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Maruyama, Tadashi; ; ; Onose, Shoji;
PNC TN9410 97-077, 177 Pages, 1997/07
Postirradiation examinations of JOYO MK-II control rods have been carried out since 1983, where 16 subassemblies with total 110 absorber pins of initial load to the fifth reload control rods have been subjected to a number of both non-destructive and destructive examinations. In the course of postirradiation examinations, a cracking of cladding tube was found in the total 15 absorber pins in five control assemblies. This paper indicates the results of postirradiation examinations and analysis of absorber pin performance using CORAL code to elucidate the cause of absorber pin cracking in JOYO MK-II control rods. No crack was found in absorber pins whose maximum burnup was lower than 39 
10
cap/m
, whereas all the cracked pins had burnup of higher than 43 10 cap/m with the initial gap between B
C pellet and cladding larger than 0.44 mm. The cracks were found at around positions corresponding to the lowest BC pellet in the stack. The ceramography analysis indicated that BC pellet exhibited extensive cracking and a part of gap between pellet and cladding closed. The cladding deformation had an ovality and the cracks tended to occur at the shorter diameter side. The cracked surface of absorber pin was of a typical grain boundary fracture. The result of He analysis for the cladding material indicated a substantial amount of He accumulation at the inner surface of cladding, but the bulk He content was not anomalously high compared with those in the neutron irradiated stainless steels. TEM observation indicated He bubbles was not clearly found in the as-irradiated cladding material. The cause of cladding failure was attributed to the ACMI where the gap closure due to relocation of BC pellet took place from early times of irradiation. The code analysis by CORAL indicated that the cladding strain due to ACMI was not fully absorbed by the irradiation creep and that the plastic strain became large enough to ...
1993) on nuclear material crossover researchKano, Shigeki; Tachi, Yoshiaki; ; ; Yoshida, Eiichi; Hirakawa, Yasushi
PNC TN9410 94-113, 70 Pages, 1994/04
(Purpose) This report describes the outline, research results obtained, interchange activities, etc. of the Phase I Program on the Nuclear Material Crossover Research, which has been conducted by related research institutes including PNC/OEC from 1989 through 1993 fiscal year, and shows the Phase II Program to be started from 1994 fiscal year. (Method) Crossover research programs, research results and interchange methods were decided through discussions at the crossover research comittee (chairman : Prof.M.Okamoto, TIT) in which PNC, JAERI, NRIM, NIRIM and NCLI were participated as main members. Forums, seminars, symposiums and workshops with domestic and foreign experts on materials research were set up as the opportunities for interchange. (Results) (1)As secretary institutes, PNC and JAERl planned eight times of forums, 3 times of seminars, twice of domestic symposiums, once of international symposium, five workshops with research institutes in France, Germany, Italy and the Netherland. The contacts with outside experts, collection of new information on advanced materials, receipt of test samples, achievement of collaborative research, etc. through these interchanges were much valuable for effective performance of PNC research. (2)The following results were obtained on PNC research. The prospects on creation of following advanced materials were obtained through these interchanges: (a)advanced ceramics having excellent corrosion resistance to sodium, (b)longer life neutron absorbing materials having higher resistance to cracking than BC, (c)high performance shielding materials having higher heat resistance than conventional materials. (3)Phase II Program to be started from 1994 fiscal year has been planned by main five institutes and authorized through the evaluation by two evaluation comittees organized separately by the crossover research comittee and PNC. (Conclusion) The prospects on creation of several advanced materials were obtained through ...
C-SS eutectic materials in the solid stateTakai, Toshihide; Furukawa, Tomohiro; Yamano, Hidemasa
no journal, ,
no abstracts in English
