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Journal Articles

Effect of proton beam profile on stress in JSNS target vessel

Kogawa, Hiroyuki; Ishikura, Shuichi*; Sato, Hiroshi; Harada, Masahide; Takatama, Shunichi*; Futakawa, Masatoshi; Haga, Katsuhiro; Hino, Ryutaro; Meigo, Shinichiro; Maekawa, Fujio; et al.

Journal of Nuclear Materials, 343(1-3), p.178 - 183, 2005/08

 Times Cited Count:8 Percentile:51.68(Materials Science, Multidisciplinary)

A cross-flow type (CFT) mercury target with flow guide blades, which has been developed for JSNS, can suppress the generation of stagnant flow region especially near the beam window where the peak heat density is generated due to spallation reaction. Then, a flat type beam window has been applied to the CFT target from the viewpoint of suppressing dynamic stress caused by a pressure wave, which has been estimated with a mercury model of the linear equation of state. The recent experimental results obtained by using a proton beam incidents to mercury led that a cutoff pressure model in the equation of state of mercury caused a suitable dynamic stress with experimental results. Dynamic stress analyses were carried out with the cutoff pressure model, in which the negative pressure less than 0.15 MPa was not generated. The generated dynamic stress in the flat beam window became much larger than that in a semi-cylindrical type window. However, the generated stress in the semi-cylindrical type beam window was over the allowable stress of SS316L under the peak heat density of 668 W/cc. In order to decrease the dynamic stress in the semi-cylindrical beam window, the incident proton beam was defocused to decrease the peak heat density down to 218 W/cm$$^{3}$$. As a result, the dynamic stress could be suppressed less than the allowable stress. On the other hand, due to defocus of the proton beam, high heat density was generated on the end of the flow guide blades, which caused high thermal stress exceeding the allowable stress. To decrease the thermal stress, several shapes of the blade ends were studied analytically, which were selected so as not to affect the mercury flow distribution. A simple thin-end blade showed low thermal stress below the allowable stress.

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

Effect of absorbed hydrogen on the stress corrosion cracking (SCC) susceptibility of unirradiated Zircaloy cladding

Amaya, Masaki; Fuketa, Toyoshi

Journal of Nuclear Science and Technology, 41(11), p.1091 - 1099, 2004/11

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

Effect of absorbed hydrogen on the stress corrosion cracking (SCC) susceptibility of unirradiated Zircaloy cladding was examined. The data obtained from literatures show that the ratios of SCC threshold stress ($$sigma$$$$_{th}$$) to 0.2% yield stress ($$sigma$$$$_{0.2}$$) in unirradiated Zircaloy claddings increase with increasing hydrogen contents below 60 ppm, irrespective of the kind of Zircaloy-2 and -4. Thermodynamic calculations were carried out for the reaction between iodine gas and zirconium containing hydrogen. The results suggested that the reactions hardly occurred at increased hydrogen content and zirconium reacted with iodine gas only below 90 ppm of hydrogen. Since these tendencies correspond to those of the ratios of $$sigma$$$$_{th}$$ to $$sigma$$$$_{0.2}$$ on the hydrogen content, it is considered that hydrogen affects the reactions between iodine gas and zirconium and reduces the SCC susceptibility of Zircaloy claddings.

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.

JAEA Reports

Study on the stress corrosion cracking of zirconium in nuclear fuel reprocessing environment

Kato, Chiaki

JAERI-Research 2003-013, 143 Pages, 2003/08

JAERI-Research-2003-013.pdf:22.12MB

This study is investigation about stress corrosion cracking (SCC) of zirconium in nuclear fuel reprocessing. Chapter 1 is described background. Chapter 2 is explained experimental apparates. Chapter 3 is described the increased oxidization potential on the heat-transfer surface and suggested the initiation of SCC on a boiling heat-transfer surface. Chapter 4 is described that the SCC susceptibility increased with increasing nitric acid concentration and solution temperature on notched specimen by SSRT. In addition, the SCC susceptibility effected by the crystal anisotropy by the hot rolling direction and increased on a parallel face to the rolling direction. Chapter 5 is described that the SCC susceptibility increased in HAZ/base metal boundary in order to the preferential orientation of cleavage plane (0002). Chapter 6 is described that the increased oxidization potential on the heat-transfer surface is attributed to the reduction of nitrous acid concentration by the thermal decomposition on the surface and the removal of the decomposition product from solution by boiling bubbles.

Journal Articles

Structural integrity of beam window of mercury target

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

Proceedings of 11th International Conference on Nuclear Engineering (ICONE-11) (CD-ROM), 7 Pages, 2003/04

The developments of a MW-class spallation neutron source facility are being carried out under the high-intensity proton accelerator project promoted by JAERI and KEK. A mercury target will be used as a neutron source in the facility. The mercury target vessel made of 316LSS will be subjected to pressure wave generated by rapid thermal expansion of mercury due to a pulsed proton beam injection. The pressure wave will make huge stress on the vessel and will deform the vessel, which would cause cavitation in mercury. To estimate the structural integrity of the mercury target vessel, especially beam window, dynamic stress behaviors due to 1MW-pulsed proton beam injection were analyzed by using FEM code. In the analyses, two types of the target vessels with semi-cylindrical and flat type windows were used as analytical models. As the results, it has been understood that the stress generated in the beam window by the pressure wave could be treated as the secondary stress. Also it was confirmed that the flat type window would be more advantageous from the structural viewpoint than the semi-cylindrical type window.

Journal Articles

Analyses on pressure wave propagation and dynamic stress in mercury targets

Ishikura, Shuichi*; Kaminaga, Masanori; *; Hino, Ryutaro; *; *; *

Proc. of 14th Meeting of the Int. Collaboration on Advanced Neutron Sources (ICANS-14), 1, p.288 - 300, 1998/00

no abstracts in English

Journal Articles

Evaluation of aseismatic integrity in HTTR core-bottom structure,VI; Dynamic strength of graphite component under stress concentration condition

Ishihara, Masahiro; Futakawa, Masatoshi; Iyoku, Tatsuo; Oku, Tatsuo*

Nihon Genshiryoku Gakkai-Shi, 38(12), p.1005 - 1012, 1996/00

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

no abstracts in English

Journal Articles

Change in dynamic Young´s modulus of nuclear-grade isotropic graphite during tensile and compressive stressing

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Journal of Nuclear Materials, 119(2-3), p.278 - 283, 1983/00

 Times Cited Count:18 Percentile:85.57(Materials Science, Multidisciplinary)

no abstracts in English

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