Evaluation of -ray dose rates on the upper core structure of Joyo by the optical fiber

Yamamoto, Takahiro; Ito, Chikara   ; Maeda, Shigetaka   ; Ito, Hideaki; Sekine, Takashi 

In the experimental fast reactor Joyo, replacement of upper core structure (UCS) was conducted in 2014. Since the UCS replacement was not anticipated in the original design, the UCS surface dose rate was evaluated for the equipment design using QAD code considering the in-vessel dose rate measurement results. In order to confirm the accuracy of the evaluation, measurement of the surface ray distribution of cask, which included the old-UCS, was conducted using a plastic scintillating optical fiber (PSF) detector. With comparing the measured ray distribution with the calculated ray distribution, it was confirmed that the C/E was approximately 11.5.