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, Athens, Greece SATIF-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 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, Switzerland

Simulation set-up 2 sets of simulations with the same, simplified geometry 1 st : Residual nuclei inventory in the target and ambient dose equivalent around the target, up to 1 meter distance, after 7 different cooling times 2 nd : 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, Switzerland

Geometry CarbonCopperIron 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, Switzerland Right, solid cylinders

Ambient dose equivalent as a function of the distance Stainless Steel – Cooling time 1 day 50MeV100MeV 200MeV 400MeV ~ 500 – 800 mSv/h ~ mSv/h ~ mSv/h ~ 50 – 100 mSv/h ~ mSv/h ~ 800 – 1000 mSv/h >1300 mSv/h ~ mSv/h

Ambient dose equivalent as a function of the distance Stainless Steel – Cooling time 3 months 50MeV100MeV 200MeV400MeV ~ mSv/h ~ 500 – 700 mSv/h ~ 9 – 12 mSv/h ~ 5-10 mSv/h ~ 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

Radionuclide Inventory Carbon (graphite) [400MeV] EOBAfter 1 week 11 C, 7 Be, 8 Be, 10 C, 12 B, 8 Li, 8 B, 6 He, 3 H 7 Be, 3 H Copper [400MeV] 62 Cu, 64 Cu, 61 Cu, 58 Co, 57 Co, 58m Co, 56 Co, 51 Cr, 60 Cu, 66 Cu, 54 Mn, 60m Co, 63 Zn, 55 Fe, 61 Co, 48 V, 52 Mn, 62 Zn, 52m Mn, 49 V, 56 Mn, 53 Fe 58 Co, 57 Co, 56 Co, 51 Cr 54 Mn, 55 Fe, 49 V, 48 V SATIF-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 (0 o - 15 o, 15 o - 45 o, 45 o - 75 o, 75 o o, 105 o – 135 o and 135 o o ) 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, 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, Switzerland

Tunnel’s width=1m Tunnel’s height: 2m Effect of concrete tunnel SATIF-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, Switzerland Ongoing study for calculations of the same quantities with the presence of the wall

Thank you !