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[National Spherical Torus Experiment]{.underline}

**NSTX**

SAFETY ASSESSMENT DOCUMENT

(SAD)

NSTX-SAD-052-00

**Revision 3**

**June 16, 2000**

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Masayuki Ono Charles Neumeyer

NSTX Project Director NSTX Project Engineering Manager

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Jerry Levine

Chairperson, PPPL Safety Review Committee

1.0 INTRODUCTION

> This Safety Assessment Document (SAD) documents the safety analysis of
> the National Spherical Torus Experiment (NSTX) at the Princeton Plasma
> Physics Laboratory (PPPL). The SAD has been prepared consistent with
> PPPL Environment, Safety and Directive 5008, Section 11, Chapter 1,
> "Operations Hazard Criteria" (Reference 1). It provides descriptions
> of the NSTX structures, systems and components, identification of
> hazards, and design features and administrative controls to mitigate
> these hazards. Failure modes and effects analyses (FMEAs) for NSTX
> systems and components are provided in Appendix 1.
>
> The National Spherical Torus Experiment (NSTX) is designed to prove
> the scientific principle of the spherical torus (ST) plasma. The ST
> plasma is nearly spherical in shape, its minor radius being slightly
> smaller than its major radius, thus giving an aspect ratio close to
> one. ST plasmas may have several advantageous features, such as a
> higher pressure for a given magnetic field. Since fusion power density
> is proportional to the square of the plasma pressure, the ST is a good
> example of an innovative alternative fusion concept that could lead to
> smaller and more economical sources of fusion energy.
>
> The design and construction of the NSTX is a joint Project of the
> Princeton Plasma Physics Laboratory (PPPL), the Oak Ridge National
> Laboratory (ORNL), Columbia University, and the University of
> Washington. The NSTX facility is located at PPPL to take advantage of
> existing equipment and infrastructure, thus saving time and money. The
> NSTX has modular components for ease of repair and upgrade, in
> response to progress in fusion science and technology. PPPL leads the
> Project and operates the NSTX facility.
>
> A National Research Team carries out the Research Program on NSTX. The
> Program covers a broad range of fusion and plasma science topics. A
> National Process has been established to promote broad research
> participation by the U.S. fusion energy sciences community.

[1.1 Mission]{.underline}

The National NSTX Research Program investigates the fusion science
principles of the ST plasma, covering:

\- noninductive start-up, current sustainment, and profile control;

\- confinement and transport;

\- pressure limits and self-driven currents;

\- scrape-off-layer and divertor physics; and

\- stability and disruption resilience.

These principles are investigated in the scientifically interesting
regimes that are relevant to near-term applications, such as volume
neutron sources (VNS) and fusion pilot and power plants of the future:

\- high average toroidal betas (25 - 45%);

\- high pressure-gradient-driven current fractions of 40 - 90%;

\- fully relaxed, noninductively sustained current profile;

\- collisionless plasmas with high temperatures and densities; and

\- aspect ratios (major radius over minor radius) as small as 1.25 and
elongations above two;

This mission supports the goals of the fusion energy sciences program in
the U.S.

[1.2 Design Features]{.underline}

The NSTX device (see Figure 1) is designed to operate with the following
baseline parameters for plasmas with several forms of divertor and
limiter configurations:

Table 1 National Spherical Torus Experiment Baseline Parameters

+-----------------------------------+-----------------------------------+
| **Parameter**                     | **Value**                         |
+-----------------------------------+-----------------------------------+
| Plasma Major Radius (R0)          | 0.85 m                            |
+-----------------------------------+-----------------------------------+
| Plasma Minor Radius (a)           | 0.68 m                            |
+-----------------------------------+-----------------------------------+
| Applied Toroidal Field (Bt)       | 3.0 kG at R0                      |
+-----------------------------------+-----------------------------------+
| Plasma Current (Ip)               | 1.0 MA                            |
+-----------------------------------+-----------------------------------+
| Plasma Elongation (Kappa)         | greater than or about equal to 2  |
+-----------------------------------+-----------------------------------+
| Plasma Triangularity (Delta)      | approximately 0.4                 |
+-----------------------------------+-----------------------------------+
| Edge Safety Factor (q)            | approximately 10                  |
+-----------------------------------+-----------------------------------+
| Plasma Pulse Flattop Length       | about 0.5 sec (inductive-only     |
| \[(Tau)pp\]                       | operation)                        |
|                                   |                                   |
|                                   | about 5.0 sec (driven-current     |
|                                   | operation)                        |
+-----------------------------------+-----------------------------------+

The NSTX project scope includes the following systems for start-up,
heating, and current drive:

\- 6 MW of high harmonic fast wave (HHFW) for up to 5 seconds,

\- 50 kA of coaxial helicity injection (CHI) injected current for up to
5 seconds, and

-   20 kW of electron cyclotron heating (ECH) for up to 5 milliseconds.

-   5 MW of Neutral Beam Injection at 80kV for 5 seconds.

The NSTX facility design further accounts for the possibility of adding
and handling 400 kW of ECH for up to 100 milliseconds for noninductive
startup. The center stack of NSTX is highly compact to permit a plasma
aspect ratio as low as 1.25. It contains the inner legs of the
toroidal-field coils, a solenoid to provide full capability for
inductive operation, a pair of poloidal-field coils most effective in
varying the plasma triangularity, the inboard vessel wall containing
these components, the protective graphite tiles, and the interface to
the remainder of the device. The center-stack is designed to be
replaceable without affecting the rest of the device.

The vacuum vessel is 3.6 meters in height and accommodates a plasma
elongation of up to 2.2 and a triangularity of up to 0.6 for an aspect
ratio of 1.25. A higher elongation of about 3 can be obtained for an
aspect ratio of 1.4 by operating plasmas with a reduced minor radius.

Auxiliary heating and current drive for current profile control address
another essential part of the NSTX mission. High-harmonic fast-wave is
expected to suit well the high-beta and high-bootstrap-current fraction
plasma discharges and fully utilize radio-frequency power sources
available on site. A conducting shell, also protected by graphite tiles,
is placed near the outboard plasma edge to enable the investigation of
maximized MHD stability limits in plasma beta and bootstrap current.
Noninductive start-up and edge current drive are accomplished by coaxial
helicity injection, an innovative technique successfully pioneered by
the University of Washington and incorporated into the NSTX design.

The plasma pulse length of 5 seconds allows investigation of fully
relaxed current profiles, a condition desirable in future fusion energy
sources. Carbon tiles cover plasma facing components in the inboard and
divertor areas to handle the anticipated heat loads for the full
5-seconds plasma pulse. All carbon tiles are bakeable to 350 degrees
Centigrade to speed recovery from a vacuum vent.

NSTX operation is assumed to consist of 96 pulses per day, 5 days per
week, 3 weeks per month, 9 months per year, for 10 years (≈ 130,000
pulses).

The NSTX device is designed to permit future low-cost upgrades for
higher currents and longer pulse lengths.

[1.3 The Spherical Torus Plasma]{.underline}

The ST plasma possesses features of tokamak and spheromak plasmas, as
seen in Figure 2. The magnetic field line of the ST plasma resembles
that of the tokamak plasma at the stable, inboard side and that of the
spheromak at the unstable, outboard side. This leads to a number of
attractive physics features of interest to fusion energy science,
estimated according to our present understanding in toroidal fusion
science. These include:

\- MHD-stable plasmas with very high average toroidal beta (plasma
pressure divided by externally applied toroidal field pressure at the
major radius) in the range of 25 - 50%.

\- Nearly complete (greater than or equal to 90%) alignment of
self-driven current profile with the required plasma current.

\- Strong magnetic shear and magnetic well (\~30%) that help stabilize
plasma microinstabilities believed responsible for plasma turbulence and
rapid energy loss.

\- Increased flow shear (by up to two orders of magnitude beyond
tokamaks) that tends to suppress the remaining plasma
microinstabilities.

\- High plasma dielectric constant that permits a new class of
potentially efficient radio-frequency heating and current drive
techniques, such as the high-harmonic fast wave and the electron
cyclotron wave conversion to electron Bernstein wave.

\- Minimized plasma magnetic flux and helicity content to ease
noninductive plasma startup including coaxial helicity injection or
bootstrap current overdrive.

\- Naturally diverted plasma scrape-off layer with large flux expansion
(up to 10 or more) and magnetic mirror ratio (up to 4 to 1).

These interesting features indicate great opportunities for discovery,
innovation, and advancement in fusion and plasma sciences. If verified,
the ST plasma will open up new opportunities for attractive applications
of magnetic fusion using compact devices. Figure 3 indicates how the ST
plasma, given successes in proof-of-principle and proof-of-performance
tests, could lend itself to a pathway for developing fusion power.

2.0 summary safety assessment

Nonradiological safety aspects of NSTX operations are discussed
throughout this document within the relevant sections on systems and
components and in the Failure Modes and Effects Analyses (FMEAs) in
Appendix 1. A hazards analysis summary is provided in Appendix 2. The
safety of personnel will be ensured by proper system design and
construction, the presence of features which mitigate the effect of
failures (e.g. redundancy, energy isolating barriers, etc.), exclusion
of personnel from areas such as the NSTX Test Cell (NTC) and the cable
spread room when hazards exist via hardwired interlocks and
administrative procedures, and through personnel training and
procedurizing of work. Based on this information and the discussion in
the rest of this chapter, NSTX can be operated and maintained in a safe
and environmentally acceptable manner, and in compliance with applicable
laws, regulations and directives.

The radiological limits and design objectives adopted for the NSTX
Project are shown in Table 2. Compliance with the relevant design
objectives is discussed in Sections 2.1 and 2.2.

**[Table 2: Radiological Limits and Design Objectives]{.underline}**

+--------+----------+---------+------------+--------+--------+-------+
|        |          | **P,    | **Public   |        | **     |       |
|        |          | Probab  | Expo       |        | Occupa |       |
|        |          | ility** | sure**[^1] |        | tional |       |
|        |          |         |            |        | Expo   |       |
|        |          |         |            |        | sure** |       |
+--------+----------+---------+------------+--------+--------+-------+
| *      |          | **Of    | **Re       | **De   | **     | **Des |
| *Condi |          | Occur   | gulatory** | sign** | Regula | ign** |
| tion** |          | rence** |            |        | tory** |       |
|        |          |         | **Limit**  | *      |        | **O   |
|        |          | **In A  |            | *Objec | **L    | bject |
|        |          | Year**  | **(rem per | tive** | imit** | ive** |
|        |          |         | yr)**      |        |        |       |
|        |          |         |            | **(rem | **(rem | *     |
|        |          |         |            | per    | per    | *(rem |
|        |          |         |            | yr)**  | yr)**  | per   |
|        |          |         |            |        |        | yr)** |
+--------+----------+---------+------------+--------+--------+-------+
| R      | Normal   | P\~1    | 0.1 total  | 0.01   | 5      | 1     |
| outine | Op       |         |            | total  |        |       |
| O      | erations |         | 0.01       |        |        |       |
| perati |          |         | ai         |        |        |       |
| on[^2] |          |         | rborne[^3] |        |        |       |
|        |          |         |            |        |        |       |
|        |          |         | 0.004      |        |        |       |
|        |          |         | drinking   |        |        |       |
|        |          |         | water      |        |        |       |
+--------+----------+---------+------------+--------+--------+-------+
|        | Ant      | 1\      | 0.5 total  | 0.05   |        |       |
|        | icipated | >P≥10-2 | (including | per    |        |       |
|        | Events   |         |            |        |        |       |
|        |          |         | normal     | event  |        |       |
|        |          |         | operation) |        |        |       |
+--------+----------+---------+------------+--------+--------+-------+
| A      | Unlikely | 10-2\   | 2.5        | 0.5    | r      | ref5  |
| cciden | Events   | >P≥10-4 |            |        | ef[^5] |       |
| ts[^4] |          |         |            |        |        |       |
+--------+----------+---------+------------+--------+--------+-------+
|        | E        | 10-4\   | 25         | 5[^6]  | ref5   | ref5  |
|        | xtremely | >P≥10-6 |            |        |        |       |
|        | Unlikely |         |            |        |        |       |
|        | Events   |         |            |        |        |       |
+--------+----------+---------+------------+--------+--------+-------+
|        | In       | P\<10-6 | NA         | NA     | NA     | NA    |
|        | credible |         |            |        |        |       |
|        | Events   |         |            |        |        |       |
+--------+----------+---------+------------+--------+--------+-------+

[2.1 Radiological Impacts of Routine NSTX Operations]{.underline}

Estimates have been performed of the maximum expected individual offsite
doses (at the PPPL site boundary) from routine NSTX operations,
including NBI. Details of this calculation are documented in Reference
3. Assumptions used in this calculation (see Reference 3 for additional
references to the sources of these assumptions) are:

a\. Negative pressure is not maintained in the NSTX Test Cell (NTC),
therefore airborne radionuclide releases from this room are assumed to
be ground level releases. Exhaust gases from NSTX operations are
released to the D-Site facility stack via the Vacuum Pumping System
(VPS; see Section 6.1).

b\. NSTX pulse capability is 96 pulses/day, 5 days/week, 3 weeks/month,
and 9 months/year. Repetition rate is 300 sec and the pulse length is 5
sec.

c\. NSTX D-D neutron generation rate is 2 x 1014 neutrons/sec.

d\. Since NSTX D-D reactions will produce some tritium, some D-T
reactions are assumed to take place. The D-T neutron generation rate in
NSTX is assumed to scale in the same manner as was assumed for TPX (see
Reference 5, Appendix A). The NSTX D-T neutron generation rate is thus
assumed to be 4 x 1012 neutrons/sec.

e\. Production of Ar41 from NTC air activation by NSTX neutrons is based
on TPX calculations for the TFTR Test Cell, scaled as the ratio of the
NTC-to-TFTR Test Cell volumes (0.38). No accounting is made for the
effects of the non-borated NTC floor. Boration of the TFTR Test Cell
center support plug and the first one-foot of the TFTR Test Cell floor
may reduce Ar41 production in that room by absorption of thermalized
neutrons. Not accounting for the absence of this effect in the NTC
should not significantly alter the NSTX offsite dose projection because
Ar41 contributes \<10% of the total offsite dose.

f\. Maximum offsite dose/Ci for airborne tritium and Ar41 is as noted in
Reference 6, Table 1. Offsite dose/Ci from routine ground level releases
(i.e., due to Ar41 releases from the NTC) are assumed to scale in the
same manner as indicated in Reference 6, Table 1 for accidental releases
(i.e., dose/Ci from ground level releases are three times higher than
dose/Ci from stack releases).

g\. Tritium condensed on NTC HVAC coils is sent to the liquid effluent
collection tanks (see Chapter 3) for eventual discharge to the sanitary
sewer system. The quantity of tritium released via this pathway is
assumed to be twice the maximum percentage of stack released tritium
(4.7%) that was experienced during the four years (1989-92) preceding
TFTR D-T operations. Liquid releases of tritium are thus assumed to be
10% of airborne tritium releases. Dose calculation for this pathway is
as described in Section 8.2.3 of Reference 7.

