Eutectic Target Research Articles

Separation of 206Po from alpha particle irradiated lead bismuth eutectic target

Lead bismuth eutectic (LBE) target was bombarded with 46 MeV α-particle. Possibility of separation of no-carrier-added (NCA) polonium radioisotopes from the bulk lead-bismuth eutectic target was explored. Differential precipitation showed presence of Po with bulk Bi, leaving behind bulk Pb in aqueous medium. NCA 206Po radioisotope was then separated from bulk Bi using trioctylamine (TOA) as the extractant. At best condition of 0.01 M TOA+0.1 M HCl, highest separation factor (>500) was achieved between NCA Po and bulk Bi.

Quantification of radioisotopes produced in 1.4 GeV proton irradiated lead–bismuth eutectic targets

Six cylindrical lead bismuth eutectic (LBE) targets having fixed diameter of 6 mm and varying lengths of 8–50 mm were irradiated with a 1.4 GeV proton beam at CERN-ISOLDE. Both short-lived ( $$5\hbox { h } {<}\hbox {T}_{1/2} {<}5\hbox { days}$$ ) and long-lived ( $$\hbox {T}_{1/2} {>}5\hbox { days}$$ ) radionuclides were identified by off-line $$\upgamma $$ -spectrometry and their activities at the end of bombardment (EOB) were determined. Total 80 $$\upgamma $$ -emitting radionuclides, ranging from $$^{7}\hbox {Be}$$ to $$^{209}\hbox {At}$$ , were identified in the 50 mm long LBE target. The yields of all the radioisotopes were compared with the Monte Carlo Code FLUKA. The spallation reaction was the dominant mode whereas fission induced reactions had no significant contribution. The high energy proton irradiated LBE target may act as a large source of several clinically important and other exotic radionuclides.

Separation of Pb and Bi from proton irradiated lead–bismuth eutectic target using different anion exchangers

Lead–bismuth eutectic (LBE) is the proposed material for use as converter targets in the ISOL facilities globally. In this paper, an LBE target was irradiated with 22 MeV proton beam for 7.6 h to produce 203,204,205,206Bi, 203Pb along with 207Po. Separation of bulk Pb and Bi has been carried out using Aliquat-336 (tricaprylmethylammonium chloride), TOA (trioctyl amine) and DOWEX-1 as extractants. Bi was selectively extracted to the organic/solid phase leaving Pb in aqueous medium. High separation factor between Pb and Bi was observed when 0.5 M TOA and 1 M HNO3 were used as organic and aqueous phase respectively.

Shielding analysis of Transmutation Experimental Facility

The Japan Atomic Energy Agency is planning to construct the Transmutation Experimental Facility (TEF) to promote research, development, and demonstration of elemental technologies for accelerator-driven systems (ADSs). At ADS Target Test Facility (TEF-T), 250-kW H– beams accelerated by the 400-MeV LINAC will be derived to a lead-bismuth eutectic target. Toward the construction of TEF, a shielding analysis is carried out for the whole structure of the TEF-T in detail. The analysis for the beam tunnel shows that backward neutrons produced from the LBE target have large a impact on the radiation dose in the TEF beam tunnel. This paper presents the analytical results for components such as target station, hot cell and beam tunnel, and the shielding structure of the whole TEF.

Separation of no-carrier-added astatine radionuclides from α-particle irradiated lead bismuth eutectic target: A classical method

Possibility of separation of no-carrier-added (NCA) astatine radionuclides from the bulk lead-bismuth-eutectic (LBE) target was explored in a simple way in the laboratory scale. A LBE target was irradiated by 40MeV α-particles delivered from a cyclotron facility, India. Quantitative analysis of the irradiated target indicated the production of 210,209At, 207Po radionuclides in the target matrix. The 210,209At radionuclides were separated by precipitation of bulk Pb, Bi and NCA radiotoxic Po radionuclides.

