | between             | detector      | replace    |
| antiparallel     | antiparallel        | section and   | modules if |
| configurations   | strings, possible   | module        | damaged    |
| due to operator  | electrical          | overcurrent   |            |
| error            | breakdown of        |               |            |
| (administrative  | thyristors/snubber  |               |            |
| procedures not   | components,         |               |            |
| correctly        | suppress/bypass per |               |            |
| followed),       | HCS Level 1 fault   |               |            |
| unequal number   |                     |               |            |
| of power supply  |                     |               |            |
| sections in      |                     |               |            |
| parallel or      |                     |               |            |
| antiparallel     |                     |               |            |
| strings          |                     |               |            |
+------------------+---------------------+---------------+------------+
| CHI power supply | Pulse inhibited     | PSRTC         | Open       |
| connected (line  |                     |               | switches   |
| switches closed) |                     |               | or switch  |
| but PSRTC not in |                     |               | PSRTC      |
| normal (plasma)  |                     |               | modes      |
| mode             |                     |               |            |
+------------------+---------------------+---------------+------------+
| Upper/lower PF   | Repulsive instead   | Abnormal      | R          |
| coil currents    | of attractive axial | magnetic      | econfigure |
| opposite         | forces between      | topology and  | links,     |
| polarity due to  | coils, possible     | coil          | repair     |
| operator error   | mechanical damage   | impedance     | damage (if |
| (administrative  | to coil supports,   |               | any)       |
| procedures not   | coil displacement,  |               |            |
| correctly        | possible coil       |               |            |
| followed)[^49],  | damage              |               |            |
| incorrect SDS    |                     |               |            |
| bus link         |                     |               |            |
| configuration    |                     |               |            |
| (PF1aU/L,        |                     |               |            |
| PF2aU/L,         |                     |               |            |
| PF3aU/L)         |                     |               |            |
+------------------+---------------------+---------------+------------+

WBS Element: Operations (con't) Component:

+--------------+---------------------+----------------+---------------+
| Failure Mode | Effect              | Detection      | # Recovery    |
+--------------+---------------------+----------------+---------------+
| Attempt to   | None, prevented by  | No response to | Open ground   |
| operate      | HCS interlock       | command to HIS | switches      |
| power supply |                     | arm permissive |               |
| system with  |                     |                |               |
| SDS ground   |                     |                |               |
| switches     |                     |                |               |
| closed       |                     |                |               |
+--------------+---------------------+----------------+---------------+
| Attempt to   | None, prevented by  | No response to | Disarm power  |
| open SDS     | HCS interlock       | EPICS process  | supplies,     |
| line         | (power supply and   | control        | place HIS     |
| switches     | configure           | command        | system into   |
| under load   | permissives are     |                | "configure"   |
|              | mutually exclusive) |                |               |
+--------------+---------------------+----------------+---------------+

\*\*\*\* END OF FMEA \*\*\*\*

[^1]: ^1^ During pulse, cooling is not significant and is not required

[^2]: ^2^ Flow switches are located on return manifold such that flow
    must pass through coil in order to reach flow switch

[^3]: ^3^ Multiple ground faults not considered herein

[^4]: Maximum stored magnetic energy in any NSTX coil is 3.75 MJoule
    (NSTX-SRD-5X-019)

[^5]: During pulse, cooling is not significant and is not required

[^6]: Flow switches are located on return manifold such that flow must
    pass through coil in order to reach flow switch

[^7]: Multiple ground faults not considered herein

[^8]: Maximum stored magnetic energy in any NSTX coil is 3.75 MJoule
    (NSTX-SRD-5X-019)

[^9]: During pulse, cooling is not significant and is not required

[^10]: Flow switches are located on return manifold such that flow must
    pass through coil in order to reach flow switch

[^11]: Multiple ground faults not considered herein

[^12]: There are 8 parallel cooling water circuits; blockage of multiple
    circuits is not considered herein

[^13]: Sources of heat are I2R losses in coil plus heat flow inward from
    center stack casing

[^14]: During pulse, cooling is not significant and is not required

[^15]: Flow switches are located on return manifold such that flow must
    pass through coil in order to reach flow switch