A summary of the contributions to the total offsite dose from routine
NSTX operations is provided in Table 3.

Table 3: Dose Projections from Routine NSTX Operations

  --------------------- --------------------- ---------------------------
  **PATHWAY**           **ROUTINE ANNUAL      **MAXIMUM SITE BOUNDARY
                        RELEASE OR            DOSE**
                        GENERATION**          

  Airborne Tritium (HTO 0.63 Ci/yr            0.0016 mrem/yr
  or T2O)                                     

  Liquid Tritium (HTO)  0.063 Ci/yr           0.0013 mrem/yr

  Activated Air (Ar41)  0.117 Ci/yr           0.0014 mrem/yr

  Direct/Scattered      1.3 x 1019 DD         0.0151 mrem/yr
  Neutron and Gamma     neutrons/yr + 2.6 x   
  Radiation             1017 DT neutrons/yr   

                                              TOTAL = 0.0194 mrem/yr
  --------------------- --------------------- ---------------------------

The total estimated maximum site boundary dose from routine NSTX
operations is 0.0194 mrem/yr, which is much less than the design
objective of 10 mrem/yr (see Table 2).

[2.2 Radiological Impacts of Postulated Tritium Leak from NSTX
Machine]{.underline}

Entrainment inside the NSTX torus vacuum vessel of tritium produced by
D-D reactions may cause a buildup of releasable tritium in the machine
over time. Most of the tritium produced would be vented to the stack by
the VPS, but as much as 45% may be trapped in the torus (note that the
routine dose calculation in Section 2.1 conservatively assumed that all
tritium produced is vented to the stack). Assuming that this trapped
tritium is not deliberately cleaned out of the torus, the maximum amount
of tritium that could be held up in the torus after 10 years of NSTX
operation (using assumptions b and c in Section 2.1) could be 10 yr x
0.63 Ci/yr x 0.45 = 2.84 Ci. Based on the results of deliberate air
venting of the TFTR torus in 1995, about 15% of this inventory or 0.43
Ci could be released due to an NSTX torus leak. If such a leak was too
large to be pumped on to maintain negative pressure in the torus, this
quantity of tritium could be released to the room and subsequently to
the environment. The maximum individual site boundary dose from the
release of 0.43 Ci of tritiated water vapor would be 0.43 Ci x 0.0157
mrem/Ci = 0.007 mrem, much less than the design objective of 50 mrem for
this event (which based on information in Reference 7, would have an
estimated probability of 3.7 x 10-2/yr). Maximum worker exposures
resulting from this release are calculated to be less than 50 mrem, well
within the requirements of Table 2. See Reference 3 for additional
information and references.

[2.3 Radioactive Waste]{.underline}

Small amounts of tritium contaminated pump oil (\< 0.001 Ci per year)
are anticipated to be produced during NSTX D-D operations. This oil will
be disposed offsite as low level radioactive waste (e.g., at the low
level waste disposal facility at the DOE Hanford Site in Richland,
Washington as has been past practice at PPPL).

3.0 site

The NSTX device is located in the NSTX Test Cell (NTC) at D-Site of the
Princeton Plasma Physics Laboratory (PPPL); see Figures 4 and 5. The NTC
was formerly known as the Hot Cell during TFTR operations, and was
originally designed for testing of TFTR heating neutral beamlines and
their components, and to effect maintenance, repairs, or modifications
on large, highly radioactivated components and assemblies from the TFTR
Test Cell. The NTC is 60 ft x 114 ft and has a ceiling height of 54 ft.
The floor is at the same level as that of the adjacent Test Cell for the
TFTR. Construction is of reinforced concrete throughout, with a 2 ft
thick floor slab. The roof is 5-1/2 ft thick at the high point, the
north, south and west walls (the latter separating the area from the
TFTR Test Cell) are 4 ft thick, and the east wall is 3 ft thick. A 3-ft
wide, 7-ft high, and 1-ft thick tritium seal door (usually open) backed
by a three-hour fire door (with crash bar for emergency egress),
provides access to the north end of the NTC from the adjacent gallery. A
similar pair of doors leads into the south end of the room. A
concrete-filled large (15 ft wide, 13 ft high, 1 ft thick) tritium seal
door is located between the NTC south high bay area and the Neutral Beam
Power Conversion (NBPC) building. This door is normally closed except
for movement of major pieces of equipment. A 16-ft x 26-ft x 4-ft thick
concrete-filled tritium seal door also exists between the TFTR Test Cell
and the NTC south high bay area.

A 32 ft by 60 ft platform with a working surface height of 9 ft is
installed around the NSTX device to allow easy access to machine
components and to support device appurtenances. The platform has
aluminum structural members with a fire retardant wood deck and masonite
top. Lighting and fire detection/suppression are installed under the
platform. A 2 ft thick concrete shield wall with labyrinth and door
(with crash bar for emergency egress), is placed in the NTC south of the
NSTX device (see Figure 5).

The NTC air is conditioned to maintain 70°F dry bulb temperature and 40%
relative humidity. The NTC is maintained at atmospheric pressure using
supply and exhaust fans at flow rates up to 16,000 cfm. Room exhaust
that is not recirculated is directed to the D-Site facility stack, which
is monitored for tritium.

The NTC fire detection system consists of ionization smoke detectors and
rate of rise heat detectors located at the ceiling and aspirated smoke
detection (VESDA) under the platforms. Fire suppression is via a
preaction type automatic water sprinkler system similarly located. The
detection system, in addition to providing appropriate notification,
operates the preaction valve and charges the pipes with water to provide
flow to any sprinkler heads which have been caused to open by high
temperature. Fire dampers are included in HVAC ductwork where they
penetrate the NTC wall (see Figure 5.3-1 of Reference 7). Each damper
has a heat sensitive link which melts and shuts the fire damper at a
temperature of 212°F. NTC HVAC duct smoke detectors are designed to shut
down HVAC and provide local and remote alarms.

NTC floor drains (located in the trenches for the large tritium seal
doors leading to the NBPC Building and the TFTR Test Cell) and HVAC
condensate are piped to three 15,000 gallon liquid effluent collection
(LEC) tanks located outside the D-Site experimental complex (see Section
8.2.2.2 of Reference 7). The contents of these tanks are sampled
periodically and, if regulatory criteria are met (tritium concentration
≤ 2 x 106 pCi/liter, cumulative tritium discharge of ≤ 1 Ci per calendar
year), the tank liquid is discharged to the sanitary sewer system.

The NTC, along with the rest of the D-Site experimental complex
structures, has been determined to have adequate capacity to remain
functional under the overall loads due to an earthquake with a
horizontal ground acceleration of 0.13g. The NSTX platform has been
designed for the seismic requirements of the NSTX torus structure (see
Section 4.2).

The NTC is structured with a crane haunch and rails to support a 75-ton
bridge crane outfitted with an auxiliary 15-ton hoist.

All instrumentation is isolated via optical and/or magnetic (isolation
transformer) means prior to exiting the NTC boundary. The isolation is
rated to withstand a one minute AC hipot test at 20 kV AC rms.

NSTX machine control functions are executed from the NSTX Control Room
(former TFTR Main Control Room) at C-Site (in the basement of the Lyman
Spitzer Building).

For plasma operations (and depending on experimental plans and
operational experience), fixed and/or portable gamma and neutron
radiation monitors may be set up at various locations inside the NTC,
outside the north, east and west walls of the NTC; south of the 2 ft
thick concrete shield wall in the NTC; on the roof of the NTC; and in
the Mechanical Equipment Room underneath the NTC.

Additional details on the NTC and the C- and D-Site facilities that
support NSTX can be found in Reference 7.

4.0 torus systems

The Torus Systems consist of the Plasma Facing Components (PFCs), Vacuum
Vessel and Torus Support Structure, and Magnet Systems (see Figure 1).

[4.1 Plasma Facing Components (PFCs)]{.underline}

All surfaces which face the plasma (Plasma Facing Components (PFCs))
consist of carbon based materials designed to absorb the heat and
particle flux from the plasma and heating systems, to minimize the
influx of impurities to the plasma, and to withstand the electromagnetic
forces associated with plasma disruption. The PFCs are required to: (1)
accommodate a high temperature (350°C) bakeout mode to liberate trapped
impurities; (2) accommodate a helium glow discharge cleaning mode; and
(3) be electrically connected to the Vacuum Vessel via their mounting
structures. The plasma facing components include the inner wall armor,
divertor area strike plates, passive stabilizers, and associated plasma
facing tiles (some of which may not be necessary or present for first
plasma operations).

For baseline operation, there will be no active cooling of the inner
wall plasma facing components during a plasma discharge. However, the
plasma facing tiles on the outer passive stabilizer and in the divertor
regions will be thermally attached to actively cooled plates, such that
the tiles will cool to the plate temperature between discharges. The
inner wall armor will be thermally isolated from the center stack casing
and must rely on radiation cooling to the other plasma facing tiles
between discharges.

PFCs are designed to accommodate the heat loads due to 6MW of auxiliary
(RF + NBI) heating power for pulse lengths up to 5 seconds, and
repetition period of 300 seconds for Natural Divertor, Single Null, and
Double Null plasma configurations. In case the combined RF + NBI heating
power exceeds 6 MW the pulse length must be shortened accordingly such
that the energy dissipation remains within the power handling limit of
the PFCs.

Additional details on the PFCs can be found in References 8 and 9. FMEAs
are provided in Appendix 1 (WBS Element 1.1).

[4.1.1 Passive Stabilizers]{.underline}

The passive stabilizers consist of primary (closest to midplane) and
secondary (furthest from midplane) pieces, one set above the midplane
and one set below the midplane of the NSTX device. Each stabilizer is
made up of a series of conical shaped copper plates that can be
electrically connected in the toroidal and poloidal directions using
jumpers. The stabilizer connections to the Vacuum Vessel allow for
alignment adjustments and facilitate removal of individual plates for
modification to accommodate access for future diagnostic upgrades. The
plasma facing surfaces of the stabilizers are protected with graphite
tiles. (Union Carbide - ATJ or equivalent).

[4.1.2 Inner Wall Armor]{.underline}

The inner wall armor is composed of alternating columns of graphite and
carbon fiber composite (CFC) tiles attached to the center stack casing.
The tiles are mounted in such a way that heat transfer from the tiles to
the center stack casing is minimized. Slots are provided in the backside
of at least half the tiles such that diagnostic wires and magnetic
diagnostics can be positioned between the center stack casing and the
tiles.

[4.1.3 Inboard Divertor Area Strike Plates]{.underline}

The inboard divertor area strike plates consist of graphite tiles
attached to the center stack casing. The poloidal extent of the inboard
divertor strike plates is such that it eliminates all line of sight
between the upper and lower ceramic ring/bellows assemblies and the
plasma. The inboard divertor plates are not traced for active
temperature control, but are thermally connected to the upper and lower
flanges of the center stack casing. The center stack casing flanges have
active temperature control.

[4.1.4 Outboard Divertor Area Strike Plates]{.underline}

The outboard divertor area strike plates consist of segmented upper and
lower toroidal rings composed of copper plates covered with graphite
tiles. The outboard divertor plates are attached to the upper and lower
domes of the vacuum vessel, and are traced with stainless steel tubing
for active temperature control during bakeout and operation.

[4.1.5 Neutral Beam Protective Plates]{.underline}

Protective Plate Armor mounted on the midplane at Bays H and I is
provided to receive beam energy in the absence of plasma, beam shine
through during plasmas, and brief tuning beam shots at abbreviated pulse
lengths. The Armor is designed to absorb one full power full duration
neutral beam shot in the absence of plasma without failure. Interlocks
prohibit the pulse or limit the pulse injected into the vacuum vessel
protective plates to 50 ms when plasma is not present. Energy deposition
for this duration does not appreciably heat the plates. The short pulse
is useful for conditioning the beams between injection shots.

