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Journal Articles

Effect of local plastic component on crack opening displacement and on J-integral of a circumferential penetrated crack

Machida, Hideo*; Arakawa, Manabu*; Wakai, Takashi

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05

This paper describes the effect of local plastic component on J-integral and crack opening displacement (COD) evaluation of a circumferential penetrated crack, applicable to the leak before break (LBB) assessment for sodium cooled fast reactor (SFR) components. J-integral COD evaluation methods are generally formulated as a summation of elastic and plastic components, and so far many evaluation formulae based on these two components have been proposed. However, strictly, the plastic component consists of local plastic and fully plastic components. Many of the conventional evaluation methods often consider only the fully plastic component as the plastic component. The reason for this is that the effect of the local plastic component is much smaller than that of the fully plastic component excluding materials with extremely small work hardening. In contrast, for materials with high yield stress and small work hardening, such as modified 9Cr-1Mo steel which is one of the candidate materials for SFR piping, the effect of the local plastic component on J-integral and COD cannot be ignored. Therefore, the authors propose formulae taking the effect of local plastic component on J-integral and COD into account, based on finite element analysis (FEA) results, so that it is easy to apply to crack evaluation. The formulae will be employed in the guidelines on LBB assessment for SFR components published from Japan Society of Mechanical Engineers (JSME).

Journal Articles

Study on creep damage assessment method for Mod.9Cr-1Mo steel by sampling creep testing with thin plate specimen

Kanayama, Hideyuki*; Hiyoshi, Noritake*; Ogawa, Fumio*; Kawabata, Mie*; Ito, Takamoto*; Wakai, Takashi

Zairyo, 68(5), p.421 - 428, 2019/05

This study presents creep damage assessment method for Mod. 9Cr-1Mo steel by sampling creep testing with thin plate specimen. Tensile creep rupture tests were performed using three different sizes of specimen under two different test environments to verify the creep testing with the thin plate specimen. Time to rupture of Mod. 9Cr-1Mo steel using three different sizes were almost same. In addition, there was no effect of environment on time to rupture. Pre-damaged thin plate specimens were machined from a bulk specimen's gage section that pre-damage test was performed with. Pre-damage based on life fraction rule were 8%, 16% and 25%. No effect of the process of machining pre-damaged specimen on time to rupture was confirmed by verification tests in same test condition as pre-damage test. Stress acceleration creep rupture tests were performed to estimate creep damage assessment. Creep damage assessment by stress acceleration creep rupture tests was sufficiently accurate estimate. Creep damage assessments by Vickers hardness and lath width were compared with the assessment by stress acceleration creep rupture tests to study applicability of these methods.

Journal Articles

Development of a crack opening displacement assessment procedure considering change of compliance at a crack part in thin wall pipes made of modified 9Cr-1Mo steel

Wakai, Takashi; Machida, Hideo*; Arakawa, Manabu*; Yanagihara, Seiji*; Suzuki, Ryosuke*; Matsubara, Masaaki*

Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 9 Pages, 2018/07

This paper studies crack opening displacement (COD) evaluation methods used in Leak-Before-Break (LBB) assessment of Sodium cooled Fast Reactor (SFR) pipe. For SFR pipe, the continuous leak monitoring will be adopted as an alternative to a volumetric test of the weld joints under conditions that satisfy LBB. The sodium pipes are made of ASME Gr.91 (modified 9Cr-1Mo steel). Thickness of the pipes is small, because the internal pressure is very small. Modified 9Cr-1Mo steel has a relatively large yield stress and small work hardening coefficient comparing to the austenitic stainless steels which are currently used in the conventional plants. In order to assess the LBB behavior of the sodium pipes made of modified 9Cr-1Mo steel, the coolant leak rate from a through wall crack must be estimated properly. Since the leak rate is strongly related to the crack opening displacement (COD), an appropriate COD assessment method must be established to perform LBB assessment. However, COD assessment method applicable for SFR pipes - having thin wall thickness and made of small work hardening material - has not been proposed yet. Thus, a COD assessment method applicable to such a pipe was proposed in this study. In this method, COD was calculated by classifying the components of COD; elastic, local plastic and fully plastic. In addition, the verification of this method was performed by comparing with the results of a series of four-point bending tests using modified 9Cr-1Mo steel pipe having a circumferential through wall notch. As a result, in some cases, COD were over-estimated especially for large cracks. Although the elastic component of COD is still over-estimated for large cracks, leak evaluation from small cracks is much more important in LBB assessment. Therefore, this study recommends that only the elastic component of COD should be adopted in LBB assessment of SFR pipes.

