Development of evaluation method for SiC temperature monitor (III)

; Maruyama, Tadashi*;

PNC TJ9607 89-001, 100 Pages, 1989/06

PNC-TJ9607-89-001.pdf:4.33MB

The purpose of this study is to improve the accuracy of SiC temperature monitors by clarifing the effects of (a)heavy neutron irradiation, (b)flux and fluence of neutron, and (c)variation of temperature during shut-down sequence on recovery behavior of SiC monitors. Several types of uninstrumented in-core temperature monitors were reviewed. Especially, from the literature survey of the SiC temperature monitor, some problems which should be solved were presented. Recovery curves of eighteen SiC temperature monitors irradiated in the fast breeder reactors, JOYO, Rapsodie and Phenix to fast neutron fluences from 1.510 to 1.710n/cm (E0.1MeV) were measured by means of the following three methods; (1)Macroscopic length measurement using a micrometer, (2)Lattice parameter measurement by X-ray diffractometry and (3)Macroscopic length measurement at high temperature by a step-heating dilatometry. Merit and demerit, and requirements for specimen of the three methods were pointed out. The method of step-heating dilatometry was recommended as more convenient and suitable method to obtain annealing curves than the others. The following results were obtained from the recovery curve measurement. (1)For heavily irradiated specimens up to 1.710n/cm, recovery curve is obtainable by means of the macroscopic length measurement. (2)Macroscopic length or lattice parameter change shows a step-like decrease with increase in annealing temperature for the specimens which were finally irradiated in the slowly shut-downed reactor cycle. (3)Different neutron-spectrum irradiation affects on the microstructure development, but slightly on recovery behavior of SiC temperature monitor. Relation between annealing intersection temperature and irradiation temperature was not assessed because insufficient specimens were available. (4)Macroscopic length or lattice parameter did not always decrease constantly with increasing annealing ...