[4.2 Vacuum Vessel and Torus Support Structure]{.underline}

The functions of the vacuum vessel are to:

a\. Provide a vacuum boundary around the plasma suitable for high vacuum
conditions;

b\. Provide structural support for plasma facing components (PFCs);

c\. Provide access and structural support for vacuum pumping ducts,
plasma heating and current drive, and diagnostics; and

d\. Provide a structural support for the coil systems.

The function of the torus support structure is to provide the overall
support mechanism for the vacuum vessel and all torus components that
are attached to it, as well as support for the centerstack assembly.

The vacuum vessel assembly is capable of operation in high vacuum
conditions with a base partial pressure of ≤1x10-8 torr, and is capable
of handling the heat load resulting from the 350°C bakeout of the plasma
facing components.

The NSTX vacuum vessel is constructed of 304 stainless steel and has a
nominal wall thickness of 0.625-in. It consists of upper and lower domes
attached to an outer cylindrical section, and an inner cylindrical
section, constructed of Inconel 718, referred to as the center stack
casing. The center stack casing is mechanically connected to, but
electrically isolated from, the upper and lower domes via a ceramic
insulator. This completes the vacuum boundary but allows for an
electrical potential difference between the center stack casing and the
remainder of the vacuum vessel for Coaxial Helicity Current Drive (CHI;
see Section 5.2). Ports are provided with dimensions compatible with the
requirements of all types of Heating & Current drive systems, as well as
diagnostic systems. Additional openings are provided for personnel
access. Unused openings, including windows, are covered to prevent
potential personnel injury or damage to windows.

The lower dome of the outer section of the Vacuum Vessel is electrically
connected via four toroidally symmetric connections to a single point
connection which is designed to provide a ground connection and a return
path for the CHI current. Connections are sized to carry the current
during CHI operations as well as the return of the current during
bakeout heating of the center stack casing.

The NSTX torus structure is designed to satisfy the Department of Energy
(DOE) standard for natural phenomena hazard (NPH) events[^7]. Only the
effects of earthquakes are considered for the NSTX torus structure. DOE
requires the use of Performance Categories (PC) to specify the relative
risk, environmental impact, importance, and cost of each facility. The
assessment for seismic loading and evaluation for seismic response is
being followed to determine that the design of the structure is
acceptable with respect to the performance goals[^8]. There are no
safety class items associated with the NSTX machine since its failure
would not result in the release of significant quantities of hazardous
materials. On this basis the seismic performance goal for the NSTX torus
structure is to maintain worker safety, placing it in NPH Performance
Category 1 (PC-1). Any structures, systems & components (SSCs) whose
failure would adversely effect the performance of the NSTX torus
structure or create a threat to worker safety are also placed in PC-1.
All other systems are placed in PC-0 and thus have no seismic design
requirements. For the PPPL Site, a PC-1 earthquake has a maximum
horizontal ground acceleration of 0.09g

Additional details on the vacuum vessel and torus support structure can
be found in References 10 and 11. FMEAs are provided in Appendix 1 (WBS
Element 1.2).

[4.3 Magnet Systems]{.underline}

The magnet systems consist of the outer poloidal field (PF) coils, outer
legs of the toroidal field (TF) coils and the center stack assembly. The
center stack assembly includes the inner legs of the TF coils, two
additional PF coils (PF1a and 1b), and the OH coil, as well as the
center stack casing (see Figure 1). The magnet systems are designed to
satisfy the seismic loading for NPH Performance Category 1 (PC-1) (see
Section 4.2 above).

[4.3.1 Outer Poloidal Field (PF) Coils]{.underline}

The function of the poloidal field (PF) coil system is to: support the
plasma against radially expanding current and pressure forces; provide
plasma shaping and divertor/scrape-off control; provide vertical/radial
position stability control using feedback; help compensate for the error
fields of the ohmic heating solenoids; and provide additional flux to
the plasma. The outer PF magnets consist of four pairs of water-cooled
copper coils designated as PF 2a/2b, 3a/3b, 4b/4c, and 5a/5b. The pairs
are symmetric about the same horizontal mid-plane of the NSTX device. PF
1a/1b are part of the center stack subsystem. Coils identified on the
formerly operated S-1 spheromak as EF coils #1, #2 and #3 are used for
the outer PF coils PF2, PF3 and PF4 on NSTX; PF5 is a new coil. The
outer PF coils are supported off the vacuum vessel structure (the
support mechanism is compatible with the vacuum vessel thermal expansion
during bakeout).

The maximum current and maximum equivalent square wave for the outer PF
magnets (which can be conducted once every 300 seconds) are:

**[Table 4 Outer PF Coil Currents]{.underline}**

+-----------------------+-------------------------+--------------------+
| **Coil**              | **Max Current (kA)**    | **Max ESW**        |
|                       |                         |                    |
|                       |                         | **(sec)**          |
+-----------------------+-------------------------+--------------------+
| PF 2a/2b              | 20.0                    | 5.0                |
+-----------------------+-------------------------+--------------------+
| PF 3a/3b              | 20.0                    | 5.0                |
+-----------------------+-------------------------+--------------------+
| PF 4b/4c              | 20.0                    | 5.0                |
+-----------------------+-------------------------+--------------------+
| PF 5a/5b              | 20.0                    | 5.0                |
+-----------------------+-------------------------+--------------------+

Initial operations of the PF4 and PF5 coils are mutually exclusive.
Switchover to operate one or the other is made by manually repositioning
bus/cable connections in the NSTX Test Cell (NTC). Future upgrades may
provide for simultaneous operations of these coils.

[4.3.2 Outer Toroidal Field (TF) Coils]{.underline}

The function of the toroidal field (TF) coil system is to provide the
toroidal magnetic field, which is necessary to magnetically confine the
NSTX plasma. The outer TF coils consist of an outer array of twelve
water-cooled copper coil bundles, each containing the return conductors
for three turns. The inner legs of the TF coils are part of the center
stack subsystem. Demountable joints are provided in the TF outer legs to
allow removal/replacement of the center stack assembly. The deadweight
of the outer legs is supported through the torus support structure to
the floor.

The baseline design of the outer legs of the TF coils is capable of
producing the following toroidal fields once every 300 seconds:

> **[Table 5 TF Outer Leg Performance]{.underline}**

+-----------------------------------+----------------------------------+
| **Flat Top Duration**             | **BTF (R=85.4cm)**               |
|                                   |                                  |
| **(sec)**                         | **(kG)**                         |
+-----------------------------------+----------------------------------+
| 0.6                               | 6.0                              |
+-----------------------------------+----------------------------------+
| 5.0                               | 3.0                              |
+-----------------------------------+----------------------------------+

The outer legs of the TF coils which are installed as part of the
baseline are capable of conducting the currents required to produce
toroidal fields of 3.0 kG for a flat top duration of 60 seconds, once
every 3600 seconds, in case a NSTX long pulse upgrade is undertaken.

[4.3.3 Center Stack Assembly]{.underline}

The center stack subsystem includes the inner legs of the TF coils, the
Ohmic Heating (OH) solenoid, shaping coils - PF coils 1a/1b, and the
center stack casing. The Ohmic Heating solenoid\'s primary function is
to provide sufficient loop voltage for plasma initiation, and sufficient
flux swing for inductive plasma current drive. The center stack casing
functions as the internal vacuum and thermal barrier and provides
support for the center stack coils and inner wall armor. PF and TF coil
functions are described in Sections 4.3.1 and 4.3.2, respectively. The
center stack radial build is comprised of the TF inner legs located in
the core of the center stack surrounded by the OH solenoid. The PF1a
coils are located over the OH coil symmetrically above and below the mid
plane. The PF1b coil is located below the mid plane only.

[4.3.3.1 TF Inner Legs]{.underline}

The inner legs of the TF coils consist of tightly-nested fully-bonded
copper conductors. The baseline design of the inner legs of the TF coils
is capable of producing the same toroidal fields once every 300 seconds
as for the outer TF coils.

[4.3.3.2 Ohmic Heating (OH) Coil]{.underline}

The OH coil consists of a solenoid surrounding the inner legs of the TF
coil. For fully inductive NSTX operations, using a bipolar current, the
OH coil is capable of providing a flux swing of 0.6 volt-seconds. The
coil has a peak current of 24kA with a maximum equivalent square wave
(ESW) of 0.525 sec and a repetition period of 600 seconds. For partial
inductive NSTX operations, using a unipolar current, the OH coil is
capable of providing a flux swing of 0.3 volt-seconds, with a repetition
period of 300 seconds. For partial inductive operations, the fully rated
heating and current drive power is assumed deposited within the NSTX
machine such that the maximum allowable operating temperature of the
center stack casing is, in effect, coincident with the fully rated
operation of the OH in the partial inductive, unipolar mode.

[4.3.3.3 Inner PF Coils]{.underline}

The shaping coils consist of upper and lower coil pair, PF1a, and lower
coil PF1b. Current carrying requirements (once every 300 seconds) for
these coils are:

> **[Table 6 PF1a/PF1b Current Requirements]{.underline}**

+-----------------------+-----------------------+----------------------+
| **Coil**              | **Peak Current**      | **ESW**              |
|                       |                       |                      |
|                       | **(kA)**              | **(sec)**            |
+-----------------------+-----------------------+----------------------+
| PF1a                  | 15.0                  | 5.0                  |
+-----------------------+-----------------------+----------------------+
| PF1b                  | 20.0                  | 1.0                  |
+-----------------------+-----------------------+----------------------+

[4.3.3.4 Center Stack Casing]{.underline}

The center stack casing is electrically isolated from the outer vacuum
vessel and is compatible with operation in high vacuum conditions.
Electrical breaks are provided between the vacuum vessel and the center
stack casing to support coaxial helicity injection (CHI) during startup.
The electrical isolation is rated for 2kV DC CHI operations, 5kV DC
hipot. The center stack casing includes suitable axisymmetric terminals
for electrical connections for CHI, and accommodates the passage of a
current in the Z direction for the purpose of resistive heating as a
source of heat during the bakeout mode. The center stack casing is
bakeable to a temperature [\>]{.underline} 350°C.

The center stack includes an air gap and/or insulating material in the
annular region surrounding the OH coil for the purpose of thermal and
electrical isolation between the coil and the casing. Electrical
isolation is designed to withstand 2kV due to the CHI. Thermal isolation
is designed to protect the OH coil and surrounding magnetics diagnostics
from excess temperatures due to heat influx from bakeout and from normal
operations.

Additional details on the magnet systems can be found in References 12
and 13. FMEAs are provided in Appendix 1 (WBS Element 1.3).

5.0 plasma heating and current drive systems

The Plasma Heating and Current Drive Systems (H&CD systems) consist of
the High Harmonic Fast Wave (HHFW) System, the Coaxial Helicity
Injection Current Drive (CHI) System, the Electron Cyclotron Heating
(ECH) System, and the Neutral Beam Injection (NBI) System. These systems
provide energy input into the plasma either directly or as a consequence
of providing momentum. This energy input is required to increase and
sustain the thermal energy of the plasma. All H&CD systems may be called
on to provide current drive in the NSTX plasmas. This current drive may
be useful for ramping up the current at the beginning of a discharge,
maintaining the flat-top current, or providing radial localized currents
for current profile control. These systems may also be used for plasma
initiation, breakdown of the prefill gas and preheating.

Additional details on the plasma heating and current drive systems can
be found in References 14 and 15. FMEAs are provided in Appendix 1 (WBS
Elements 2.1, 2.2, 2.3 & 2.4).

[5.1 High Harmonic Fast Wave (HHFW) System]{.underline}

The High Harmonic Fast Wave Heating and Current Drive system consists of
the RF generators, transmission lines (see Figure 6), tuning and
matching systems, RF feedthroughs and internal transmission lines,
antennas with Faraday shields and protective limiters, and the
associated diagnostic and control systems. The functions of the High
Harmonic Fast Wave (HHFW) system are to:

a\. Provide electron heating power to the NSTX plasma via the fast
magnetosonic wave.

b\. Provide non inductive current drive.

c\. Provide control over the heating/current drive deposition profile,
through the antenna phasing.

The HHFW system is designed to deliver at least 6 MW of power to the
NSTX plasma for 5 seconds, once every 300 seconds. This system utilizes
RF power produced by the six existing Tokamak Fusion Test Reactor (TFTR)
Ion Cyclotron Range of Frequencies (ICRF) sources (see Section 4.8 of
Reference 7). The HHFW system uses twelve antennas mounted on the vacuum
vessel wall in the gap between the upper and lower passive stabilizing
plates. The antennas are arranged toroidally between the NSTX vacuum
vessel mid plane ports. Each antenna consists of a current strap, a back
plane, a Faraday shield, and a local (bumper) limiter structure. The
antennas are compatible with bakeout and glow discharge modes of
operation as well as abnormal operating events such as disruptions,
plasma control failures, power supply failures, bus opens or shorts, or
magnetic faults. The set of six sources (and twelve antennas) are
capable of operation at frequencies of 30 MHz. DC shorting stubs are
incorporated in the transmission line prior to the point where the line
exits the NSTX test cell. A decoupling system provides a DC short
circuit across the transmission line to keep the center and outer
conductors at the same potential if a Faraday shield fault allows plasma
to contact the antenna strap.

