Attenuation curves in concrete of neutrons from 100-400 MeV per nucleon HE, C and NE ions (original) (raw)
Related papers
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
Double differential distributions of neutrons produced by 100, 150, 200 and 250 MeV protons stopped in a thick iron target were simulated with the FLUKA Monte Carlo code at four emission angles: forward, 45°, transverse and 135°backwards. The attenuation in ordinary concrete of the dose equivalent due to secondary neutrons, protons, photons and electrons was calculated. Some of the resulting attenuation curves are best fitted by a double-exponential function rather than a single-exponential. The effect of various approximations introduced in the simulations is thoroughly discussed. The contribution to the total ambient dose equivalent from photons and protons is usually limited to a few percent, except in the backward direction where photons contribute more than 10% and up to 35% to the total dose for a shield thickness of 1-2 m. Source terms and attenuation lengths are given as a function of energy and emission angle, along with fit to the Monte Carlo data. An extensive comparison is made of values obtained in the present work with published experimental and computational data.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1999
The attenuation in ordinary concrete of the total dose equivalent due to neutrons produced by 710 MeV α-particles on steel and water and by 337–390 MeV/u Ne ions on Al, Cu and Pb was calculated with the FLUKA Monte Carlo code. Experimental data (taken from the literature) of the neutron double differential distributions were utilized for the source in the calculations. The contribution of all secondaries (neutrons, photons and protons) produced in the concrete shield was considered. Source terms and attenuation lengths are given as a function of energy and emission angle.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2004
Data on transmission of neutrons in concrete generated by heavy ions of intermediate energies (of typically up to 1 GeV per nucleon) are of interest for shielding design of accelerators for use in both the research and in the medical field. The energy distributions of neutrons produced by ions of different species (from He to Xe) striking various targets at energies from 100 to 800 MeV per nucleon were recently measured by Kurosawa et al. in the angular range 0º -90º. These spectra were used as input data for Monte Carlo simulations to determine source terms and attenuation lengths in ordinary concrete. The present paper presents calculations for 100 MeV/u helium ions on a Cu target, 100 MeV/u carbon ions on C, Al, Cu and Pb, 100 MeV/u neon ions on Cu and Pb, 400 MeV/u carbon ions on C, Al, Cu and Pb, 400 MeV/u neon ions on Cu, 400 MeV/u Ar ions on Cu, 400 MeV/u Fe ions on Cu and 400 MeV/u Xe ions on Cu. The results include the contributions of all secondaries. Some of the resulting attenuation curves are best fitted by a double-exponential function rather than the usual single-exponential. The effect of various approximations introduced in the simulations is discussed. A comparison is made with shielding data for protons scaled with the ion mass number. A comparison is also made with a simple analytical model in use at GANIL.
A modified code system for transport of accelerator produced neutrons through ordinary concrete
Annals of Nuclear Energy, 1997
This paper reports the development of a computational system to estimate the production and subsequent transport of neutrons produced from the interactions of 50 and 100 MeV protons, 150 MeV carbons and 500 MeV lithium with thick tantalum targets. The energy-angle distributions of these neutrons are calculated by a hybrid nuclear reaction model code, ALICE91, using Kalbach systematics and modified to estimate neutron yield distributions from thick target interactions. Transmission of these neutrons is subsequently treated with the Anisotropic Source-Flux Iteration Technique (ASFIT) in the framework of a coupled neutron-gamma transport. The estimated transmitted dose through ordinary concrete is compared with the results obtained using empirical formulations as recommended by IAEA.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2004
Simple empirical expressions for transmission of flux and dose through concrete are presented for neutrons from proton induced reactions. For this purpose the neutron emission from different targets in proton induced reactions in the energy range 25-200 MeV have been considered. The calculated effective dose outside a concrete shield shows overall good agreement with the effective dose estimated from measured neutron flux in the framework of the Moyer model. The calculated effective attenuation length shows a rising trend with incident proton energy and shield thickness.
