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Katsuyama, Jinya; Ito, Hiroto*; Li, Y.*; Osakabe, Kazuya*; Onizawa, Kunio; Yoshimura, Shinobu*
International Journal of Pressure Vessels and Piping, 117-118, p.56 - 63, 2014/05
Times Cited Count：9 Percentile：58.71(Engineering, Multidisciplinary)Several probabilistic fracture mechanical (PFM) analysis codes have been improved or developed in Japan, such as PASCAL-SP developed at JAEA, and PRAISE-JNES developed at JNES for structural integrity assessment of aged piping in nuclear power plants. Although they were developed for different purposes, they have similar functions. In this paper, in order to confirm the reliability and applicability of two PFM analysis codes, PASCAL-SP and PRAISE-JNES, benchmark analyses on piping failure probability have been carried out considering typical aging mechanisms, such as fatigue crack growth for piping materials in BWR plants Moreover, a criterion is proposed to judge whether the differences between the analysis results from two codes can be acceptable. Based on the proposed criterion, it is concluded that the analysis results of these two codes are in good agreements.
Li, Y.*; Ito, Hiroto*; Osakabe, Kazuya*; Onizawa, Kunio; Yoshimura, Shinobu*
International Journal of Pressure Vessels and Piping, 99-100, p.61 - 68, 2012/11
Times Cited Count：7 Percentile：50.73(Engineering, Multidisciplinary)A benchmark analysis was conducted using two probabilistic fracture mechanics analysis codes for aged piping in nuclear power plants, in order to confirm their reliability and applicability. These analysis codes have been improved or developed in Japan for the structural integrity evaluation and risk assessment considering the age related degradation mechanisms. In the benchmark analysis, the primary loop recirculation system piping in the boiling water reactor was selected as the typical piping system and stress corrosion cracking and fatigue were taken into account as the typical aging mechanisms. Moreover, a criterion was proposed for judging whether the differences between analysis results from the two codes are acceptable. Based on the benchmark analysis results and numerical investigation, it was concluded that the analysis results of these two codes agree very well.
Ito, Hiroto*; Li, Y.*; Osakabe, Kazuya*; Onizawa, Kunio; Yoshimura, Shinobu*
Journal of Mechanical Science and Technology, 26(7), p.2055 - 2058, 2012/07
Times Cited Count：2 Percentile：15.24(Engineering, Mechanical)Probabilistic fracture mechanics is a rational methodology in the structural integrity evaluation and risk assessment for aged piping in nuclear power plants. Several probabilistic fracture mechanical analysis codes have been improved or developed in Japan. In this paper, to verify the reliability and applicability of two of these codes, a benchmark analysis was conducted using their basic functions in consideration of representative piping systems in nuclear power plants and typical aging mechanisms. Based on the analysis results, we concluded that the analysis results of these two codes are in good agreement.
Katsuyama, Jinya; Tobita, Toru; Ito, Hiroto*; Onizawa, Kunio
Journal of Pressure Vessel Technology, 134(2), p.021403_1 - 021403_9, 2012/04
Times Cited Count：10 Percentile：45.01(Engineering, Mechanical)Stress corrosion crackings (SCCs) in recirculation pipes of Type 316L stainless steel (SS) have been observed near butt-welding joints. These SCCs in Type 316L SS grow near the welding zone mainly due to high tensile residual stress by welding. In present work, scatters of welding conditions such as heat input and welding speed were measured experimentally by fabricating a series of butt-welded pipes. Residual stress distributions were measured by stress relief and X-ray diffraction methods. The effects of welding conditions on residual stress have been evaluated by parametric FEM analyses considering the variation of some welding parameters based on the experiments. The effects of welding conditions on crack growth behavior have been also evaluated by using calculated residual stress distributions. It was clearly shown that the uncertainties on welding heat input and speed have strong influences on SCC growth behavior.
Katsuyama, Jinya; Ito, Hiroto; Tobita, Toru; Onizawa, Kunio
Yosetsu Gakkai Rombunshu (Internet), 28(2), p.193 - 202, 2010/06
Weld residual stress near the welded joint of pipe is one of the most important factors to assess the structural integrity of piping because the tensile residual stress becomes a driving force of a stress corrosion cracking (SCC). In this study, a weld simulation method has been developed and verified. An effect of uncertainty of welding conditions, such as scatters of heat input and welding speed during welding, on weld residual stress at the piping butt-welds was evaluated using the simulation method by varying the welding conditions. Probabilistic fracture mechanics analysis using PASCAL-SP was also performed to evaluate the effect of uncertainty of weld residual stress on the break probability of piping. It was clarified that the break probability increased with increasing the uncertainties of residual stress.
