Nanostructures Formation in Al-B4C Neutron Absorbing Materials after Accelerated Irradiation and Corrosion Tests

Abstract

Al/B 4 C metal matrix composite (MMC) is an important neutron absorbing material used in both wet storage pools and dry storage casks of spent nuclear fuel for preventing criticality. Because of the high neutron absorption cross-section of 10 B, the material can effectively absorb fast and thermal neutrons, but at the same time suffers neutron irradiation damage from the nuclear spent fuel. Moreover, interactions of fast and thermal neutrons with boron lead to the production of several transmutation species such as helium, lithium and others, according to the transmutations reactions induced by neutron irradiation, including the 10 B (n, 4 He) 7 Li reaction and others. The most abundant product of these reactions is energetic helium (~1.47MeV), which may induce further radiation damage and be precipitated out in the material as helium bubbles. The formation and coalescence of the helium bubbles in boron carbide and on boundaries, especially phase boundaries, would affect the corrosion performance of the material in its working environment. The degradation of the material may lead to boron loss which is the critical element to control the criticality of spent fuel. To evaluate the radiation and corrosion effects for interim storage of two hundred years accelerated He + irradiation and corrosion tests were carried out.

Simulation of Radiation Damage and He Accumulation Induced by 10B(n, α)7Li Reactions in Al‐B4C Neutron Absorbers Used in Spent Fuel Pools

“…These studies may perform charged-particle irradiation experiments in an accelerated manner, the design of which requires computational tools for the estimation of the accumulated radiation damage and He concentration in the neutron absorbers. A few experiments using chargedparticle irradiation facilities have already been conducted on Al-B 4 C MMC neutron absorbers to investigate their performance, but these studies employed empirically determined heavy ion doses [24][25][26]. Thus, computational estimation of the radiation damage and He atom accumulation by the newly considered MeV-level charged particles from 10 B(n, α) 7 Li reactions is required in order to more fully understand the degradation mechanism and certify the service life of neutron absorbers.…”