EPJ Web of Conferences, 2017
A shielding benchmark experiment has been performed using a quasi-monoenergetic 7 Li(p,n) neutron source with the peak energies of 244 and 387 MeV at the Research Center for Nuclear Physics (RCNP) of Osaka University, in order to assess the accuracy of nuclear data and calculation codes used in high-energy accelerator shielging design. Energy spectra behind bulk shields of 10-to 100-cm-thick iron, 25-to 300-cm-thick concrete and their composite are measured using a NE213 organic liquid scintillator with a diameter and thickness of 25.4 cm each with a time-of-flight and an unfolding method. The neutron attenuation lengths are illustared for iron and concrete as a function of the incident energy.
Neutron spectra were measured at the GSI heavy ion accelerator using the Bonner sphere spectrometer NEMUS. The irradiation experiments were carried out at Cave A, an experimental area at the GSI heavy ion synchrotron SIS. A 400 MeV/u carbon ion beam impinging on a thick graphite target was used as neutron source. Spectral distributions were determined by unfolding the measured readings using the unfolding code MAXED for four positions outside the shielding and for four positions in the entry maze of Cave A. First results are presented for two positions from Monte Carlo simulations carried out with a newer version of FLUKA considering both the particle production in nucleus-nucleus collisions and the transportation of particles through the shielding. Measured and calculated neutron spectra are compared for these positions.
Radiation Physics and Chemistry
Concretes are popularly used as shielding materials in nuclear radiation facilities. Special concrete features are employed in the facilities where Fast neutrons, including corresponding 'prompt gamma' rays, are prevalent. The conventional shielding calculations for fast neutrons are complicated and constrained with energy-limited formulas. In this research work, a concrete bunker model has been developed with a variety of compositions and densities. Eleven following appropriate composite materials were used in this case; G4_C (2.3), Ordinary (2.5), Barytes BA-a (3.5), Magnetite M-a (3.55), Ilmenite I-Ia (3.5), Limonite with Steel Punch LS-a (4.54), (80% G4_C+20%Fe+10%B) Mix-1 (2.9), (80%G4_C+20%B4C) Mix-2 (2.35), (80%G4_C+20%BaSO4) Mix-3 (2.74), Serpentine (3) and Serpentine (3.3). Depth-dose profiles for each concrete composition were investigated by Monte Carlo simulation, subjected against an 18.5 MeV neutron source. Shielding properties, like Relaxation lengths, Half Value Layers, and Tenth Value Layers have been deduced harnessing these data. The most efficient materials for shielding fast neutrons regarding half value layers found for the two physics lists, QGSP_BERT_HP and Shielding, successively are, 5.78 and 12.48 cm for Serpentine (3.3), 14.88 and 9.18 cm for Ilmenite I-Ia (3.5), 14.28 and 25.18 cm for Limonite with Steel Punch LS-a (4.54), and 13.58 and 13.48 cm for (80%G4_C+20% Fe+10%B) Mix-1 (2.9). This model could be used to determine the radiation shielding parameters made of any kind of materials and composites using different sources of radiation.
Measurements of Neutron Attenuation through Iron and Concrete at ISIS
Journal of Nuclear Science and Technology, 2000
A deep penetration experiment through a thick bulk shield was performed at an intense spallation neutron source facility, ISIS, of the Rutherford Appleton Laboratory. ISIS is an 800MeV-200 µ A proton accelerator facility. Neutrons are produced from a tantalum target, and are shielded with approximately 3m thick iron and lm thick ordinary concrete. On the top of the shield, we measured the neutron flux attenuation through concrete and iron shields which were additionally placed up to 1.2 m and 0.6m thicknesses, respectively, using activation detectors of carbon, aluminum and bismuth, and also indium-loaded multimoderator spectrometer. The dose attenuation was simultaneously measured with the neutron and photon survey meters. The attenuation lengths of concrete and iron for high energy neutrons above 20MeV were obtained from the 12 C(n,2n) reaction of carbon, and the neutron spectra penetrated through the additional shield and on the target shield top were obtained from the 12 C(n,2n), 27 Al(n,a) and 209 Bi(n, xn) reactions, and multi-moderator spectrometer. We are now analyzing the measured results to compare with the shielding calculation.