Optimization of breeding properties of the spallation neutron source target for ADS

One of the main components of an ADS (accelerator-driven reactor systems) is the spallation target, generating neutrons for power plant. Neutrons are generated due in spallation reactions induced on heavy nuclei by accelerator beam of high-energy protons with subsequent multiplication of neutrons in the cascade process of interactions of secondary intermediate-energy particles with target nuclei, subcritical core and blanket.On average, from 20 (for Hg and Pb targets) to 50 (for U target) neutrons are produced per 1-GeV proton in spallation reactions in the target containing nuclei of heavy elements (for example, Hg, Ta, W, U,).Heavy elements such as lead, bismuth, mercury, tantalum, and tungsten are considered as suitable materials for the targets. Lead-bismuth eutectic targets are successfully developed.It is demonstrated in the present paper that there exist optimal size of the target material allowing obtaining for the given incident particle energy maximum number of “spallation” neutrons. Results of calculations of energy spectrum of neutrons generated in the proton interactions with heavy targets for the energy range of incident protons from 0.8 to 1.4GeV.Implemented analysis of variation of neutron generation rate for cylindrical target with 10cm diameter and length from 1 to 120cm at impinging proton energies from 0.8 to 1.4GeV allowed calculating optimal target dimensions consisting of heavy nuclei for the nuclear power installations under design.Optimization of dimensions of neutron generating targets consisting of natural natBi, natHg, natPb и natW isotopes was implemented.

Validation of PHITS Spallation Models from the Perspective of the Shielding Design of Transmutation Experimental Facility

The impact of different spallation models implemented in the particle transport code PHITS on the shielding design of Transmutation Experimental Facility is investigated. For 400-MeV proton incident on a lead-bismuth eutectic target, an effective dose rate at the end of a thick radiation shield (3-m-thick iron and 3-m-thick concrete) calculated by the Liege intranuclear cascade (INC) model version 4.6 (INCL4.6) coupled with the GEMcode (INCL4.6/GEM) yields about twice as high as the Bertini INC model (Bertini/GEM). A comparison with experimental data for 500-MeV proton incident on a thick lead target suggest that the prediction accuracy of INCL4.6/GEM would be better than that of Bertini/GEM. In contrast, it is found that the dose rates in beam ducts in front of targets calculated by the INCL4.6/GEMare lower than those by the Bertini/GEM. Since both models underestimate the experimental results for neutron-production doubledifferential cross sections at 180◦ for 140-MeV proton incident on carbon, iron, and gold targets, it is concluded that it is necessary to allow a margin for uncertainty caused by the spallation models, which is a factor of two, in estimating the dose rate induced by neutron streaming through a beam duct.

Post-irradiation analysis of an ISOLDE lead-bismuth target: Stable and long-lived noble gas nuclides

We measured the isotopic concentrations of long-lived and stable He, Ne, Ar, Kr, and Xe isotopes in a sample from a lead-bismuth eutectic target irradiated with 1.0 and 1.4 GeV protons. Our data indicate for most noble gases nearly complete release with retention fractions in the range of percent or less. Higher retention fractions result from the decay of long-lived radioactive progenitors from groups 1, 2, or 7 of the periodic table. From the data we can calculate a retention fraction for 3H of 2–3%. For alkaline metals we find retention fractions of about 10%, 30%, and 50% for Na, Rb, and Cs, respectively. For the alkaline earth metal Ba we found complete retention. Finally, the measured Kr and Xe concentrations indicate that there was some release of the halogens Br and I during and/or after the irradiation.

Preliminary optimization of proton energy and target for Lead-Bismuth Eutectic target of a demonstration ADS

Accelerator Driven subcritical System (ADS) is recognized as an efficient nuclear waste transmutation device. Recently Chinese Academy of Sciences has made a plan to research and develop ADS. As one of the main options, Lead-Bismuth Eutectic (LBE) is chosen to be both of target material and coolant in the target system. In the present work, the generated neutrons of the liquid lead-Bismuth spallation target were studied for an ADS demonstration facility of 1000 MW thermal power. We have investigated the variation of neutron yield, neutron leadage and spatial energy deposition in terms of the different incident proton energy, target height, buffer height and buffer thickness. The information of generated neutrons, including energy spectrum, neutron angle distribution and neutron spatial distribution of the most effective scheme was studied.