Journal Articles

Proposal of simplified J-integral evaluation method for a through wall crack in SFR pipe made of Mod.9Cr-1Mo steel

Wakai, Takashi; Machida, Hideo*; Arakawa, Manabu*; Kikuchi, Koichi*

Proceedings of ASME Symposium on Elevated Temperature Applications of Materials for Fossil, Nuclear, and Petrochemical Industries, 7 Pages, 2018/04

A simplified J-integral evaluation method applicable to unstable failure analysis in Leak Before Break (LBB) assessment of Sodium-cooled Fast Reactor (SFR) in Japan was proposed. Mod.9Cr-1Mo steel is supposed to be a candidate material for the coolant systems of SFR in Japan. This steel has relatively high yield strength and poor fracture toughness comparing to those of conventional austenitic stainless steels. In addition, SFR pipe has small thickness and large diameter. As a J-integral evaluation method for circumferential through-wall crack in a cylinder, EPRI has proposed a fully plastic solution method. However, the geometry of SFR pipe and material characteristics of Mod.9Cr-1Mo steel exceed the applicable range of EPRI's method. Therefore, a series of elastic, elasto-plastic and plastic finite element analyses (FEA) were performed for a pipe with a circumferential through-wall crack to propose a J-integral evaluation method applicable to such loading conditions. J-integrals obtained from the FEA were resolved into elastic, local plastic and fully plastic components. Each component was expressed as a function of analytical parameter, such as pipe geometries, crack size, material characteristics and so on. As a result, a simplified J-integral evaluation method was proposed. The method enables to conduct 2 parameter failure analysis using J-integral without any fracture mechanics knowledge.

Journal Articles

Influence of cyclic softening on high temperature material properties in Mod.9Cr-1Mo steel

Onizawa, Takashi; Nagae, Yuji; Kato, Shoichi; Wakai, Takashi

Zairyo, 66(2), p.122 - 129, 2017/02

The applicability of Modified 9Cr-1Mo steel (ASME Grade 91 steel) as the main structural material in advanced loop-type sodium cooled fast reactor has been explored to enhance the safety, the credibility and the economic competitiveness of fast reactor plants. It is well-known that the steel exhibits cyclic softening behavior. Decrease of tensile and creep strength in softened materials has been already reported by other researchers. This paper discusses the relationship between cyclic softening conditions and high temperature material properties. Grade 91 steel was softened by repeat of plastic strain. The softening behavior could be evaluated by the index of the softening rate. Decrease of tensile and creep strength in softened materials can be evaluated by the softening rate and it depends on the cyclic softening conditions.

Journal Articles

Behavior of high-burnup advanced LWR fuels under accident conditions

Amaya, Masaki; Udagawa, Yutaka; Narukawa, Takafumi; Mihara, Takeshi; Taniguchi, Yoshinori

Proceedings of Annual Topical Meeting on LWR Fuels with Enhanced Safety and Performance (TopFuel 2016) (USB Flash Drive), p.53 - 62, 2016/09

In order to evaluate adequacy of present safety criteria and safety margins in terms of advanced fuels and provide a database for future regulation on them, JAEA started an extensive research program called ALPS-II program, which has been sponsored by NRA, Japan. This program is primarily composed of tests simulating a RIA and a LOCA on the high-burnup advanced fuels irradiated in commercial PWR or BWR. Recently, the failure limits of the high-burnup advanced fuels under RIA conditions were investigated at NSRR, and post-test examinations on the fuel rods after the pulse irradiation tests are being performed. In terms of the simulated LOCA test, integral thermal shock tests and high temperature oxidation tests were carried out at RFEF, and the fracture limits, high temperature oxidation rate, etc. of the high-burnup advanced fuel cladding were investigated. This paper mainly describes some recent experimental results obtained in this program with respect to RIA and LOCA.

Journal Articles

A Study on evaluation method of penetrate crack length for LBB assessment of fast reactor pipes

Wakai, Takashi; Machida, Hideo*; Sato, Kenichiro*

Nippon Kikai Gakkai M&M 2015 Zairyo Rikigaku Kanfarensu Koen Rombunshu (Internet), 3 Pages, 2015/11

This paper describes a through-wall crack length evaluation procedure applicable to Leak Before Break (LBB) assessment of Japan Sodium cooled Fast Reactor (JSFR) pipes made of Mod.9Cr-1Mo steel. In LBB assessment of JSFR pipes, it is required to calculate virtual through-wall crack length, though the crack growth is quite small under design condition. Generally, it is known that the through-wall crack length depends on loading condition, namely the load ratio between tensile and bending and that the length under pure bending load condition is largest. This study proposes a simplified method to evaluate the through-wall crack length both for axial and circumferential cracks as a function of load ratio and fatigue crack growth characteristics. Using the method, through-wall crack length can be predicted as far as we know the loading condition and material properties.

