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Yamaguchi, Yoshihito; Mano, Akihiro; Li, Y.
Transactions of the 27th International Conference on Structural Mechanics in Reactor Technology (SMiRT 27) (Internet), 10 Pages, 2024/03
The steam generator (SG) is an important component of a pressurized water reactor. In addition, local wall-thinning has been reported in SG tubes. The burst differential pressure, considering both the internal and external pressures from the primary and secondary coolant systems, should be predicted for the failure probability evaluation or structural integrity assessment of SG tubes. In this study, based on the results of burst tests performed in Japan and the United States, we improved the existing burst pressure estimation method for SG tubes with wall-thinning. In addition, as an example of the utilization of the improved burst pressure estimation method, the conditional failure probabilities for SG tubes with local wall-thinning, which is necessary for probabilistic risk assessment and risk-informed decision making, are calculated considering the dimensions of the wall-thinning.
Yamaguchi, Yoshihito; Nishida, Akemi; Li, Y.
Proceedings of ASME 2022 Pressure Vessels and Piping Conference (PVP 2022) (Internet), 7 Pages, 2022/07
The wall-thinning is one of the most important age-related degradation phenomena in nuclear piping systems. Furthermore, in recent years, several nuclear power plants in Japan have experienced severe earthquakes. Therefore, failure probability analysis and fragility evaluation of piping systems, taking both wall-thinning and seismic response stresses into consideration, have become increasingly important in seismic probabilistic risk assessment. In Japan Atomic Energy Agency, in order to evaluate the failure probability of aged piping system with wall-thinning, a probabilistic analysis code PASCAL-EC was developed. In this study, to evaluate the seismic fragility of a wall-thinned pipe, a model of seismic response stress considering the wall-thinning effect, a failure evaluation method for wall-thinned pipes, and functions related to uncertainties treatment for important influence parameters have been introduced to PASCAL-EC. In this paper, the improved PASCAL-EC is outlined and preliminary results of the seismic fragility evaluation performed using this code are provided.
Yamaguchi, Yoshihito; Mano, Akihiro; Li, Y.
Proceedings of ASME 2022 Pressure Vessels and Piping Conference (PVP 2022) (Internet), 10 Pages, 2022/07
The steam generator (SG) tube is one of the important components in pressurized water reactors. Flaws such as wall-thinning or stress corrosion cracking have been reported in SG tubes. The burst pressure where both the internal and external pressures from the primary and secondary coolant systems are considered must be predicted to assess the structural integrity of SG tubes. Burst tests were performed by various organizations. On the basis of the test results, failure estimation methods were proposed. In this study, previous burst test data and existing failure estimation methods for SG tubes with wall-thinning or crack were investigated. As a result, the coefficient of the existing estimation method for SG tube with uniform wall-thinning was updated. In addition, failure estimation methods that are suitable for SG tubes with crack or local wall-thinning were proposed by considering the effects of the flaw shape and size on the burst pressure. The applicability of the failure estimation methods was confirmed by comparing the predicted results with the burst test data in actual SG tubes.
Okajima, Satoshi
Nihon Kikai Gakkai 2017-Nendo Nenji Taikai Koen Rombunshu (DVD-ROM), 3 Pages, 2017/09
Fitness-For-Service (FFS) assessment for the component with metal-loss is desired to reflect the effect of usual maintenance. Introduction of evaluation method based on reliability is one of the effective measures to achieve this. High Pressure Institute of Japan published HPIS Z 109TR:2016 "Metal loss assessment for pressure equipment based on reliability", which provides methods and technical backgrounds of metal loss assessment for pressure equipment based on reliability. This technical report provides evaluation method for simply evaluating reliability of the pressure equipment with metal loss based on the partial safety factor method. We present outline of the evaluation method based on the partial safety factor method.
Hasegawa, Kunio; Li, Y.; Bezensek, B.*; Hoang, P. H.*; Rathbun, H. J.*
Journal of Pressure Vessel Technology, 138(1), p.011101_1 - 011101_8, 2016/02
Times Cited Count：1 Percentile：8.17(Engineering, Mechanical)Piping components in power plants may experience combined bending and torsion moments during operation. There is a lack of guidance for pipe evaluation for pipes with local wall thinning under the combined bending and torsion moments. ASME Code Section XI Working Group is currently developing fully plastic bending pipe evaluation procedures for pressurized piping components containing local wall thinning subjected to combined torsion and bending moments. Using elastic fully plastic finite element analyses, plastic collapse bending moments under torsion were obtained for 114.3 mm to 609.6 mm diameter pipes with various local wall thinning flaw sizes. The objective of this paper is to introduce an equivalent moment, which combines torsion and bending moments by a vector summation, and to establish the applicable range of wall thinning lengths, angles and depths, where the equivalent moments are equal to pure bending moments.
