Current status of the high intensity pulsed spallation neutron source at J-PARC

Takada, Hiroshi

Plasma and Fusion Research (Internet), 13(Sp.1), p.2505013_1 - 2505013_8, 2018/03

http://www.jspf.or.jp/PFR/PFR_articles/pfr2018/pfr2018_13-2505013.html

The pulsed spallation neutron source of Japan Proton Accelerator Research Complex (J-PARC) has been supplying users with high intensity and sharp pulse cold neutrons using the moderators with following distinctive features; (1) 100% para-hydrogen for increasing pulse peak intensity with decreasing pulse tail, (2) cylindrical shape with 14 cm diam.12 cm long for providing high intensity neutrons to wide neutron extraction angles of 50.8, (3) neutron absorber made from Ag-In-Cd alloy to make pulse width narrower and pulse tails lower. Actually, it was measured at a low power operation that high neutron intensity of 4.510 n/cm/s/sr could be emitted from the coupled moderator surface for 1-MW operation, and a superior resolution of d/d = 0.035% was achieved at a beamline (BL8) with a poisoned moderator, where d is the d-spacing of reflection. Towards the goal to achieve the target operation at 1-MW for 5000 h in a year, technical developments to mitigate cavitation damages on the target vessel with injecting gas micro-bubbles into mercury target and design improvement of target vessel structure to reducing welds and bolt connections as much as possible are under way.

Surface modifications of hydrogen storage alloy by heavy ion beams with keV to MeV irradiation energies

Abe, Hiroshi; Tokuhira, Shinnosuke*; Uchida, Hirohisa*; Oshima, Takeshi

Nuclear Instruments and Methods in Physics Research B, 365(Part A), p.214 - 217, 2015/12

no abstracts in English

Development of aluminum (Al5083)-clad ternary Ag-In-Cd alloy for JSNS decoupled moderator

Teshigawara, Makoto; Harada, Masahide; Saito, Shigeru; Oikawa, Kenichi; Maekawa, Fujio; Futakawa, Masatoshi; Kikuchi, Kenji; Kato, Takashi; Ikeda, Yujiro; Naoe, Takashi*; et al.

Journal of Nuclear Materials, 356(1-3), p.300 - 307, 2006/09

https://doi.org/10.1016/j.jnucmat.2006.05.017

We adopted silver-indium-cadmium (Ag-In-Cd) alloy as a material of decoupler for decoupled moderator in JSNS. However, from the heat removal and corrosion protection points of view, the Ag-In-Cd alloy is needed to clad between Al alloys (Al5083). We attempted to obtain good bonding conditions for between Al5083 and ternary Ag-In-Cd alloys by HIPing tests. The good HIP condition was found for small test piece (20mm). Though a hardened layer due to the formation of AlAg was found in the bonding layer, the rupture strength of the bonding layer was more than 20 MPa, which was the calculated design stress. Bonding tests of a large size piece (20020030 mm), which simulated the real scale, were also performed according to the results of small size tests. The result also gave good bonding and enough required-mechanical-strength, however the rupture strength of the large size test was smaller than that of small one.

Cladding technique for development of Ag-In-Cd decoupler

Teshigawara, Makoto; Harada, Masahide; Saito, Shigeru; Kikuchi, Kenji; Kogawa, Hiroyuki; Ikeda, Yujiro; Kawai, Masayoshi*; Kurishita, Hiroaki*; Konashi, Kenji*

Journal of Nuclear Materials, 343(1-3), p.154 - 162, 2005/08

https://doi.org/10.1016/j.jnucmat.2004.08.036

For decoupled and poisoned moderator, a thermal neutron absorber, i.e., decoupler, is located around the moderator to give neutron beam with a short decay time. A B4C decoupler is already utilized, however, it is difficult to use in a MW class source because of He void swelling and local heating by (n,a) reaction. Therefore, a Ag-In-Cd (AIC) alloy which gives energy-dependence of macroscopic neutron cross section like that of BC was chosen. However, from heat removal and corrosion protection points of view, AIC is needed to bond between an Al alloy (A6061-T6), which is the structural material of a moderator. An AIC plate is divided into a Ag-In (15wt%) and Ag-Cd (35wt%) plate to extend the life time, shorten by burn up of Cd. We performed bonding tests by HIP (Hot Isostatic Pressing). We found out that a better HIP condition was holding at 803 K, 100 MPa for 1 h for small test pieces (f20mm). Though a hardened layer is found in the bonding layer, the rupture strength of the bonding layer is more than 20 MPa, which is less than that of the design stress.