Ito, Hiroto; Kato, Daisuke*; Osakabe, Kazuya*; Nishikawa, Hiroyuki; Onizawa, Kunio
JAEA-Data/Code 2009-025, 135 Pages, 2010/03
JAEA-Data-Code-2009-025.pdf:17.49MB
As a part of the aging and structural integrity research for LWR components, new PFM (Probabilistic Fracture Mechanics) analysis code PASCAL-SP (PFM Analysis of Structural Components in Aging LWR - Stress Corrosion Cracking at Welded Joints of Piping) has been developed. This code evaluates the failure probabilities at welding lines of aged piping by a Monte Carlo method. PASCAL-SP treats stress corrosion cracking (SCC) in piping, including approaches of NISA and JSME FFS Code. The development of the code has been aimed to improve the accuracy and reliability of analysis by introducing new analysis methodologies and algorithms considering the latest knowledge in the SCC assessment and fracture criteria of piping. In addition, the accuracy of flaw detection and sizing at in-service inspection and residual stress distribution were modeled based on experimental data and introduced into PASCAL-SP. This report provides the user's manual and theoretical background of the code.
Onizawa, Kunio; Nishikawa, Hiroyuki; Ito, Hiroto
International Journal of Pressure Vessels and Piping, 87(1), p.2 - 10, 2010/01
Times Cited Count：46 Percentile：90.31(Engineering, Multidisciplinary)Probabilistic fracture mechanics (PFM) analysis codes for reactor pressure vessels (RPVs) and piping, called as PASCAL series has been developed at JAEA. The PASCAL2 code can evaluate the conditional probability of flaw initiation and fracture of an RPV under transient conditions such as pressurized thermal shock considering neutron irradiation embrittlement of the materials surrounding the reactor core of the RPV. Recent improvements of PASCAL2 are related to the treatment of weld-overlay cladding. The results of PFM analysis using the improved code have indicated that the residual stress by weld-overlay cladding affects the fracture probability of RPV. The results also indicate that the fracture toughness of cladding should be taken into consideration for the evaluation of realistic through-wall cracking probability. The PASCAL-SP code has been developed recently. The PASCAL-SP evaluates the probabilities of failures such as leakage and break of safety-related piping complying with Japanese regulation and rules. Effects of welding residual stress distribution as well as inspection accuracy are focused in this study. Residual stress distributions, which affect SCC behavior, have been determined by parametric FEM analyses verified through comparisons with welding experiments and incorporated to the code.
Onizawa, Kunio; Ito, Hiroto
NEA/CSNI/R(2009)2, p.275 - 285, 2009/00
Since probabilistic fracture mechanics (PFM) analysis method treats the scatter and uncertainties of data related to aging degradation, it is, therefore, useful to apply the PFM analysis to the piping reliability evaluation. Stress corrosion cracking (SCC) has been observed at some piping joints made by Austenitic stainless steel in BWR plants. In JAEA, we have been developing PFM analysis code, PASCAL-SP, for aged piping based on the latest knowledge on SCC. The PASCAL-SP evaluates the failure probability of piping at aged welded joints under SCC by a Monte Carlo method. Although many factors have some influence on failure probabilities in the PFM analysis, we are mainly focusing on the effects of in-service inspection and welding residual stress distribution. Through parametric PFM analyses by the PASCAL-SP, the effects of in-service inspection and the uncertainties of residual stress distribution on the failure probability are studied.
Ito, Hiroto; Onizawa, Kunio; Sugino, Hideharu*
Nihon Genshiryoku Gakkai-Shi ATOMO
, 50(7), p.434 - 437, 2008/07
Magnitude of seismic motion and degradation such as crack initiation and growth on stress corrosion cracking have uncertainties in the evaluation for the structural integrity of reactor components under seismic motion. We have studied evaluation methods for the structural integrity of components such as piping, i.e. failure probabilities in operation time by probabilistic fracture mechanics (PFM) analysis method which evaluates the uncertainties quantitatively. The evaluation method for seismic motion considering uncertainties, which is most important to evaluate the safety of nuclear power plants under seismic motion, has also been developed. Though their evaluation methods were independent in past, we developed the evaluation method for the failure probabilities considering occurrence probabilities of seismic motion around a plant when seismic motion acts on aged piping by merging them together.
