Technical note for the cavitation damage inspection for interior surface of the mercury target vessel, 2; Damage depth measurement for cavitation erosion

Naoe, Takashi; Wakui, Takashi; Kinoshita, Hidetaka; Kogawa, Hiroyuki; Teshigawara, Makoto; Haga, Katsuhiro

JAEA-Technology 2023-022, 81 Pages, 2024/01

JAEA-Technology-2023-022.pdf:9.87MB

In the liquid mercury target system for the pulsed spallation neutron source of Materials and Life Science Experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC), pressure waves that is generated by the high-energy proton beam injection simultaneously with the spallation reaction, resulting severe cavitation erosion damage on the interior surface of the mercury target vessel. Because the bubble of pressure wave-induced cavitation collapsing near the interior surface of the mercury target vessel with applying the large amplitude of localized impact on the surface. Since the wall thickness of the beam entrance portion of the target vessel is designed to be 3 mm to reduce thermal stress due to the internal heating, the erosion damage has the possibility to cause the vessel fatigue failure and mercury leakage originated from erosion pits during operation. To reduce the erosion damage by cavitation, a technique of gas microbubble injection into the mercury for pressure wave mitigation, and double-walled structure of the beam window of the target vessel has been applied. A specimen was cut from the beam window of the used mercury target vessel in order to investigate the effect of the damage mitigation technologies on the vessel, and to reflect the consideration of operation condition for the next target. We have observed cavitation damage on interior surface of the used mercury target vessel by cutting out the disk shape specimens. Damage morphology and depth of damaged surface were evaluated and correlation between the damage depth and operational condition was examined. The result showed that the erosion damage by cavitation is extremely reduced by injecting gas microbubbles and the damage not formed inside narrow channel of the double-walled structure for relatively high-power operated target vessels.

Experimental validation of tensile properties measured with thick samples taken from MEGAPIE target

Saito, Shigeru; Suzuki, Kazuhiro; Hatakeyama, Yuichi; Suzuki, Miho; Dai, Y.*

Journal of Nuclear Materials, 534, p.152146_1 - 152146_16, 2020/06

https://doi.org/10.1016/j.jnucmat.2020.152146

A post-irradiation examination (PIE) was performed on the tensile specimens prepared from the MEGAPIE (MEGAwatt Pilot Experiment) target which were irradiated in flowing lead-bismuth eutectic (LBE). Thicknesses of the specimens were over two times larger than that of the standard specimen. The PIE revealed that the T91 specimens showed a 1.5-2.0 times larger total elongation (TE) compared to the literature values for a specimen with standard t/w (ratio of thickness to width). It could be suggested that the t/w and TE were strongly correlated. Then, we tried to investigate the effects of the t/w on the TE by comparing unirradiated specimens. We found that there was no t/w dependence on the strength and uniform elongation. On the other hand, the TE increases with increasing t/w. Based on the experimental data, we correlated the TE with various specimens t/w to estimate appropriate TE values, including that for the standard specimen.

Analysis of post irradiation examination of used BWR fuel with SWAT4.0

Kikuchi, Takeo; Tada, Kenichi; Sakino, Takao; Suyama, Kenya

JAEA-Research 2017-021, 56 Pages, 2018/03

JAEA-Research-2017-021.pdf:2.15MB
JAEA-Research-2017-021(errata).pdf:0.13MB

The criticality management of the fuel debris is one of the most important research issues in Japan. The current criticality management adopts the fresh fuel assumption. The adoption of the fresh fuel assumption for the criticality control of the fuel debris is difficult because the k of the fuel debris could exceed 1.0 in most of cases which the fuel debris contains water and does not contain neutron absorbers such as gadolinium. Therefore, the adoption of the burnup credit is considered. The prediction accuracy of the isotopic composition of used nuclear fuel must be required to adopt the burnup credit for the treatment of the fuel debris. JAEA developed a burnup calculation code SWAT4.0 to obtain reference calculation results of the isotopic composition of the used nuclear fuel. This code is used to evaluate the composition of fuel debris. In order to investigate the prediction accuracy of SWAT4.0, we analyzed the PIE of BWR obtained from 2F2DN23.

Study on the evaluation method to determine the radioactivity concentration in radioactive waste generated from post-irradiation examination facilities, 2

Tsuji, Tomoyuki; Hoshino, Yuzuru; Sakai, Akihiro; Sakamoto, Yoshiaki; Suzuki, Yasuo*; Machida, Hiroshi*

JAEA-Technology 2017-010, 75 Pages, 2017/06

JAEA-Technology-2017-010.pdf:2.31MB

It is necessary for reasonable disposal to be studied on evaluation methods to determine radioactivity concentrations in the radioactive wastes, which is generated from post-irradiation examination (PIE) facilities, for establishment of reasonable confirmation methods concerning radioactive wastes generated from research, industrial, and medical facilities. It has been chosen the PIE facilities of NUCLEAR DEVELOPMENT CORPORATION as a model for this study. As a result, it has been confirmed that the theoretical methods are applied for the important nuclides (H-3, C-14, Co-60, Ni-63, Sr-90, Tc-99, Cs-137, Eu-154, U-234, U-235, U-238, Pu-238, Pu-239, Pu-240, Pu-241, Am-241 and Cm-244).

