1 Henderson DUSEL Capstone 05/06/2006 Background Modeling and Clean Room Design Considerations for...
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Transcript of 1 Henderson DUSEL Capstone 05/06/2006 Background Modeling and Clean Room Design Considerations for...
11Henderson DUSEL Capstone 05/06/200Henderson DUSEL Capstone 05/06/20066
Background Modeling and Clean Background Modeling and Clean Room Design Considerations for Room Design Considerations for
HUSEPHUSEP
Zeev Shayer and Jonathan OrmesZeev Shayer and Jonathan OrmesDepartment of Physics & Astronomy Department of Physics & Astronomy
and Denver Research Instituteand Denver Research InstituteUniversity of DenverUniversity of Denver
[email protected]@du.edu
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The GoalThe Goal
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BackgroundBackground
What are Sources ?
• Cosmic Ray and Cosmic Activation• Natural Radioactivity from Rock• Natural Radioactivity in Materials• Radon in Air from U/Th decay series• Radioactive Dust• …..
How to get rid of it?
• Underground Laboratory• Passive and Active Shielding• Material Selection• Radon Trapping System (Ventilation) • Clean Room
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Simulation CodesSimulation Codes
SOURCES-4A/B Code
Input: Rock Composition
Output: Neutron Production Spectra (,n) & S.F.
MCNPXNeutron, Gamma and
Muon transport (no cascade)
+Point Depletion
FLUKA
Muon Transport and Particle Cascade
Calculations
GEANT4
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SOURCES-4A + MCNPXSOURCES-4A + MCNPX(Neutron and Gamma Background Plus Activation Analysis)(Neutron and Gamma Background Plus Activation Analysis)
• Homogenized Rock Composition For Henderson Mine (median, upper bound) ?
• Neutron Flux 1 – 3 x 10-6 n/s/cm2
• Average Energy 2.2 – 2.4 MeV
• ~70% (,n) and ~30% (S.F.)
• Reflection from walls ~20% enhancement
0.00E+00
5.00E-03
1.00E-02
1.50E-02
2.00E-02
2.50E-02
3.00E-02
3.50E-02
4.00E-02
4.50E-02
0 1 2 3 4 5 6 7 8 9 10
Neutron Energy (MeV)
Neut
ron
Prod
uctio
n Ra
te (n
orma
lized
)
(a,n)
S.F.
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Examples of Shielding DesignExamples of Shielding Design
Parrafin
Lead
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Lead
LeadParaffin
Lead
Lead
• Lead-Paraffin is preferable (Case A) for exclusively neutron sources, as inelastic scattering in the lead is complemented by elastic scattering in hydrogen of the paraffin.
• Paraffin-Lead (Case B) is preferable for gamma-ray sources, as energetic gamma-rays scattered in the paraffin (Compton Effect) are rapidly absorbed by lead, which has particularly high absorption cross-section at low energies where the photo-electric effect predominates.
• Lead-Paraffin is preferable for reduction of the activation products produced in lead through the capture of neutrons
• Paraffin-Lead is preferable for reduction of secondary gamma-rays due to less gamma-ray produced through the inelastic scattering in lead and paraffin.
HAtoms/b/cm
Parrafin C25H52 0.0853
Polyethylene CH2 0.0789
Water H2O 0.0668
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Neutron and Secondary Gamma Flux and their Neutron and Secondary Gamma Flux and their
attenuations propertiesattenuations properties
Configuration Case
Neutron Flux Secondary Gamma
Neutron Attenuation
Factor
Secondary Gamma
Production
No Shielding 22.728 1.321E-03 - -
A 4.99E-02 3.80 450 2880
B 1.01E-01 2.48E-02 225 19
C 6.37E-02 1.97E-01 357 149
D 5.10E-02 1.20E-01 445 91
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Performance of Various Shielding Block Cases Relative to the Performance of Various Shielding Block Cases Relative to the
“Homogenization” Case (Case D)“Homogenization” Case (Case D)
Reference Case D Neutron Attenuation Relative Factor (Case D/ Case #)
Gamma Ray Production Relative Factor (Case #/Case D)
D 1 1
A 0.99 32
B 2.25 0.21
C 1.25 1.64
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Gamma K-40Gamma K-40
Configuration Case K-40 Gamma Rays Attenuation Factor
A 264
B 673
C 693
D 686
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High Energy Charged ParticlesHigh Energy Charged Particles - Muon - Muon
• At sea level the muon flux is about
~120 – 140 muons/m2/s with mean energy of 4 GeV
• At 4000 mwe the muon flux is about
~1-3x10-4 muons/m2/s with mean energy of 250 GeV
About 106 Reduction Factor
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Neutron Production by Muons from Rock and ShieldingNeutron Production by Muons from Rock and Shielding
Hadronic Cascade
Electromagnetic Cascade
Spallation Cascade
• The estimated neutron production from rock (from the literature) ~ 10-9 – 10-10 n/s/cm2
• Less than 3 orders of magnitude from U/Th chain production
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High Energy Charged ParticlesHigh Energy Charged Particles (100 GeV)– Protons (100 GeV)– Protons
((Neutron Production within shield materialNeutron Production within shield material))
1.00E+01
1.00E+02
1.00E+03
1.00E+04
40 50 60 70 80 90 100 110
Distance Within Shield (cm)
Neu
tro
ns
Flu
x (a
rbit
rary
un
its)
Case C
Case D
Case A
Case B
Shielded Block
B A
D
C
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Neutron energy spectra after 5 cm of the Neutron energy spectra after 5 cm of the
shield blockshield block
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+00 1.00E+01 1.00E+02 1.00E+03
Neutron Energy (MeV)
Nu
mb
er
of
Ne
utr
on
s (
arb
itra
ry.
un
its
)
Case C
Case D
Case A
Case B
Case D1
D1
A
D
C
B
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Optimization Methodology for Case D Optimization Methodology for Case D
(homogenized case)(homogenized case)
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
1.00E+05
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Lead Weight Fraction
Att
en
ua
tio
n F
ac
tor
(ne
utr
on
&g
am
ma
)
Neutrons
2nd gamma
Gamma
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Optimization Methodology for Case D Optimization Methodology for Case D (homogenized case)(homogenized case)
1.00E+02
1.00E+03
1.00E+04
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Lead Weight Fraction
Ov
era
ll A
tte
nu
ati
on
Fa
cto
r
95%Neutrons+5%Gammas
50%Neutrons+50%Gammas
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SummarySummary
• Shielding and Clean Room Design
Detector components and shielding may become the dominant background Our shielding design approach is different from the ordinary one used in
underground laboratories (Lead and CH2 layers)
Easy to optimized for different detector options Less restriction on the contamination of lead with traces of Uranium/Thorium
Will need to specify the number of radon atoms per 1 m3 of air (1000?). (A typical room has around 105 particles/m3)
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SummarySummary
• It is possible to reduce the neutron and gamma from Henderson Mine by Factor of >105
• To reduce the neutron, gamma and from detector component 1. Ultra pure material down to ppt 2. Underground storage of important materials3. Underground assembly
• Neutrons from Muons1. Depth underground2. Active muon veto
• Radon induced neutron, gamma and 1. System for removing radon2. Ventilate volumes near detectors with radon free nitrogen