Ito, Hiroto; Katsuyama, Jinya; Onizawa, Kunio
Proceedings of 2008 ASME Pressure Vessels and Piping Division Conference (PVP 2008) (CD-ROM), 6 Pages, 2008/07
In JAEA, we have been developing probabilistic fracture mechanics (PFM) analysis methods for aged piping based on latest aging knowledge and an analytical code, PASCAL-SP. PASCAL-SP evaluates the failure probability of piping at aged welded joints under SCC and In-Service Inspection by a Monte Carlo method. We proposes a probabilistic model which can be applied to the failure probability analysis based on PFM for welded joint of piping considering the uncertainty of welding residual stress. And the probabilistic evaluation model is introduced to PASCAL-SP. A parametric PFM analysis concerning uncertainties of residual stress distribution using PASCAL-SP was performed. The PFM analysis showed that the uncertainties of residual stress distribution about heat input and welding speed largely influenced break probability. The break probability increased with increasing the uncertainties.
Katsuyama, Jinya; Tobita, Toru; Ito, Hiroto; Onizawa, Kunio
Proceedings of 2008 ASME Pressure Vessels and Piping Division Conference (PVP 2008) (CD-ROM), 9 Pages, 2008/07
Stress corrosion cracking (SCC) in recirculation pipes has been observed near butt-welding joints due to high tensile residual stress by welding. In present work, scatters of welding conditions such as heat input and welding speed were measured experimentally by producing a series of butt-welding pipe specimens. Distribution and its scattering of residual stress were also measured by non-destructive and destructive methods. The effects of welding conditions on residual stress have been evaluated by parametric FEM analyses considering the variation of some parameters based on the welding experiments. The effects of welding conditions on crack growth behavior have been also evaluated by SCC growth simulations using calculated residual stress distributions and a procedure in the fitness-for-service code. Welding conditions such as heat input and welding speed have a strong influence on crack growth rate since residual stress is also affected by scatter of these welding conditions.
Onizawa, Kunio; Nishikawa, Hiroyuki; Ito, Hiroto
Proceedings of 7th International Conference on the Integrity of Nuclear Components, p.229 - 239, 2008/07
Probabilistic fracture mechanics (PFM) analysis codes for reactor pressure vessel (RPV) and piping, called as PASCAL series are being developed at JAEA, For an RPV, PASCAL2 code has been developed which can evaluate the conditional probabilities of crack initiation and fracture under transient conditions such as pressurized thermal shock. Recent improvements on the PASCAL2 are related to weld overlay cladding. It is shown that the welding residual stress by cladding affects the fracture probability of RPV to some extent. For piping, considering stress corrosion cracking, PASCAL-SP has been developed. The PASCAL-SP evaluates the probabilities of piping failures such as leakage and break of safety-related piping according to Japanese regulation and rules. Residual stress distribution was determined by parametric FEM analyses after verifying with welding experiments. Effects of welding residual stress distribution as well as inspection accuracy have been studied.
Ito, Hiroto; Kato, Daisuke*; Onizawa, Kunio; Shibata, Katsuyuki
JAEA-Data/Code 2006-001, 33 Pages, 2006/02
JAEA-Data-Code-2006-001.pdf:1.33MB
As a part of the aging and structural integrity research for LWR components, new probabilistic fracture mechanics (PFM) analysis code PASCAL-EC (PFM Analysis of Structural Components in Aging LWR - Erosion/-Corrosion) has been developed. This code evaluates the failure probability of an aged piping with a wall thinning by Monte Carlo method. PASCAL-EC treats the wall thinning due to erosion/corrosion or flow accelerated corrosion (FAC) in piping. The development of this code has been aimed to improve the accuracy and reliability of analysis by introducing new analysis methodologies and algorithms considering the recent developments in the structural mechanics and aging researches. This report provides the user's manual and theoretical background of PASCAL-EC.
