RADIATION DAMAGE IN TUNGSTEN TARGET OF THE “KIPT NEUTRON SOURCE”

In this work, mathematical modeling of a complex of processes occurring in a tungsten target under irradiation with high-energy electrons with an energy of 100 MeV: an electromagnetic shower, the production of photo-neutrons, and particle transport along the target, damage from neutrons of the subcritical assembly. It was found that the greatest contribution to the rate of damage formation in a tungsten target give the elastic scattering of high-energy electrons on nuclei.

FEM Simulation on Diffusion Bonding of High Purity Tungsten Target

The FEM (finite element method) simulation was used to study the diffusion bonding deformation of high purity tungsten target. The influence of different welding structure, bonding temperature on the deformation of the final high-purity tungsten target was systematically studied. Meanwhile, some microscopic properties of tungsten target were developed, such as internal stress size and distributions, strain size and distributions. Finally, physical experiments are used to verify numerical simulation results. The results show that the method of adding an intermediate layer can release the residual stress between the high-purity target and back plate. The bonding stress of high-purity tungsten target is mainly concentrated with the tungsten target and the intermediate layer in between, which is easy to fail during the later leveling process. Small deformation of bonding tungsten target can be obtained by low diffusion bonding temperature.

DEVELOPMENT OF HIGH POWER MICROFOCUS X-RAY TUBE

In this paper, we propose and study a new method for increasing the power of a microfocus X-ray tube of transmission type. The proposed method is based on the idea of using a heat pipe as a tube anode. A theoretical expression is obtained for the maximum power dissipated at such an anode, depending on the diameter of the electron beam and the thickness of the tungsten target. It is shown that the power of the proposed tube can be many times higher than the power of tubes with standard composite anodes. An electron-optical scheme of a tube with electrostatic focusing is proposed and analyzed.

Internal dose assessment of 148Gd using isotope ratios of gamma-emitting 146Gd or 153Gd in accidently released spallation target particles

The pure alpha emitter 148Gd may have a significant radiological impact in terms of internal dose to exposed humans in case of accidental releases from a spallation source using a tungsten target, such as the one to be used in the European Spallation Source (ESS). In this work we aim to present an approach to indirectly estimate the whole-body burden of 148Gd and the associated committed effective dose in exposed humans, by means of high-resolution gamma spectrometry of the gamma-emitting radiogadolinium isotopes 146Gd and 153Gd that are accompanied by 148Gd generated from the operation of the tungsten target. Theoretical minimum detectable whole-body activity (MDA) and associated internal doses from 148Gd are calculated using a combination of existing biokinetic models and recent computer simulation studies on the generated isotope ratios of 146Gd/148Gd and 153Gd/148Gd in the ESS target. Of the two gamma-emitting gadolinium isotopes, 146Gd is initially the most sensitive indicator of the presence of 148Gd if whole-body counting is performed within a month after the release, using the twin photo peaks of 146Gd centered at 115.4 keV (MDA < 1 Bq for ingested 148Gd, and < 25 Bq for inhaled 148Gd). The corresponding minimum detectable committed effective doses will be less than 1 µSv for ingested 148Gd, but substantially higher for inhaled 148Gd (up to 0.3 mSv), depending on operation time of the target prior to the release. However, a few months after an atmospheric release, 153Gd becomes a much more sensitive indicator of body burdens of 148Gd, with a minimum detectable committed effective doses ranging from 18 to 77 µSv for chronic ingestion and between 0.65 to 2.7 mSv for acute inhalation in connection to the release. The main issue with this indirect method for 148Gd internal dose estimation, is whether the primary photon peaks from 146 and 153Gd can be detected undisturbed. Preliminary simulations show that nuclides such as 182Ta may potentially create perturbations that could impair this evaluation method, and which impact needs to be further studied in future safety assessments of accidental target releases.