Residence Time of Crud on Surfaces of Channel Box in JPDR

Abstract

Characterization of crud on surfaces of the channel box in JPDR has been carried out by means of chemical, radiochemical, X-ray diffraction and infrared spectrum analyses. The main cations in the crud are Fe and Ni: The sum of their weights amounts to more than 90% of the total weight of the cations found. The results of X-ray diffraction and infrared spectrum analyses revealed that the crud consisted of Ni 0 • 65 Fe 2 • 35 0 4 , NiO and r-FeOOH.Based on the neutron flux calculated from the burn-up of 235 U and 238 U in the spent fuel, the apparent residence time of elements on the surface of the channel box was calculated to be 230 d for Co, 260 d for Ni and 70 d for Fe. The value for Fe should be taken as a minimum value, because of the presence of r·FeOOH in the crud, which has been formed during the storage in a pond.The present data are discussed in correlation with the one in the reactor water.