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Journal Articles

Plasticity correction on stress intensity factor evaluation for underclad cracks in reactor pressure vessels

Lu, K.; Katsuyama, Jinya; Li, Y.

Journal of Pressure Vessel Technology, 142(5), p.051501_1 - 051501_10, 2020/10

 Times Cited Count:0 Percentile:0(Engineering, Mechanical)

Journal Articles

Application of probabilistic fracture mechanics methodology for Japanese reactor pressure vessels using PASCAL4

Lu, K.; Katsuyama, Jinya; Li, Y.; Yoshimura, Shinobu*

Proceedings of 2019 ASME Pressure Vessels and Piping Conference (PVP 2019) (Internet), 9 Pages, 2019/07

JAEA Reports

Confirmation tests for Warm Pre-stress (WPS) effect in reactor pressure vessel steel (Contract research)

Chimi, Yasuhiro; Iwata, Keiko; Tobita, Toru; Otsu, Takuyo; Takamizawa, Hisashi; Yoshimoto, Kentaro*; Murakami, Takeshi*; Hanawa, Satoshi; Nishiyama, Yutaka

JAEA-Research 2017-018, 122 Pages, 2018/03

JAEA-Research-2017-018.pdf:44.03MB

Warm pre-stress (WPS) effect is a phenomenon that after applying a load at a high temperature fracture does not occur in unloading during cooling, and then the fracture toughness in reloading at a lower temperature increases effectively. Engineering evaluation models to predict an apparent fracture toughness in reloading are established using experimental data with linear elasticity. However, there is a lack of data on the WPS effect for the effects of specimen size and surface crack in elastic-plastic regime. In this study, fracture toughness tests were performed after applying load-temperature histories which simulate pressurized thermal shock transients to confirm the WPS effect. The experimental results of an apparent fracture toughness tend to be lower than the predictive results using the engineering evaluation models in the case of a high degree of plastic deformation in preloading. Considering the plastic component of preloading can refine the engineering evaluation models.

Journal Articles

Benchmark analyses using probabilistic fracture mechanics analysis codes for reactor pressure vessels

Arai, Kensaku*; Katsuyama, Jinya; Li, Y.

Proceedings of Asian Symposium on Risk Assessment and Management 2017 (ASRAM 2017) (USB Flash Drive), 8 Pages, 2017/11

Probabilistic fracture mechanics (PFM) analysis code PASCAL has been developed to assess structural integrity of aged reactor pressure vessels (RPVs) of light water nuclear power plants by Japan Atomic Energy Agency (JAEA). PASCAL is able to obtain failure frequency such as through-wall cracking frequency (TWCF) of RPVs under several transients including pressurized thermal shock (PTS) event. On the other hand, FAVOR was developed to perform almost the same analysis by Oak Ridge National Laboratory (ORNL) under United States Nuclear Regulatory Commission (USNRC) funding and has been utilized in the US nuclear regulation. To improve the reliability of PFM analysis results of PASCAL, benchmark analyses between PASCAL and FAVOR were performed. This paper provides results of the benchmark analyses using analysis conditions and parameters of the US 3-loop pressurized water reactor (PWR) nuclear power plant. Furthermore, sensitivity analyses relating to differences of analysis models (ex. Embrittlement correlation model) between Japan and the US were also conducted.

Journal Articles

Development of Stress intensity factor coefficients database for a surface crack of an RPV considering the stress discontinuity between cladding and base metal

Onizawa, Kunio; Shibata, Katsuyuki*; Suzuki, Masahide

Proceedings of 2005 ASME/JSME Pressure Vessels and Piping Division Conference (PVP 2005), 12 Pages, 2005/07

Under a transient loading like pressurized thermal shock (PTS), the stress discontinuity near the interface between cladding and base metal of a reactor pressure vessel (RPV) is caused by the difference in their thermal expansion factors. So the stress intensity factor (SIF) of a surface crack which the deepest point exceeds the interface should be calculated by taking account of the stress discontinuity. Many SIF calculations are performed in Monte Carlo simulation of the probabilistic fracture mechanics (PFM) analysis. To avoid the time consuming process from the SIF calculation in the PFM analysis, the non-dimensional SIF coefficients corresponding to the stress distributions in the cladding and base metal were developed. The non-dimensional SIF coefficients database were obtained from 3D FEM analyses. The SIF value at the surface was determined by linear extrapolation of SIF value near the surface. Using the SIF coefficients database, the SIF values at both surface and deepest points of a surface crack can be evaluated precisely and in a reasonable time.

