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Journal Articles

Compact moving particle semi-implicit method for incompressible free-surface flow

Wang, Z.; Matsumoto, Toshinori; Duan, G.*; Matsunaga, Takuya*

Computer Methods in Applied Mechanics and Engineering, 414, p.116168_1 - 116168_49, 2023/09

 Times Cited Count:0

Journal Articles

Hierarchical Bayesian modeling to quantify fracture limit uncertainty of high-burnup advanced fuel cladding tubes under loss-of-coolant accident conditions

Narukawa, Takafumi; Hamaguchi, Shusuke*; Takata, Takashi*; Udagawa, Yutaka

Nuclear Engineering and Design, 411, p.112443_1 - 112443_12, 2023/09

 Times Cited Count:0

JAEA Reports

Investigations and consideration on conditions of contamination and measures of decontamination for motor vehicles at a nuclear emergency

Togawa, Orihiko; Hokama, Tomonori; Hiraoka, Hirokazu

JAEA-Review 2023-013, 48 Pages, 2023/08


When radionuclides are released into the atmospheric environment at a nuclear emergency, protective measures such as evacuation and temporal relocation are carried out using motor vehicles such as private cars and buses to reduce radiation exposure to residents. To confirm conditions of contamination for the evacuated or relocated residents, contamination inspection is conducted, in which it is important not to spoil its rapidity. In the present inspection, wipers and tires are designated to first measuring parts, and they are basically inspected by persons using GM survey meters. Utilization of portable radiation portal monitors is also being considered for rapid and efficient inspection of motor vehicles. In order to contribute to rapid and efficient operation of contamination inspection, this report investigated conditions of contamination and measures of decontaminations for motor vehicles at a nuclear emergency. Although available documents and information were quite few, results of the investigations described in the related documents were extracted and rearranged according to the objectives of this report. Furthermore, these results were considered from a viewpoint of rapid and efficient operation of contamination inspection.

Journal Articles

Characteristics of allowable axial cracks for pressurized pipes governed by limit load criteria

Hasegawa, Kunio; Li, Y.; Udyawar, A.*; Lacroix, V.*

International Journal of Pressure Vessels and Piping, 204, p.104952_1 - 104952_7, 2023/08

 Times Cited Count:0 Percentile:0.01(Engineering, Multidisciplinary)

When axial cracks were detected in pipes, failure stresses for high toughness pipes are estimated using the Limit Load Criteria. The allowable stresses for the cracked pipes are derived from the combination of the failure stresses and safety factors. The allowable sizes of crack depths and lengths are determined from the allowable stresses. From the comparison of the allowable and failure stresses for through-wall cracks, the allowable cracks are not uniform. They can be separated into three different characteristics, i) leak-before-break (LBB) and crack growth stability, ii) non-LBB and crack growth stability and iii) non-LBB and crack growth instability. Inspectors and users should pay special attention to allowable cracks with the third characteristic to prevent unexpected failure, particularly for thin-wall pipes. The allowable crack depths and lengths that require special attention can be expressed by appropriate equations.

Journal Articles

Behavior of FeCrAl-ODS cladding tube under loss-of-coolant accident conditions

Narukawa, Takafumi; Kondo, Keietsu; Fujimura, Yuki; Kakiuchi, Kazuo; Udagawa, Yutaka; Nemoto, Yoshiyuki

Journal of Nuclear Materials, 582, p.154467_1 - 154467_12, 2023/08

 Times Cited Count:0 Percentile:0.02(Materials Science, Multidisciplinary)

Journal Articles

Optimization of dissolved hydrogen concentration for mitigating corrosive conditions of pressurised water reactor primary coolant under irradiation, 2; Evaluation of electrochemical corrosion potential

Hata, Kuniki; Hanawa, Satoshi; Chimi, Yasuhiro; Uchida, Shunsuke; Lister, D. H.*

Journal of Nuclear Science and Technology, 60(8), p.867 - 880, 2023/08

 Times Cited Count:2 Percentile:49.42(Nuclear Science & Technology)

One of the major subjects for evaluating the corrosive conditions in the PWR primary coolant was to determine the optimal hydrogen concentration for mitigating PWSCC without any adverse effects on major structural materials. As suitable procedures for evaluating the corrosive conditions in PWR primary coolant, a couple of procedures, i.e., water radiolysis and ECP analyses, were proposed. The previous article showed the radiolysis calculation in the PWR primary coolant, which was followed by an ECP study here. The ECP analysis, a couple of a mixed potential model and an oxide layer growth model, was developed originally for BWR conditions, which was extended to PWR conditions with adding Li$$^{+}$$ (Na$$^{+}$$) and H$$^{+}$$ effects on the anodic polarization curves. As a result of comparison of the calculated results with INCA in-pile-loop experiment data as well as other experimental data, it was confirmed that the ECPs calculated with the coupled analyses agreed with the measured within $$pm$$100mV discrepancies.