Modeling astatine production in liquid lead-bismuth spallation targets

Astatine isotopes can be produced in liquid lead-bismuth eutectic targets through proton-induced double charge exchange reactions on bismuth or in secondary helium-induced interactions. Models implemented into the most common high-energy transport codes generally have difficulties to correctly estimate their production yields as was shown recently by the ISOLDE Collaboration, which measured release rates from a lead-bismuth target irradiated by 1.4 and 1 GeV protons. In this paper, we first study the capability of the new version of the Liège intranuclear cascade model, INCL4.6, coupled to the deexcitation code ABLA07 to predict the different elementary reactions involved in the production of such isotopes through a detailed comparison of the model with the available experimental data from the literature. Although a few remaining deficiencies are identified, very satisfactory results are found, thanks in particular to improvements brought recently on the treatment of low-energy helium-induced reactions. The implementation of the models into MCNPX allows identifying the respective contributions of the different possible reaction channels in the ISOLDE case. Finally, the full simulation of the ISOLDE experiment is performed, taking into account the likely rather long diffusion time from the target, and compared with the measured diffusion rates for the different astatine isotopes, at the two studied energies, 1.4 and 1 GeV. The shape of the isotopic distribution is perfectly reproduced as well as the absolute release rates, assuming in the calculation a diffusion time between 5 and 10hours. This work finally shows that our model, thanks to the attention paid to the emission of high-energy clusters and to low-energy cluster induced reactions, can be safely used within MCNPX to predict isotopes with a charge larger than that of the target by two units in spallation targets, and, probably, more generally to isotopes created in secondary reactions induced by composite particles.

A dc arc plasma torch as a tailored heat source for thermohydraulic simulation of proton beam–target interaction in ADSS

Currently, research on accelerator driven subcritical systems (ADSS) is gaining significance due to their high safety levels and extremely attractive potential in terms of both thorium utilization and nuclear waste transmutation. While high energy and high current proton beams are being built worldwide, intensive efforts are being undertaken in parallel towards the development of complex lead bismuth eutectic target systems. The major focus is directed towards understanding of the material compatibility and detailed thermohydraulic simulation of the liquid metal flow. The requisite heat flux is being deposited using innovative and easily controllable heat sources. This paper presents an experimental and simulation study to explore the potential of using dc arc plasma torches as a tailored heat source for thermohydraulic simulation of proton beam–target interaction in such systems.

Tensile testing of EP-823 and HT-9 after irradiation in STIP II

The predicted operating conditions for a lead–bismuth eutectic target to be used in an accelerator driven system for the Advanced Fuel Cycle Initiative spans a temperature range of 300–600 °C while being irradiated by a high energy (∼600 MeV) proton beam. Such spallation conditions lead to high displacement rates coupled with high accumulation rates of helium and hydrogen up to 150 appm/dpa. Two candidate ferritic/martensitic materials for these applications include HT-9 and EP-823. To investigate the effect of irradiation on these materials, the tensile properties were measured at 25, 250, and 400 °C after irradiation in the STIP II irradiation to doses up to 20 dpa at temperatures up to 350 °C. Losses in ductility concomitant with increases in yield stress are observed in both alloys although the embrittlement is more severe in the EP-823. This stronger embrittlement is attributed to the high silicon content in EP-823.

The high temperature three point bend testing of proton irradiated 316L stainless steel and Mod 9Cr–1Mo

The predicted operating conditions for a lead–bismuth eutectic target to be used in an accelerator driven system for the Advanced Fuel Cycle Initiative span a temperature range of 300–600 °C while being irradiated by a high energy (∼600 MeV) proton beam. Such spallation conditions lead to high displacement rates coupled with high accumulation rates of helium and hydrogen up to 150 appm/dpa. Some candidate materials for these applications include Mod9Cr–1Mo and 316L stainless steel. To investigate the effect of irradiation on these materials, the mechanical properties are being measured through three point bend testing on Mod 9Cr–1Mo and 316L at 25, 250, 350 and 500 °C after irradiation in a high energy proton beam (500–800 MeV) to a dose of 9.8 dpa at temperatures from 200 to 320 °C. By comparing measurements made in bending to tensile measurements measured on identically irradiated materials, a measurement of 0.2% offset yield stress was obtained from 0.05% offset yield stress measured in three point bend testing. Yield stress increased by more than a factor of two after irradiation to 9.8 dpa. Observation of the outer fiber surface of 316L showed very localized deformation when tested after irradiation at 70 °C and deformation on multiple slip systems when tested after irradiation at 250–320 °C.