JAEA Reports

Failure probability analysis on mercury target vessel

Ishikura, Shuichi*; Shiga, Akio*; Futakawa, Masatoshi; Kogawa, Hiroyuki; Sato, Hiroshi; Haga, Katsuhiro; Ikeda, Yujiro

JAERI-Tech 2005-026, 65 Pages, 2005/03

JAERI-Tech-2005-026.pdf:2.86MB

Failure probability analysis was carried out to estimate the lifetime of the mercury target which will be installed into the JSNS (Japan spallation neutron source) in J-PARC (Japan Proton Accelerator Research Complex). The lifetime was estimated as taking loading condition and materials degradation into account. Considered loads imposed on the target vessel were the static stresses due to thermal expansion and static pre-pressure on He-gas and mercury and the dynamic stresses due to the thermally shocked pressure waves generated repeatedly at 25 Hz. Materials used in target vessel will be degraded by the fatigue, neutron and proton irradiation, mercury immersion and pitting damages, etc. The imposed stresses were evaluated through static and dynamic structural analyses. The material-degradations were deduced based on published experimental data. As results, it was quantitatively confirmed that the failure probability for the lifetime expected in the design is very much lower, 10$$^{-11}$$ in the safety hull, meaning that it will be hardly failed during the design lifetime. On the other hand, the beam window of mercury vessel suffered with high-pressure waves exhibits the failure probability of 12%. It was concluded, therefore, that the leaked mercury from the failed area at the beam window is adequately kept in the space between the safety hull and the mercury vessel to detect mercury-leakage sensors.

Journal Articles

Importance of fracture criterion and crack tip material characterization in probabilistic fracture mechanics analysis of an RPV under a pressurized thermal shock

Shibata, Katsuyuki; Onizawa, Kunio; Li, Y.*; Kato, Daisuke*

International Journal of Pressure Vessels and Piping, 81(9), p.749 - 756, 2004/09

 Times Cited Count:5 Percentile:35.81(Engineering, Multidisciplinary)

The paper describes the procedure to evaluate the ductile crack extension, where an increase in fracture resistance by a ductile crack extension is considered. Two standard ${it J}$-resistance curves are prepared for applying the elasto-plastic fracture criterion. Case studies concerning the effect of elasto-plastic fracture criterion were carried out using a severe PTS transient. The introduction of the elasto-plastic fracture criterion significantly contributes to remove the over-conservatism in applying the linear elastic fracture criterion. It was also found that the algorithm of the re-evaluation of crack tip characterization also has a significant effect on the failure probability.

Journal Articles

Probabilistic fracture mechanics analyses of reactor pressure vessel under PTS transients

Onizawa, Kunio; Shibata, Katsuyuki; Kato, Daisuke*; Li, Y.*

JSME International Journal, Series A, 47(3), p.486 - 493, 2004/07

The probabilistic fracture mechanics (PFM) analysis code PASCAL has been developed in JAERI. This code can evaluate the conditional probabilities of crack initiation and fracture of a reactor pressure vessel (RPV) under transient conditions such as pressurized thermal shock (PTS). Based on the temperature and stress distributions in the vessel wall for four PTS sequences in a typical 3-loop PWR, parametric PFM analyses are performed using PASCAL on the variables such as pre-service inspection model, crack geometry, fracture toughness curve and irradiation embrittlement prediction equation. The results showed that the good perfomance inspection model had a significant effect on the fracture probability and reduced it by more than 3 orders of magnitude. The fracture probability calculated by the fracture toughness estimation method in Japan was about 2 orders of magnitude lower than that by the USA method. It was found that the treatment of a semi-elliptical crack in PASCAL reduced the conservatism in a conventional method that it is transformed into an infinite length crack.

