Neutron double differential distributions, dose rates and specific activities from accelerator components irradiated by 50 – 400 MeV protons F. Cerutti 1 , N. Charitonidis 1,2 and M. Silari 1 1 CERN, 1211 Geneva 23, Switzerland 2 Department of Physics, National Technical University of Athens, Zografou Campus, 157 80 Athens, Greece SATIF-10, 2-4 June 2010, CERN, Geneva, Switzerland SATIF-10, 2-4 June 2010, CERN, Geneva, Switzerland
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F. Cerutti 1 , N. Charitonidis 1,2 and M. Silari 1 1 CERN, 1211 Geneva 23, Switzerland
Neutron double differential distributions, dose rates and specific activities from accelerator components irradiated by 50 – 400 MeV protons. F. Cerutti 1 , N. Charitonidis 1,2 and M. Silari 1 1 CERN, 1211 Geneva 23, Switzerland - PowerPoint PPT Presentation
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Neutron double differential distributions, dose rates and specific activities from accelerator
components irradiated by 50 – 400 MeV protons
F. Cerutti1, N. Charitonidis1,2 and M. Silari1
1CERN, 1211 Geneva 23, Switzerland2 Department of Physics, National Technical University of Athens,
Zografou Campus, 157 80 Athens, Greece
SATIF-10, 2-4 June 2010, CERN, Geneva, SwitzerlandSATIF-10, 2-4 June 2010, CERN, Geneva, Switzerland
Scope
• Activation data concerning the materials involved in CERN experimental facilities are rather specific
• Systematic Monte-Carlo simulations with the FLUKA code using a simplified geometry were performed
• The ambient dose equivalent rate, the residual nuclei inventory as well as the neutron spectra were scored for 5 common accelerator materials for proton energies in the 50 - 400 MeV range
• The results of the present study aim to provide a simple database for a first estimate of the radiological risk
SATIF-10, 2-4 June 2010, CERN, Geneva, SwitzerlandSATIF-10, 2-4 June 2010, CERN, Geneva, Switzerland
Simulation set-up
• 2 sets of simulations with the same, simplified geometry
• 1st: Residual nuclei inventory in the target and ambient dose equivalent around the target, up to 1 meter distance, after 7 different cooling times
• 2nd: Prompt neutron spectra escaping from the target
The effect of a concrete tunnel around the target was studied with a special set of simulations
SATIF-10, 2-4 June 2010, CERN, Geneva, SwitzerlandSATIF-10, 2-4 June 2010, CERN, Geneva, Switzerland
Geometry
Carbon Copper Iron
H=1.34cm
50MeV
250MeV
400MeV
H=23.04cm
H=50.04cm
H=0.46cm
H=7.50cm
H=16cm
H=0.50cm
H=8.18cm
H=17.6cm
Irradiation Profile: 9 months constant irradiation, 6E12 p/s or 1 µA beam current
SATIF-10, 2-4 June 2010, CERN, Geneva, SwitzerlandSATIF-10, 2-4 June 2010, CERN, Geneva, Switzerland
Right, solid cylinders
Ambient dose equivalent as a function of the distance
Stainless Steel – Cooling time 1 day
50MeV 100MeV
200MeV 400MeV
~ 500 – 800 mSv/h
~ 10-20 mSv/h
~ 1000-1500 mSv/h
~ 50 – 100 mSv/h
~ 40-50 mSv/h
~ 800 – 1000 mSv/h
>1300 mSv/h
~ 100-200 mSv/h
Ambient dose equivalent as a function of the distance
Stainless Steel – Cooling time 3 months
50MeV 100MeV
200MeV 400MeV
~ 100-300 mSv/h
~ 500 – 700 mSv/h
~ 9 – 12 mSv/h
~ 5-10 mSv/h
~500-800 mSv/h
> 80 mSv/h
~ 6-7 mSv/h
~ 2-10 mSv/h
Ambient dose equivalent rate as a function of cooling time
BN
Cu
SS
Self absorption
The slope does not change accordingly to the width of the target
SATIF-10, 2-4 June 2010, CERN, Geneva, SwitzerlandSATIF-10, 2-4 June 2010, CERN, Geneva, Switzerland
Prompt neutron yield(escaping from the target)
• The neutron double differential yield was scored in 6 angular bins on the target boundary (0o - 15o, 15o - 45o, 45o - 75o, 75o - 105o, 105o – 135o and 135o - 180o) with respect to the beam axis
• Same geometry, same energy range, same materials
• Importance biasing to compensate for the attenuation of low energy neutrons
SATIF-10, 2-4 June 2010, CERN, Geneva, SwitzerlandSATIF-10, 2-4 June 2010, CERN, Geneva, Switzerland
Neutron Spectra
100MeV 400MeV
Total Yield: 0.16 n/p
Total Yield: 2.02 n/p
100MeV
400MeV
Total Yield: 0.03 n/p
Total Yield: 0.65 n/p
Copper
Carbon
Effect of concrete tunnel
• The effect of a concrete tunnel around the target was examined
• The tunnel was modeled as a concrete sphere enclosing the target
• The material chosen was Iron, and the beam energy chosen was 400MeV
• The escaping neutron spectra, as well as the ambient dose equivalent was scored
SATIF-10, 2-4 June 2010, CERN, Geneva, SwitzerlandSATIF-10, 2-4 June 2010, CERN, Geneva, Switzerland
Tunnel’s width=1m
Tunnel’s height: 2m
Effect of concrete tunnel
SATIF-10, 2-4 June 2010, CERN, Geneva, SwitzerlandSATIF-10, 2-4 June 2010, CERN, Geneva, Switzerland
Ambient dose equivalent
Increase of H*(10) due to concrete activation and thermal neutrons production increase (target activation)
Neutron population
5 orders of magnitude !
Conclusions
• An evaluation of the radiological risk through a simple database
• Critical role of the neutron thermalisation on the tunnel’s concrete and its effect on ambient equivalent dose
SATIF-10, 2-4 June 2010, CERN, Geneva, SwitzerlandSATIF-10, 2-4 June 2010, CERN, Geneva, Switzerland
• Ongoing study for calculations of the same quantities with the presence of the wall