radiological design considerations of synchrotron radiation facilities
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
BROOKHAVEN SCIENCE ASSOCIATES
Radiological Design Considerations of Synchrotron Radiation Facilities
P.K. JobRadiation Physicist
National Synchrotron Light Source ProjectBrookhaven National Laboratory
BROOKHAVEN SCIENCE ASSOCIATES
Radiological Design Considerations for Synchrotron Radiation Facilities
• 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.
BROOKHAVEN SCIENCE ASSOCIATES
Radiation Shielding Analysis of Accelerators
• Radiation Sources at the SR Facilities
• Shielding Design Objectives
• Calculational Tools and Procedures
• Accelerator Shielding Examples
• Beamline Shielding
• Summary Comments
BROOKHAVEN SCIENCE ASSOCIATES
Radiation Sources at SR Facilities
Electromagnetic Shower• 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
BROOKHAVEN SCIENCE ASSOCIATES
Properties of EM Shower
6 GeV e- on concrete
BROOKHAVEN SCIENCE ASSOCIATES
Shielding Design Objectives
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
BROOKHAVEN SCIENCE ASSOCIATES
Calculational Tools and Procedures
• 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)
BROOKHAVEN SCIENCE ASSOCIATES
Swanson’s Formalism
Thick target approximation for bulk shielding calculations
BROOKHAVEN SCIENCE ASSOCIATES
Swanson’s Formalism
Radiation Component
Dose equivalent factors(mrem.m2/J)
(Swanson)
Dose equivalent factors(mrem.m2/J)(Sullivan)
Bremsstrahlung 2.80 1.39Giant Resonance Neutrons
0.63 0.27
High Energy Neutrons
0.075 0.043
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
BROOKHAVEN SCIENCE ASSOCIATES
PHOTON Program for Synchrotron Radiation
• 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
For x-ray Beamline Shielding Design
BROOKHAVEN SCIENCE ASSOCIATES
STAC8 Program for Synchrotron Radiation
• 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.
For x-ray Beamline Shielding Design
BROOKHAVEN SCIENCE ASSOCIATES
Electron Gamma Shower Program (EGS4)
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
BROOKHAVEN SCIENCE ASSOCIATES
MCNPX Monte Carlo Program for Photons and Neutrons
• 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
BROOKHAVEN SCIENCE ASSOCIATES
FLUKA Monte Carlo Program for Photons and Neutrons
BROOKHAVEN SCIENCE ASSOCIATES
Bulk Shielding Calculations
• 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
Input :• Beam loss assumptions• Attenuation lengths of materials
BROOKHAVEN SCIENCE ASSOCIATES
Beam Loss Assumptions at NSLS-II
Accelerator system
Loss (%)
Energy (MeV)
Power Loss (W)
Charge Loss (nC)
Linac - general
- Momentum slit (b)
- Beam dumps (b)
10 %
(distri.)
50%
100%
200
200
200
0.20(a)
1.5
3
1 nC/s(a)
7.5 nC/s
15 nC/s
Booster - general
- injection septum (b)
- extraction septum
(b)
- beam dump (b)
2 %
50%
20%
100%
3000
200
3000
3000
0.015
0.025
0.15
0.73
0.3 nC/min 7.5 nC/min 3 nC/min 15 nC/min
Storage Ring – general
- injection region (b)
~6 %
~ 70%(c)
3000
3000
0.053
0.632
1.1 nC/min 13 nC/min
BROOKHAVEN SCIENCE ASSOCIATES
Beam Loss Assumptions at NSLS-II
BROOKHAVEN SCIENCE ASSOCIATES
Beam Loss Assumptions at Other SR Facilities
Accelerator system
NSLS2
(%) 3/0.200
ALBA
(%) 3/0.130
Diamond
(%) 3/0.100
AusLS
(%) 3/0.300
Spear3
(%) 3
APS (%)
7/0.450 Linac - general
- Momentum slit
- Beam dumps
10
(distri.)
50
100
10 -
100
10
-
100
50/20
-
100
5.5
100
Booster - general
- injection septum
- extraction
septum
2
50
20
15
20
15
10
(distri.) 50
50
15
(distri.) 20
20
2
50
Storage Ring – gen.
- injection septum
- injection region
~6
~ 20
70
30
(distri.) 40
20
50
80
45.5
(distri.) 12.5
3 16
10
(distr.) 50
BROOKHAVEN SCIENCE ASSOCIATES
Bulk Shielding Comparison
Bulk Shield at Foor Side
020
4060
80100
120140
Concrete
HD Concrete
Bulk Shields at Floor Side
BROOKHAVEN SCIENCE ASSOCIATES
Bulk Shielding Comparison
Bulk Shield - Ratchet Wall
0
20
40
60
80
100
120
140
160
SOLEIL
DIAM
ONDAPS
SPEAR3
ELETTR
A
SPRING8
BESSYII
ESRF
NSLSII
Lead
HD Concrete
Concrete
At NSLS-II HD concrete was replaced by equivalent ND concrete
BROOKHAVEN SCIENCE ASSOCIATES
Radiation Dose due to Scattering from a Scraper
Beam at 1 mm from the edge of the 10 mm Cu scraper
Scraper
FLUKA Calculations with Dipole Field
BROOKHAVEN SCIENCE ASSOCIATES
Radiation Dose due to Scattering from Scraper- FLUKA Results
Beam
HD Concrete
HD Concrete
BROOKHAVEN SCIENCE ASSOCIATES
Top-off Injection Accident - FLUKA Simulations
Fixed Mask
FOE
Collimator Photon Shutter Collimator
Safety Shutters
BROOKHAVEN SCIENCE ASSOCIATES
FLUKA Results - Beam on the FE Mask (SS Open)Total Dose Equivalent Rates
Beam
Mas
k
BROOKHAVEN SCIENCE ASSOCIATES
FLUKA Results - Beam on the FE Mask (SS Open)Neutron Dose Equivalent Rates
Beam
Mas
k
BROOKHAVEN SCIENCE ASSOCIATES
Top-off Accident Analysis (FLUKA Simulations) Injected Beam in the First Optics Enclosure
FOE
BROOKHAVEN SCIENCE ASSOCIATES
Total Dose Equivalent Rates (FLUKA Results) Injected Beam in the First Optics Enclosure
BROOKHAVEN SCIENCE ASSOCIATES
Neutron Dose Equivalent Rates (FLUKA Results) Injected Beam in the First Optics Enclosure
BROOKHAVEN SCIENCE ASSOCIATES
Radiation Dose to Insertion Devices – MCNP Calculations
BROOKHAVEN SCIENCE ASSOCIATES
Radiation Dose to Insertion Devices – MCNP Results
BROOKHAVEN SCIENCE ASSOCIATES
Beamline Shutter Thickness- EGS4 Calculation
BROOKHAVEN SCIENCE ASSOCIATES
Beamline Shutter Thickness- EGS4 Results
BROOKHAVEN SCIENCE ASSOCIATES
Bremsstrahlung Scattering in Hutches -EGS4 results
BROOKHAVEN SCIENCE ASSOCIATES
SR Scattering in the Hutches –STAC8 Calculations
BROOKHAVEN SCIENCE ASSOCIATES
Typical STAC8 Results for Hutches
BROOKHAVEN SCIENCE ASSOCIATES
A Word of Caution
• 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.