| Al-B4C composite materials with good mechanical and neutron absorbent properties by powder metallurgy technology can be used in the field of protective screen especially for spent fuel storage as structural frame and functional pieces. It is necessary for such a material to check its corrosion and irradiation behaviors in order to guarantee the security of the spent fuel storage.Al-B4C composite materials with 15wt.% B4C was used for corrosion test in orthogonal design with different concentration of boric acid solution at different temperature. And accelerate radiation test is also done for such a material to simulate the radiation conditions of MCNP program based on the demand of 60 year storage.The results based on the analyses of pH value, conductivity and ICP parameters show that 1) the solution pH is slightly increased at the initial stage of corrosion; 2) the conductivity of solution is increased at the initial stage of corrosion. The increasing rate of conductivity becomes greater with increasing corrosion temperature, while reaching balance need more time; 3) Al ions and Mg ions in boric acid solution were significantly increased at higher concentration (2500-25000ppm) and the Al ions was increased linearly with corrosion time. But they have no obvious change at lower concentration (0-500ppm).The results based on the analyses of XRD for phase examination, SEM for morphologic observation and EDS for composition measurement of corroded samples as well as weight change of those samples show that 1 A dense layer of Al(OH)3 with a lower conducting ability was formed after corrosion in boric acid solution at 0 or 500 ppm and the samples became heavy, which can play a little protective role. 2) An amorphous Al(OH)3 sediments like wadding shape can be found after corrosion in boric acid solution at 2500 ppm.3) Inter-granular corrosion happened for the samples after corrosion in boric acid solution at 1000-25000 ppm and the samples became light, corroded pits can be observed in the local area on the surface of the samples.4) Corrosion rate increased with increasing temperature, and it reached the highest at 40℃. 5) The corrosion resistance of the samples became worse with increasing concentration of boric acid, hence it can be used for accelerate corrosion test of Al-B4C materials.Corrosion tests at 0,1000, and 25000 ppm boric acid solution for Al-B4C composite materials prepared by powder metallurgy technology indicate that such a material can be applied to the BWR reactor spent fuel storage but could not be suitable for PWR reactor spent fuel storage, where the corrosion rate reached -2.16～-3.45μm/y. Surface protective treatments such as anodization method, micro-arc oxidation etc. should be done.MCNP model was used to simulate two irradiation schemes. The scheme of irradiation test with 1 mm Cd cladding is better due to that the samples can get much higher y dose rate, while much less thermal neutron fluent rate and heat generation rate according to the comparison with y dose rate, thermal neutron fluent rate, fast neutron fluent and heat generation rate. The y distribution in the irradiated area show that the relative deviation is less than 2% with measurements of 7LiF and gamma dose meter and less than 4% with theoretic calculation. Therefore, such a model could be used as reference of pre-irradiation and accelerated irradiation tests. |
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