RF transmission lines are grounded to the perimeter ground in the NSTX
test cell (NTC), and are grounded immediately outside the NTC wall to a
plate that is bonded to building steel.

Switches are provided to isolate HHFW power from the NTC. These switches
are interlocked with the NTC access control system. Both electrical and
mechanical (Kirk Key) interlocks are provided. Whenever personnel must
enter the NTC, an emergency stop (E-Stop) is sent to all HHFW sources if
any switch is not in the safe (dummy load) position. Local (dummy load)
operation of RF sources can be performed during NTC access provided that
all of the switches are locked in the safe position. This ensures that
the NTC transmission lines are disconnected from the RF sources and that
the source outputs are terminated in dummy loads.

An RF survey will be performed upon system commissioning and repeated
annually. In addition, HHFW operating personnel are procedurally
required to check RF radiation at low power before proceeding to high
power whenever any high power transmission line configuration is
changed.

To provide reliability and a margin of safety, the RF vacuum feed
through can withstand a pressure of 30 psig. The antenna, limiter, and
transmission line system is designed to satisfy the seismic loading for
NPH Performance Category 1 (PC-1) (see Section 4.2 above).

[5.2 Coaxial Helicity Injection Current Drive (CHI) System]{.underline}

The Coaxial Helicity Injection (CHI) Current Drive system is provided
for non-inductive start-up. The CHI system relies on poloidal breaks
that electrically isolate the center stack from the outer vacuum vessel.
The electrical isolation is rated for 2kV DC CHI operations, 5kV DC
hipot. This break is provided by two toroidal ceramic insulators
incorporated into the vacuum vessel design. When the CHI electrodes thus
formed are energized, a poloidal component of current flows which, due
to the influence of the toroidal field, results in a toroidal component
of plasma current. The PFCs which form the electrodes from which the CHI
current flows, are designed to dissipate the local power generation due
to the CHI current during normal and fault conditions, and are designed
to withstand the electromagnetic forces due to the fault current
deliverable by the CHI power supply system. The lower dome of the outer
section of the Vacuum Vessel is electrically connected via four
toroidally symmetric connections to a single point connection which is
designed to provide a ground connection and a return path for the CHI
current. Connections are sized to carry the current during CHI
operations as well as the return of the current during bakeout heating
of the center stack casing. The CHI power system is designed to provide
a controlled current waveform with a peak current of 50.0 kA and rise
time ≤ 27ms. Switches are provided to isolate CHI power from the NSTX
test cell (NTC), and these switches are interlocked with the NTC access
control system.

[5.3 Electron Cyclotron Heating (ECH) System]{.underline}

The electron cyclotron heating (ECH) system consists of a microwave
source and power supply, a transmission system, a vacuum interface and a
launching structure along with suitable diagnostics and controls. The
function of the ECH system, which is designed to deliver 20 kW for 5 mS,
is to provide pre-ionization for plasma breakdown. One ECH launcher is
installed at an outboard location in the Vacuum Vessel to direct the
microwave radiation toward the desired absorption location. The launcher
is compatible with bakeout and glow discharge modes. The launcher has a
vacuum window connecting it to the external transmission system. The
transmission system (consisting of a waveguide and special components
for power measurement) efficiently transports the microwave power from
the RF sources to the vacuum window. Switches are provided to isolate
480V AC power from the ECH System in the NSTX test cell (NTC), and these
switches are interlocked with the NTC access control system.

To provide reliability and a margin of safety, the vacuum window can
withstand a pressure of 30 psig. The launcher and transmission line
system is designed to satisfy the seismic loading for NPH Performance
Category 1 (PC-1) (see Section 4.2 above).

4.  [Neutral Beam Injection (NBI) System]{.underline}

The NSTX NBI system is designed to inject 80 keV neutral deuterium atoms
into the plasma at a power level of 5 MW, with pulse duration up to 5
seconds. The system includes one TFTR neutral-beam line with three ion
sources (see Sections 4.3, 4.4.2, 4.4.3, 4.5, and 7.3.4 of Reference 7),
operated at a reduced voltage (TFTR injection was 120keV). All NBI
systems utilize the original TFTR design and recycled or spare
components, or newly fabricated components in accordance with the
original TFTR design, with the exception of the NBI-to-NSTX torus duct
which has a physical interface requirement different than that of TFTR.
The NBI beam box and the HVEs are designed to satisfy the seismic
loading for NPH Performance Category 1 (PC-1) (see Section 4.2 above).

Deuterium ions are generated by passing an electric arc discharge
through low pressure deuterium gas to form a plasma within the source.
The deuterium ions are extracted and accelerated to a specified energy
level by electric fields. The ions are neutralized by charge-exchange on
a gas target. Particles which are not neutralized are deflected out of
the beam by a deflection magnet and directed onto an ion-beam dump. The
beam of energetic neutral particles penetrate the confining magnetic
fields of the torus and interact with the plasma. The NBI system
consists of the following main components (see Figures 13 and 14):

a.  Each of the three ion sources produces a low-voltage, high-current
    discharge from which deuterium ions are extracted and accelerated by
    a multiple-slot accelerator. The extraction potential gradient is
    established between the source grids. The decelerating potential
    between the suppressor grid and the grounded exit grid prevents
    electrons in the neutralizer region from being drawn into the
    accelerator structure.

b.  The ion deflection magnet serves to deflect ions from the mixed beam
    leaving the neutralizer. The magnet is inclined 45 degrees to the
    beam axis, and consists of six water cooled coils. To minimize stray
    field at the torus the magnet is shielded by high permeability
    material.

c.  The ion dump absorbs the energy of positive ions deflected out of
    the beam line by the deflection magnet. The dump consists of three
    plates positioned based on the expected trajectories of the three
    deuterium ion energy components (full, 1/2, and 1/3 energy).

d.  The calorimeter consists of three copper v-shaped elements and a
    screw/bellows actuator assembly which allow the elements to be
    lowered in to the path of the beam for calibration purposes.
    Thermocouples are installed to measure the energy distribution. The
    calorimeter is raised to permit shots into the NSTX torus.

e.  The NBI vacuum vessel, or "beam box", is of rectangular shape
    constructed of 3/4" thick 304 stainless steel with suitable
    reinforcing elements. A 78" port at the rear is provided for
    mounting the source and a 48" port is provided at the front for
    attachment of the duct to the torus. Additional ports are provided
    on the lid of the box for attachment of the calorimeter and
    magnet/ion dump assemblies.

f.  The Source Mounting, Neutralizer, and Terminal assembly mounts to
    the rear of the NBI vacuum vessel and contains the water cooled
    copper duct neutralizers, the SF6 pressurized source housing, and
    terminals for electrical connection of the source with the power
    supplies at the bottom of the source housing. The source mount is a
    two-axis gimbal with motor drive which allows vertical and
    horizontal aiming adjustment of +/- 0.5 degrees.

g.  The NBI support stand consists of five 8" x 8" box tube columns
    which are welded to plates which are in turn welded to the beam box
    and bolted to the floor. The support stand is designed to
    accommodate the unbalanced vacuum load which tends to push the beam
    box radially inward toward the NSTX vacuum vessel.

h.  The NB-torus connecting duct provides a passage through which the
    beam can pass with sufficient clearance from wall. The duct includes
    a ceramic break to electrically isolate the NBI system from the
    torus vacuum vessel, a gate valve, duct scrapers and protective
    plates, attachment bellows, duct joints, and flanges. The gate valve
    between the torus and NBI vacuum enclosures provides a seal when
    either the NBI vessel or NSTX vacuum vessel is under vacuum while
    the other is at atmospheric pressure. The valve has a clear opening
    of at least 90 cm diameter. Actuation time is less than 30 s for
    translation of the gate from the full-closed and sealed position to
    the full-open position, or vice versa. Bolted mating flanges are
    provided at several planes in the NB duct to permit removal of
    individual components without disturbing the entire NBL. The NB duct
    scrapers are mounted inside the NB-torus duct and consist of thick
    copper plates. The NBI attachment bellows are required to allow for
    assembly and disassembly of the duct onto the NSTX torus.

i.  The cryopumping system is required to limit the pressure in the duct
    during a pulse via cryocondensation on to liquid helium cooled
    panels which are guarded by liquid nitrogen panels and chevron
    baffles (see Section 4.5 of Reference 7 for details on the Cryogenic
    Supply System, and Sections 9.1.7.1 and 9.2.7.1 of Reference 7 for
    discussions of cryogenic hazards and methods for their mitigation).

j.  The NBI power supply system consists of the Accel Power Supply
    system, the Auxiliary Power Supply system, and the Local Control
    System. The Accel Power Supply system consists of the primary power
    selector switch, fast vacuum interrupter, voltage controller, high
    voltage transformer/rectifier, crowbar, capacitor bank, and
    modulator/regulator, and serves to provide electric power to the ion
    sources, along with suitable protection. The Auxiliary Power Supply
    System consists of the arc, filament, decel, and magnet power
    supplies. The arc and filament supplies are housed together in an
    auxiliary tank known as the high voltage enclosure (HVE), which is
    located on the north end of the NSTX Test Cell, near the NBI. The
    HVE vessel is pressurized with SF6 for high voltage insulation. The
    Local Control System provides interlocking which protects against
    misoperation of the various components of the NBI power supply
    system . See Section 7.3.4 of Reference 7 for additional details on
    the NBI power supply system.

k.  The NBI vacuum pumping system consists of turbomolecular, backing,
    and roughing systems. The roughing system does dual duty in that it
    can be valved to the NBI vacuum vessel or to the NSTX vacuum vessel,
    and serves as the NSTX vacuum vessel roughing system. See Section
    4.4.2 of Reference 7 for additional details on the NBI vacuum
    pumping system.

l.  The NBI I&C system is a PLC based operating system for monitoring,
    control, and interlocking of all NBI parameters, which also provides
    an interface with the NSTX Hardwired Interlock System (HIS). Main
    NBI control is from the D-site 138' Level.

6.0 Auxiliary systems

The auxiliary systems consist of the vacuum pumping system, the gas
delivery system, the glow discharge system, the cooling water system,
the bakeout heating/cooling system, the instrument air system and the
gaseous nitrogen system. Components whose failure could impact the NSTX
torus structure are supported in a manner that satisfies the seismic
loading for NPH Performance Category 1 (PC-1) (see Section 4.2 above).

Additional details on the auxiliary systems can be found in References
16 and 17. FMEAs are provided in Appendix 1 (WBS Elements 3.1, 3.2, 3.3,
3.4 & 3.5).

[6.1 Vacuum Pumping System (VPS)]{.underline}

The NSTX vacuum pumping system establishes and maintains the vacuum
environment within the NSTX torus vacuum vessel (see Figure 7). It
consists of a pumping system, associated piping and valves capable of
achieving high vacuum, various pressure sensing elements and
transducers, and an analytical system capable of discriminating gas
species. The functions of the VPS are to:

a\. Roughdown the NSTX device from atmosphere to base pressure.

b\. Provide a high vacuum environment compatible with the NSTX
experimental program.

c\. Remove plasma exhaust and restore base pressure between pulses.

d\. Minimize and maintain impurity levels.

e\. Provide analytical capability for monitoring and control of machine
vacuum conditions.

f\. Provide pumping and control of pressure for Glow Discharge/Pulse
Discharge Cleaning modes (GDC/PDC).

g\. Be compatible with, and provide pumping for vacuum vessel bakeout.

h\. Provide appropriate safety interlocks for personnel and equipment
safety.

The VPS consists of a high vacuum (Hi-Vac) system, a roughing system and
a backing system. All components are located in the NSTX Test Cell
(NTC). Supports for VPS piping are adequate to satisfy the seismic
loading for NPH Performance Category 1 (PC-1) (see Section 4.2 above).

The Hi-Vac system includes two 3000 liter/sec turbomolecular pumps
(TMPs) mounted on a 24 inch inner diameter pump duct. The TMPs are
located about 21 ft from the center line of the NSTX torus (as
determined by magnetic fields). The Hi-Vac system has a pumping speed of
approximately 2200 liters/sec, and is capable of pumping the torus
(volume about 30,000 liters) down from a pressure of 10-3 Torr to the
low 10-8 Torr range of free gas in approximately three minutes between
discharges.

The roughing system provides torus pumpdown from atmosphere (760 Torr)
to less than 100 mTorr in less than one hour, at which point the TMPs
pump the torus to high vacuum. This is accomplished through the use of a
roughing mechanical pump (\~300 CFM) and a roughing booster pump (\~2700
CFM) connected to a 10 inch diameter roughing line.

The backing system provides backing for the TMPs via one mechanical pump
(\~100 CFM) and one booster pump (\~1600 CFM) connected to a 6 inch
diameter backing line.

The VPS includes pressure gauges capable of monitoring pressure from
atmosphere to high vacuum, and Residual Gas Analyzers (RGAs) capable of
discriminating gas species. Service ports, strategically located on the
vacuum system and the vacuum vessel are provided to facilitate
maintenance and leak checking. Provisions are made to bring the vacuum
system up to atmospheric pressure using dry gaseous nitrogen. A
Programmable Logic Controller (PLC) is used for main control and logic
functions of the VPS. The PLC communicates with NSTX Central
Instrumentation & Control and uses engineering displays for process
control from the Control Room.

