Concepts and Requirements for GIMM Structures

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Concepts and Requirements for GIMM Structures

• Thomas Kozub, Charles Gentile, Irving Zatz - PPPL
• Mohamed Sawan - FTI UW
• John Pulsifer, Mark Tillack - UCSD
• Malcolm McGeoch - PLEX
• Tom Lehecka - Penn State

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Project Overview

• A Conceptual Design for a Grazing Incidence Metal
  Mirror (GIMM) Structural Support System.
• The objective of this task is to develop a viable
  supporting system for the GIMM that is integrated
  into the overall facility structure.

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Design Overview

• The system design will need to address
• Static support of the GIMM structures to the
  facilities foundation.
• Structural elements to maintain stability and
  alignment within the prescribed tolerances of the
  optical components.
• A GIMM base that provides a mirror surface
  flatness to a quarter wavelength.
• Elimination of high frequency vibration at GIMM
  that is beyond the dynamic tracking response of
  the steering mirrors.
• Methods for mounting the GIMM within the vacuum
  beam duct at the several various required
  orientations.
• Necessary features for the installation,
  adjustment, servicing and replacement of the GIMM
  components.

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Design Basis

• This design is based on the October, 2007 GIMM
  configuration as presented in the report Nuclear
  Environment at Final Optics of HAPL by Mohamed
  Sawan.

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• Drawing by Malcolm McGeoch

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Project Scope

• GIMM support project scope
• Each of the forty GIMM units consists of a mirror
  assembly contained within a long stainless steel
  vacuum duct
• The duct which forms the beam line is contained
  within a large shielding block
• All forty units are geometrically arranged around
  a shielding sphere centered around the target
  chamber
• Together the GIMM units and shield sphere fill a
  volume of 260,000m3.

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GIMM Shield Units Located Around the Central
Shielding Sphere
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GIMM System Baseline Specifications

• Number of GIMMs 40
• GIMM surface size 3.1m x 5.2m
• Angle of incidence 85 degree
• Surface orientation from horizontal Varies
• GIMM surface material Al with 1 Cu
• GIMM surface flatness l/4 RMS maximum
• GIMM center distance from target 24m (to focal
  point)
• Beam duct size 0.3m x 1.4m to 0.8m x 4.4m
• Shielding size About 7m x 7m x 18m
• Shielding volume About 880m3
• Shielding weight 2,000,000 kg
• Optical tracking and steering Assume fast enough
  to 50Hz

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Design Objectives

1. Meet the optical stability requirements for the
   GIMM units as located within the facility
2. Meet the operational and service needs of the
   GIMM units

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Design Approach

• To meet the optical stability requirements the
  design incorporates two major elements
• The details of the GIMM attachment to the shield
  block unit.
• The facility structure supporting the individual
  GIMM shielding blocks.

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• Facility structure supporting the individual GIMM
  shielding block and duct unit

• GIMM base mounting inside beam line duct

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Primary Design Challenge

• The primary design challenge is maintaining the
  GIMM surface location with respect to the optical
  beam path.

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Focal Point Error Analysis

• The displacement of the beam focal point at
  target is determined for the GIMM displacement in
  each of three axes of displacement and three axes
  of rotation.

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GIMM Displacement Effects on Focal Point(Ridged
Body Mirror Base)
Displacement Effect Magnitude Factor Motion
Translation x None - -
Translation y None - -
Translation z Translation z 2 mm/mm Linear
Rotation x Rotation x 2.4 mm/mrad Arc
Rotation y Translation z 24 mm/mrad Linear
Rotation z None - -
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Low Frequency Displacement Effects

• Design assumes low frequency (lt50Hz) and small
  amplitude displacements will be compensated by
  the active tracking and steering system.
• Examples
• Thermal variations of structural elements
• All low frequency sources of vibration
• Structural settling

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Compensation for Low Frequency Effects

• All elements in the optical system must be
  designed with
• Sufficient static adjustment range
• Sufficient dynamic range for an effective
  steering system.
• Beam duct aperture size
• Window aperture size
• Mirror surface size

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Mirror Base Design Goals

1. Manageable mirror base size in line with
   standard commercial equipment
2. Isolate mirror base from beam vacuum duct
3. High attenuation factor for frequencies above
   50Hz using vibration isolation
4. Minimum mirror base fundamental frequencies
   gt400Hz (achievable with the nine smaller mirror
   segments)
5. Use commercial off the shelf (COTS) equipment
   directly or modified to meet the unique
   environment

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GIMM Shielding Block Unit Section
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GIMM Base Support System Details

• Each GIMM face is divided into 3x3 array of GIMM
  segment faces (this provides a more manageable
  size and the ability to use COTS components).
• Each GIMM segment is mounted on a segment base
  (1.1m x 1.8m) constructed from stainless steel
  or SiC in a honey comb configuration and
  incorporating active cooling.
• Each base is mounted on frame with legs passing
  through the wall of the vacuum vessel and sealed
  with welded bellows.
• The legs for each GIMM segment are joined
  together outside of the vacuum chamber with a
  robust table structure.
• The table structure is directly mounted on
  vibration isolators.
• The isolators are directly anchored into the
  surrounding concrete structure.