; ; Ueno, Fumiyoshi; ; ; ;
JNC TN2400 2000-005, 103 Pages, 2000/12
JNC-TN2400-2000-005.pdf:3.98MB
Inelastic analyses of the floor liner subjected to thermal loading due to sodium leakage and combustion were carried out, considering thinning of the liner plate due to molten salt type corrosion. Because the inelastic strain obtained by the analyses stayed below the ductility limit of the material, mechanical integrity, i.e., there exist no through-wall crack on the floor liner, was confirmed. Partial structural model tests were conducted, with a band of local thinning of the liner plate. Displacements were controlled to give specimens much larger strains than those obtained by the inelastic analyses above. No through-wall crack was observed by these tests. Mechanical integrity of the floor liner was confirmed by these results of the inelastic analyses and the partial structural model tests.
; ; Ohno, Shuji;
JNC TN9400 2000-092, 247 Pages, 2000/08
JNC-TN9400-2000-092.pdf:20.29MB
Small-scale sodium pool combustion tests Run-F7-3 and Run-F8-1 were performed to investigate the corrosion of floor liner under high moisture condition. ln the both tests, which were performed using the 3m
FRAT-1 vessel at the SAPFIRE facility, the sodium of 507deg-C was leaked on the carbon steel catch pan about for 25 minutes with the flow rate of around 25 kg/h. The air in the vessel was ventilated with the flow rate of 5m/min containing the moisture of 25000-28000 vol.ppm. The duration of combustion was different in two tests by changing the starting time of argon gas injection into the vessel. As the results of post-test analysis such as observation of catch pan surface and chemical analysis of the deposits, it was confirmed that 'Na-Fe double oxidization type corrosion' was dominant in the both tests and that the catch pan and deposits were not under the condition leading to the occurrence of 'molten salt type corrosion.'
Tsukimori, Kazuyuki
JNC TN9400 2000-086, 103 Pages, 2000/08
JNC-TN9400-2000-086.pdf:3.67MB
ln order to evaluate the integrity of the floor liner of "MONJU" at sodium leakage accident, nonlinear finite element analyses have been conducted considering the effect of thinning of the liner due to molten salt type corrosion. Modeling by shell elements is appropriate since liner is composed of thin plates, however, it is difficult to deal with the very local strain behaviors. 0n the other hand, modeling by solid elements makes the numerical calculation impractical. If we extract the small part of the liner which includes local discontinuities, it is possible to evaluate local strain behaviors practically by using the solid element analysis model of the part. To realize this approach, the method to generate all the boundary displacements of the part model from the shell element analysis result of total structure is needed. The aims of this study are to develop the method to deal with the incompatibility between shell and solid elements at part model boundary, and to build numerical analysis circumstances including this method to make the detailed nonlinear finite element analyses of the floor liner of "MONJU" possible. Summary of the results is shown below, (1)The problem of the incompatibility between shell and solid elements was solved by introducing weighting function at 'T' and 'L' type corners and the interpolation function of 4-node rectangular plate bending element at the connection between liner plate and frame. (2)Software system was developed by using 'FINAS' and verified. (3)This approach was applied to one of the cases of the floor liner analyses of "MONJU" at sodium leakage accident. The analysis result showed that three-dimensional local strain behavior could be evaluated directly. ln addition, it was confirmed that the result by shell element analysis was conservative in evaluation of strain compared with that by solid element analysis in this case.
