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Radiological Design Considerations of Synchrotron Radiation Facilities

Radiological Design Considerations of Synchrotron Radiation Facilities. P.K. Job Radiation Physicist National Synchrotron Light Source Project Brookhaven National Laboratory. Radiation Shielding Analysis of the Accelerator Enclosures and Beamlines

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Radiological Design Considerations of Synchrotron Radiation Facilities

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  1. Radiological Design Considerations of Synchrotron Radiation Facilities P.K. Job Radiation Physicist National Synchrotron Light Source Project Brookhaven National Laboratory

  2. Radiation Shielding Analysis of the Accelerator Enclosures and Beamlines Activation and Radiation Damage Analysis of the Accelerator Components Environmental Impact of Accelerator Operations like Soil, Air and Water Activation Skyshine Estimates due to High Beam Loss Points like Beam Dumps, Injection Septa etc. Radiological Design Considerations for Synchrotron Radiation Facilities

  3. Radiation Sources at the SR Facilities Shielding Design Objectives Calculational Tools and Procedures Accelerator Shielding Examples Beamline Shielding Summary Comments Radiation Shielding Analysis of Accelerators

  4. Radiation Sources at SR Facilities • Bremsstrahlung (High Energy Photons)produced in EM shower due to the beam loss • e+ e- Charged Particles generated in the EM shower • Neutrons produced in EM shower due to photonuclear interactions • Synchrotron Radiation (x-rays) generated by dipoles and insertion devices 50 GeV e- in Pb

  5. Properties of EM Shower 6 GeV e- on concrete

  6. Regulatory Documents at BNL Code of Federal Regulations 10 CFR 835 DOE Accelerator Order 420.2B Site Radiation Control Manual NSLS Design Criteria Accelerator Enclosures < 1000 mrem/y Experimental Stations <100 mrem/y On site non-NSLS staff < 25 mrem/y BNL Site Boundary < 5 mrem/y Shielding Design Objectives

  7. Semi-empirical Methods Swanson’s Formalism (thick target approximation) Analytical Simulation Programs SHIELD11 (1-D, 4 group simulation program for EM shower) PHOTON (1-D, Multi-energy Simulation program for x-ray shielding) STAC8 (1-D, Multi-energy Simulation program for x-ray shielding) Monte Carlo Simulation Programs EGS4 (3-D, Multi-energy simulation program for electrons-gammas) MCNPX (3-D, Multi-group, Multi-particle program) FLUKA (3-D, Multi-group, Multi-particle program) Calculational Tools and Procedures

  8. Thick target approximation for bulk shielding calculations Swanson’s Formalism

  9. Swanson’s Formalism Radiation Dose equivalent Factors at transverse direction from a thick target SHIELD11 computer program adopts similar methodology with additional neutron groups for bulk shielding calculations of the accelerator enclosures

  10. PHOTON is a 1-dimensional multi-energy analytical simulation program for x-ray shielding Generate Bending Magnet Radiation Spectrum Simulate Photon Transport by Compton Scattering (isotropic) and photo-absorption through different materials Calculate Scattered Photon Flux as a function of Energy and Angle Convert the Resulting Photon Flux into Dose Rate PHOTON Program for Synchrotron Radiation For x-ray Beamline Shielding Design

  11. STAC8 is a 1-Dimensional multi-energy program for x-ray shielding Generate Bending Magnet and Undulator Radiation Spectrum Generate Monochromatic Undulator Beams with fixed Bandwidths Simulate Photon Transport by Compton Scattering (anisotropic), Rayleigh Scattering and Photo-absorption Calculate scattered photon flux as a function of energy and angle Convert the flux into dose rate. STAC8 Program for Synchrotron Radiation For x-ray Beamline Shielding Design

  12. Simulates Electron-Gamma Coupled Monte Carlo Transport through different materials and geometry by the following interactions; (cross sections generated from physics models) Photoelectric Effect Compton and Rayleigh Scattering Pair Production (electron and nuclear field) Multiple Elastic Scattering Bremsstrahlung Production Moller and Bhabha Scattering Annihilation of Electron-Positron Pairs Continuous Slowing Down (Bethe-Bloch) Note: No photonuclear interactions Electron Gamma Shower Program (EGS4)

  13. Multi-group, Multi-dimensional Monte-Carlo program Models the interactions of radiation/particles (34 particle kinds) Heavy ions are being added Uses both table and model physics for cross sections All standard and 150-MeV neutron, proton, photonuclear libraries Photon, Electron physics (upto 1 GeV) Bertini, ISABEL, CEM, INCL, and FLUKA 3-Dimensional, continuous energy, fully time-dependent Supported on UNIX, PC Windows, Mac G5 Auto configuration, build system FORTRAN90/95, dynamic allocation Distributed memory and parallel processing MCNPX Monte Carlo Program for Photons and Neutrons

  14. FLUKA Monte Carlo Program for Photons and Neutrons

  15. Shielding specifications are based upon maximum allowed design dose criteria (1000 mrem/year or 100 mrem/year) Recommendations based upon 2000 work-hours of exposure per year on contact at the exterior of the bulk shielding Analysis for bremsstrahlung, Giant Resonance Neutrons and High Energy Neutrons has been done separately Bulk Shielding Calculations • Input : • Beam loss assumptions • Attenuation lengths of materials

  16. Beam Loss Assumptions at NSLS-II

  17. Beam Loss Assumptions at NSLS-II

  18. Beam Loss Assumptions at Other SR Facilities

  19. Bulk Shielding Comparison Bulk Shields at Floor Side

  20. Bulk Shielding Comparison At NSLS-II HD concrete was replaced by equivalent ND concrete

  21. Radiation Dose due to Scattering from a Scraper FLUKA Calculations with Dipole Field Scraper Beam at 1 mm from the edge of the 10 mm Cu scraper

  22. Radiation Dose due to Scattering from Scraper- FLUKA Results HD Concrete Beam HD Concrete

  23. Top-off Injection Accident - FLUKA Simulations FOE Safety Shutters Fixed Mask Collimator Photon Shutter Collimator

  24. FLUKA Results - Beam on the FE Mask (SS Open)Total Dose Equivalent Rates Beam Mask

  25. FLUKA Results - Beam on the FE Mask (SS Open)Neutron Dose Equivalent Rates Beam Mask

  26. Top-off Accident Analysis (FLUKA Simulations)Injected Beam in the First Optics Enclosure FOE

  27. Total Dose Equivalent Rates (FLUKA Results) Injected Beam in the First Optics Enclosure

  28. Neutron Dose Equivalent Rates (FLUKA Results) Injected Beam in the First Optics Enclosure

  29. Radiation Dose to Insertion Devices – MCNP Calculations

  30. Radiation Dose to Insertion Devices – MCNP Results

  31. Beamline Shutter Thickness- EGS4 Calculation

  32. Beamline Shutter Thickness- EGS4 Results

  33. Bremsstrahlung Scattering in Hutches -EGS4 results

  34. SR Scattering in the Hutches –STAC8 Calculations

  35. Typical STAC8 Results for Hutches

  36. A variety of well benchmarked, accurate simulation tools are available for the shielding design of electron storage rings The simulation is probably the most accurate step in the assessment process. The beam loss estimations and attenuation lengths are often less precise than the simulation. In many cases a quick and purposely simplified simulation which is made in time may be more valuable than a detailed and accurate simulation which may be costly and take time to complete. In all cases the real cost of a detailed simulation must be balanced against the extra cost which might be engendered if conservative, empirical methods are used. However, in some cases it may be self-defeating to offer such accurate simulations when other parameters in the problem are known with much less precision. A Word of Caution

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