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- Pasalic, M., et al.
(författare)
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Fatigue testing and microstructural characterization of tungsten heavy alloy Densimet 185
- 2014
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Ingår i: International Journal of Refractory Metals and Hard Materials. - : Elsevier BV. - 0263-4368. ; 42, s. 163-168
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Tidskriftsartikel (refereegranskat)abstract
- A rotating target consisting of helium-cooled tungsten has been chosen for the European Spallation Source (ESS) facility to be built in Lund. Thermo-mechanical cycling due to the incidence of the proton beam every 2 s on any given tungsten slab in the rotating wheel could lead to crack formation and failure over the lifetime of the target. This work reports tensile and fatigue data obtained at room temperature for the Densimet 185 alloy in the non-irradiated condition. Methods for extracting relevant parameters from fatigue curves with small sets of data are discussed. Fatigue results show a large spread of data for which the application of such methods is challenging. Stress controlled fatigue testing was carried out in this study with mean stress approaching zero and amplitudes in the range 250 to 450 MPa, with 50 MPa increments. A frequency of 25Hz was employed and the fatigue tests lasted until failure was registered or until the upper limit of 2 x 10(6) cycles was reached. No failure due to fatigue occurred in specimens subjected to stress amplitudes below 300 MPa. Microstructural and fractographic studies on the fatigue samples using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) showed that the samples had low porosity, large and nearly spherical tungsten grains, and with a fairly uniform distribution of the ductile phase rich in nickel andiron. However, bonding between tungsten grains in some areas was found to be inadequate. Intergranular fracture was predominant in the specimens at room temperature. Data for the D185 alloy are compared to those for IT180 and D176 alloys obtained in a previous study and strategies for improving the fatigue strength are discussed. (C) 2013 Elsevier Ltd. All rights reserved.
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- Zanini, Luca, et al.
(författare)
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Measurement of Volatile Radionuclides Production and Release Yields followed by a Post-Irradiation Analysis of a Pb/Bi Filled Ta Target at ISOLDE
- 2014
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Ingår i: Nuclear Data Sheets. - : Elsevier BV. - 0090-3752. ; 119, s. 292-295
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Tidskriftsartikel (refereegranskat)abstract
- A crucial requirement in the development of liquid-metal spallation neutron target is knowledge of the composition and amount of volatile radionuclides that are released from the target during operation. It is also important to know the total amount produced, which could be released if there was an accident. One type is the lead-bismuth eutectic (LBE) target where different radionuclides can be produced following interaction with a high-energy proton beam, notably noble gases (Ar, Kr, Xe isotopes) and other relative volatile isotopes such as Hg and At. The results of an irradiation experiment performed at ISOLDE on a LBE target are compared with predictions from the MCNPX code using the latest developments on the Liege Intranuclear Cascade model (INCL4.6) and the CEM03 model. The calculations are able to reproduce the mass distribution of the radioisotopes produced, including the At production, where there is a significant contribution from secondary reactions. Subsequently, a post-irradiation examination of the irradiated target was performed. Investigations of both the tantalum target structure, in particular the beam window, and the lead-bismuth eutectic were performed using several experimental techniques. No sign of severe irradiation damage, previously observed in other ISOLDE targets, was found.
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