Journal Articles

J-integral evaluation method for a through wall crack in thin-walled large diameter pipes made of Mod.9Cr-1Mo steel

Wakai, Takashi; Machida, Hideo*; Arakawa, Manabu*; Sato, Kenichiro*

Nippon Kikai Gakkai 2015-Nendo Nenji Taikai Koen Rombunshu (DVD-ROM), 5 Pages, 2015/09

This paper describes a J-integral evaluation procedure applicable to unstable failure analysis for a circumferential through wall crack in a pipe. Japan Sodium cooled Fast Reactor (JSFR) pipes are made of Mod.9Cr-1Mo steel. The fracture toughness of the material is inferior to that of conventional austenitic stainless steels. In addition, JSFR pipe has small thickness and large diameter and displacement controlled load is predominant. Therefore, the load balance in such piping system changes by crack extension and 2 parameter method using J-integral is applicable to unstable failure analysis for the pipes under such conditions. As a J-integral evaluation method for circumferential through wall crack in a cylinder, EPRI has proposed a fully plastic solution method. However, the geometry of JSFR pipe and material characteristics of Mod.9Cr-1Mo steel exceed the applicable range of EPRI's method. Therefore, a series of elastic, elastoplastic and plastic finite element analyses (FEA) were performed for a pipe with a circumferential through-wall crack to establish a J-integral evaluation method applicable to such conditions. J-integrals obtained from the FEA were resolved into elastic, local plastic and fully plastic components. Each component was expressed as a function of analytical parameter, such as pipe geometries, crack size, material characteristics and so on. As a result, a simplified J-integral evaluation method was proposed.

Journal Articles

Requirements for fracture toughness to satisfy LBB behavior of a pipe made of high chromium steel

Machida, Hideo*; Wakai, Takashi; Sato, Kenichiro*

Nippon Kikai Gakkai 2015-Nendo Nenji Taikai Koen Rombunshu (DVD-ROM), 5 Pages, 2015/09

The volumetric test for piping in a sodium cooled fast reactor (SFR) is difficult from the poor accessibility. Detection of a crack, therefore, is difficult before its penetration of a pipe wall, an SFR has a strategy to detect sodium leakage from a through wall crack before fracture of a pipe. Plant safety is ensured by shutting down a plant as soon as possible to detect small quantity of sodium leakage even if a crack penetrates a pipe wall. Consequently, it is important to ensure establishment of leakage-before-break (LBB) in this strategy. Effects of fracture resistance curve on fracture strength of a cracked pipe made of high chromium steel (Mod. 9Cr-1Mo steel), which is one of the candidates for fast reactor piping material, are evaluated in this study; and requirements for fracture resistance curve to achieve the LBB were proposed.

Journal Articles

Behavior of high burnup advanced fuels for LWR during design-basis accidents

Amaya, Masaki; Udagawa, Yutaka; Narukawa, Takafumi; Mihara, Takeshi; Sugiyama, Tomoyuki

Proceedings of Annual Topical Meeting on Reactor Fuel Performance (TopFuel 2015), Part.2 (Internet), p.10 - 18, 2015/09

Advanced fuels which consist of cladding materials with high corrosion resistance and pellets with lower fission gas release have been developed by utilities and fuel vendors to improve fuel performance even in the high burnup region and also raise the safety level of current nuclear power plants to a higher one. In order to evaluate the adequacy of present safety criteria and safety margins in terms of such advanced fuels and provide a database for future regulation on them, Japan Atomic Energy Agency (JAEA) has started a new extensive research program called ALPS-II program (Phase II of Advanced LWR Fuel Performance and Safety program). This program is primarily composed of tests simulating a reactivity-initiated accident (RIA) and a loss-of-coolant accident (LOCA) on high burnup advanced fuels shipped from European nuclear power plants. This paper describes an outline of this program and some experimental results with respect to RIA and LOCA which have been obtained in this program.

