brookhaven science associates radiological design considerations of synchrotron radiation facilities...

BROOKHAVEN SCIENCE ASSOCIATES

Radiological Design Considerations of Synchrotron Radiation Facilities

P.K. JobRadiation Physicist

National Synchrotron Light Source ProjectBrookhaven National Laboratory


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.


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


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


Properties of EM Shower

6 GeV e- on concrete


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


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)


Swanson’s Formalism

Thick target approximation for bulk shielding calculations


Swanson’s Formalism

Radiation Component

Dose equivalent factors(mrem.m2/J)

(Swanson)

Dose equivalent factors(mrem.m2/J)(Sullivan)

Bremsstrahlung 2.80 1.39

Giant 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


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


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


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


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


FLUKA Monte Carlo Program for Photons and Neutrons


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


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


Beam Loss Assumptions at NSLS-II


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


Bulk Shielding Comparison

Bulk Shield at Foor Side

0

20

40

60

80

100

120

140

Concrete

HD Concrete

Bulk Shields at Floor Side


Bulk Shielding Comparison

Bulk Shield - Ratchet Wall

0

20

40

60

80

100

120

140

160

SOLE

IL

DIAM

ONDAPS

SPEAR3

ELETTR

A

SPRING8

BESSYII

ESRF

NSLSII

Lead

HD Concrete

Concrete

At NSLS-II HD concrete was replaced by equivalent ND concrete


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


Radiation Dose due to Scattering from Scraper- FLUKA Results

Beam

HD Concrete

HD Concrete


Top-off Injection Accident - FLUKA Simulations

Fixed Mask

FOE

CollimatorPhoton Shutter Collimator

Safety Shutters


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

Beam

Mas

k


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

Beam

Mas

k


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

FOE


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


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


Radiation Dose to Insertion Devices – MCNP Calculations


Radiation Dose to Insertion Devices – MCNP Results


Beamline Shutter Thickness- EGS4 Calculation


Beamline Shutter Thickness- EGS4 Results


Bremsstrahlung Scattering in Hutches -EGS4 results


SR Scattering in the Hutches –STAC8 Calculations


Typical STAC8 Results for Hutches


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.

brookhaven science associates radiological design considerations of synchrotron radiation facilities...

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