[^16]: Multiple ground faults not considered herein

[^17]: OH coil conductor lifetime is fatigue limited (function of number
    of pulses at various load levels)

[^18]: Maximum stored magnetic energy in any NSTX coil is 3.75 MJoule
    (NSTX-SRD-5X-019)

[^19]: During pulse, cooling is not significant and is not required

[^20]: Flow switches are located on return manifold such that flow must
    pass through coil in order to reach flow switch

[^21]: Multiple ground faults not considered herein

[^22]: Maximum stored magnetic energy in any NSTX coil is 3.75 MJoule
    (NSTX-SRD-5X-019)

[^23]: Note: No personnel will be present in NSTX Test Cell during ECH
    operations

[^24]: "R-Temp" high flame temperature oil

[^25]: Protective plate armor is designed to absorb 5MW-5sec without
    damage.

[^26]: Water circulation systems use standby diesel generator power,
    plus an additional back-up electrical generator in case of failure
    of main standby diesel generator

[^27]: Leakage along route from NBPC through pump room and mechanical
    equipment room to NTC is considered extremely unlikely due to use of
    all-welded piping.

[^28]: Administrative procedures limit maximum allowable condensed
    H~~,~~. PLC control sequence includes N~2~ purge before and after
    pumping gases liberated from both routine and emergency
    regenerations. These measures are taken to preclude potential
    development of explosive mixtures.

[^29]: Very unlikely due to all-welded pipe construction.

[^30]: Every NSTX coil cooling water path is equipped with a flow switch

[^31]: Most likely on coil side of flow switch since venturi and
    subsequent connection to return manifold consists of hard piping
    with predominantly welded joints

[^32]: Every NSTX coil cooling water path is equipped with a flow switch

[^33]: "keep alive" signal is the regularly transmitted PLC scanning
    signal (approx. once per second) which, if not received by output
    module, will trip "scan loss detector" and cause PAUX relay dropout

[^34]: Personnel access to test cell will be limited to qualified
    personnel during bakeout; bakeout skid area will be roped off.

[^35]: Hydrogen gas inventory less than 311 cubic feet (per cylinder),
    insufficient volume to develop an explosive concentration in the NTC

[^36]: A large variety of diagnostics are planned for NSTX. The
    diagnostic components evaluated herein are those which are essential
    for machine operations

[^37]: See FMEA for Center Stack Casing (WBS 1.3.3) for electrical
    failure of center stack thermal insulation

[^38]: SeeFMEA for Center Stack Casing (WBS 1.3.3) for electrical
    failure of center stack thermal insulation

[^39]: See FMEA for Center Stack Casing (WBS 1.3.3) for electrical
    failure of center stack thermal insulation

[^40]: Latent heat due to bakeout could overheat the OH coil after
    approx. 5 hours if water cooling is entirely absent

[^41]: PSRTC shuts down circuits individually, whereas HCS faults result
    in common shutdown amongst mutually coupled circuits

[^42]: RIS protection is applied to TF, OH, PF2L, PF3U&L only

[^43]: Probability of overall event sequence leading to SLD transition
    to safe state with switches open is remote because, in addition to
    the electrical interlock, the air supply is cut off and vented and
    the ground switches, which require air pressure to remain open, will
    be forced closed by mechanical springs and will remain closed even
    if commanded to open.

[^44]: Spark gaps are not required for NSTX but cannot be removed (built
    into the ground switches); they will be adjusted out of normal range
    of voltage

[^45]: RIS coverage for TF, OH, PF2L, PF3U&L only

[^46]: RIS coverage for TF, OH, PF2L, PF3U&L only

[^47]: RIS coverage for TF, OH, PF2L, PF3U&L only

[^48]: Kirk Keys which permit the insertion of power supplies not
    planned for NSTX use will be removed and stored elsewhere via
    administrative procedures (e.g. in the D-site Shift Supervision lock
    box); therefore the probability of this failure is considered to be
    remote

[^49]: Reconfiguration of bus links is a lengthy procedure typically
    performed by one or more technicians under the supervision of the
    FCPC EIC via administrative procedures; therefore this failure mode
    would require incorrect action on the part of several individuals
    over a period of several hours. On this basis the probability of
    this failure is considered to be small.