Journal Articles

CT injection experiment in JFT-2M

Ogawa, Hiroaki; Ogawa, Toshihide; Tsuzuki, Kazuhiro; Kawashima, Hisato; Kasai, Satoshi*; Kashiwa, Yoshitoshi; Hasegawa, Koichi; Suzuki, Sadaaki; Shibata, Takatoshi; Miura, Yukitoshi; et al.

Fusion Science and Technology, 49(2), p.209 - 224, 2006/02

 Times Cited Count:3 Percentile:73.46(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Numerical visualization of water-vapor flow configurations in fusion reactors during ingress of coolant events

Ose, Yasuo*; Takase, Kazuyuki; Yoshida, Hiroyuki; Akimoto, Hajime

Proceedings of 10th International Conference on Nuclear Engineering (ICONE 10) (CD-ROM), 8 Pages, 2002/00

no abstracts in English

JAEA Reports

Water permeability test of rock specimen with natural fractures using high viscosity liquid

*;

JNC-TN8430 2001-006, 72 Pages, 2001/10

JNC-TN8430-2001-006.pdf:1.71MB

We had been conducted to study hydraulic permeability along fracture intersection by NETBLOCK system using natural rock specimen. Since the permeability of this rock specimen fracture is high, it was suggest that turbulent flow might be occurred in available range of measurement system. In case of turbulent flow, estimated permeability and fracture aperture from test data tend to be low. Therefore we should achieve laminar flow. This study was used the high viscosity liquid instead of water, and test conditions which could attain laminar flow with the rock specimen was examined. The rock specimen is granite rock, has natural Y-type fractures intersection. A solution of Methyl-cellulose is used as high viscosity liquid. Due to the high viscosity liquid, hydraulic head could be measured in the wide range, and high viscosity liquid improved the accuracy of measurement. Laminar flow could be achieved in the rock specimen by the high viscosity liquid over 0.1wt%.

Journal Articles

${it Potato virus Y}$-resistance in the progeny of haploid mutants obtained by the culture of ${it Nicotiana Tabacum}$ L. Anthers exposed to ion beams

Hamada, Kentaro*; Inoue, Masayoshi*; Tanaka, Atsushi; Watanabe, Hiroshi

Plant Biotechnology, 18(4), p.251 - 257, 2001/04

no abstracts in English

JAEA Reports

Examination of hydraulic property of natural rock specimen

*; *;

JNC-TN8430 2001-003, 64 Pages, 2001/03

JNC-TN8430-2001-003.pdf:2.15MB

Handling methods and test conditions of hydraulic tests for NETBLOCK system had been examined by using acrylic and/or artificial rock specimen. A natural rock specimen (granite : excavated from Kamaishi mine) with fracture intersection was formed into practicable size for NETBLOCK system. Recently, we conducted a series of hydraulic test, in order to study the influence of fracture intersection by using the natural rock specimen. Hydraulic tests were conducted under several centimeters of head, which could be controlled by improved system because hydraulic permeability of target fractures were high. As a result, 10$$^{-4}$$$$sim$$10$$^{-5}$$(m$$^{2}$$/s) orders of hydraulic transmissivity of target fractures could be measured. A low permeability in the NW direction at the lower fracture was estimated from the heterogeneous head distribution. However, it is also expected that turbulence flow might be occurred under this study condition because fracture permeability is high and flow rate through the fracture is relatively high. In case of turbulence-flow, an estimated hydraulic transmissivity is low. High-viscosity fluid hydraulic test to achieve laminar flow will be needed for correcting an evaluated transmissivity.

Journal Articles

Status report on the JAERI AVF cyclotron system

Nakamura, Yoshiteru; Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; Tamura, Hiroyuki; Kurashima, Satoshi; Yokota, Wataru; Okumura, Susumu; Fukuda, Mitsuhiro; Akaiwa, Katsuhiro*; et al.

Proceedings of 13th Symposium on Accelerator Science and Technology, p.193 - 195, 2001/00

The AVF cyclotron system at JAERI Takasaki has been smoothly operated without serious troubles since the first beam extraction in March, 1991. A yearly operation time is about 3200 hours on an average for recent eight years. In last two years, we performed some improvements and developments as followings: stabilization of the cyclotron beam by addition on an exclusive cooling system, designing and investigation of the flat-top system using fifth-harmonic RF, reconstruction of the rotary shutter for radiation shielding and reinforcement of the magnetic channel and its power supply. Furthermore, the renewal of main circulation pump for cooling system, replacement of shunt resistor in the power supplies and re-alignment of the several magnets along the trunk beam transport line were also carried out.