Journal Articles

Embedded crack treatments and fracture toughness evaluation methods in probabilistic fracture mechanics analysis code for the PTS analysis of RPV

Onizawa, Kunio; Shibata, Katsuyuki; Suzuki, Masahide; Kato, Daisuke*; Li, Y.*

RPV Integrity and Fracture Mechanics (PVP-Vol.481), p.11 - 17, 2004/07

At JAERI, the prpbabilistic fracture mechanics analysis code PASCAL has been developed. Using the PASCAL, the treatment methods of an embedded crack and the fracture toughness evaluation methods were studied on the probability of crack initiation and fracture of a RPV. For calculating the stress intensity factor (SIF) of an embedded crack, the ASME and CRIEPI procedures were introduced into PASCAL. Under a severe pressurized thermal shock condition, the crack growth analysis models with different SIF calculation points and crack growth directions are compared. The results showed that the crack tip at the inner side was most important to the fracture probability. The conditional fracture probability for an embedded crack when the same crack size distribution is assumed is approximately one order of magnitude lower than that of a surface crack. Fracture toughness curves based on Weibull distribution were incorporated into PASCAL. The comparison between these new curves and the current curves showed little effect on the conditional fracture probability of a RPV.

Journal Articles

Micro pit formation by mercury-sphere collision

Ishikura, Shuichi*; Kogawa, Hiroyuki; Futakawa, Masatoshi; Kaminaga, Masanori; Hino, Ryutaro; Saito, Masakatsu*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(1), p.59 - 66, 2004/03

The development of a MW-class spallation neutron source facility is being carried out under the Japan Proton Accelerator Research Complex (J-PARC) Project promoted by JAERI and KEK. A mercury target working as the spallation neutron source will be subjected to pressure waves generated by rapid thermal expansion of mercury due to a pulsed proton beam injection. The pressure wave will impose dynamic stress on the vessel and deform the vessel, which would cause cavitation in mercury. To evaluate the effect of mercury micro jets, driven by cavitation bubble collapse, on the micro-pit formation, analyses on mercury sphere collision were carried out: single bubble dynamics and collision behavior on interface between liquid and solid, which take the nonlinearity due to shock wave in mercury and the strain rate dependency of yield stress in solid metal into account. Analytical results give a good explanation to understand relationship between the micro-pit formation and material properties: the pit size could decrease with increasing the yield strength of materials.

JAEA Reports

Structural integrity of heavy liquid-metal target installed in spallation neutron facility, 4; Consideration by fracture mechanics of target container window

Ishikura, Shuichi*; Kogawa, Hiroyuki; Futakawa, Masatoshi; Kikuchi, Kenji; Haga, Katsuhiro; Kaminaga, Masanori; Hino, Ryutaro

JAERI-Tech 2003-093, 55 Pages, 2004/01

JAERI-Tech-2003-093.pdf:5.41MB

To estimate the structural integrity of the heavy liquid-metal (Hg) target used in a MW-class neutron scattering facility, static and dynamic stress behaviors due to the incident of a 1MW-pulsed proton beam were analyzed. In the analyses, two-type target containers with semi-cylindrical type and flat type window were used as analytical models of the structural analysis codes LS-DYNA. As a result, it is confirmed that the stress generated by dynamic thermal shock becomes the largest at the center of window, and the flat type window is more advantageous from the structural viewpoint than the semi-cylindrical type window. It was confirmed to erosion damage the target container by mercury's becoming negative pressure in the window and generating the cavitation by the experiment. Therefore, it has been understood that the point top of the window was in the compression stress field by the steady state thermal stress because of the evaluation from destroying the dynamic viewpoint for the crack in the generated pit and the pit point, and the crack did not progress.

Journal Articles

Bubble dynamics in the thermal shock problem of the liquid metal target

Ishikura, Shuichi*; Kogawa, Hiroyuki; Futakawa, Masatoshi; Kikuchi, Kenji; Hino, Ryutaro; Arakawa, Chuichi

Journal of Nuclear Materials, 318, p.113 - 121, 2003/05

 Times Cited Count:12 Percentile:64.02(Materials Science, Multidisciplinary)

The thermal shock stress in the mercury target vessel was analyzed: the target receives the incident proton beam at the energy of 1 MW with the pulse duration of 1ms. Negative pressure of maximal 61MPa was generated when the initial pressure of 52MPa propagated in mercury. It is expected then that the cavitation may be arisen by the negative pressure. So in order to know the cavitation behavior, the simulation study was carried out by using the equation of motion based on the bubble dynamics for a single bubble, and fundamental parameter analysis was carried out. It is found that a bubble has a potential expansion more than 1000 times with a change of the pressure at the window of the target vessel. Consequently wave propagation will be affected. Theoretical consideration was given to the wave motion of propagation in bubbly liquid. The equation of state in bubbly liquid can be approximated by the polynomial. The diameter of a bubble and the bubble volume fraction inherent in mercury can be decided if the critical pressure, the sound velocity, and resonance frequency is successfully measured by static and dynamic experiment.

