Shielding and activation calculations for the EURISOL MW power target
RAPP Benjamin CEA/DSM/DAPNIA/SPhN
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1
I. Shielding & dose calculations with MCNPX II. Activation calculations
Concrete & steel shielding activation
Air activation
III. Conclusion
RAPP Benjamin CEA/DSM/DAPNIA/SPhN
Join SAFERIB/Task 5 meeting, October 2006
2
Shielding calculations for 4MW target with MCNPX Air
FLUKA (CERN)
MCNPX Geometry
4MW target
Steel (1m) UCx
⇨Calculations with FLUKA (CERN, M. Felcini et al. SATIF-8 proceeding) have shown that a dose debit lower than 1µSv/h can be achieve outside of the shielding with 1m of steel + 5.5 m (θ=90°) to 9 m (θ=0°) of concrete
concrete
Beam p (1GeV,1mA)
concrete Steel (1m)
mercury Graphite
RAPP Benjamin CEA/DSM/DAPNIA/SPhN
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3
Shielding calculations : dose distribution MCNPX
θ=0°
θ=90°
beam
concrete
steel
steel
concrete
Concrete, θ=90°, 1m60
1 µSv/h ⇨Neutron dose calculated with MCNPX (4MW proton beam, Ep=1GeV)
⇨”Exponential transform” biasing method was used in concrete and steel shielding to calculate the neutron flux (stretching of distance between collisions in the forward direction by modifying total macroscopic cross section)
RAPP Benjamin CEA/DSM/DAPNIA/SPhN
Join SAFERIB/Task 5 meeting, October 2006
4
Shielding calculations : MCNPX variance reduction method Weight window mesh
⇨”Weight window” variance reduction method in MCNPX ⇨The mesh-based weight window generator of MCNPX is producing an optimal importance function (for a specific cell) on a virtual grid covering the geometry
cell Beam
Iteration #1
Iteration #2
Neutron flux at 0 degree calculated iteratively with weight window (for a fix number of generated protons) : Iteration #3 Iteration #4
(analog simulation)
RAPP Benjamin CEA/DSM/DAPNIA/SPhN
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5
Shielding calculations : neutron spectra Air (~10m3, ~60-70 cm of thickness )
90°
0° steel @70cm
concrete @2m70
Steel @60cm
concrete @1m70
concrete @2m60
concrete @3m70
Concrete @1m60
Concrete @3m60
steel
concrete @4m70
RAPP Benjamin CEA/DSM/DAPNIA/SPhN
concrete @4m60 concrete
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Activation calculations with CINDER'90 Neutron flux in ith cell (63 energy groups up to 25 MeV)
Geometry and materials description
⇨The neutron flux is assumed to be constant over the irradiation period and not being modified by the irradiated medium
MCNPX
Residues in ith cell
CINDER'90
Irradiation scheme
Activation products in ith cell RAPP Benjamin CEA/DSM/DAPNIA/SPhN
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Shielding activation : material composition ⇨Real concrete chemical composition (analysis of ordinary concrete of “Ulysse” reactor at Saclay, ρ=2.3 g/cm3) ⇨Steel composition from AFNOR norm (ρ=7.92 g/cm3) ⇨Air composition : RMR (1/3/05) Scaled LANL 7200 ft composition/density to 820 ft density (ρ=1.24e-3 g/cm3) ⇨Stable neutron spectrum shape in concrete for depth > 2m60
Concrete chemical composition : ( more than 70 elements up to uranium)
Symbol H Li Be N B F C O Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni
...
RAPP Benjamin CEA/DSM/DAPNIA/SPhN
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Wf. Frac. (ppm) 3500 20 0,95 0 16 0 37170 528800 920 2775 14555 217600 262 3400 100 3,06 5150 174000 3,3 960 39 39,2 252 9640 6,82 26
...
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Shielding activation : Total activity after shutdown After 1 year
10 years
40 years irradiation at 2.28 MW 1 MBq/g < A < 1GBq/g 1 kBq/g < A < 1MBq/g 1 Bq/g < A < 1kBq/g A < 1Bq/g
1 century
10 centuries Zone 2 / 90 deg.
Zone 1 / 0 deg.
RAPP Benjamin CEA/DSM/DAPNIA/SPhN
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Shielding activation : radionuclide production in steel & concrete 40 years irradiation at 2.28 MW Concrete, 0 degree, at 1m70
Steel, 0 degree, at 70cm
Total Total
Mn56 Ar37
H3
Co60 Cr51 Fe55
Ca45
H3
Fe55
Ni63 Ni59
Ca41 Ar39
⇨Most internal shielding is steel : surface dose given by Mn56 after shutdown and Co60 up to dismantlement. Waste activity dominated by Ni63.
RAPP Benjamin CEA/DSM/DAPNIA/SPhN
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10
Shielding activation : radionuclide production at different depth Concrete, 90 degree comparison at constant neutron flux of activity with 1m60 and 2m60 neutron energy spectra
-----1m60 2m60
40 years irradiation at 2.28 MW
Neutron spectra at different depth for CINDER'90 (same normalization for the both) :
H3
1m60 2m60 Total
Ar39
Ca41 Ar39
⇨A factor ~1.6 in total activity up to 1 century, the increased difference after is coming from Ar39 (produced by fast neutrons)
RAPP Benjamin CEA/DSM/DAPNIA/SPhN
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Air activation inside shielding
Flux neutrons < 20 Mev
CINDER'90
Flux neutrons > 20 Mev
Atomic densities
Cross sections
Calculated atomic density for neutrons > 20 MeV (atoms/cm3/s/prim) C 14 C 11 O 15 N 13
3.93e-12 2.70e-15 1.58e-12 3.61e-12
Activation products RAPP Benjamin CEA/DSM/DAPNIA/SPhN
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Air activation inside shielding Air activation (inside shielding) 3000 h irradiation at 4mA
After shutdown
Under irradiation Total
N13 N16 O15
Total H3, C14 Ar41
Ar37
C11
Ar 41 N 13 N 16 O 15 Total
EURISOL-4MW (Air volume=10 m3) irradiation=30min irradiation=3000 hours 7.1e+11 Bq 23% Ar 37 8.5e+10 Bq 1% 1.2e+12 Bq 39% Ar 41 4.1e+12 Bq 57% 7.4e+11 Bq 24% C 14 1.6e+11 Bq 2% 4.0e+11 Bq 13% H3 1.7e+11 Bq 2% 3.1e+12 Bq N 13 1.4e+12 Bq 20% N 16 7.4e+11 Bq 10% O 15 4.0e+11 Bq 6% Total 7.1e+12 Bq
RAPP Benjamin CEA/DSM/DAPNIA/SPhN
TRIUMF – ISAC target pre-separator vault, 3000 hours/y, 50kW on UCX target Ar 41 Be 7 C 11 H3 N 13 0 15 Total
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2.1e+09 1.2e+06 8.6e+09 1.5e+05 6.9e+10 1.0e+11 1.8e+11
Bq Bq Bq Bq Bq Bq Bq
1%