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GIMM Isolated Base Support
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Major Structure Design Goals

1. Meet the static load requirements for reactor
   core infrastructure
2. Stable foundation below grade located at a
   suitable site
3. A ridged structure encompassing the long beam
   paths
4. Structure must have a high damping factor and low
   transmissibility
5. Main structure fundamental modes of gt10Hz
6. Meet Vibration Criteria standards VC-E and
   NIST-A1 or better classifications
7. Attenuate all detrimental sources of vibration
   through isolation

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Design Development Criteria

• Basic structural elements considered
• Static loading
• Load to foundation
• Fundamental modes of vibration
• Horizontal and vertical dynamic stability
• Vibration dampening
• Arch construction
• Concrete vs. steel
• Designs developed for other low vibration
  facilities
• NIST Advanced Measurement Laboratory
• New semiconductor, metrology and nanotechnology
  buildings

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Initial Investigation of Structural Stability
Stainless Steel Frame FEA
Cylindrical Concrete Arch FEA
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Steel Frame Supporting Large Mass

• Large static deformations (gtgt 1-inch)
• Numerous low frequency modes lt10 Hz.
• Prone to buckling and other instabilities
• Conclusion Unrealistically massive steel
  structures would be required to reduce these
  effects to an acceptable level

1st Mode ltlt 1 Hz.
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Cylindrical Concrete Arch Structure

• Much smaller static
• deformations
• Much higher
• frequency modes
• Greater structural
• stability

(Deformations are greatly magnified for ease of
viewing)
Static Deformation Delta Zmax 0.06 in.
1st Mode 6.5 Hz.
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Integrated Facility Structure
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Advantages of Concrete Arch Construction

• Reduction in material volume
• Provides service paths and access
• Good stability and strength to weight ratio
• Established and proven technology
• Reduced resonance peaks, minimizes node points
• Cost advantages

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Structurally Integrated GIMM Shield Blocks
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Advantages of Proposed Configuration

• Employment of concrete in this manner provides an
  elegant solution.
• Concrete performs the dual roles of shielding
  material and structural material
• Constructing the intervening structural elements
  from concrete provides for a continuous
  homogeneous structure with the shielding and
  foundation.
• Eliminates connection points and nodes between
  different structural materials.
• Provides good damping characteristics.
• Provides higher fundamental modes than steel
  framing.
• Provides the ability to cast shapes as required.
• This configuration provides a stable platform.
• Utilizes proven commercial construction methods.

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Section View of Structure
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Comparison of Concrete Volume in Selected Power
Facilities
FACILITY VOLUME OF CONCRETE m3 PRODUCED POWER Gw
Hoover Dam 3,333,000 2
Fission Plant 305,000 1
HAPL IFE Plant 400,000 2
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Future work

• Complete static loading analysis
• Detailed dynamic vibration analysis
• Vibration isolator design
• A further refinement in the integration of the
  GIMM shield units into the structure
• GIMM cooling methods minimizing vibration
• Servicing features
• Integrated facility structural details
• Dust mitigation and removal

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Conclusions

• This design strategy provides a scalable and
  flexible approach to meeting the structural
  requirements of an evolving project.
• This design efficiently incorporates the required
  shielding materials into the core structure
  providing increased stability and functionality
• This design rigidly binds together critical
  components and infrastructure while minimizing
  the effects vibration.

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For Additional Information Please See Poster
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Extra Materials for Poster
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Sources of Vibration

• Reducing the sources of vibration to an minimum
  is as important as the attenuation of vibration.
• Sources of vibration grouped by strength of
  coupling to the GIMM
• Sources acting directly on the GIMM.
• IFE Process sources acting on the central core
  structure.
• Facility and other sources dispersed throughout
  the plant.

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Sources of Vibration Acting Directly on the GIMM

• Thermal shock from target detonation
• Impulse at rate 5Hz
• Thermal shock from laser pulse
• Impulse at rate 5Hz
• Flow of GIMM coolant
• Continuous source
• Electromagnetic effects
• To be determined

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IFE Process Sources of Vibration Through the
Facility Structure

• Target detonation impulse
• Ion, radiation and thermal impulse at 5Hz
• Magnetic Intervention field pulse
• Field force response into structure at 5Hz

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Facility and Other Sources of Vibration

• Rotating machinery pumps, motors, etc.
• Valves operating
• Fluid flow through pipes
• Transformers and other electrical devices
• Elevators, cranes, trucks, doors
• External sources through foundation
• Atmospheric and Seismic

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Other GIMM Issues

• Dust and Contamination Issues
• Suitable Vibration Isolators
• Servicing Issues

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GIMM Dust and Contamination Issues

• GIMM surface contamination from dust and other
  materials can compromise the performance of the
  mirror
• The beam ducts will probably be a source of
  contamination
• Counter gas flows may introduce excessive gas
  loading on the pumps and fuel recovery system to
  be effective
• Electrostatic collection may be of some value

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Vibration Isolators

• Use COTS components when possible
• Solid elastomer units can not be used do to the
  harsh radiation environment
• Pneumatic units
• COTS units will probably work in the radiation
  environment with some modification and the
  removal of elastomer seals
• Typical load capability of 2000 lb per unit
• Non magnetic versions available
• Typical attenuation factor of gt100 for both
  horizontal and vertical frequencies gt30Hz
  (multi-staging can be used to reach greater
  attenuation factors)
• Non vertical applications
• COTS units will require some modification for non
  vertical use
• It may be possible to use vertical vibration
  isolators with counterbalanced support frame

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Servicing Issues

• Access to GIMM for
• Adjustment and inspection
• Maintenance and cleaning
• Cooling system service
• Unit replacement
• Material and equipment
• Beam vacuum duct penetrations
• Remote servicing possibilities