Journal Articles

Numerical simulation of bubble hydrodynamics for pool scrubbing

Okagaki, Yuria; Shibamoto, Yasuteru; Wada, Yuki; Abe, Satoshi; Hibiki, Takashi*

Journal of Nuclear Science and Technology, 60(8), p.955 - 968, 2023/08

 Times Cited Count:0 Percentile:0.02(Nuclear Science & Technology)

Journal Articles

Analytical study for low ground contact ratio of buildings due to the basemat uplift using a three-dimensional finite element model

Choi, B.; Nishida, Akemi; Shiomi, Tadahiko; Kawata, Manabu; Li, Y.; Ota, Akira*; Sonobe, Hideaki*; Ino, Susumu*; Ugata, Takeshi*

Mechanical Engineering Journal (Internet), 10(4), p.23-00026_1 - 23-00026_11, 2023/08

In the seismic evaluation of nuclear facility buildings, basemat uplift-the phenomenon during which the bottom of the basemat of a building partially rises from the ground owing to overturning moments during earthquakes-is a very important aspect because it affects not only structural strength and integrity, but also the response of equipment installed in the building. However, there are not enough analytical studies on the behavior of buildings with a low ground contact ratio due to basemat uplift during earthquakes. In this study, we conducted a simulation using a three-dimensional finite element model from past experiments on basemat uplift; further, we confirmed the validity of this approach. In order to confirm the difference in the analytical results depending on the analysis code, the simulation was performed under the same analytical conditions using the three analysis codes, which are E-FrontISTR, FINAS/STAR and TDAPIII, and the obtained analysis results were compared. Accordingly, we investigated the influence of the difference in adhesion on the structural response at low ground contact ratio. In addition, we confirmed the effects of significant analysis parameters on the structural response via sensitivity analysis. In this paper, we report the analytical results and insights obtained from these investigations.

Journal Articles

A Simple correlation to estimate agglomerated debris formation based on experiments of melt jet-breakup using a metallic melt

Iwasawa, Yuzuru; Sugiyama, Tomoyuki; Kaneko, Akiko*

Nuclear Engineering and Design, 409, p.112348_1 - 112348_15, 2023/08

 Times Cited Count:0 Percentile:0.02(Nuclear Science & Technology)

JAEA Reports

Data report of ROSA/LSTF experiment IB-HL-01; 17% hot leg intermediate break LOCA with totally-failed high pressure injection system

Takeda, Takeshi

JAEA-Data/Code 2023-007, 72 Pages, 2023/07


An experiment denoted as IB-HL-01 was conducted on November 19, 2009 using the Large Scale Test Facility (LSTF) in the Rig of Safety Assessment-V (ROSA-V) Program. The ROSA/LSTF experiment IB-HL-01 simulated a 17% hot leg intermediate break loss-of-coolant accident due to a double-ended guillotine break of pressurizer surge line in a pressurized water reactor (PWR). The break was simulated by a long nozzle upwardly mounted flush with a hot leg inner surface. The test assumptions included total failure of both high pressure injection system of emergency core cooling system (ECCS) and auxiliary feedwater system. In the experiment, relatively large size of break led to a fast transient of phenomena. The primary pressure steeply dropped after the break, and became lower than steam generator (SG) secondary-side pressure. Break flow turned from single-phase flow to two-phase flow soon after the break. Core uncovery started simultaneously with liquid level drop in downflow-side of crossover leg before loop seal clearing (LSC). The LSC was induced in both loops by steam condensation on accumulator (ACC) coolant of ECCS injected into cold legs. The whole core was quenched owing to the rapid recovery in the core liquid level after the LSC. Peak cladding temperature of simulated fuel rods was detected almost concurrently with the LSC. During the ACC coolant injection, liquid levels recovered in the hot legs and SG inlet plena because of liquid entrainment from the hot leg into the SG inlet plenum by high-velocity steam flow. After the continuous core cooling was confirmed through the actuation of low pressure injection system of ECCS, the experiment was terminated. This report summarizes the test procedures, conditions, and major observations in the ROSA/LSTF experiment IB-HL-01.

Journal Articles

Occurrence of radioactive cesium-rich micro-particles (CsMPs) in a school building located 2.8 km south-west of the Fukushima Daiichi Nuclear Power Plant

Fueda, Kazuki*; Komiya, Tatsuki*; Minomo, Kenta*; Horie, Kenji*; Takehara, Mami*; Yamasaki, Shinya*; Shiotsu, Hiroyuki; Onuki, Toshihiko*; Grambow, B.*; Law, G. T. W.*; et al.