Prior to NBI operations the roughing skid (TFTR NBI type) was "borrowed"
and connected to the vacuum pumping duct and controlled by the VPS PLC.
As of this issue of the SAD, the NBI roughing skid is connected to both
the NBI vacuum vessel and the NSTX vacuum pumping duct (with suitable
interlocked isolating valves), and the roughing pump is controlled by
the NBI PLC control system.

The VPS directs NSTX exhaust gases to the D-Site facility exhaust stack
via piping through the NTC floor to the basement Mechanical Equipment
Room, and connecting to the line that had been used for TFTR vacuum
exhaust to the stack prior to TFTR D-T operations. Passive stack
monitors continuously sample the exhaust for tritium (see Reference 7,
Chapter 12). The maximum annual stack discharge of tritium produced
during 5-sec D-D operations will be ≤ 0.63 Ci/yr, resulting in a maximum
offsite individual dose of 0.0016 mrem/yr (see Table 3). During NBI
cryopanel regeneration a relatively large quantity of hydrogen gas is
boiled off and exhausted by the vacuum pumping system through the stack.
By administrative procedures, the maximum allowable amount of condensed
hydrogen build-up is limited to 13 Torr, and the NBI PLC control
sequence includes nitrogen purge before and after pumping gases
liberated from both routine and emergency regenerations. These actions
prevent the formation of potentially explosive mixtures of hydrogen and
oxygen in the NBI vacuum vessel and D-site facility exhaust stack

The VPS is protected against improperly configured operation via an
interlocking control program in the PLC. Loss of electric power or a PLC
failure will result in components defaulting to safe states. A \"watch
dog timer\" is incorporated in the PLC field distribution network to
ensure the removal of electric power until normal conditions for
operation are restored. The RGAs and ion gauge controllers have built-in
self protection to prohibit operation above design-specified pressures.

[6.2 Gas Delivery System (GDS)]{.underline}

The Gas Delivery System (GDS) provides the following functions (see
Figure 8):

a\. Provides gas for plasma fueling.

b\. Provides gas for glow discharge cleaning (GDC).

c\. Provides instrumentation and control for gas injection

d\. Provides capability to select gas to be injected.

The following features are incorporated into the GDS design:

a\. A gas bottle bank with manifolding.for up to eight gas bottles.

b.  Three gas injection points on the outer vacuum vessel (two midplane,
    one top).

c.  Four gas injection points on the lower flange of the center stack
    casing for CHI, using a single gas injector.

d\. Injection valves allowing feedback for real time control.

e\. Minimization or elimination of the potential to form explosive
mixtures in the system piping and hardware.

f\. Remote operation of system.

The GDS, whose components (including gas supply bottles) are located in
the NTC, is designed to deliver gasses required for operation of the
NSTX device (e.g., deuterium, helium, etc.). Gas is provided by supply
gas cylinders for each specified gas. The gasses are routed via
austenitic stainless steel tubing to injection assemblies at three
locations on the outer vacuum vessel and four locations on the lower
flange of the center stack casing (CSC).

Each outer vacuum vessel injection assembly consists of a pneumatically
operated isolation valve, a fast acting (approximately 10msec response
time for full cycle) piezo-electric valve, and a vacuum vessel isolation
valve. Gas is selected for delivery and routed to any one or all of the
four injection assemblies by configuration of valves in the distribution
manifolds.

The CSC injector assemblies are electrically isolated from ground
potential via a ceramic break. Gas is fed into storage volumes on the
CSC side of the ceramic break, after which isolating valves are closed
and the volume containing the ceramic break is pumped out to ensure
suitable pressure and high dielectric strength conditions as required to
withstand the CHI voltage. The pressure in the line section containing
the ceramic break is monitored and interlocked with the CHI power
supply. The storage volumes are sized to limit the gas pressure in the
vacuum vessel to a value which is suitable for CHI and which will not
lead to spurious electrical breakdown at unintended locations.
Electrical actuators are insulated from ground potential as required for
CHI.

Injection to the vacuum vessel, continuously or in discrete pulses, is
metered by the piezo-electric valve (maximum delivery rate of about 80
Torr-liters/sec). Injection can be performed in closed loop mode
(setpoint control using the vessel ion or capacitance manometer gauges),
in open loop mode (waveform control during plasma), or by manual control
of the piezo-electric valves opening. Evacuation of the system is
provided by a rotary vane vacuum pump.

Exhaust gasses from the GDS are routed to the D-Site stack via the same
line that exhausts the VPS (see Section 6.1). The content of the largest
gas cylinder (311 cubic ft.) constitutes less than 0.1% of the volume of
the room (approximately 354,000 cubic ft.). Thus, oxygen concentrations
in the NTC would remain at safe levels for personnel even if a gas
cylinder's entire contents were released to the room.

A Programmable Logic Controller (PLC) is used for main control and logic
functions of the GDS. The PLC communicates with NSTX Central
Instrumentation & Control and uses engineering displays for process
control from the Control Room. The GDS is protected against improperly
configured operation via an interlocking control program in the PLC.
Loss of electric power or a PLC failure would result in components
defaulting to safe states (gas supply and torus interface valves would
close, drive voltage would be removed from the piezo-electric valves,
and all injectors would be disabled and disarmed). A \"watch dog timer\"
is incorporated in the PLC field distribution network to ensure the
removal of electric power until normal conditions for operation are
restored. Loss of communication with the Central I&C System for more
than five (5) seconds will cause the PLC to inhibit GDS operations by
disabling valve drivers and removing drive voltage from the
piezo-electric valves until communications are restored.

The Bay K Top Gas Injector is actively cooled by the Bakeout
Heating/Cooling System (see Section 6.5) which removes heat radiated by
the Center Stack Assembly during high temperature bakeout.

[6.3 Glow Discharge Cleaning System (GDC)]{.underline}

The Glow Discharge Cleaning System (GDC) establishes and controls the
GDC process in NSTX. GDC is a mode of vacuum conditioning in which
vacuum vessel internal surfaces are "scrubbed" clean by the bombardment
of ions formed during the glow process. The GDC system is highly
integrated with the VPS and GDS. The following features are incorporated
into the GDC design:

a.  Two in-vessel fixed probes which act as the anodes.

b.  Power supply for the anode probes.

c.  Two in-vessel filaments to facilitate GDC initiation.

d.  Instrumentation and control for operation.

The GDC is remotely configurable and operable, is capable of operating
with helium and other gases, and is capable of steady state operation.
The system is comprised of two "glow probes", power supply and cabling
to the probes, and instrumentation to monitor and control performance.
Each probe is driven by a regulated power supply, and acting as an
anode, applies a voltage potential across the gas filled vacuum vessel,
stripping electrons from the gas. The ions accelerate toward the vessel
wall, which is connected to the negative leg of the power supply. The
bombardment of the walls by these energetic ions releases contaminants
which are removed by the VPS. Control of the system is accomplished
through the NSTX I&C system via a console in the control room. The GDC
can be started at lower pressure and voltage using one or more of the
in-vessel filaments provided for this function.

During operation, the torus vacuum vessel is filled with the desired gas
(typically helium or deuterium) to a desired pressure. These parameters
are controlled by the GDS and VPS. The operator then selects a current
to be applied to the circuit. Depending on the "cleanliness" of the
vessel, the gas pressure, and the impedance of the circuit, a potential
forms across the gas and current flows. The operator then adjusts the
current until the desired glow conditions are achieved.

To protect diagnostics from GDC and to prevent coating of windows from
impurities generated during GDC, a remotely controlled shutter/torus
interface valve (TIV) system is utilized. These diagnostic TIVs and
shutters are controlled and monitored using the TVPS PLC. The system can
accommodate up to 48 TIVs and shutters and provides an operator
interface both in the NSTX control room or from the NSTX Test Cell. Each
shutter is operated remotely by a rotary vacuum feedthrough with a vane
actuator using a pair of spur gears. Physical stops and two (2) limit
switches are used to limit and sense the position of each actuator
output shaft.

The GDC operating parameters are:

Voltage- 400-800 volts.

Current- \~ 3 amperes.

Pressure (He or D~2~)- 2 -- 4 mTorr

Throughput- \~ 8 Torr-liter/sec.

[6.4 Cooling Water System (CWS)]{.underline}

The cooling water system (CWS) provides active cooling and over-heating
protection for the coil systems, bus bars and diagnostics that support
NSTX (not including the D-site MG system which is cooled by the D-Site
Cooling Tower Water System, see Section 5.7.3.1 of Reference 7; and the
NBI and NBI power supply system components which are cooled by systems
described in Sections 5.6.2 and 5.6.6 of Reference 7). Specific
functions include (see Figures 9 and 10):

a\. Providing chilled deionized water for heat removal in the TF, OH and
PF coils.

b\. Providing chilled deionized water for bus bar systems, HHFW system
and diagnostics. (Note: VPS and the bakeout heating/cooling system are
cooled by the HVAC Chilled Water System; see Section 5.7.3.2 of
Reference 7).

c\. Providing flow monitoring to prevent damage due to loss of flow.

d\. Providing coil protection for loss of temperature dew point control
or pressure.

The NSTX CWS combines a new design with the extensive use of existing
equipment (in the D-Site Pump Room) to provide cooling water to coils,
buswork, and various components. Deionized water is provided from the
existing 33,000 gallon storage tank in the Pump Room (which is polished
using a deionized water polishing loop and the existing Deionized Water
System; see Sections 5.6.1 and 5.6.5 of Reference 7). Water is
circulated through a 100 hp centrifugal pump at up to 600 gpm to an
existing 400 ton flat plate heat exchanger, which chills the deionized
water using the HVAC Chilled Water System as a heat sink (see Section
5.7.3.2 of Reference 7). The chilled water is supplied to and returned
from the NSTX coils and other loads via 4\" supply and return piping
through the Mechanical Equipment Room to the NTC. Automatic valves on
the main supply and return lines provide capability for remotely
isolating the CWS from NSTX via the NSTX Control Room.

Cooling water is supplied to the TF and PF supply headers at a pressure
of about 120 psig. High pressure (420 psig) water is provided to the OH
coils by a 5 hp booster pump. A second booster pump with potable water
as an alternate supply of cooling provides emergency backup for OH coil
cooling. These pumps can be powered from the standby diesel generator
(see Section 7.4 of Reference 7). In addition, on loss of all electric
power, a manual valve can be opened to introduce potable water into the
CWS to help cool the Center Stack (i.e., during bakeout).

For coil protection, a programmable logic controller (PLC) processes
data from pressure, temperature, water resistivity and flow
instrumentation on the supply and return paths. NTC dew point is
monitored and compared to inlet water temperature. If the water
temperature drops below the dew point temperature, the CWS PLC will
inhibit the next machine pulse and shut down the CWS.

Component malfunctions (e.g., inadvertent valve alignments) that may
result in pressure transients are prevented from causing systems
failures by: (1) inclusion of relief valves (to LEC drain); (2)
interlocks which prevent adverse conditions from developing (e.g., via
shutting down pumps or prevention of supply valve openings); and (3)
system design for maximum anticipated pressures.

An emergency stop (E-Stop) button is provided to shut down the CWS
(e.g., if water leakage occurs). The CWS will also be shutdown
automatically on low water level in the Pump Room storage tank. A flow
switch failure during a run day coincident with an actual loss of flow
in the affected flow path has the potential to cause coil damage from
overheating (adequate cooling is lost and undetected while experiments
continue). This dual failure is considered unlikely because the flow
switches are effectively tested with each cycle (i.e., the PLC looks for
open switches every time water is shutoff).

[6.5 Bakeout Heating/Cooling System]{.underline}

The NSTX vacuum vessel and plasma facing components (PFCs) must undergo
a bakeout scenario which raises the PFC temperature to 350°C and the
vacuum vessel temperature to 150°C. These components are brought up to
temperature within 48 hours, held at temperature for 24 hours, and then
re-cooled to operating temperature within 24 hours. Bakeout
Heating/Cooling System equipment is designed to operate in the bakeout
mode 10 times per year.

The passive stabilizer plates, divertors and vacuum vessel are heated
and cooled by flowing a heat transfer fluid through tubes intermittently
welded to the surface of the outer vacuum vessel (with heat conductive
putty applied to aid heat transfer), and brazed into slots in the copper
backing plates of the internal hardware PFC tiles. Due to space
limitations, the center stack (CS) inner wall tiles cannot be heated and
cooled by this method. These tiles are heated and cooled by thermal
radiation from the center stack casing which is ohmically heated. The CS
tiles are cooled by radiating to the actively cooled passive stabilizer
plates and the vacuum vessel. To protect the center stack coils, the OH
and PF1a coils must be water cooled during the entire bakeout cycle (see
Section 6.4).

The initial operation of the Bakeout Heating/Cooling System will use
water as the heat transfer fluid. During this mode of operation ("low
temperture bakeout") the system will be operated at a maximum
temperature of 150°C. Future operations will increase the bakeout
temperature to 350^o^C, but no system design exists to support "high
temperature bakeout" as of this issue of the SAD. A revision to this SAD
and the FMEA will be made prior to implementing a high temperature
bakeout system.

For low temperature bakeout the system will be thoroughly
hydrostatically tested to at least 1.5 times its operating pressure.
Precautions will be taken to prevent personnel contact with hot
surfaces, including restricting access to areas where hot pipe or
components are present, posting of warning signs, and personnel
training. An FMEA for this system is included in Appendix 1.

