Damage evaluations for BWR lower head in severe accident based on multi-physics simulations

Katsuyama, Jinya; Yamaguchi, Yoshihito; Nemoto, Yoshiyuki; Furuta, Takuya; Kaji, Yoshiyuki

Proceedings of ASME 2022 Pressure Vessels and Piping Conference (PVP 2022) (Internet), 9 Pages, 2022/07

A Study on applicability of elasto-plastic constitutive model to mechanical behavior of buffer material in salt water conditions

Takayama, Yusuke; Kikuchi, Hirohito*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 27(1), p.12 - 21, 2020/06

https://doi.org/10.3327/jnuce.27.1_12

In this study, an applicability of the modified Cam clay model to the buffer material under saltwater conditions was examined. First, consolidated-undrained triaxial test was conducted using NaCl solution and artificial seawater. Based on the consolidated-undrained triaxial compression test results and the existing consolidation test results, the difference in the mechanical behavior of the buffer material under distilled water and saltwater condition was clarified. In particular, there was a difference in the unloading behavior in the consolidation test. Through reproducibility analysis of these experimental data, it was confirmed that the mechanical behavior of the buffer material can be roughly reproduced by setting the swelling index according to the salt concentration.

Notch toughness evaluation of diffusion-bonded joint of alumina dispersion-strengthened copper to stainless steel

Nishi, Hiroshi

Fusion Engineering and Design, 81(1-7), p.269 - 274, 2006/02

https://doi.org/10.1016/j.fusengdes.2005.07.011

Tensile strength of the diffusion bonded joint was as large as that of Alumina dispersion-strengthened copper (DS Cu), however, the Charpy absorbed energy of the joint was considerably lower than that of DS Cu. Instrumented Charpy impact test and slow-bend Charpy test of diffusion bonded joints were performed to clarify the degradation of Charpy absorbed energy. Elasto-plastic analyses were also carried out in order to study the deformation behavior of the tensile and V-notched specimens for joints. As the results, the fracture behaviors of the impact and slow-bend tests were almost the same. Elasto-plastic analyses showed that the maximum strain occurred at the DS Cu apart from the interface for tensile specimen, however, the strain concentrated at the DS Cu near the interface for the notched specimen. This strain concentration arose from the mechanical heterogeneity between stainless steel and DS Cu in the bonded zone and attributed to the degradation of the absorbed energy of the joints.

Simulation of creep test on 316FR stainless steel in sodium environment at 550

Satmoko, A.*;

JNC TN9400 99-035, 37 Pages, 1999/04

JNC-TN9400-99-035.pdf:1.54MB

In sodium environment, materia1 316FR stainless steel risks to suffer from carburization. In this study, an analysis using a Fortran program is conducted to evaluate the carbon influence on the creep behavior of 316FR based on experimental results from uni-axial creep test that had been performed at temperature 550C in sodium environment simulating Fast Breeder Reactor condition. As performed in experiments, two parts are distinguished. At first, elastic-plastic behavior is used to simulate the fact that just before the beginning of creep test, specimen suffers from load or stress much higher than initial yield stress. In second part, creep condition occurs in which the applied load is kept constant. The plastic component should be included, since stresses increase due to section area reduction. For this reason, elastic-plastic-creep behavior is considered. Through time carbon penetration occurs and its concentration is evaluated empirically. This carburization phenomena are assumed to affect in increasing yield stress, decreasing creep strain rate, and increasing creep rupture strength of material. The model is capable of simulating creep test in sodium environment. Material near from surface risks to be carburized. Its material properties change leading to non-uniform distribution of stresses. Those layers of material suffer from stress concentration, and are subject to damage. By introducing a damage criteria, crack initialization can thus be predicted. And even, crack growth can be evaluated. For high stress levels, tensile strength criterion is more important than creep damage criterion. But in low stress levels, the latter gives more influence in fracture. Under high stress, time to rupture of a specimen in sodium environment is shorter than in air. But for stresses lower than 26 kgfmm, the time to rupture of creep in sodium environment is the same or little longer than in air. Quantitatively, the carburization effect at ...

None

Ichikawa, Yasuaki*

PNC TJ1603 98-001, 67 Pages, 1998/03

PNC-TJ1603-98-001.pdf:2.92MB

no abstracts in English

None

PNC TJ1205 96-002, 68 Pages, 1996/02

PNC-TJ1205-96-002.pdf:1.96MB

None

Homologous ductile failure criterion for generalized stress states

Futakawa, Masatoshi; N.Butler*

Engineering Fracture Mechanics, 54(3), p.349 - 359, 1996/00

https://doi.org/10.1016/0013-7944(95)00205-7

no abstracts in English

Development of creep-fatigue evaluation method for welde structures considering metallurgical and geometrical discontinuities; Application of elastic follow-up model to welded joints

kasahara, Naoto

PNC TN9410 95-213, 38 Pages, 1995/08

PNC-TN9410-95-213.pdf:1.72MB

In order to evaluate thermal transient strength of welded components in nuclear plants, conventional structural design codes provide conservative strength reduction factors, which are desired to be rationalized. Author extended the generalized clastic follow-up model to evaluate main causes of strength reduction of welded joints. As main causes of strength reduction of welded joints subjected to cyclic thermal transients, attention was given to (1)Metallurgical discontinuity in which the different deformation response between base metal and weld metal can result in nonuniform stresses and strain across the weldment, (2)Structural discontinuity at penetration beads of welded joints, and (3)Degradation of Weld Metal. In order to evaluate (1) and (2) of above factors, an elastic follow-up model was successfully applied. Thermal transient strength test results provide further substantiation of the validity of the elastic follow-up model for ensuring adequate life in elevated temperature component weldments. Author applied the creep-fatigue life prediction methods based on the elastic follow-up model to evaluate test results of a welded vessel model. Proposed method was proved to be adequate through comparison of predicted damagc with observed cracks data.

Report of phase I program (19891993) on nuclear material crossover research

Kano, Shigeki; Tachi, Yoshiaki; ; ; Yoshida, Eiichi; Hirakawa, Yasushi

PNC TN9410 94-113, 70 Pages, 1994/04

PNC-TN9410-94-113.pdf:3.67MB

(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 ...

Small specimen test techniques for the evaluation of toughness degradation

Suzuki, Masahide; Eto, Motokuni; Nishiyama, Yutaka; Fukaya, Kiyoshi; *; *

Journal of Nuclear Materials, 191-194, p.1023 - 1027, 1992/00

https://doi.org/10.1016/0022-3115(92)90629-Y

no abstracts in English