Neutron irradiation effects on
B
C and recovery by annealing
Donomae, Takako
; Tachi, Yoshiaki
; Sekine, Manabu*; Morohashi, Yuko
; Akasaka, Naoaki; Onose, Shoji 
Use of moderator materials in Fast Breeder Reactor (FBR) is effective for transmutation technology, and
B
C is one of the candidates. Up to now, the behavior of
B
C as the Control rod material is well known, but that of
B
C is hardly investigated. In this paper, the radiation effects of
B
C pellets, neutron irradiated in the experimental fast reactor JOYO were studied. From the experimental results, it was observed that no macro-cracks were recognized in the irradiated
B
C pellets. But, bubble nucleation was found in grain and along grain boundaries of
B
C. And, it was shown that the conductivity of
B
C was higher than that of
B
C. During the annealing from room temperature to 1400
C, three recovery stages were found on thermal conductivity. It was suggested that, the recovery of B
C was related to the dispersion behavior of helium. Judging from these results, as
B
C was mechanically more stable compared with
B
C under irradiation, it was shown that
B
C had high applicability for a moderator.