gas cooled reactor; ; Mizuta, Shunji
JNC TN9400 2000-040, 41 Pages, 2000/03
JNC-TN9400-2000-040.pdf:0.85MB
The corrosion behavior of ferritic stainless steels applied to core components under C0 gas environment was investigated in order to be helpful to fuel design in C0 gas cooled reactor as the feasibility study for fast breeder reactor. The dependence of the corrosion behavior, before a breakaway occurs, on C0 gas temperature, Si and Cr contents of ferritic steels was determined quantitatively. The following correlations to calculate the metal loss thickness was established. X = 4.4w w = √(k
t) k = 
exp( - 5.45[Si]) exp( - 1.09[Cr]) exp( - 11253/T) = 1.65 10
4.40 10
X : metal loss thickness[
ml, w : corrosion weight gain [mg/cm
] k : parabola constant [(mg/cm)/hr], t : time [hr], : constant [Si] : Si content[wt.%], [Cr] : Cr content [wt.%], T : temperature [K]
;
JNC TN9400 2000-031, 15 Pages, 2000/03
JNC-TN9400-2000-031.pdf:0.53MB
For the irradiation performance of metallic fuel, many of the analyses were conducted in USA using EBR-l and EBR-II. ln this study, based on the published data and papers on the above results, the appropriate methods to the evaluation of the irradiation performance of FBR metallic fuel for the design study were considered, as the fbasibility study for FBR. The followings are the targets in this work; (1)deformation of cladding (2)deformation of fuel slug (3)FP gas release (4)fluctuation of the bonding Na level in the fuel pin (5)FCCI
O-NaOH System)Yoshida, Eiichi; Aoto, Kazumi; Hirakawa, Yasushi;
JNC TN9400 2000-024, 42 Pages, 1999/10
JNC-TN9400-2000-024.pdf:1.63MB
For the purpose of improving the reliability of evaluation, the corrosion rate equation of the carbon steel SM400B (JIS G3106) in the high-temperature sodium compounds (NaOH-Na0 system) was revised. ln this revision, the data acquired after 1997 was used. Based on the experimental results, the evaluation was made to be an approach to the following; (1)Metal loss of carbon steel in NaOH-Na0 system was evaluated as increases in exposure to the time, which is linear rate law. (2)There were no significant effects of the experiment atmosphere and mixing speed of the reagent on corrosion rate. (3)The concentration of Na0 in sodium compound is considered for the evaluation. The concentration under experiment is made to be the over concentration necessary for maintaining the dominant reaction between Fe and Na20. As a result of the evaluation, the additional data are 67 points. The data for the revision of the evaluation equation became the total of 105 points, when existing data of 38 points were added. The statistical evaluation of 105 points was carried out, and following recommended equation was obtained. C
= C exp(-Q/RT) Where; C : Corrosion rate, mm/h C : Material constant Q : Apparent activation energy, cal/mol R : Gas constant, 1.986 cal/mol K T ; Absolute temperature, K Q = 9.61 kcal/mol C = 148.29 (average), 262.11 (99% UCL), 83.90 (99% LCL)
Fujisaku, Kazuhiko*; Ishibashi, Yuzo; Takeda, Seiichiro; ; *
PNC TN8410 98-115, 50 Pages, 1998/09
None
Aoto, Kazumi; ; Hirakawa, Yasushi
PNC TN9410 97-055, 128 Pages, 1996/07
Several material analyses on damage of the floor liner made of a mild steel which was in the test cell of the second sodium leak and combustion experiment (Test-2) performed in OEC/PNC on June 7 in 1996 were carried out to clarify the following issues. (1)Difference of the corrosion mechanism of Test-2 liner to that of the first sodium leak and combustion experiment(Test-1) liner. (2)The vital factor which can desides corrosion mechanism and damage location. The following analyses were accomplished. (a)Microstructure observation (b)EPMA for cross-section of vicinity of corroded area (c)X-ray diffraction(XRD) for the interface between corrosion product-liner(mild steel) The differences between the corrosion mechanism of Test-1 liner which is seemed to be the same that of "MONJU" liner and that of Test-2 liner is discussed based on the results of these material analyses. As the result, the Na-Fe double oxidization with mechanical/chemical removal of reaction product can be occurred on the Test-1 and "MONJU" liner. On the other hand, a hot-corrosion, taht is the molten salt type corrosion is subject to be thinning of the Test-2 liner. All failures of Test-2 liner surround at the halfway up a convex. Considering the above corrosion mechanism, that fact leads that significant damage is occurred at the molten salt level.
; ; ; ; ; Shibahara, Itaru
PNC TN9410 92-321, 30 Pages, 1992/10
Integrity evaluations have been performed for the 2nd Fugen pressure tube test (8 years irradiation, 5.6 10
n/cm (E
1Mev)). Test items mainly consist of tensile test, bending test, corrosion test and hydrogen analysis. It has become clear using these data that the pressure tube material has maintained its integrity during the irradiation by the integrity assessment on both tensile and fracture toughness properties. Besides, both thickness loss by corrosion and absorbed hydrogen content were lower than those of design values.
Ebine, Noriya; Yamaguchi, Yoshihito; Katsuyama, Jinya; Nishida, Akemi; Li, Y.
no journal, ,
A probabilistic analysis code PASCAL-EC (PFM Analysis of Structural Components in Aging LWR - Erosion and Corrosion) have been improved for evaluating structural integrity of wall thinned pipes on the basis of the Monte Carlo method. In order to perform the fragility evaluation for wall-thinned pipes, several functions are introduced to PASCAL-EC in this work, such as probabilistic evaluation model to consider the uncertainty of seismic response stress, a simple evaluation model to considered the increase of the seismic stress due to wall thinning and failure evaluation methods for wall-thinned pipes. This paper provides some details of these models and preliminary results of fragility evaluation using improved PASCAL-EC code for wall-thinned pipes in nuclear power plants.
