Concepts and Requirements for GIMM Structures

1. 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

2. 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.

3. 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.

4. 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.

5. Drawing by Malcolm McGeoch

6. 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.

7. GIMM Shield Units Located Around the Central Shielding Sphere

8. GIMM System Baseline Specifications • Number of GIMM’s: 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

9. Design Objectives • Meet the optical stability requirements for the GIMM units as located within the facility • Meet the operational and service needs of the GIMM units

10. 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.

11. Facility structure supporting the individual GIMM shielding block and duct unit GIMM base mounting inside beam line duct

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

13. 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.

14. GIMM Displacement Effects on Focal Point(Ridged Body Mirror Base)

15. Low Frequency Displacement Effects • Design assumes low frequency (<50Hz) 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

16. 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

17. Mirror Base Design Goals • Manageable mirror base size – in line with standard commercial equipment • Isolate mirror base from beam vacuum duct • High attenuation factor for frequencies above 50Hz using vibration isolation • Minimum mirror base fundamental frequencies >400Hz (achievable with the nine smaller mirror segments) • Use commercial off the shelf (COTS) equipment directly or modified to meet the unique environment

18. GIMM Shielding Block Unit Section

19. 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.

20. GIMM Isolated Base Support

21. Major Structure Design Goals • Meet the static load requirements for reactor core infrastructure • Stable foundation below grade located at a suitable site • A ridged structure encompassing the long beam paths • Structure must have a high damping factor and low transmissibility • Main structure fundamental modes of >10Hz • Meet Vibration Criteria standards VC-E and NIST-A1 or better classifications • Attenuate all detrimental sources of vibration through isolation

22. 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

23. Initial Investigation of Structural Stability Stainless Steel Frame FEA Cylindrical Concrete Arch FEA

24. Steel Frame Supporting Large Mass • Large static deformations (>> 1-inch) • Numerous low frequency modes <10 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 << 1 Hz.

25. 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.

26. Integrated Facility Structure

27. 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

28. Structurally Integrated GIMM Shield Blocks

29. 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.

30. Section View of Structure

31. Comparison of Concrete Volume in Selected Power Facilities

32. 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

33. 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.

35. For Additional Information Please See Poster

36. Extra Materials for Poster

37. 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.

38. 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

39. 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

40. 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

41. Other GIMM Issues • Dust and Contamination Issues • Suitable Vibration Isolators • Servicing Issues

42. 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

43. 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 >100 for both horizontal and vertical frequencies >30Hz (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

44. 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