Swelling and microcracking of boron carbide subjected to fast neutron irradiations

Abstract

The neutron absorbing ceramic boron carbide was irradiated in the Phenix fast breeder reactor between 600 and 1500 °C. Selected pellets were observed at different magnifications using optical ceramography, scanning electron microscopy, and transmission electron microscopy. The bulk swelling was measured as a function of the burn-up and compared to a recent model based on microstructural observations. Intergranular microcracking was identified as the main source of troubles in the use of boron carbide at high fluence levels and studied in relation with our recent models.

Unusual properties of icosahedral boron-rich solids

“…The experiments by the Zuppiroli-group indicate remarkable resistance tolerance of icosahedral boron-rich solids [9][10][11][12]. To confirm the self-healing that these experiments imply, additional radiation damage experiments on many icosahedral boron-rich solids have been conducted in collaboration with the Ewing-group at facilities at the University of Michigan and at Argonne National Laboratory using samples provided by T.L.…”

“…High-resolution transmission electron microcopy was used to interrogate several icosahedral boron-rich solids (b-rhombohedral boron and boron carbides) during and after heavy bombardments [9][10][11]. The damage, clustering of defects and amorphization, expected of common semiconductors was not observed even when bombardments were carried out at a very low temperature, $12 K [7].…”

Development of Hydride Absorber for Fast Reactor—Application of Hafnium Hydride to Control Rod of Large Fast Reactor—

“…The -particles produce helium (He) gas and the He gas agglomerates in bubbles, which induces a large swelling and high stresses, and leads to the destruction of the material. The lifetime of B 4 C control rods is limited by the AbsorberCladding Mechanical Interaction (ACMI) failure due to the large swelling and the extensive microcracking, 11) as shown in Fig. 1.…”

Development of Hydride Absorber for Fast Reactor —Evaluation of Design Method for Hydride Absorber Rod—

“…The large swelling and high stresses are caused by agglomerates in bubbles of helium gases as a result of (n, ) reactions of boron. 1,2) Moreover, the control rod worth decreases with exposure by boron depletion. The fast reactor core is equipped with a lot of control rod assemblies because its excess reactivity has to be suppressed by the control rod assemblies only.…”