ACCELERATED CORROSION TESTING OF ALUMINUM BORON CARBIDE METAL MATRIX COMPOSITE IN SIMULATED PWR SPENT FUEL POOL SOLUTION

The MAXUS® Al/B4C MMC plate has been developed by Nippon Light Metal as a neutron absorber for basket plates in both dry storage casks and wet storage racks. The material's relatively low weight, high thermal conductivity, high mechanical strength and other properties makes it attractive for both applications. If MAXUS® is to be used as neutron absorber for storage racks immersed in spent fuel pools, the MMC must maintain its stability during long-term exposure to the pool environment. In order to investigate the long-term stability of the MAXUS® Al/B4C MMC plate for use in wet storage racks, accelerated corrosion testing has been performed with a simulated PWR spent fuel pool solution for 10,080 hours. The MAXUS® plate is produced using a powder metallurgy process and has a sandwich structure with Al/B4C MMC core and thin aluminum skins. Samples for corrosion testing were cut from plates having a 15 wt%-B4C core. Corrosion testing of anodized and non-anodized samples was performed at 363 K in accordance with ASTM G31-72 (2004) [1]. After the accelerated corrosion testing, the aluminum surface cladding and its anodic film were slightly hydrated; however, all coupons had no blisters, swelling or other abnormalities that cause loss of boron carbide. The metal loss measured by corrosion weight loss after removal of the aluminum hydrate layer is small and it is not considered to be significant for practical use. Because the metal loss shows no difference between 4,320 hours and 10,080 hours, it can be considered that the hydration reaction with solution has stopped after 4,320 hours. These results confirm that MAXUS® has good corrosion resistance in the simulated PWR spent fuel pool solution.