Neutronic performance of the MEGAPIE spallation target under high power proton beam

The MEGAPIE project, aiming at the construction and operation of a megawatt liquid lead-bismuth spallation target, constitutes the first step in demonstrating the feasibility of liquid heavy metal target technologies as spallation neutron sources. In particular, MEGAPIE is meant to assess the coupling of a high power proton beam with a window-concept heavy liquid metal target. The experiment has been set at the Paul Scherrer Institute (PSI) in Switzerland and, after a 4-month long irradiation, has provided unique data for a better understanding of the behavior of such a target under realistic irradiation conditions. A complex neutron detector has been developed to provide an on-line measurement of the neutron fluency inside the target and close to the proton beam. The detector is based on micrometric fission chambers and activation foils. These two complementary detection techniques have provided a characterization of the neutron flux inside the target for different positions along its axis. Measurements and simulation results presented in this paper aim to provide important recommendations for future accelerator driven systems (ADS) and neutron source developments.     

Improved modelling of helium and tritium production for spallation targets

Reliable predictions of light charged particle production in spallation reactions are important to correctly assess gas production in spallation targets. In particular, the helium production yield is important for assessing damage in the window separating the accelerator vacuum from a spallation target, and tritium is a major contributor to the target radioactivity. Up to now, the models available in the MCNPX transport code, including the widely used default option Bertini-Dresner and the INCL4.2-ABLA combination of models, were not able to correctly predict light charged particle yields. The work done recently on both the intranuclear cascade model INCL4, in which cluster emission through a coalescence process has been introduced, and on the de-excitation model ABLA allows correcting these deficiencies. This paper shows that the coalescence emission plays an important role in the tritium and ³He production and that the combination of the newly developed versions of the codes, INCL4.5-ABLA07, now lead to good predictions of both helium and tritium cross-sections over a wide incident energy range. Comparisons with other available models are also presented.     

Sensitivity studies of the neutron multiplicity spectrum in the spallation of Pb targets

The number of neutrons produced per incident proton in the spallation of Pb targets is of direct relevance to the design of accelerator breeders. The nuclear cascade initiated by high-energy protons in spallation targets is usually described by an intranuclear cascade evaporation (INCE) model. Even though this model describes various average nuclear properties of spallation targets fairly well, differential quantities such as energy spectra, angular spectra etc. are not reproduced within the limits of experimental uncertainty. One of the reasons for this is the uncertainty in the magnitude of the parameters involved in the model, notably the level density parameter B₀ whose magnitude is quoted by different workers to be in the range of 8–20 MeV. The accuracy of B₀ could be improved if we could experimentally determine a quantity which is much more sensitive to B₀ than the average neutron yield. In this paper we discuss one such quantity, namely the neutron multiplicity spectrum (MS). We compute the MS due to the spallation of Pb targets of different sizes at proton energies of 1.5, 1.0 and 0.59 GeV using the Monte Carlo code HETC. It is noticed that for the 1.5 GeV proton case the probability P(v) for leakage of v neutrons for v in the range of 60–65, changes by about 70% when B₀ is varied from 8 to 20 MeV. The corresponding change in the average neutron yield is <20%. It is therefore suggested that an accurate measurement of the MS can serve as a useful tool to narrow down the range of uncertainty in the B₀ parameter.     

Fundamental and applied researches on the VVR-SM reactor at the Nuclear Physics Institute,Uzbek Academy of Sciences

Translated from Atomnaya Énergiya, Vol. 64, No. 5, pp. 338–349, May, 1988.     

中国散裂中子源快周期同步加速器磁铁电源系统的研究

目前正在进行可行性研究的中国散裂中子源的主体结构是1台强流质子同步加速器。该加速器的一期目标为注入能量70MeV、引出能量1.6GeV、束流功率100kW、循环工作频率25Hz。文章阐述系统总体结构的设计原则以及二极磁铁（B）和四极磁铁（Q）磁场的跟踪误差要求。     

Assessment of the power deposition on the MEGAPIE spallation target using the GEANT4 toolkit

This work aims at evaluating the reliability of the GEANT4(GEometry ANd Tracking 4) Monte Carlo(MC) toolkit in calculating the power deposition on the Megawatt Pilot Experiment(MEGAPIE), the first liquid–metal spallation target worldwide. A new choice of codes to study and optimize this target is provided. The evaluation of the GEANT4 toolkit is carried out in comparison with the MCNPX and FLUKA MC codes. The MEGAPIE is an international project led by the Paul Scherrer Institute in Switzerland. It aims to demonstrate the safe operation of an intense neutron source to power the next generation of nuclear reactors, accelerator-driven systems(ADSs). In this study, we used the GEANT4 MC toolkit to calculate the power deposited by fast protons on the MEGAPIE target.The calculation focuses on several structures and regions.The predictions of our calculations were compared and discussed with that of the MCNPX and FLUKA codes,adopted by the MEGAPIE project. The comparison shows that there is a very good agreement between our results and those of the reference codes.     

Development of a high intensity Al beam from SiC targets for accelerated beam experiments at ISAC

An intense beam of ^26gAl has been developed for accelerated beam experiments at TRIUMF’s ISAC facility. Studies of the on-line production of Al radionuclides from thick silicon carbide targets have been performed as part of a program of beam development for astrophysical reaction studies at ISAC. While the release of short-lived Al nuclides from SiC was found to be slow, development of new target material forms and high-power target containers has allowed operation of SiC targets with proton currents of up to 70 μA on target. In addition, operation with the TRIUMF resonant ionization laser ion source (TRILIS) has produced ^26gAl beam intensities of 5.1 × 10¹⁰ s⁻¹.     

Prospects for developing renewable energy sources for local power generation

Unconventional renewable energy sources can and must find practical applications in our country, first and foremost, in regions with autonomous power generation. In this niche, where high power generation costs are the norm, power plants using renewal energy sources are already attractive for economic and ecological reasons.     

Neutron-Capture Therapy with Thermal Neutrons at the Institute of Radiation Therapy at the Moscow Engineering Physics Institute

The results of the development of an irradiation base for neutron-capture therapy at the Institute of Radiation Therapy at the Moscow Engineering Physics Institute, the production and study of boron- and gadolinium-containing preparations, and preclinical investigations on large laboratory animals (dogs with spontaneous melanoma) are presented.     

Determination of stopping power for ions by backscattering from thin targets

A new procedure is presented for extracting the stopping power from the widths of a number of backscattering spectra. It can be applied irrespectively of the magnitude of the kinematic factor. For this method we introduce a function dependent on four parameters, the shape of which is sufficiently adaptable not to cause a relevant bias. This is demonstrated by fitting this function to the proton stopping power tables of Janni: for all 92 elements we list the fit parameters together with the mean and the maximum deviation. By computer simulation it is shown that the projectile energies in the backscattering measurements have to cover a certain range — depending on the kinematic factor — to give the correct stopping cross section. Finally, we applied this procedure to the measurement of the stopping cross section of Al for He-ions.     

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_O2=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.     

Study of Ohmic loss of high power polarizers at 170 GHz for ITER

ECCD system in ITER needs the polarizer for obtaining suitable polarization in a magnetize plasma. The Ohmic loss evaluation code was developed for high power grooved mirror polarizers. The Ohmic loss strongly depends on the mirror rotation angle and the rotation angle of incident linear polarization. Calculation results can explain the strange loss dependences.