Journal Articles

Application of a stacked elastically bent perferct Si monochromator with identical and different crystallographic planes for single crystal and powder neutron diffractometry

Tanaka, Ichiro; Ahmed, F. U.*; Niimura, Nobuo

Physica B; Condensed Matter, 283(4), p.295 - 298, 2000/06

 Times Cited Count:4 Percentile:71.11(Physics, Condensed Matter)

no abstracts in English

JAEA Reports

Ultra-High temperature strength properties on Mod.9Cr-1Mo steel

; Yoshida, Eiichi; Aoto, Kazumi

JNC-TN9400 2000-042, 112 Pages, 2000/03

JNC-TN9400-2000-042.pdf:8.55MB

A sodium-water reaction drove from the single tube break in steam generator of FBR might overheat labor tubes rapidly under internal pressure loadings. lf the temperature of tube wall becomes too high, it has to be evaluated that the stress of tube does not exceed the material strength limit to prevent the propagation of tube rupture. This study clarified the tensile and creep properties of Mod.9Cr-1Mo steel at ultra-high temperature which will be used in evaluation of the tube burst by sodium-water reaction. The strain rates for tensile test are from 10%/min to 10%/sec, and creep-rupture time is maximum 277sec. The range of test temperature is 700$$^{circ}$$C to 1300$$^{circ}$$C. The main results obtained were as follows; (1)The evaluation data on the relationship between tensile strength and strain rate and creep-rupture strength in shorter time on Mod.9Cr-1Mo steel were acquired. (2)Short-term mechanical properties of Mod.9Cr-1Mo steel were evaluated based on the results of tensile and creep-rupture tests up to 1300$$^{circ}$$C. As a result of the evaluation, recommended equation of creep-rupture strength in the short-term was proposed. (3)Tensile and creep-rupture strength of Mod.9Cr-1Mo steel tube showed the value which was higher than the 2 1/4Cr-1Mo steel, and it was proven to have the superior properties.

Journal Articles

Shielding design for steam generator of advanced integral marine reactor MRX

Odano, Naoteru; Yamaji, Akio*; Ishida, Toshihisa

Journal of Nuclear Science and Technology, 37(Suppl.1), p.78 - 82, 2000/03

no abstracts in English

JAEA Reports

Irradiation creep of modified 316 and 15Cr-20Ni base austenitic S.S. fuel pins (MFA-1, 2) irradiated in FFTF

; ; Mizuta, Shunji

JNC-TN9400 2000-023, 126 Pages, 2000/02

JNC-TN9400-2000-023.pdf:2.94MB

Modified 316 and 15Cr-20Ni base austenitic stainless steels had been developed by Japan Nuclear Cycle Development lnstitute as the candidate materials for Monju and Demonstration fast breeder reactor. Previously, irradiation creep correlation of modified 316 and 15Cr-20Ni had been evaluated using pressurized tubes irradiated in FFTF/MOTA. 0n the other hand, for other austenitic S.S. developed abroad, it was reported that irradiation creep behavior of fuel pin could not be sufficiently described using results of pressurized tube experiments. ln this study, irradiation creep properties of modified 316 and 15Cr-20Ni fuel pins (MFA-I, 2) irradiated in FFTF were evaluated. And irradiation deformation of MFA-1, 2 fuel pins were estimated using the irradiation creep correlation based on MOTA data. The results are summarized as follows : (1)Irradiation creep compliance B$$_{0}$$ calculated from MFA-I, 2 data are 5.6$$sim$$ 15.0$$times$$10$$^{-6}$$ [($$times$$I0$$^{26}$$n/m$$^{2}$$, E>0.1Mev)$$^{-1}$$(MPa)$$^{-1}$$], Which are larger than B$$_{0}$$ based on MOTA data of 2.2$$sim$$6.4$$times$$10$$^{-6}$$ and are within the range of B$$_{0}$$ of other austenitic S.S. abroad. (2)Creep-swelling coupling coefficient D derived from MFA-1, 2 data tend to decrease with increasing swelling rate. And the range of D based on MFA-1, 2 data include values calculated from MOTA data of 3.8$$sim$$8.2$$times$$10$$^{-3}$$ [(MPa)$$^{-1}$$] and for other austenitic S.S. abroad. (3)As the result that irradiation creep deformation of MFA-1, 2 fuel pins could be appropriately estimated using the irradiation creep correlation derived from MOTA data, it is considered that the creep, correlation based on MOTA data can be applied to estimation of fuel pin deformation.

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