Development of a GEM-TPC for H-dibaryon search experiment at J-PARC

Sako, Hiroyuki; Ahn, J. K.*; Baek, K. H.*; Bassalleck, B.*; Fujioka, H.*; Guo, L.*; Hasegawa, Shoichi; Hicks, K.*; Honda, R.*; Hwang, S. H.*; et al.

Journal of Instrumentation (Internet), 9(4), p.C04009_1 - C04009_10, 2014/04

https://doi.org/10.1088/1748-0221/9/04/C04009

A TPC has been developed for J-PARC E42 experiment to search for H-dibaryon in (, ) reaction. An event with 2 and 2 protons decaying from H-dibaryon is searched for inside the TPC. The TPC has octagonal prism shape drift volume with about 50 cm diameter with 55 cm drift length filled with Ar-CH (90:10) gas. At the end of the drift volume, 3-layer GEMs are equipped. In order to analyze momenta of produced particles, the TPC is applied with 1 T dipole magnetic field parallel to the drift electric field with a superconducting Helmholz magnet. In order to maximize the acceptance of H-dibaryon events, a diamond target is installed inside the TPC drift volume, in a cylindrical hole opened from the top to the middle of the drift volume. Since extremely high-rate beam is directly injected into the TPC drift volume to the target, a gating grid and GEMs are adopted to suppress positive-ion feedback.

Evaluation of applicability on multi-axis residual stress formed by hard sphere indentation for stress corrosion cracking test

Ioka, Ikuo; Kiuchi, Kiyoshi*; Takizawa, Masayuki*; Ito, Takeshi*

Nihon Kinzoku Gakkai-Shi, 78(1), p.16 - 22, 2014/01

https://doi.org/10.2320/jinstmet.J2013061

A multi-axis stress field is indispensable to quick and quantitative evaluation of stress corrosion cracking for constructional materials and weld joints of existing industrial plants. The applicability of multi-axis residual stress field into SCC tests was evaluated. The hard sphere ball was stuffed into small flat-plate of type 304SS. Numerical analysis was conducted in order to compare with the experimental results. The numerical analysis was comparatively in agreement with the experimental results. Parameters of the test were selected by numerical analysis to optimize the residual stress of specimen. SCC test in MgCl was performed using the specimen with optical residual stress condition. It is confirmed that the multi-axis residual stress field was useful in quick and quantitative SCC test by comparing the initiation of cracks with the distribution of residual stress obtained by numerical analysis.

Microstructural evolution and void swelling in extra high purity Ni-base superalloy under multi-ion irradiation

Kim, G.; Shiba, Kiyoyuki; Sawai, Tomotsugu; Ioka, Ikuo; Kiuchi, Kiyoshi; Nakayama, Jumpei*

Proceedings of 2nd International Workshop on Structural Materials for Innovative Nuclear Systems (SMINS-2), p.273 - 279, 2012/12

http://www.oecd-nea.org/science/docs/2012/6896-smins-korea-proceedings.pdf

Radiation hardening and IASCC susceptibility of extra high purity austenitic stainless steel

Ioka, Ikuo; Ishijima, Yasuhiro; Usami, Koji; Sakuraba, Naotoshi; Kato, Yoshiaki; Kiuchi, Kiyoshi

Journal of Nuclear Materials, 417(1-3), p.887 - 891, 2011/10

https://doi.org/10.1016/j.jnucmat.2010.12.154

Fe-25Cr-35Ni EHP alloy was developed with conducting the countermeasure for IASCC. It is composed to adjust major elements, to remove harmful impurities and so on. The specimens were irradiated at 553 K for 25000h using JRR-3. The fluence was estimated to be 1.510n/m. Type 304SS was also irradiated as a comparison material. SSRT test was conducted in oxygenated water at 561 K in 7.7 MPa. The fracture mode of EHP alloy was ductile. IGSCC was not observed in the fracture surface. On the other hand, the fraction of IGSCC on the fracture surface of type 304 was about 70%. Microstructural evolution of EHP and type 304 after irradiation was examined by TEM. The defects induced by irradiation mostly consisted of black dots and frank loops in both specimens. No void was also observed in grain and grain boundary of both specimens. There was a little difference in microstructure after irradiation. It is believed that EHP alloy is superior to type 304 in irradiation.

A Study to control chemical reactions using Si:2p core ionization; Site-specific fragmentation

Nagaoka, Shinichi*; Fukuzawa, Hironobu*; Prmper, G.*; Takemoto, Mai*; Takahashi, Osamu*; Yamaguchi, Takuhiro*; Kakiuchi, Takuhiro*; Tabayashi, Kiyohiko*; Suzuki, Isao*; Harries, J.; et al.

Journal of Physical Chemistry A, 115(32), p.8822 - 8831, 2011/07

https://doi.org/10.1021/jp203664r

Application of extra high purity austenitic stainless steel to weld overlay

Ioka, Ikuo; Suzuki, Jun; Kiuchi, Kiyoshi; Nakayama, Jumpei*

Proceedings of 18th International Conference on Nuclear Engineering (ICONE-18) (CD-ROM), 6 Pages, 2010/05

https://doi.org/10.1115/ICONE18-30197

An Extra High Purity austenitic stainless steel (EHP alloy) was developed with conducting the new multiple refined melting in order to suppress the harmful impurities less than 100 ppm. EHP alloy has great intergranular corrosion resistance. It is considered that intergranular corrosion becomes initiation of SCC. So, we try to apply EHP alloy to weld overlay materials to prevent from SCC. EHP alloy was melted by the new multiple refined method. The conventional weld metals were also prepared as comparisons. Specimens were machined from the welded metal of each material. Intergranular corrosion tests were performed in boiling 8 kmol/m HNO solutions containing 1 kg/m Cr(VI) ions. The intergranular corrosion of conventional weld metals was severer than those of EHP alloys. Crevice Beam bending tests to evaluate susceptibility of SCC were carried out in high temperature water of 561 K with saturated oxygen for 1000 h. Cracks and intergranular corrosion of conventional weld metals were much more than those of EHP alloys. It was confirmed that EHP alloy had excellent SCC resistance in comparison with conventional materials when EHP alloy was used as a weld metal.