Sugino, Hideharu*; Ito, Hiroto*; Onizawa, Kunio; Suzuki, Masahide
Nihon Genshiryoku Gakkai Wabun Rombunshi, 4(4), p.233 - 241, 2005/12
The purpose of this research is to establish the reliability evaluation method of aged nuclear power components for seismic events from a viewpoint of long-term use of the existing light water reactor nuclear power plants. For this purpose, we developed a piping failure probability evaluation code "PASCAL-SC" based on probabilistic fracture mechanics, and a probabilistic seismic hazard evaluation code "SHEAT-FM" for calculating the seismic occurrence probability of a plant site, paying attention to aging such as fatigue crack progress by the stress corrosion cracking and seismic load in primary coolant piping system. We proposed the reliability evaluation method of aged piping for seismic events by combination of these codes. Using this method, we evaluated the reliability of a weld line in the PLR(Primary Loop Recirculation system) piping of the BWR model plant for seismic events.
Ito, Hiroto*; Onizawa, Kunio; Shibata, Katsuyuki*
JAERI-Data/Code 2005-007, 118 Pages, 2005/09
JAERI-Data-Code-2005-007.pdf:5.23MB
As a part of the aging and structual integrity research for LWR components, new PFM (Probabilistic Fracture Mechanics) codes PASCAL-SC and PASCAL-EQ have been developed. These codes evaluate the failure probability of an aged welded joint by Monte Carlo method. PASCAL-SC treats Stress Corrosion Cracking (SCC) in piping, while PASCAL-EQ takes fatigue crack growth by seismic load into account. The development of these codes has been aimed to improve the accuracy and reliability of analysis by introducing new analysis and methodologies and algorithms considering the recent development in the fracture machanics methodologies and computer performance. The crack growth by an irregular stress due to seismic load in detail is considered in these codes. They also involves recent stress intensity factors and fracture criteria. In addition, a user's friendly operation of a GUI (Graphical User Interface) which generates input data, supports calculations and plots results is introduced. This report provides the user's manual and theoretical background of these codes.
fuelsUne, Katsumi*; Nogita, Kazuhiro*; Suzaka, Yojiro*; Hayashi, Kimio; Ito, Kunio*; Eto, Yoshinori*
International Topical Meeting on Light Water Reactor Fuel Performance, 2, p.775 - 785, 2000/00
no abstracts in English
Ichikawa, Michio*; *; *; *; *; Mitsugi, Takeshi; *; Ito, Kunio*; *; Doi, Soichi*; et al.
Nihon Genshiryoku Gakkai-Shi, 39(2), p.93 - 111, 1996/00
None
*; *; Takeda, Kunio; *; Atsumo, Hideo
PNC TN941 76-59, 24 Pages, 1976/06
Three permanent magnet type small-size sodium flow meters which were installed in General Purpose Sodium Test Loop have been used in sodium for about ten thousand hours. Based on the data obtained in this periods, the characteristics of these flow meters were checked about the effect of sodium tamperature and elapsed time. Flowing results were obtained. (1)Good linearity was observed between output voltage and flow rate. (2)The output voltage of these flow meters were from 77% to 92% of the designed value. (3)The output voltage decreased as sodium temperature increased and the rate was nearly equal to the calculated value (-0.009 %/
C). (4)Output voltage decrease with elapsed time was not observed.
Ito, Hiroto; Onizawa, Kunio
no journal, ,
This study proposes models for ultrasonic testing (UT) accuracy at In-Service Inspection (ISI) in probabilistic fracture mechanics (PFM) analysis. Regression analysis of the data brought by Ultrasonic Test & Evaluation for Maintenance Standards (UTS) project and modeling for successful candidates of Performance demonstration certification system provided the models for accuracy of flaw detection and sizing. New PFM analysis code, which evaluates failure probabilities at weld lines in piping aged by Stress Corrosion Cracking, has been developed by JAEA. The models were introduced into the code. Failure probabilities under the UT models at a weld line were evaluated by the code.
Ito, Hiroto; Onizawa, Kunio
no journal, ,
New code of probabilistic fracture mechanics (PFM) analysis, which evaluates failure probabilities in piping, has been developed by JAEA. The methodology of Rules on Fitness-for-Service for Nuclear Power Plants of JSME is introduced into the code. It involves initiation and growth of Stress Corrosion Cracking (SCC) etc, then evaluates the failure probabilities in piping. In-Service Inspection frequencies to weld lines in PLR piping which is sensitive to SCC, largely influence the failure probabilities. Therefore, effect on the frequency differences to the failure probabilities was evaluated by the code.
