Structural Materials

Materials used in structures operate under chemical conditions that are not common in other sectors. For instance, the primary water chemistry at PWR is characterised by the addition of boron as boric acid which has neutronic properties, lithium as lithine LiOH to raise the pH creating a slightly basic environment, and hydrogen to prevent radiolysis creating a reducing environment, all at temperatures between 280°C and 320°C and at a pressure of 150 bars. The secondary water itself is rather peculiar. Additionally, the crevices between tube and tubesheet are positioned on the heat transfer side due to the unique design of the steam generator in PWR, which uses main pressurised water within tubes and water vapour on the outside side of the tubes. The use of boiling nitric acid at a high temperature with a high concentration of oxidising ions in reprocessing facilities is also quite distinctive. Therefore, specialised research is required to identify alloys that can withstand these conditions.