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Overview of the JET results
- 2015
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 55:10
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Tidskriftsartikel (refereegranskat)
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| 5. |
- Batistoni, P., et al.
(författare)
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Benchmark experiments on neutron streaming through JET Torus Hall penetrations
- 2015
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Ingår i: Nuclear Fusion. - : IOP PUBLISHING LTD. - 0029-5515 .- 1741-4326. ; 55:5
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Tidskriftsartikel (refereegranskat)abstract
- Neutronics experiments are performed at JET for validating in a real fusion environment the neutronics codes and nuclear data applied in ITER nuclear analyses. In particular, the neutron fluence through the penetrations of the JET torus hall is measured and compared with calculations to assess the capability of state-of-art numerical tools to correctly predict the radiation streaming in the ITER biological shield penetrations up to large distances from the neutron source, in large and complex geometries. Neutron streaming experiments started in 2012 when several hundreds of very sensitive thermo-luminescence detectors (TLDs), enriched to different levels in (LiF)-Li-6/(LiF)-Li-7, were used to measure the neutron and gamma dose separately. Lessons learnt from this first experiment led to significant improvements in the experimental arrangements to reduce the effects due to directional neutron source and self-shielding of TLDs. Here we report the results of measurements performed during the 2013-2014 JET campaign. Data from new positions, at further locations in the South West labyrinth and down to the Torus Hall basement through the air duct chimney, were obtained up to about a 40m distance from the plasma neutron source. In order to avoid interference between TLDs due to self-shielding effects, only TLDs containing natural Lithium and 99.97% Li-7 were used. All TLDs were located in the centre of large polyethylene (PE) moderators, with Li-nat and Li-7 crystals evenly arranged within two PE containers, one in horizontal and the other in vertical orientation, to investigate the shadowing effect in the directional neutron field. All TLDs were calibrated in the quantities of air kerma and neutron fluence. This improved experimental arrangement led to reduced statistical spread in the experimental data. The Monte Carlo N-Particle (MCNP) code was used to calculate the air kerma due to neutrons and the neutron fluence at detector positions, using a JET model validated up to the magnetic limbs. JET biological shield and penetrations, the PE moderators and TLDs were modelled in detail. Different tallying methods were used in the calculations, which are routinely used in ITER nuclear analyses: the mesh tally and the track length estimator with multiple steps calculations using the surface source write/read capability available in MCNP. In both cases, the calculated neutron fluence (C) was compared to the measured fluence (E) and hence C/E comparisons have been obtained and are discussed. These results provide a validation of neutronics numerical tools, codes and nuclear data, used for ITER design.
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- Vasilopoulou, T., et al.
(författare)
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Neutron streaming along ducts and labyrinths at the JET biological shielding : Effect of concrete composition
- 2015
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Ingår i: Radiation Physics and Chemistry. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0969-806X .- 1879-0895. ; 116, s. 359-364
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Tidskriftsartikel (refereegranskat)abstract
- Experiments and Monte Carlo simulations were performed at the Joint European Torus (JET) in order to validate the computational tools and methods applied for neutron streaming calculations through penetrations in the JET Hall biological shielding. In the present work the sensitivity of the simulations on the hydrogen and boron content in concrete shielding was investigated. MCNP code was used to simulate neutron streaming along the JET Hall personnel entrance labyrinth for deuterium-deuterium and deuterium-tritium plasma sources for different concrete wall compositions. Neutron fluence and ambient dose equivalent along the labyrinth were calculated. Simulation results for the "as built" JET concrete composition were compared against measurements performed using thermoluminescence detectors. This study contributes to the optimization of the radiation shielding of JET and, furthermore, provides information from JET experience that may assist in optimizing and validating the radiation shielding design methodology used in its successor fusion devices ITER and DEMO.
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- Obryk, B., et al.
(författare)
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TLD calibration for neutron fluence measurements at JET fusion facility
- 2018
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : ELSEVIER. - 0168-9002 .- 1872-9576. ; 904, s. 202-213
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of neutron streaming through penetrations in biological shields are being carried out at JET fusion device by means of thermoluminescence (TL) detectors with the objective to validate the neutronics codes and nuclear data widely applied in ITER nuclear analyses in a real fusion environment. TLDs response due to the neutron component of the radiation field is related to the neutron fluence in a well-defined neutron energy spectrum. Therefore, a TLDs calibration in real fusion radiation fields is necessary to allow neutron fluence from TL measurements at JET to be more precisely calculated. Hence, a MCP-N and MCP-7 TLDs produced at the IFJ PAN in Krakow were calibrated at the ENEA facilities of Frascati and Casaccia laboratories. The obtained results have been analysed and new calibration factors are proposed. The detection system based on TLDs developed and calibrated for JET experiments can then be generally applied not only to fusion neutron fields, but also to ITER to monitor the neutron fluence outside the biological shield.
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