Component Testing and Materials Development for Fusion Applications Using Materials Test Reactors
Fusion power plant operation will strongly depend on the economy and reliability of crucial components, such as first wall modules, tritium breeding blankets and divertors. Their operating temperature shall be high to accomplish high plant efficiency. The materials properties and component fabrication routes shall also assure long reliable operation to minimize plant outage. The components must be fabricated in large quantities based on demonstrations with a limited amount of test beds. Mock-ups and test loops will, through iteration processes, demonstrate the reliable operation under reference thermal-hydraulic conditions. 14 MeV neutrons escaping the plasma dominate the nuclear conditions near the first wall. Neutron transport analyses have shown that large portions of the components near the plasma have to cope with a neutron spectrum resembling that of a fission core. MTR's, Materials Test Reactors, have been used successfully to test components for fusion power plants. Their space and availability will also ensure their role as future test bed for (sub) components such as blankets, first walls and divertors. The future generation of MTR's will allow faster testing, because of the higher neutron fluxes possible with advanced driver fuels. The strong limitation of MTR's for fusion testing will remain the limited production of helium and hydrogen, because of the lack of 14 MeV neutrons. Though large parts of the fusion components are subjected to nearly fission neutron spectra, in the domain near the burning plasma 14 MeV neutrons are dominant. IFMIF will produce the 14 MeV neutrons to fill that gap by the end of the next decade. In the meantime the MTR's will generate relevant data for fusion power plant component design. After IFMIF is operational the new generation MTR's will still have a function in testing components in a nuclear environment. The new generation test reactors will also be used for the development of component operating at high temperature in the generation-4 fission power plants. The R&D climate will be most stimulating for cross fertilization of fission and fusion component development, leading to more efficient use of the earth's resources.
The impact of materials selection on long-term activation in fusion power plants
Abstract Neutron-induced transmutation of materials in a D–T fusion power plant will give rise to the potential for long-term activation. To ensure that the attractive safety and environmental characteristics of fusion power are not degraded, careful design choices are necessary. An aim of optimising power plant design must be to minimise both the level of activation and the total volume of active material that might ultimately be categorised as waste requiring disposal. Materials selection is central to this optimisation. In this paper we assess the influence of materials choices for a power plant on the waste volume and the potential to clear (i.e. remove from regulatory control) and recycle material. Although the use of low activation materials in regions of high neutron flux is an important part of the strategy to minimise the level of activation, different choices may result from a strategy aimed at minimising the volume of active waste.
Failure analysis for poor solderability of Au surface of PCB
Nonwetting is one of the common problems and is always rejected in electronic assemblies. ENIG pads of a PCBA exhibited nonwetting after lead-free reflow soldering. With the aid of stereomicroscope, SEM&EDS and XRF, a series of analysis was performed. And after visual inspection, surface and cross section analysis, thickness measurement and solderability test, it can be inferred that oxidation of plating surface was the main reason for nonwetting, and corrosion in Ni plating caused an adverse impact on solderalibity.