Radiological Design Considerations of Synchrotron Radiation Facilities

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BROOKHAVEN SCIENCE ASSOCIATES

Radiological Design Considerations of

Synchrotron Radiation Facilities

P.K. Job

Radiation Physicist

National Synchrotron Light Source Project

Brookhaven National Laboratory

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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.


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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

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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

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Properties of EM Shower

6 GeV
e
-

on concrete

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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


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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)



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Swanson’s Formalism


Thick target approximation for bulk shielding calculations



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Swanson’s Formalism

Radiation

Component

Dose equivalent
factors(mrem.m
2
/J)

(Swanson)

Dose equivalent
factors(mrem.m
2
/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

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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

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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

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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


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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


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FLUKA Monte Carlo Program for Photons and Neutrons

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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

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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


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Beam Loss Assumptions at NSLS
-
II

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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


Spear
3
(%)

3


APS

(%)

7/
0.
45
0


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





1
0

(distri.)

50



50





1
5

(distri.)

20



20













2


50




Storage Ring

gen.


-

injection
septum



-
injection region


~6


~ 20


70


30

(distri.)

40


20


5
0


80


45.5

(distri.)

12.5


3


16


10

(distr.)

50


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Bulk Shielding Comparison


Bulk Shield at Foor Side
0
20
40
60
80
100
120
140
SOLEIL
DIAMOND
APS
SPEAR3
ELETTRA
SPRING8
BESSYII
ESRF
NSLSII
Concrete
HD Concrete
Bulk Shields at Floor Side

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Bulk Shielding Comparison

Bulk Shield - Ratchet Wall
0
20
40
60
80
100
120
140
160
SOLEIL
DIAMOND
APS
SPEAR3
ELETTRA
SPRING8
BESSYII
ESRF
NSLSII
Lead
HD Concrete
Concrete
At NSLS
-
II HD concrete was replaced by equivalent ND concrete

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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

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Radiation Dose due to Scattering from Scraper
-

FLUKA Results

Beam

HD Concrete

HD Concrete

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Top
-
off Injection Accident
-

FLUKA Simulations

Fixed Mask


FOE


Collimator

Photon
Shutter

Collimator

Safety Shutters

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FLUKA Results
-

Beam on the FE Mask (SS Open)

Total Dose Equivalent Rates

Beam

Mask

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FLUKA Results
-

Beam on the FE Mask (SS Open)

Neutron Dose Equivalent Rates

Beam

Mask

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Top
-
off Accident Analysis (FLUKA Simulations)


Injected Beam in the First Optics Enclosure

FOE

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Total Dose Equivalent Rates (FLUKA Results)


Injected Beam in the First Optics Enclosure

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Neutron Dose Equivalent Rates (FLUKA Results)


Injected Beam in the First Optics Enclosure

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Radiation Dose to Insertion Devices


MCNP Calculations

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Radiation Dose to Insertion Devices


MCNP Results

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Beamline Shutter Thickness
-

EGS4 Calculation

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Beamline Shutter Thickness
-

EGS4 Results

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Bremsstrahlung Scattering in Hutches
-
EGS4 results

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SR Scattering in the Hutches

STAC8 Calculations

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Typical STAC8 Results for Hutches

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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.