A heating/cooling skid is provided in the NTC to supply and circulate
water for the low temperature bakeout (see Figure 11). During the
bakeout cycle, the High Temperature System (HTS) is not used. The Low
Temperature System (LTS) is used to circulate water at 150^o^C through
the circuits on the vacuum vessel to maintain it and its appendages at
or near that temperature. The Bay K Top Gas Injector is also heated by
the LTS during bakeout (see Section 6.2).

During experimental operations mode, two sub modes exist: low power
operations and high power operations. During low power operations, the
HTS circulates water nominally at 50°C through the PFCs while the LTS
circulates 50°C water through the vacuum vessel circuits. During high
power operations, the HTS is not required, and the LTS circulates 50°C
water through the PFCs and vacuum vessel. In both modes, the PFCs and
vacuum vessel are maintained at 50°C.

The major components of the LTS and HTS (see Figure 11) are the water
storage tank, nitrogen blanketed expansion tank, water circulation pumps
(one for LTS, one for HTS), electrical heater (HTS), and pressure relief
storage tank. Secondary containment (in the form of drip pans under the
skids) is provided to contain any spilled or leaked water.

Protective interlocks are provided to prevent excess fluid temperatures
(via heater overtemperature switch) and to prevent operation of pumps
with misaligned valves. The following conditions will result in alarms
that will alert operators to shutdown the bakeout heating/cooling
system:

> 1\. Major fluid leak which causes level in expansion tank to drop
> below alarm point.
>
> 2\. Blockage in HTS pipeline causing differential expansion due to
> uneven heating of PFCs and vacuum vessel (vacuum vessel thermocouples
> will alarm this differential).
>
> 3\. Loss of nitrogen blanket causing fluid level in the expansion tank
> to rise to alarm point.
>
> 4\. Loss of cooling water for water heat exchanger causing vacuum
> vessel thermocouples to alarm as vessel temperature rises above 50°C.
>
> 5\. Failure of low temperature pump causing vacuum vessel
> thermocouples to alarm as vessel temperature rises above 50°C during
> operations or above 150°C during bakeout.

The skid is equipped with an Emergency Stop pushbutton which, when
manually actuated, trips the incoming 480V power, thus shutting down all
pumps and heaters and forcing solenoid operated valves to their safe
position. Loss of 120V AC signal (i.e., loss of AC power) will initiate
an automatic Emergency Stop. Operation of the circulating pumps and
heater is predicated on receipt of a permissive signal. Operational and
fault status of the LTS and HTS is provided by normally open and
normally closed contacts on each skid. Manual reset of the contacts is
required under fault conditions.

[6.6 Instrument Air System]{.underline}

This system provides an instrument air utility to operate pneumatic
devices in the NTC. It consists of a manifold with valves using the
existing D-Site Instrument Air System (see Section 5.11 of Reference 7).

The Instrument Air System provides dry air at approximately 100 psig to
operate vacuum, water, and cryogenic valves and other instruments. Air
is supplied from compressors in the D-Site Mechanical Equipment Room
(located below the NTC). The NSTX manifold connects to the D-Site
Instrument Air System via a connection on the east wall of the NTC, and
consists of 1\" diameter piping with about twenty-five (25) ports with
ball valves. Process valves and instruments are connected to the nearest
port connection on the manifold.

[6.7 Gaseous Nitrogen System]{.underline}

The Gaseous Nitrogen System provides a source of dry nitrogen to
eliminate the introduction of contaminants and water vapor into vacuum
spaces. This system is an extension of the existing D-Site gaseous
nitrogen system that distributes the gas throughout the facility at a
dew point temperature of -70°C and a pressure of 60 psig. Gaseous
nitrogen from this system is supplied to a manifold with approximately
twenty (20) valves located around the NSTX platform in the NTC. The gas
pressure is reduced to 1.3 psig for use by NSTX components via
connection to the nearest manifold port.

7.0 plasma diagnostics

The purpose of plasma diagnostics is to provide information on discharge
parameters to characterize NSTX plasmas and guide NSTX operations for
optimized performance. Those diagnostics which are essential for machine
operations and other diagnostics which will be available in the
beginning phase of NSTX operations are called baseline diagnostics, and
they are listed in Table 7. There is an emphasis on using equipment
which is presently available at PPPL.

The near-term NSTX program emphasis is on detailed measurements of
plasma profiles for understanding the basic confinement and transport
properties of 5 second, radio frequency-driven NSTX discharges.
Diagnostics which are available for first plasma operations are
indicated as \"Day 0\"; diagnostics available after first plasma are
indicated as \"Day 1\".

The long-term objective is to upgrade and expand the diagnostic set
further for the study of fluctuations and transport in long pulse,
neutral beam-heated NSTX plasmas. In addition, plasma diagnostics will
provide input for advanced plasma control systems. New concepts and
systems developed by the national NSTX team to implement these goals
also will be encouraged.

All diagnostics connected to NSTX are compatible with a 150o C bakeout
temperature at the torus isolation valve. All coils, loops, and other
diagnostics mounted inside the vacuum vessel are compatible with a 350o
C bakeout temperature for the plasma facing components and a 150o C
bakeout temperature at the flanges which provide the interfaces to the
diagnostics. All coils, loops, and other diagnostics mounted inside the
vacuum vessel are installed in a way that minimizes damage due to
interaction with the plasma. This includes protection against high
voltages and large heat loads, particularly for components located on
the center column. All materials utilized within the primary vacuum
boundary are included on the PPPL Vacuum Committee approved list, or
have been separately approved by the committee.

All diagnostics are isolated via optical and/or magnetic (isolation
transformer) means prior to exiting the NTC boundary; this isolation is
rated to withstand a one minute AC hipot test at 20 kV AC rms. All
ancillary components which are in mechanical contact with the vacuum
vessel are electrically isolated from the vacuum vessel; this isolation
is rated to withstand a one minute DC hipot test at 3 kV DC (the outer
vacuum vessel is normally operated near ground potential, including CHI
operations). Diagnostic elements which are located in the center stack
between the OH coil ground plane and the center stack casing (e. g.,
Rogowski coils and flux loops) are insulated to withstand the full
coaxial helicity injection (CHI) voltage, and can be operated either
referenced to the center stack casing (at CHI potential) or to ground;
this insulation is rated for a one minute DC hipot test at 5 kV.
Diagnostic elements which are located on the vacuum side of the center
stack are referenced to the inner vacuum vessel wall. Data connections
to and from diagnostic equipment in the NTC are with optical fiber, as
are connections between the data acquisition systems for each
diagnostic. Each diagnostic exterior to the vacuum vessel is
independently grounded to a single point ground as determined by the
NSTX machine grounding specifications. Diagnostic components located
outside the NSTX Test Cell are electrically isolated to permit safe
access while NSTX is operating.

Other safety aspects of NSTX diagnostics operations (e.g., laser and
microwave safety) are required to comply with the requirements of the
PPPL ES&H Manual (ES&HD 5008). Also, see Sections 4.7 and 9.2 of
Reference 7 for additional relevant information.

Table 7 Baseline NSTX Diagnostics Set

+-----------+----------------------------+----------------------------+
| > **Avail | #######  Diagnostic        | ########  Function         |
| ability** |                            |                            |
+-----------+----------------------------+----------------------------+
| > Day 0   | > Plasma current Rogowski  | > Total plasma current     |
|           | > coils                    |                            |
+-----------+----------------------------+----------------------------+
|           | > Flux loops               | > Plasma control and       |
|           |                            | > equilibrium              |
|           |                            | > reconstruction           |
+-----------+----------------------------+----------------------------+
|           | > Visible TV camera        | > External shape for       |
|           |                            | > plasma control           |
+-----------+----------------------------+----------------------------+
|           | > 1 mm microwave           | > Line-integrated plasma   |
|           | > interferometer           | > density                  |
+-----------+----------------------------+----------------------------+
| > Day     | > IR camera                | > Heat loads               |
| > 1/Day 2 |                            |                            |
+-----------+----------------------------+----------------------------+
|           | > "Slow" diamagnetic loop  | > Stored energy            |
|           | >                          |                            |
|           | > (using toroidal field    |                            |
|           | > coil)                    |                            |
+-----------+----------------------------+----------------------------+
|           | > Halo current Rogowski    | > Halo currents in center  |
|           | > coils                    | > stack                    |
+-----------+----------------------------+----------------------------+
|           | > Eddy current Rogowski    | > Eddy currents in passive |
|           | > coils                    | > plate supports           |
+-----------+----------------------------+----------------------------+
|           | > Br, Bz coils             | > Plasma control/magnetic  |
|           |                            | > fluctuations             |
+-----------+----------------------------+----------------------------+
|           | > Mirnov coils             | > Magnetic fluctuations    |
+-----------+----------------------------+----------------------------+
|           | > Langmuir                 | > Divertor parameters      |
|           | > probes/thermocouples1    |                            |
+-----------+----------------------------+----------------------------+
|           | > Multichannel bolometer   | > Radiated power profile   |
+-----------+----------------------------+----------------------------+
|           | > Survey spectrometer      | > Plasma impurities        |
|           | > (SPRED)                  |                            |
+-----------+----------------------------+----------------------------+
|           | > Soft X-ray imaging       | > Plasma instabilities and |
|           | > system                   | > fluctuations             |
+-----------+----------------------------+----------------------------+
|           | > Ultra-soft X-ray array   | > Start-up and impurity    |
|           |                            | > studies                  |
+-----------+----------------------------+----------------------------+
|           | > Hα detectors             | > Edge recycling           |
+-----------+----------------------------+----------------------------+
|           | > CHERS2                   | > Ion temperature and      |
|           |                            | > toroidal rotation        |
+-----------+----------------------------+----------------------------+
|           | > Visible bremsstrahlung   | > Zeff(r) from visible     |
|           | > array                    | > continuum                |
+-----------+----------------------------+----------------------------+
|           | > X-ray pulse height       | > Core electron            |
|           | > analysis                 | > temperature              |
+-----------+----------------------------+----------------------------+
|           | > Neutral particle         | > Core ion temperature and |
|           | > analyzer                 | > fast ions                |
+-----------+----------------------------+----------------------------+
|           | > Visible spectrometer     | > Edge/divertor            |
|           |                            | > spectroscopy             |
+-----------+----------------------------+----------------------------+
|           | > Multi Pulsed Thomson     | > Electron temperature and |
|           | > Scattering               | > density profile          |
+-----------+----------------------------+----------------------------+
|           | > Far Infrared Tangential  | > Density profile          |
|           | > Interferometer           |                            |
+-----------+----------------------------+----------------------------+

1Diagnostics incorporated into plasma facing components

2CHERS: Charge-Exchange Recombination Spectroscopy

The Multi Pulsed Thomson Scattering (MPTS) Diagnostic includes a Class
IV YAG laser, laser steering optics, laser input tube, laser beam dump,
collection optics and mount, fiber optics and polychromators. The laser
and detectors are located in a room on the mezzanine in the NSTX gallery
to allow personnel access during NSTX operation. The beam is directed
horizontally into the vacuum vessel by a mirror mounted on the south
shield wall. The beam exits through a window at the end of the vacuum
pumping duct. This system is operated under an approved Laser Safe
Operating Procedure (LSOP). Entry to the NTC during MPTS laser
operations will be performed only under carefully controlled Hot Access
conditions (see Section 9.1.2).

The Far Infrared Tangential Interferometer (FIReTIP) system in the NSTX
Test Cell provides toroidal field and two-dimensional density profile
plasma measurements on NSTX. This system consists of three Class IIIB
far infrared lasers (\~30 mW each) pumped by a Class IV CO2 laser (\~100
W). A Class IIIa He-Ne laser is used for alignment purposes. The system
is located on an enclosed commercially available optical table for the
lasers under the NSTX vacuum pumping duct. Components include an optics
table, windows and shutters at Bays K & F, retro-reflectors at Bay F,
power supply (15 kV), chiller, vacuum pumps, gas rack (outside the NTC),
PC-based control system (controllable from the NSTX control room or
locally for maintenance), and assorted optics (mirrors, etc.). This
system is operated under an approved Laser Safe Operating Procedure
(LSOP) that specifies protective measures to: prevent laser exposures to
personnel; isolate hazards during operation, maintenance and testing;
and prevent accidental laser burn through of the enclosure.

Vacuum systems, when required for diagnostics, exhaust to the NSTX
Vacuum Pumping System (see Section 6.1).

Additional details on the plasma diagnostics can be found in References
18 and 19. FMEAs are provided in Appendix 1 (WBS Element 4X).

8.0 power systems

The Power Systems supply and deliver all electrical power to equipment
associated with the NSTX. These systems utilize the existing connection
between PPPL and the local utility (PSE&G), the existing D-Site
facilities and equipment that had been used for TFTR (AC Distribution
System and Field Coil Power Conversion System), and existing C-Site
facilities and equipment for the High Harmonic Fast Wave (HHFW) System
(see Section 5.1). Power is routed from the existing D-Site equipment to
the NSTX Test Cell (NTC) by new cabling from the Transition Area
(southeast corner of the TFTR Test Cell Basement) through a penetration
to the Mechanical Equipment Room, and up through a penetration to the
NTC. In the NTC, the power cables are terminated at a Power Cable
Termination Structure (PCTS), from which power feeds are extended to the
proximity of the machine via buswork and cabling to supply loads. Power
cables whose failure could damage tritium bearing equipment are
supported in a manner that satisfies the seismic loading for NPH
Performance Category 1 (PC-1) (see Section 4.2 above).

