Measurement of thick-target gamma-ray production yields of the 7Li(p,p′)7Li and 7Li(p, γ)8Be reactions in the near-threshold energy region for the 7Li(p,n)7Be reaction

The gamma-ray production reactions, ⁷Li(p, p′)⁷Li and ⁷Li(p, γ)⁸Be, occur along with the neutron production reaction ⁷Li(p, n)⁷Be in a p-Li neutron source. These gamma-ray production reactions contribute to a patient's absorbed dose in boron neutron capture therapy (BNCT) when using a neutron beam from the ⁷Li(p, n)⁷Be reaction. The present work experimentally determined the thick-target gamma-ray production yields of the ⁷Li(p, p′)⁷Li and ⁷Li(p, γ)⁸Be reactions at incident proton energies of 1.670 and 1.870 MeV. The present results were compared with previous measurements. The gamma-ray production yield of ⁷Li(p, p′)⁷Li was measured to be 30%–50% smaller than as reported by previous studies. For the ⁷Li(p, γ)⁸Be reaction, the present thick-target yield is 30% smaller than one estimated from cross-section data measured in previous studies. The results must be included in future dose evaluation for BNCT using a p–Li neutron source.     

Effects of gamma-ray irradiation on electronic and non-electronic equipment of Large Helical Device

In a deuterium operation on the Large Helical Device,the measurement and control equipment placed in the torus hall must survive under an environment of radiation.To study the effects of gamma-ray irradiation on the equipment,an irradiation experiment is performed at the Cobalt-60 irradiation facility of Nagoya University.Transient and permanent effects on a personal computer,media converters,programmable logic controllers,isolation amplifiers,a web camera,optical flow meters,and water sealing gaskets are experimentally surveyed.Transient noise appears on the web camera.Offset of the signal increases with an increase of the integrated dose on the programmable logic controller.The DeviceNet module on the programmable logic controller is broken at the integrated dose of 72 Gy,which is the expected range of the integrated dose of the torus hall.The other equipment can survive under the gamma-ray field in the torus hall.     

中子及伽马射线复合屏蔽材料的研究进展

原子能工业的日益发展带来了核泄漏、核污染等安全隐患,人们必须采取严密的防护措施来保障涉核人员的身体健康和环境安全.众多核辐射类型中,中子和γ射线穿透性最强,屏蔽难度最大.然而,传统的中子屏蔽材料如硼、水、聚乙烯和伽马屏蔽材料如铅、铁、钨等屏蔽功能单一,屏蔽性能有限,有的热力学性能不佳,难以满足现代辐射防护的要求.在这方...     

Structural changes on the surfaces of borosilicate glasses induced by gamma-ray irradiation

Vitrification is a kind of glass that can solidify high-level radioactive waste (HLW). As the basic material of vitrification, borosilicate glass was studied extensively. To keep HLW away from the biosphere, the tolerance of borosilicate glass to irradiation is important. In this work, various samples of borosilicate glass with different compositions were irradiated with gamma rays at ambient temperature to study their stability. The hardness, moduli, and microscopic changes on surfaces of the borosilicate glasses were measured at specific absorbed doses. Upon the gamma irradiation, the structural changes on surfaces of borosilicate glasses were identified, which were strongly influenced by the composition of borosilicate glasses. The results demonstrate that gamma irradiation, as well as beta irradiation, might strongly influence the properties of vitrification. The irradiation effects on vitrification induced by gamma irradiation should be paid more attention to than before.     

Solid hold-up measurement in a jet-impactor assisted fluidized bed using gamma-ray densitometry

A jet-impactor assisted-fluidized bed (JIAFB) for continuous de-agglomeration of nanopowder agglomerates was presented in previous work. Therein, a jet caused agglomerates to impinge up an impactor, where they would break. However, efficient impactor positioning will be dictated by particle momentum: the product of solid concentration and velocity must be highest. Herein, the variation of solid hold-up was measured in a fluidized bed of Fe₂O₃ nanoparticles using gamma-ray densitometry. Behaviour was compared under minimum fluidization and bubbling regimes, over a wide range of jet velocities (0–200 m s⁻¹). A new line-decomposition approach allowed mapping local solid distribution across seven axial and five radial positions, tangibly demonstrating how increasing the gas velocity enhanced the fluidization quality by increasing axial solid diffusivity. Conversely, increasing jet velocity locally decreased solid hold-up in the jet-affected zone, and brought about inhomogeneities. With this information in hand, jet-to-impactor distance was optimized and validated experimentally.