Field emission-type scanning electron microscope for examination of irradiated fuels

Yasuda, Ryo; Mita, Naoaki; Nishino, Yasuharu; Nakata, Masahito; Nozawa, Yukio; Harada, Katsuya; Kushida, Teruo; Amano, Hidetoshi

Nuclear Technology, 151(3), p.341 - 345, 2005/09

https://doi.org/10.13182/NT05-A3656

The Field Emission type Scanning Electron Microscope (FE-SEM), which is one of effective tools for observation of micr-structures, was installed at the Reactor Fuel Examination Facility (RFEF) in JAERI. The FE-SEM is equipped in a large shield vessel with remote handling systems to keep safety of operators and is modified to enable to manipulate high radioactive materials. The Energy Dispersive Spectrometer (EDS) with radiation-shielded collimators has been also equipped on the FE-SEM to determine element compositions of the observed material samples. Characterization tests were carried out using deposited gold film and Zircaloy cladding tubes with hydrides to confirm the machine performance after the modifications. In the results of the tests, high-resolution images without some noises and fogs were obtained with high magnification above 10,000. Those results show that the FE-SEM keeps the high performance after some improvements and modifications for shielding -rays and handling radioactive samples.

Study of irradiation effects on fuels and materials in JMTR hot laboratory

Omi, Masao

Nihon Genshiryoku Gakkai Kaku Nenryo Bukai Dai-20-kai "Kaku Nenryo, Kaki Semina" Kogi Tekisuto, 8 Pages, 2005/07

no abstracts in English

Bend-fatigue properties of 590 MeV proton irradiated JPCA and 316F SS

Saito, Shigeru; Kikuchi, Kenji; Usami, Koji; Ishikawa, Akiyoshi; Nishino, Yasuharu; Kawai, Masayoshi*; Dai, Y.*

Journal of Nuclear Materials, 329-333(Part1), p.1093 - 1097, 2004/08

https://doi.org/10.1016/j.jnucmat.2004.04.152

In several institutes, research and development for an accelerator-driven spallation neutron source have been progressed. A beam window of a target will be subjected to proton/neutron irradiation, pressure wave and thermal stresses accompanied by high-energy proton beam injection. To obtain the irradiation data, the SINQ target irradiation program (STIP) at Paul Scherrer Institute (PSI) has been progressing. JAERI takes part in STIP and shares the PIE work. The STIP specimens are very small so that we developed a new fatigue-testing machine with ceramic piezoelectric actuator. The results showed that the numbers of cycles to failure (Nf) on the irradiated specimens were less than that of unirradiated specimens. Dpa dependence of Nf was not clearly seen in the irradiation conditions. On the other hand, fracture surface varied with irradiation conditions. Specimens irradiated at low temperature fractured in ductile manner. However, interglanular fractured surface was observed for 316F SS irradiated up to 12.5 dpa at 360C.

Selection of important nuclides from the viewpoint of safety assessment for disposal of radioactive waste arising from research institutes, 2; Analytical scheme for nuclide composition in radwastes arising from research and testing reactor and post-irradiation examination facilities

Asai, Shiho; Sakai, Akihiro; Yoshimori, Michiro; Kihara, Shinji

JAERI-Tech 2003-071, 46 Pages, 2003/08

JAERI-Tech-2003-071.pdf:4.31MB

As part of survey concerning radioactive inventory of radwastes arising from research institutes, an analytical scheme has been studied for verifying their nuclide composition based on calculation analysis and record, in consideration of the its characteristics. In this study, radwastes are used as samples, which arise from research and testing reactors and post-irradiation examination facilities (PIE facilities). Though separation procedures are simplified and rationalized, quantifiable values could be obtained with relative errors under 10% for almost all the samples containing nuclides like Ni and U which concentrations are low, and recoveries were high on the whole. These show that the analytical scheme is useful for chemical separation of radwastes arising from research and testing reactors and PIE facilities.

Development of remote controlled type field-emission type scanning electron microscope

Yasuda, Ryo; Nishino, Yasuharu; Mita, Naoaki; Nakata, Masahito; Harada, Katsuya; Nozawa, Yukio; Amano, Hidetoshi

JAERI-Tech 2002-081, 34 Pages, 2002/10

JAERI-Tech-2002-081.pdf:11.76MB

Information about the fuel behavior under high burn-up operation is needed to assess the safety of the high burn-up fuels. Microstructures in irradiated fuel pellets and Zircaloy tubes influence on their integrity. The fundamental information about microstructures is necessary to estimate the formation mechanism and change in the properties of the fuels.The Field Emission type Scanning Electron Microscope (FE-SEM) has been hence installed at the Reactor Fuel Examination Facility (RFEF). FE-SEM is designed for the remote handling type to use high radioactive materials and has equipments to keep safety for operators. Charctarization tests were carried out using Zircaloy cladding tubes with oxide films and hydrides to confirm machine performance. In the results of the tests, high-resolution images with a magnification of 30,000 were obtained. Those results show that the apparatus is maintained high performance as well as standard type.

Revised burnup code system SWAT; Description and validation using postirradiation examination data

Suyama, Kenya; Mochizuki, Hiroki*; Kiyosumi, Takehide*

Nuclear Technology, 138(2), p.97 - 110, 2002/05

https://doi.org/10.13182/NT02-A3282

no abstracts in English