The existing D-Site electrical power systems being utilized by NSTX,
including safety evaluations and failure modes and effects analyses, are
described in Chapter 7 of Reference 7. Details on the NSTX Power Systems
can be found in References 20 and 21. FMEAs are provided in Appendix 1
(WBS Element 5X).

[8.1 AC Power System]{.underline}

The AC Power System is divided into two major subelements, namely the
Experimental AC Power System (which includes all loads due to TF, PF,
and H&CD systems) and the Auxiliary Systems AC Power System (which
includes all NSTX auxiliary or \"house\" power demands). The function of
the AC Power System is to provide the source of all electric power
required for the NSTX facility. The AC Power System must establish the
connection between the PPPL facility and the local utility network in a
fashion which permits the pulsed loading required by the NSTX
experiment, while maintaining a power source of suitable quality for
existing house loads.

The specific functions of the Experimental AC Power System include:

a\. Delivery of power to D-Site 13.8kV S1 bus, from primary AC input
terminals of transformer XST-1 to S1 bus.

b\. D-site MG equipment, including excitation and cycloconverter drive
systems, from S1 bus to variable frequency busses SV1 and SV2 (see
Figure 12).

c\. AC distribution from SV1 and SV2 busses to converter transformer
primary AC input terminals, including feeds to neutral beam (NB)
equipment.

d\. AC distribution from secondary terminals of C-site transformer XQT-1
or XQT-2 to HHFW converter transformer primary AC input terminals.

The specific functions of the Auxiliary Systems AC Power System include:

a\. Delivery of power to D-Site 13.8kV S2 bus, from primary AC input
terminals of transformer XST-2 to S2 bus.

b\. All auxiliary system AC distribution at D-Site, from S2 bus to
points of utilization at 13.8kV, 4.16kV, 480V, 208V, and 120VAC levels.

c\. 2600 KW standby power diesel generator and all associated equipment.

d\. Uninterruptible Power Supply (UPS) systems and all associated
equipment.

Experimental power is taken nominally through one of the two D-site
Motor-Generator (MG) units (maximum pulsed load is \<125 MVA, maximum
energy required is 170 MJ \[compared with 2250 MJ available from one MG
unit; only 10% of the pulsed lifetime of the MG units had been used
prior to NSTX operations\]). The only exception is the HHFW system, for
which the sources are located at C-site.

When the experimental power load is such that the total composite load
required by NSTX can be supplied directly by the grid, the configuration
of the AC systems permits operation directly from the grid without the
use of the MG set. Therefore, the AC input to the TF, OH, and PF
converters, and the AC input to the CHI equipment, are each separately
connectable either to the MG set or to the grid. The most likely mode in
which the MG set would not be used is during non-inductive NSTX
operations when the OH system is not used.

[8.2 Power Conversion Systems (TF, PF/OH, CHI, HHFW)]{.underline}

The TF Power Conversion System is designed to provide a constant current
in the TF magnets during an NSTX discharge based on a reference current
input signal provided in real time. This system includes all equipment
from the AC input power interface through to the DC bus connections to
the magnets, converter transformers, thyristor converters, DC cable, DC
bus, disconnect switches and bus links, and all associated monitoring,
control, and protection equipment.

The PF/OH Power Conversion System provides a variable current in the PF
and OH magnet circuits during an NSTX discharge based on a reference
voltage or current input signal provided in real time. This system
includes all equipment from the primary terminals of the converter
transformers through to the DC bus connections to the magnets,
consisting of phase controlled thyristor converters, disconnect switches
and bus links, and all associated monitoring, and protection equipment.

The function of the CHI power system is to energize the CHI electrodes
and impart a poloidal component of current flow which, due to the
influence of the toroidal field, results in a toroidal component of
plasma current. This power system consists of thyristor rectifier power
supplies to provide CHI current drive sustainment for the full plasma
flat top duration.

The HHFW power system utilizes RF power produced by the six existing
Tokamak Fusion Test Reactor (TFTR) Ion Cyclotron Range of Frequencies
(ICRF) sources. These are described in Section 4.8 of Reference 7.

Features common to the TF, PF/OH and CHI Power Conversion Systems
include:

a\. No-load disconnect line switches provided to isolate the Power
Conversion Systems from the connections to the magnets or the CHI load
circuit. In addition, no-load grounding switches are provided to ground
the terminals of the connections to the magnets or CHI load circuit. The
line switches must be open, the grounding switches must be closed, and
the compressed air supply (which actuates the switches) must be vented
to permit the Safety Lockout Device (SLD) to be moved to its safe
position and allow access to the NTC.

b\. The TF and PF/OH Power Conversion Systems include protection to
avoid the delivery of current which would overheat the magnets.

The TF Power Conversion System is grounded via high resistance
connections at the (+) and (-) coil terminals. A ground fault protection
system is used in conjunction with the grounding scheme to detect
grounds within the TF circuit. The TF Power Conversion System equipment
and bus system external to the NTC are totally enclosed so that access
can be maintained around the operating equipment without danger to
personnel. Ground detection and protection are also provided for other
systems.

The CHI power conversion equipment and bus system are totally enclosed
so that access can be maintained around the operating equipment without
danger to personnel. Protective features are included to prevent the
application of excess voltage to the electrodes associated with the
center stack. The instantaneous voltage limit is 2.0kV.

The TFTR Hardwired Control System (HCS; see Section 7.3.1.3.2 of
Reference 7) is being used for the TF, PF/OH and CHI Power Conversion
Systems. Other safety features of the TFTR power conversion systems
(e.g., kirk key interlocks, safety lockout device) are also continuing
to be used for NSTX (see Section 7.3.1.3.2, 7.5 and 9.3 of Reference 7).

9.0 CENTRAL instrumentation and control

The Central Instrumentation and Control (I&C) System provides remote
control, monitoring, data acquisition and data management for the NSTX
subsystems during machine operation. The system provides researchers
with access to the facility in support of the operation, physics
planning, analysis and coordination of experimental objectives. The
Central I&C system provides all supervisory control and monitoring of
the NSTX facility, including:

a\. Plant Control and Monitoring (asynchronous routine control and
monitoring).

b\. Synchronization (synchronization of triggered actions from master
clock events).

c\. Plasma Control Processor and Input/Output Interface (digital
processor and I/O hardware for interface with plasma control
measurements and actuators).

d\. Safety Interlocks (master supervisory control of experiments).

e\. Access Control (control and monitoring of access to the NSTX Test
Cell).

f\. Data Acquisition (periodic sampling, acquisition and display of
regularly sampled data, and acquisition and display of data sampled and
stored by remote devices).

The Central I&C System consists of the Control System and the Data
Acquisition System. It is installed at various PPPL locations, including
the C-Site NSTX Control Room (Lyman Spitzer Building (LSB) room B006;
formerly the TFTR Control Room), the C-site NSTX Computer Room (LSB room
B003; formerly the CICADA Computer Room), the D-Site NSTX Test Cell, the
D-Site NSTX Diagnostic Facility (formerly the D-Site Neutral Beam Test
Stand Control Room), the D-Site Junction Area (Field Coil Power
Conversion Junction Area), the D-site Motor Generator Control Room, the
D-site FCPC (Field Coil Power Conversion TF and PF wings and second
floor), the D-Site Mock-Up Area RF Enclosure, the C-Site RF Source Room,
C-Site Administration Building Computer Addition room (PPL Computer
Center (PPLCC)), and the D-site 138' Level for NBI..

Details on the NSTX Central I&C System can be found in References 22 and
23. FMEAs are provided in Appendix 1 (WBS Element 6X).

[9.1 Control System]{.underline}

The Control System includes the Process Control System, Safety System,
the Control Room and Cable Tray System, the Network System, and the
hardware portion of the Plasma Control System.

[9.1.1 Process Control System]{.underline}

The NSTX Central I&C Process Control System provides remote control
and/or monitoring of the following NSTX subsystems: High Harmonic Fast
Wave (HHFW), Coaxial Helicity Injection Current Drive (CHI), Electron
Cyclotron Heating (ECH), Vacuum Pumping System (VPS), Gas Delivery
System (GDS), Glow Discharge Cleaning System (GDC), Cooling Water System
(CWS), Bakeout Heating/Cooling System, AC Power Systems, Toroidal Field
(TF) Power Conversion System, Poloidal Field/Ohmic Heating (PF/OH) Power
Conversion System, and CHI Power Conversion System. It interfaces with
existing PPPL CAMAC links and field modules, new I/O points, and
stand-alone subsystem controllers to provide supervisory monitoring and
control. The Process Control System provides engineering displays in the
NSTX Control Room (and at other selected locations) to serve as the user
interface to the engineering processes, and provides a secure method for
transferring engineering subsystem diagnostic data and status
information from the Process Control System to the Data Acquisition
System

[9.1.2 Safety System]{.underline}

All NSTX subsystems\' equipment must have built-in self**-**protection.
However, the NSTX Safety System provides system-wide coordination for
personnel and hardware safety. This is accomplished by monitoring Kirk
Keys, E-Stops, and door limit switches via relays to report safety
status to operations personnel in the NSTX Control Room.

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.

The Safety System provides the following functions:

a\. Monitoring and alarming of critical systems, and invoking mitigating
action to ensure personnel and hardware protection when required.

b\. Inhibiting personnel access to the NSTX Test Cell (NTC) and cable
spread room if the Safety Lockout Device (SLD) is in an unsafe position.

c\. Controlling and monitoring personnel entry via the existing doors to
the NTC to ensure personnel safety. The Safety System must ensure
personnel safety before machine operation is permitted.

d\. Providing a continuously available user interface which presents
subsystem equipment permissive status, inter-system interlock status,
SLD status, and access mode status.

The following access modes provide a foundation for operational
interlocks that regulate personnel access to the NTC:

FREE ACCESS: Free Access imposes no restrictions on personnel entry to
the NTC for safety reasons. This form of access may only take place when
the SLD is in its safe position (vented). Access is permitted through
both the north and south door of the NTC via badge reader.

NO ACCESS: No form of access is permitted to the NTC for safety reasons
(e.g., during experimental operations). Prior to entering the NO ACCESS
mode from FREE ACCESS, a "Free Access" key is removed from the door
status panel at the north door. This step disables the north and south
door badge readers simultaneously. A Search and Secure procedure is
implemented to establish that no personnel remain in the NTC following
Free Access, after which a search and secure key is used to set the NSTX
Access Loop. A similar process of search and secure followed by the
setting of an access control loop is used for the cable spread room.

HOT ACCESS: Hot Access permits personnel to be present in the NTC while
equipment that may present a safety hazard to personnel is operational
(e.g., field coils). The formation of a plasma is prevented by
precluding any combination of subsystems that could generate a plasma
from being enabled. This mode requires turning a key in the Control Room
to prevent simultaneous enabling of TF and PF power supplies, and
locking personnel (who retain this key) in the NTC before pressurizing
the SLD. The Hot Access key will be used in the NTC to prevent the Multi
Pulsed Thompson Scattering (MPTS) laser from being enabled with its
shutter open when the NTC Access Loop is set (except for Hot Access
sessions for trained MPTS laser personnel). Hot Access is not allowed in
the cable spread room.

Opening an NTC door will disable the Power Conversion Systems (Section
8.2), the HHFW System (Section 5.1), the MPTS laser, the GDC system, the
ECH System (Section 5.3), and AC power for the NBI Accel power system
and arc and filament power supplies. Global E-Stops to deenergize all
NSTX Systems are provided inside the NTC at each exit door (2), at the
ground and platform level near the center of the NSTX Vacuum Vessel (4),
outside the NTC north door (1), and in the Test Cell Basement (2 buttons
located near the Waterfall bus work area). A break-glass key box located
outside the north door provides emergency access to the NTC; breaking
the glass will cause a global E-Stop and release a door key. Local
systems E-Stops are discussed in previous sections of this SAD. Access
to the Test Cell Basement (TCB), through which NSTX power cables pass
mainly inside a fenced area, is controlled during NSTX operations by the
D-Site shift supervisor. The shift supervisor, who will control the key
to the TCB, will only allow access to personnel at these times when the
procedure and work permit require that precautions commensurate with the
proximity to the power cable fenced area are taken. A system of Kirk
Keys is used to prevent access to the fenced area when the SLD is
pressurized. Height, fencing, and warning signs are used to prevent
access to NSTX power cables which pass for a brief distance through the
D-site Basement Mechanical Equipment Room.

The Safety System operates from an Uninterruptible power source to
ensure continuous operation.

[9.1.3 Control Room and Cable Tray System]{.underline}

The NSTX Control Room, which is installed in the location previously
occupied by the TFTR Control Room (LSB room B006), provides a
centralized location for researchers to direct and monitor the
experimental operation of the NSTX device. A cable tray system is
installed to economically and easily route power cables, signal cables,
and fiber optic cables in the NSTX Test Cell and Gallery for Central I&C
System use.

[9.1.4 Network System]{.underline}

The Network System interconnects the NSTX locations identified at the
beginning of Chapter 9. The System can accommodate expansion to other
areas when required.

The NSTX Process Control System Network provides a dedicated
TCP/IP-based Local Area Network to enable data transfer and inter-system
communication for the Process Control System. The NSTX Process Control
System Network is isolated from the Internet to protect engineering
subsystems from inadvertent or malicious incidents.