Chemosphere, 328, p.138566_1 - 138566_12, 2023/07

 Times Cited Count:0 Percentile:0(Environmental Sciences)

Journal Articles

Revision of allowable planar flaw tables of ASME B&PV Code Section XI for ferritic steel materials

Dulieu, P.*; Lacroix, V.*; Hasegawa, Kunio

Proceedings of ASME 2023 Pressure Vessels & Piping Conference (PVP 2023) (Internet), 7 Pages, 2023/07

When defects were found during in-service inspection in nuclear components, the ASME Code Section XI provides allowable flaw sizes to assess the flaw severity. For ferritic steel materials, the sizes of allowable planar flaws given in Table IWB-3510-1 were determined by the stress intensity factors. The objective of this methodology is including some basic criteria to prevent plastic collapse and brittle failure. As far as the prevention from plastic collapse, a uniform limit load reduction is considered whatever the flaw aspect ratios. For the prevention of brittle failure, a reference surface flaw configuration is defined to derive a reference stress intensity factor. This methodology is applied to surface flaws with various aspect ratios. It is also coherently applied to subsurface flaws considering the proximity of the flaw to the surface as an additional parameter. Finally, a revision of the allowable planar flaw Table IWB-3510-1 of ASME Code Section XI is proposed.

Journal Articles

Towards an improvement of allowable planar flaws of ASME Code Section XI acceptance standards for ferritic steel materials

Lacroix, V.*; Dulieu, P.*; Hasegawa, Kunio

Proceedings of ASME 2023 Pressure Vessels & Piping Conference (PVP 2023) (Internet), 5 Pages, 2023/07

In case of flaw detection during In-Service inspection of nuclear components, ASME Code Section XI provides Acceptance Standards. For ferritic steel materials, the size of allowable planar flaws is given in Table IWB-3510-1. The allowable flaw size only depends on three parameters: the component thickness, the flaw aspect ratio and the proximity of the flaw to the surface. However, a graphical analysis of the impact of those parameters highlights some inconsistencies. Consequently, the need to revise the allowable planar flaws of ASME Code Section XI Acceptance Standards using a robust technical basis is brought to light. This paper details the inconsistencies related to the present allowable planar flaws table and proposes improvement points to revise the allowable planar flaw Table IWB-3510-1.

Journal Articles

Effect of calcium on niobium solubility in alkaline solutions

Ohira, Saki; Abe, Takeyasu; Iida, Yoshihisa

Radiochimica Acta, 111(7), p.525 - 531, 2023/07

 Times Cited Count:0 Percentile:0.02(Chemistry, Inorganic & Nuclear)

The solubility of $$^{94}$$Nb in calcium alkaline solutions is one of the important parameters in safety assessment of intermediate-depth disposal which are assumed to use cementitious materials. Nb solubility and solubility-limiting solid phases of Nb in these systems remain unclear. The oversaturation solubility experiments were performed systematically in the 0.001-0.1 M CaCl$$_{2}$$ solutions under alkali conditions, and the characterization of precipitated solid phase controlling Nb solubility was conducted. The negative dependence of Nb solubilities on pH and Ca concentration was observed in solubility experiments, the molar ratio of Nb to Ca of precipitated solid phase was 0.66. The pH and Ca dependence of Nb solubilities was reproduced by the reaction with Nb aqueous species Nb(OH)$$_{6}$$$$^{-}$$ and Ca-Nb oxide with the molar ratio of Nb to Ca 0.66, e.g., Ca$$_{4}$$Nb$$_{6}$$O$$_{19}$$(am).

Journal Articles

The Effects of unburned-gas temperature and pressure on the unstable behavior of cellular-flame fronts generated by intrinsic instability in hydrogen-air lean premixed flames under adiabatic and non-adiabatic conditions; Numerical simulation based on the detailed chemical reaction model

Thwe Thwe, A.; Kadowaki, Satoshi; Nagaishi, Ryuji

Journal of Nuclear Science and Technology, 60(6), p.731 - 742, 2023/06

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

In this study, we performed numerical calculations of unsteady reaction flow considering detailed chemical reactions, investigated the unstable behavior of hydrogen-air dilute premixed flame due to intrinsic instability, and clarified the effects of unburned gas temperature and pressure. I made it. The unstable behavior of the flame in a wide space was simulated, and the burning rate of the cellular flame was obtained. Then, the effects of heat loss and flame scale on flame unstable behavior were investigated. The burning velocity of a planar flame increases as the unburned-gas temperature increases and it decreases as the unburned-gas pressure and heat loss increase. The normalized burning velocity increases when the pressure increases and heat loss becomes large, and it decreases when the temperature increases. This is because the high unburned-gas pressure and heat loss promote the unstable behavior and instability of flame.