Correlation between intergranular corrosion and impurities of extra high purity austenitic stainless steels

Ioka, Ikuo; Suzuki, Jun; Motooka, Takafumi; Kiuchi, Kiyoshi; Nakayama, Jumpei*

Journal of Power and Energy Systems (Internet), 4(1), p.105 - 112, 2010/02

https://doi.org/10.1299/jpes.4.105

An intergranular corrosion is an important degradation mechanism of austenitic stainless steels for use in a nuclear fuel reprocessing plant. The intergranular corrosion is caused by the segregation of impurities to grain boundaries. An extra high purity austenitic stainless steel (EHP) was developed with conducting the new multiple refined melting to suppress the impurities less than 100ppm. The intergranular corrosion behavior of EHP alloys added various impurities was examined in boiling nitric acid solution with highly oxidizing ions. A multi regression analysis was performed using the obtained data. The degree of influence of the impurities on intergranular corrosion was shown from the analysis. The influence on corrosion rate became small in order of B, P, Si, C, S and Mn. There is little effect of Mn on corrosion rate of EHP-SSs in case of 10000appm or less.

Evaluation method of thermal deformation for Fast Spectrum Light Water Reactor (FLWR)

Ishijima, Yasuhiro; Ioka, Ikuo; Kiuchi, Kiyoshi; Kaneko, Tetsuji*; Okubo, Tsutomu; Yamamoto, Masahiro

Atsuryoku Gijutsu, 47(1), p.12 - 17, 2009/01

http://joi.jlc.jst.go.jp/JST.Journalarchive/hpi1972/14.12

We investigate one of these innovative water reactors; Fast Spectrum Light Water Reactor (FLWR). It has unique construction for the reactor core but the fuel cladding material will be exposed in high internal pressure and axial load and complex temperature distribution. Therefore, we conducted a specially designed fatigue-creep test that were simulated several parameters (thermal distribution, temperature variation, internal pressure variation and binding stress) to evaluate an applicability of fuel cladding material for FLWR. Zircalloy-2, which is common cladding material, was used for the test. Test result was confirmed to compare the deformation value between tested and calculated. The result showed the evaluation method could be controlled several parameters simultaneously and the deformation value after the test coincided to the calculated value. This method is sufficient to evaluate thermal deformation characteristics for FLWR.

Effects of -ray irradiation on the high temperature oxidation of austenitic stainless steel in supercritical water

Nakahara, Yukio; Yamamoto, Masahiro; Karasawa, Hidetoshi*; Kiuchi, Kiyoshi; Katsumura, Yosuke*

Proceedings of 16th Pacific Basin Nuclear Conference (PBNC-16) (CD-ROM), 6 Pages, 2008/10

Three types of commercial-grade austenitic stainless steel, Type 304L, Type 316L, and Type 310S, were immersed in deaerated supercritical water (SCW) of 25 MPa, 550 C with -ray irradiation for 1000 hours in total. Absorbed dose rates in SCW are estimated at 5-15 kGy h. High temperature oxidation experiments resulted in the formation of two-layer oxide film in which the outer layer is porous iron oxide and the inner layer is dense iron-chromium-nickel oxide. Rate constants of parabolic rate law in net weight gains of Type 304L SS and Type 310S SS are decreased as the -ray exposure rate is increased. The net weight gain of -ray irradiated Type 316L SS is sharply fluctuating and decreasing, because the flaking of the outer layer occurred. Hematite is formed in the outer layer on all irradiated samples of examined alloys. The concentration of chromium on the surface is increased by -ray irradiation. A chromium-rich part in the inner layer accompanying a nickel-rich part in the metal is formed along to the oxide/metal interface of -ray irradiated Type 304L SS, non-irradiated and -ray irradiated Type 316L SS.

Excitation effect of low energy electrons on high temperature oxidation of corrosion resistant alloys in low pressure oxygen and role of chromium

Ogawa, Hiroaki; Kiuchi, Kiyoshi

Hyomen Gijutsu, 58(9), p.543 - 549, 2007/09

https://doi.org/10.4139/sfj.58.543

The oxidation mechanism of nuclear system components accelerated under irradiation was basically examined using a micro-balance device installed an rf low energy plasma source. Six alloys with different Cr contents of Fe-Ni alloy, stainless steels, Ni base alloys and metallic Cr were used in the experiment. The difference in the oxidation behavior between the low energy plasma and thermal equilibrium in oxygen atmosphere of 20 Pa was evaluated at 873 K for 20 hours. The oxidation behavior was analyzed with the in-situ weight change and the surface analysis by X-ray photoelectron spectroscopy (XPS). On the thermal equilibrium, the weight gain is depressed with increasing Cr contents. On the other hand, the weigh loss was observed in the materials with high Cr contents in the low energy oxygen plasma with the high excitation condition. The oxidation behavior was analyzed with the mechanistic model, by considering the evaporation rate of volatile CrO on the surface and the migration rate of O into the substrate.