Study on forming condition of rim structure and the effect on integrity in a fast reactor fuel

Naganuma, Masayuki  ; Kamei, Miho; Maeda, Koji  

In the LWR fuel irradiated up to high burn-up, the obscure structure called "rim structure" is known to be formed and affect the integrity. The structure has been observed in the high burn-up fuel irradiated in the experimental fast reactor "Joyo", too. Thus, the fuel behavior analyses were conducted for the post irradiation examinations results by using the analysis code, and the forming conditions in the FR fuel were evaluated. As a result, it was found that there was difference in the forming condition between LWR and FR fuels according to the difference of irradiation behaviors between the two. Then, the effects of forming rim structure on FR fuel integrity were investigated and confirmed to be benign.