Journal Articles

Probabilistic fracture mechanics analyses of RPV under some PTS transients

Onizawa, Kunio; Shibata, Katsuyuki; Kato, Daisuke*; Li, Y.*

Proceedings of 11th International Conference on Nuclear Engineering (ICONE-11) (CD-ROM), 8 Pages, 2003/04

Probabilistic Fracture Mechanics (PFM) has been used in the fields of reliability analysis for important structural components. At JAERI, the PFM analysis code PASCAL has been developed. This code evaluates the conditional probabilities of crack initiation and fracture of a reactor pressure vessel (RPV) under transient conditions such as pressurized thermal shock (PTS). Four cases of PTS transients were selected based on the severity for a typical 3-loop PWR. Based on thermal stress analyses, PFM analyses were performed by using PASCAL code focusing on some important variables on the RPV fracture probability. The results showed that non-destructive examination methods had a significant effect on the fracture probability by more than three orders of magnitude. The comparisons of the results using fracture toughness estimation methods between in Japan and USA, and crack geometries between a semi-elliptical surface crack and an infinite surface crack are also made.

Journal Articles

Examination of flaw acceptance standard in JSME fitness for service rule based on failure probability

Shibata, Katsuyuki; Onizawa, Kunio; Li, Y.*; Kanto, Yasuhiro*; Yoshimura, Shinobu*

Nihon Kikai Gakkai M&M 2003 Zairyo Rikigaku Bumon Koenkai Koen Rombunshu, No.03-11, p.939 - 940, 2003/00

no abstracts in English

Journal Articles

Thermal shock analysis of liquid-mercury spallation target

Ishikura, Shuichi*; Kogawa, Hiroyuki; Futakawa, Masatoshi; Hino, Ryutaro; Date, Hidefumi*

Koon Gakkai-Shi, 28(6), p.329 - 335, 2002/11

The developments of the neutron scattering facilities are carried out under the high-intensity proton accelerator project promoted by JAERI and KEK. To estimate the structural integrity of the heavy liquid-metal (Hg) target used as a spallation neutron source in a MW-class neutron scattering facility, dynamic stress behavior due to the incident of a 1MW-pulsed proton beam were analyzed by using FEM code. Two-type target containers with semi-cylindrical type and flat-plate type window were used as models for analyses. As a result, it is confirmed that the stress (pressure wave) generated by dynamic thermal shock becomes the largest at the center of window, and the flat-plate type window is more advantageous from the structural viewpoint than the semi-cylindrical type window. It has been understood that the stress generated in the window by the pressure wave can be treated as the secondary stress.

Journal Articles

Development of a PFM code for evaluating reliability of pressure components subject to transient loading

Shibata, Katsuyuki; Kato, Daisuke*; Li, Y.*

Nuclear Engineering and Design, 208(1), p.1 - 13, 2001/08

 Times Cited Count:20 Percentile:80.57(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Development of probabilistic fracture mechanics code PASCAL and user's manual

Shibata, Katsuyuki; Onizawa, Kunio; Li, Y.*; Kato, Daisuke*

JAERI-Data/Code 2001-011, 233 Pages, 2001/03

JAERI-Data-Code-2001-011.pdf:7.42MB

no abstracts in English

Journal Articles

Sensitivity analysis of failure probability on PTS benchmark problems of pressure vessel using a probabilistic fracture mechanics analysis code

Li, Y.*; Kato, Daisuke*; Shibata, Katsuyuki

JSME International Journal, Series A, 44(1), p.130 - 137, 2001/01

no abstracts in English

Journal Articles

Introduction of effect of annealing into probabilistic fracture mechanics code and results of benchmark analyses

Shibata, Katsuyuki; Kato, Daisuke*; Li, Y.*

Emerging Technologies: Risk Assessment, Computational Mechanics and Advanced Engineering Topics (PVP-Vol.400), p.49 - 54, 2000/00

no abstracts in English

Journal Articles

Study on spallation thermal shock for mercury target vessel

Kikuchi, Kenji; Futakawa, Masatoshi; Ishikura, Shuichi*; Kogawa, Hiroyuki

Nihon Kikai Gakkai Zairyo Rikigaku Bumon Koenkai (M&M'99) Koen Rombunshu, p.467 - 468, 1999/10

no abstracts in English

23 (Records 1-20 displayed on this page)