The NSTX Data Acquisition System Network provides a TCP/IP-based Local
Area Network to enable data transfer and inter-system communication for
the Data Acquisition System. Internet Protocol (IP) filtering for the
Data Acquisition System Network blocks undesirable or potentially unsafe
packets based on the source and destination IP addresses.

Access in the NSTX Control Room to the existing PPPL Ethernet network is
also provided to support desktop computers, printers, display terminals,
data transfer and inter-system communication, and to provide access to
the ESnet and the Internet.

[9.1.5 Plasma Control System]{.underline}

A digital computer system, consisting of a VME-based host computer and
parallel real time processors, is used to perform feedback control on
plasma current, position and shape. Measurements consist of various
magnetic diagnostics (plasma current (Ip) rogowski coils, flux loops,
and B probes), suitably conditioned (vacuum vessel eddy current
estimates are subtracted from the Ip rogowski measurement), along with
the coil currents. Output signals are used to control the voltage
applied by the power supply sytems to the coils. The development of the
algorithms used by the plasma control system is one of the aims of the
research program and will evolve with time.

[9.2 Data Acquisition System]{.underline}

The Data Acquisition System gathers data for the plasma diagnostics set
listed in Table 7 (Chapter 7). The Data Acquisition System interfaces
with a data management structure to store, catalog, and secure
experimental results for subsequent retrieval and analysis. System
design facilitates access to archived NSTX data, as well as the control
of diagnostic data acquisition systems, by parties outside of the NSTX
control room (e.g., remote collaborators and physicists inside and
outside of PPPL). Multiple electrically isolated, general purpose signal
channels are provided between the NTC and the NSTX Control Room. These
signals are displayed in the Control Room in real-time. A subset of
these general purpose signal channels are dedicated to coil and gas
injection system real time displays.

The Synchronization System generates and distributes synchronous events
(preprogrammed) to the NSTX subsystems. Synchronous events prescribe a
predefined schedule of occurrences to be initiated at preselected times
prior to, during, and after the operation of the experiment. The
Synchronization System generates and distributes a shot number that is
counted sequentially to uniquely identify each shot. In addition, the
Synchronization System generates and distributes synchronized clock
pulses to subsystems and the Central I&C System devices to initiate and
execute time dependent processes by counting periodically generated
clock pulses.

10.0 references

1\. PPPL Environment, Safety and Health Directive 5008, Section 11,
Chapter 1, "Operations Hazard Criteria", January 1999.

2\. National Spherical Torus Experiment (NSTX) General Requirements
Document (GRD), NSTX-RQMTS-GRD-018.

3\. NSTX Project Memo, J. Levine to M. Ono, "Estimated Offsite Doses
from NSTX Operations", 71-961217-JDL-01, December 17, 1996.

4\. PPPL Environment, Safety and Health Manual, ES&HD-5008.

5\. Environmental Assessment, "The Tokamak Fusion Test Reactor
Decontamination and Decommissioning Project and the Tokamak Physics
Experiment at the Princeton Plasma Physics Laboratory", DOE/EA-0813,
U.S. Department of Energy, May 1994.

6\. PPPL Memo, J. Levine to J.W. Anderson, "Offsite Doses from TFTR
Facility", JL-457, July 2, 1992.

7\. TFTR Final Safety Analysis Report (FSAR), DTSD-FSAR-17, Amendment 6,
September 4, 1997.

8\. NSTX Plasma Facing Components System Requirements Document,
NSTX-SRD-11-013.

9\. NSTX Plasma Facing Components System Design Description,
NSTX-SDD-11-028.

10\. NSTX Vacuum Vessel and Torus Support Structure System Requirements
Document, NSTX-SRD-12-014.

11\. NSTX Vacuum Vessel and Torus Support Structure System Design
Description, NSTX-SDD-12-029.

12\. NSTX Magnet Systems System Requirements Document, NSTX-SRD-13-015.

13\. NSTX Magnet Systems System Design Description, NSTX-SDD-13-030.

14\. NSTX Plasma Heating and Current Drive Systems System Requirements
Document, NSTX-SRD-2X-020.

15\. NSTX Plasma Heating and Current Drive Systems System Design
Description, NSTX-SDD-2X-026.

16\. NSTX Auxiliary Systems System Requirements Document,
NSTX-SRD-3X-021.

17\. NSTX Auxiliary Systems System Design Description, NSTX-SDD-3X-034.

18\. NSTX Plasma Diagnostics System Requirements Document,
NSTX-SRD-4X-016.

19\. NSTX Plasma Diagnostics System Design Description, NSTX-SDD-4X-031.

20\. NSTX Power Systems System Requirements Document, NSTX-SRD-5X-019.

21\. NSTX Power Systems System Design Description, NSTX-SDD-5X-024.

22\. NSTX Central Instrumentation and Control System System Requirements
Document, NSTX-SRD-6X-012.

23\. NSTX Central Instrumentation and Control System System Design
Description, NSTX-SDD-6X-027.

######### **[APPENDIX 1]{.underline}**

NSTX

FAILURE MODES AND EFFECTS ANALYSIS

(FMEA)

######### **[APPENDIX 2]{.underline}**

## NSTX Hazard Analysis Summary

+---------------+------------------------------------------------------+
| # Hazard      | # Barrier                                            |
+---------------+------------------------------------------------------+
| Radiation:    | \_ See SAD, sections 2.1, 2.2, 2.3.                  |
|               |                                                      |
|               | \_ Personnel occupancy of the NTC and other areas    |
|               | deemed necessary by Health Physics will be excluded  |
|               | during plasma operation and neutral beam             |
|               | conditioning.                                        |
|               |                                                      |
|               | \_ During a hot access into the NTC, interlocks      |
|               | prevent simultaneous PF and TF fields to prevent     |
|               | initiation of a plasma and attendant radiation.      |
+---------------+------------------------------------------------------+
| Electrical    | \_ In order to ensure the protection of personnel    |
|               | from electrical hazards, the selection of electrical |
|               | equipment and the design and construction of         |
|               | electrical distribution systems complies with        |
|               | national codes and standards wherever possible. In   |
|               | cases where special designs were needed, e.g., the   |
|               | pulse power DC distribution system, the High         |
|               | Harmonic Fast Wave Heating and Current Drive system, |
|               | Electron Cyclotron Heating / Pre-Ionization System,  |
|               | Coaxial Helicity Injection System, Neutral Beam      |
|               | Injection System, etc access to hazardous areas is   |
|               | controlled by the NSTX Safety System. See Section    |
|               | 9.1.2.                                               |
|               |                                                      |
|               | \_ To prevent electrical hazards from being          |
|               | transmitted outside the NTC boundary all             |
|               | instrumentation is isolated via optical and/or       |
|               | magnetic (magnetic transformer) means prior to       |
|               | exiting the NTC boundary. The isolation is rated to  |
|               | withstand a one-minute AC hi-pot test at 29 kV AC    |
|               | rms.                                                 |
+---------------+------------------------------------------------------+
| Fire          | \_ The NTC fire detection system consists of         |
|               | ionization smoke detectors and rate of rise heat     |
|               | detectors located at the ceiling and aspirated smoke |
|               | detection (VESDA) under the platforms.               |
|               |                                                      |
|               | \_ The NTC fire suppression is a pre-action type     |
|               | automatic water sprinkler system similarly located.  |
+---------------+------------------------------------------------------+
| Earthquake    | \_ The NTC along with the rest of the D-Site         |
|               | experimental complex structures, has been determined |
|               | to have adequate capacity to remain functional under |
|               | the overall loads due to an earthquake with a        |
|               | horizontal ground acceleration of 0.13g.             |
|               |                                                      |
|               | \_ The NSTX platform has been designed for 0.09g,    |
|               | the seismic requirements of the NSTX torus structure |
|               | (see Section 4.2).                                   |
+---------------+------------------------------------------------------+
| Vacuum        | \_ See ES&HD 5008, sect 9, ch 14.                    |
| Windows       |                                                      |
+---------------+------------------------------------------------------+

#########  **[APPENDIX 2]{.underline}**

## NSTX Hazard Analysis Summary

+---------------+------------------------------------------------------+
| **[Hazard]{   | **[Barrier]{.underline}**                            |
| .underline}** |                                                      |
+---------------+------------------------------------------------------+
| Magnetic      | \_ Personnel are prevented from entering the NTC     |
| Fields        | during plasma operations by an access control        |
|               | system. See Section 9.1.2.                           |
|               |                                                      |
|               | \_ During a hot access, the magnetic field strength  |
|               | that personnel are exposed to shall not exceed the   |
|               | threshold limit value, BTLV, for routine             |
|               | occupational exposure. For NSTX, BTLV \~ 48 gauss,   |
|               | which corresponds to a distance of 7 meters or more  |
|               | from the machine center line at maximum PF + OH      |
|               | fields. See DOE Standard STD-6003-96.                |
+---------------+------------------------------------------------------+
| RF Fields     | \_ RF systems (HHFW & ECH) have been designed with   |
|               | leakage levels that comply with IEEE Standard        |
|               | C95.1-1991 (outside the test cell) and are routinely |
|               | checked for leakage. In addition, RF transmission    |
|               | into the NTC is prevented whenever personnel have    |
|               | access to the NTC.                                   |
+---------------+------------------------------------------------------+
| Mechanical    | \_ During a hot access into the NTC, personnel are   |
|               | required to stay in a protective enclosure to        |
|               | protect against magnetically propelled projectiles   |
|               | or possible arc splatter that may attend an          |
|               | electrical bus failure.                              |
|               |                                                      |
|               | \_ Gas cylinders are stored/installed in accordance  |
|               | with PPPL safety procedures to prevent breaking the  |
|               | cylinder heads, which could that could propel the    |
|               | cylinders due to a rapid release of gas.             |
+---------------+------------------------------------------------------+
| Hot Fluids    | \_ The Bakeout Heating/Cooling System, which will be |
|               | run with water at temperatures up to 150°C, will be  |
|               | hydrostatically tested to at least 1.5 times its     |
|               | operating pressure prior to operations.              |
|               |                                                      |
|               | \_ Precautions will be taken to prevent personnel    |
|               | contact with hot surfaces, including restricting     |
|               | access to areas where hot pipe or components are     |
|               | present, posting of warning signs, and personnel     |
|               | training.                                            |
+---------------+------------------------------------------------------+

+---------------+------------------------------------------------------+
| **[Hazard]{   | **[Barrier]{.underline}**                            |
| .underline}** |                                                      |
+---------------+------------------------------------------------------+
| Gas           | \_ The content of the largest gas cylinder (311      |
| es/Cryogenics | cubic ft.) constitutes less than 0.1% of the volume  |
|               | of the NTC (approximately 354,000 cubic ft.). Thus,  |
|               | oxygen concentrations in the NTC would remain at     |
|               | safe levels for personnel even if a gas cylinder's   |
|               | entire contents were released to the room.           |
|               |                                                      |
|               | \_ Since SF6 is heavier than air and can displace    |
|               | oxygen, leakage of the gas could be hazardous to     |
|               | personnel occupying an enclosed area below the leak  |
|               | point. Personnel protection is provided by strategic |
|               | location of SF6 detection in the NTC to provide      |
|               | local evacuation alarms.                             |
|               |                                                      |
|               | \_ Cryogenic system subsections which may be         |
|               | isolated by valves or other means are provided with  |
|               | pressure relief devices. Appropriate personal        |
|               | protective equipment will be used by personnel       |
|               | engaged in handling cryogenic fluids. Pressure       |
|               | relief devices have been installed to preclude       |
|               | rupture of sections of the system by excessive       |
|               | internal pressure. All piping has been designed for  |
|               | maximum operating pressure and tested in accordance  |
|               | with applicable ANSI codes. Only materials suitable  |
|               | for cryogenic service are used if in contact with    |
|               | cryogenic fluids or subject to cryogenic             |
|               | temperatures (see also Sections 9.1.7.1 and 9.2.7.1  |
|               | of Reference 7).                                     |
+---------------+------------------------------------------------------+

In general, proper system design, construction and the presence of
features that mitigate the effect of failures (e.g. redundancy, energy
isolating barriers, etc.) will ensure the safety of personnel. Personnel
will be excluded from areas such as the NSTX Test Cell (NTC) and the
cable spread room, when hazards exist, by the use of hardwired
interlocks, procedures, and training.

[^1]: Evaluated at the PPPL site boundary.

[^2]: Dose equivalent to an individual from routine operations (rem per
    year unless otherwise indicated)

[^3]: Compliance with this limit is to be determined by calculating the
    highest effective dose equivalent to any member of the public at any
    off site point where there is a residence, school, business, or
    office.

[^4]: Dose equivalent to an individual from an accidental release (rem
    per event)

[^5]: See Reference 4, Section 10, Item 10.1302 for exposure limits for
    emergency situations.

[^6]: For design basis accidents (DBAs), i.e., postulated accidents or
    natural forces and resulting conditions for which the confinement
    structure, systems, components, and equipment must meet their
    functional goals, the design objective is 0.5 rem.

[^7]: U.S. Department of Energy, \"Natural Phenomena Hazards Performance
    Categorization Criteria for Structures, Systems, and Components\',
    DOE-STD-1021-93, July 1993

[^8]: U.S. Department of Energy, \"Natural Phenomena Hazards Design and
    Evaluation Criteria for Department of Energy Facilities\",
    DOE-STD-1020-934 April 1994