Journal Articles

Study on borehole sealing corresponding to hydrogeological structures by groundwater flow analysis

Sawaguchi, Takuma; Takai, Shizuka; Sasagawa, Tsuyoshi; Uchikoshi, Emiko*; Shima, Yosuke*; Takeda, Seiji

MRS Advances (Internet), 8(6), p.243 - 249, 2023/06

In the intermediate depth disposal of relatively high-level radioactive waste, a method to confirm whether the borehole for monitoring is properly sealed should be developed in advance. In this study, groundwater flow analyses were performed for the hydrogeological structures with backfilled boreholes, assuming sedimentary rock area, to understand what backfill design conditions could prevent significant water pathways in the borehole, and to identify the confirmation points of borehole sealing. The results indicated the conditions to prevent water pathways in the borehole and BDZ (Borehole Disturbed Zone), such as designing the permeability of bentonite material less than or equal to that of the host rock, and grouting BDZ.

Journal Articles

Experimental study on scabbing limit of local damage to reinforced concrete panels subjected to oblique impact by projectile with semispherical nose

Okuda, Yukihiko; Kang, Z.; Nishida, Akemi; Tsubota, Haruji; Li, Y.

Mechanical Engineering Journal (Internet), 10(3), p.22-00370_1 - 22-00370_12, 2023/06

Many experimental studies have been reported on the impact resistance of reinforced concrete (RC) structures. However, most formulas were derived from impact tests based on normal impact to target structures using rigid projectiles that do not deform during impact. Therefore, this study develops a local damage evaluation method considering the rigidity of projectiles and oblique impacts that should be considered in realistic projectile impact phenomena. Specifically, we focused on scabbing, defined as the peeling off the back face of the target opposite the impact face, and conducted impact tests on RC panels to clarify the scabbing limit by changing the impact velocity in an oblique impact. The effects of the projectile rigidity and oblique impact on the scabbing limit were investigated based on the test results. This work presents the test conditions, equipment, results, and the scabbing limit on the local damage to RC panels subjected to oblique impacts.

Journal Articles

Proposition of confirmation items on the borehole sealing for the disposal of radioactive waste

Murakami, Hiroaki; Nishiyama, Nariaki; Takeuchi, Ryuji; Iwatsuki, Teruki

Oyo Chishitsu, 64(2), p.60 - 69, 2023/06

In order to confirm the quality control items for borehole closure in radioactive waste disposal projects, in-situ borehole sealing tests using bentonite material were conducted. As a result, the closure performance was successfully demonstrated by comparing the data of water injection tests conducted before and after the installation of the closure material. However, the breakthrough was observed after closing, probably due to high differential pressure applied to the seal section. Thus, it is important to ascertain throughout the entire operation that the borehole is adequately closed. The placement and specifications of the closure material should be determined according to the hydrogeological structure in the borehole. The confirmation items to use bentonite for sealing material are identified to be: to consider swelling and density loss in the borehole; to place the planned depth using appropriate emplacement technique; to be placed without damage to seals when use some backfilling materials, considering effect of permeability on adjacent seals.

Journal Articles

Revision of the criticality safety handbook in light of the reality of the nuclear fuel cycle in Japan; With a view to transportation and storage of fuel debris

Suyama, Kenya; Ueki, Taro; Gunji, Satoshi; Watanabe, Tomoaki; Araki, Shohei; Fukuda, Kodai

Proceedings of 20th International Symposium on the Packaging and Transportation of Radioactive Materials (PATRAM22) (Internet), 5 Pages, 2023/06

Since the 1990s, the importance of the handbook has changed significantly, as the computational power has improved and continuous energy Monte Carlo codes have become widely used, which enables highly accurate criticality calculations, when necessary, irrespective of the complexity of the system. Because the value of performing a large number of calculations in advance and summarizing the data has decreased, since the second edition was published publicly in 1999, there has been no revision of criticality safety handbooks in Japan for nearly a quarter of a century. In Japan, where the Fukushima Daiichi Nuclear Power Plant accident occurred in 2011, it became necessary to deal with criticality safety issues in the transport and storage of the fuel debris which contains complex constituent elements, and the summary the criticality safety management for such material is an urgent issue. In the area of burnup credit, the transport and storage of fuel assemblies with low achieved burnups due to the consequences of accidents might be the problem. In addition, nuclear data, which is the input for the continuous energy Monte Carlo code, has been improved several times, now JENDL-5 is available from the end of 2021, and its incorporation becomes a need in the field. This report provides an overview of the latest criticality safety research in Japan and the planned revision of the Criticality Safety Handbook, which could be applied to the transport and storage sectors.

Journal Articles

Accident sequence precursor analysis of an incident in a Japanese nuclear power plant based on dynamic probabilistic risk assessment

Kubo, Kotaro

Science and Technology of Nuclear Installations, 2023, p.7402217_1 - 7402217_12, 2023/06

 Times Cited Count:0 Percentile:0.02(Nuclear Science & Technology)

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