Characterization of lead–bismuth eutectic target material for accelerator driven transmuters

Lead–bismuth eutectic (LBE) is under consideration as a target material with high-energy protons for generating neutrons to drive actinide and fission product transmuters. A characterization has been performed to study the performance of this target material as a function of the main variables and the design selections. The characterization includes the neutron yield, the spatial energy deposition, the neutron spectrum, the beam window performance, and the target buffer requirements. The characterization has also considered high-energy deuteron particles to study the impact on the target neutronic performance. The obtained results quantify the LBE target material performance with proton or deuteron particles as a function of the target variables and selections.

Review of liquid metal corrosion issues for potential containment materials for liquid lead and lead–bismuth eutectic spallation targets as a neutron source

Lead (Pb) and lead–bismuth eutectic (44Pb–56Bi) have been the two primary candidate liquid metal target materials for the production of spallation neutrons. Selection of a container material for the liquid metal target will greatly affect the lifetime and safety of the target subsystem. For the liquid lead target, niobium–1 wt% zirconium (Nb–1Zr) is a candidate containment material for liquid lead, but its poor oxidation resistance has been a major concern. In this paper, the oxidation rate of Nb–1Zr was studied based on the calculations of thickness loss resulting from oxidation. According to these calculations, it appeared that uncoated Nb–1Zr may be used for a 1-year operation at 900°C at P O 2 =1×10 –6 Torr, but the same material may not be used in argon with 5-ppm oxygen. Coating technologies to reduce the oxidation of Nb–1Zr are reviewed, as are other candidate refractory metals such as molybdenum, tantalum, and tungsten. For the liquid lead–bismuth eutectic target, three candidate containment materials are suggested, based on a literature survey of the materials’ compatibility and proton irradiation tests: Croloy 2-1/4, modified 9Cr–1Mo, and 12Cr–1Mo (HT-9) steel. These materials seem to be used only if the lead–bismuth is thoroughly deoxidized and treated with zirconium and magnesium.

Thermofluid behaviour of the lead bismuth eutectic target for the spallation neutron source at SIN

The thermofluid behaviour of a PbBi eutectic (LBE) target for a spallation neutron source have been studied numerically, in order to investigate the effects of (1) target height, (2) beam power, (3) beam radius and (4) adiabatic side walls on the behaviour of natural convection. The results show that within the parameter values studied, the natural convection of target fluid is stabilized and the temperature distribution is not complicated. There is a steep temperature gradient only in a boundary layer region. In the core region the temperature distribution is relatively smooth. It can be expected that the cooling mechanism using natural convection in a vertical target with proton beam entering from below is feasible.

Sputtering of the gallium-indium eutectic alloy in the liquid phase

We have measured sputtering yields and angular distributions of sputtered atoms from both the solid and liquid phases of gallium, indium, and the gallium-indium eutectic alloy. This was done by Rutherford backscattering analysis of graphite collector foils. The solid eutectic target shows a predominance of indium crystallites on its surface which have to be sputtered away before the composition of the sputtered atoms equals the bulk target composition. The size of the crystallites depends upon the conditions under which the alloy is frozen. The sputtering of the liquid eutectic alloy by 15 keV Ar+ results in a ratio of indium to gallium sputtering yields which is 28 times greater than would be expected from the target stoichiometry. Furthermore, the angular distribution of gallium is much more sharply peaked about the normal to the target surface than the indium distribution. When the incident Ar+ energy is increased to 25 keV, the gallium distribution broadens to the same shape as the indium distribution. With the exception of the sharp gallium distribution taken from the liquid eutectic at 15 keV, all angular distributions from liquid targets fit a cos2 θ function. An ion-scattering-spectroscopy analysis of the liquid eutectic alloy reveals a surface layer of almost pure indium. A thermodynamic explanation for this highly segregated layer is discussed. The liquid eutectic alloy provides us with a unique target system which allows us to estimate the fraction of sputtered material which comes from the first monolayer of the surface.