Characterization of rust layer formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich environment by Cl and Fe K-edge XANES measurements

Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro

Materials Transactions, 46(2), p.329 - 336, 2005/02

https://doi.org/10.2320/matertrans.46.329

Chloride in atmosphere considerably reduces the corrosion resistance of conventional weathering steel containing a small amount of Cr. Ni is an effective anticorrosive element for improving the corrosion resistance of steel in a Cl-rich environment. In order to clarify the structure of the protective rust layer of weathering steel, Cl and Fe K-edge X-ray absorption near edge structure (XANES) spectra of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich atmosphere were measured. The Fe K-XANES measurements enable the characterization of a mixture of iron oxides such as rust. The chemical composition of the rust was determined by performing pattern fitting of the measured spectra. All the rust is composed mainly of goethite, akaganite, lepidocrocite and magnetite. Among these iron oxides, akaganite in particular is the major component in the rust. Additionally, the amount of akaganite in the rust of Fe-Ni alloy is much greater than that in rust of Fe-Cr alloy. Akaganite is generally considered to facilitate the corrosion of steel, but our results indicate that akaganite in the rust of Fe-Ni alloy is quantitatively different from that in rust of Fe-Cr alloy and does not facilitate the corrosion of steel. The shoulder peak observed in Cl K-XANES spectra reveals that the rust contains a chloride other than akaganite. The energy of the shoulder peak does not correspond to that of any well-known chlorides. In the measured spectra, there is no proof that Cl, by combining with the alloying element, inhibits the alloying element from acting in corrosion resistance. The shoulder peak appears only when the content of the alloying element is lower than a certain value. This suggests that the generation of the unidentified chloride is related to the corrosion rate of steel.

Hardening of Fe-Cu model alloys induced by electron irradiation and neutron irradiation

Tobita, Toru; Aizawa, Kazuya; Suzuki, Masahide; Iwase, Akihiro*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(4), p.331 - 339, 2004/12

https://doi.org/10.3327/taesj2002.3.331

Nevertheless, there is a possibility that -ray induces embrittlement more efficiently than fast neutron, the irradiation effect of -ray has not been fully clarified. Comparative experiments on irradiation hardening by 2.5MeV electron irradiation for the purpose of -ray irradiation and neutron irradiation were performed to the Fe-Cu model alloys. We obtained the dose dependence and the temperature dependence on irradiation induced hardening. The growth of Cu clusters with increase in irradiation dose was confirmed by the small angle neutron scattering measurements. Although the differences in hardening between electron and neutron irradiations were very small on a displacement-per-atom (dpa) basis, the electron irradiation hardening initiated slightly earlier than the neutron. The growth of Cu clusters with increase in irradiation dose was the principal cause of hardening. The present results suggested that, from an engineering point of view, both the -ray induced and neutron induced hardening can be well scaled by using dpa.

Microstructural development and radiation hardening of neutron irradiated Mo-Re alloys

Nemoto, Yoshiyuki; Hasegawa, Akira*; Sato, Manabu*; Abe, Katsunori*; Hiraoka, Yutaka*

Journal of Nuclear Materials, 324(1), p.62 - 70, 2004/01

https://doi.org/10.1016/j.jnucmat.2003.09.007

In this study, stress-relieved specimens and recrystallized specimens of pure Mo and Mo-Re alloys (Re content=2,4,5,10,13 and 41wt%) were neutron irradiated up to 20dpa at various temperatures (681-1072K). On microstructure observation, sigma phase and chi phase precipitates were observed in all irradiated Mo-Re alloys. Voids were observed in all irradiated specimen, and dislocation loops and dislocations were observed in the specimens that were irradiated at lower temperatures. On Vickers hardness testing, all of the irradiated specimens showed hardening. Especially Mo-41Re were drastically embrittled after irradiation at 874K or less. From these results, authors discuss about relation between microstructure development and radiation hardening, embrittlement, and propose the most efficient Re content and thermal treatment for Mo-Re alloys to be used under irradiation condition.

Hardening of Fe-Cu alloys by swift heavy ion irradiation

Iwase, Akihiro; Hasegawa, Tadayuki*; Chimi, Yasuhiro; Tobita, Toru; Ishikawa, Norito; Suzuki, Masahide; Kambara, Tadashi*; Ishino, Shiori*

Nuclear Instruments and Methods in Physics Research B, 195(3-4), p.309 - 314, 2002/10

https://doi.org/10.1016/S0168-583X(02)01131-X

no abstracts in English

Report of Joint Research Committee for Fusion Reactor and Materials; July 16, 2001, Tokyo, Japan

Research Committee for Fusion Reactor; Research Committee for Fusion Materials

JAERI-Review 2002-008, 79 Pages, 2002/03

JAERI-Review-2002-008.pdf:9.92MB

Joint research committee for fusion reactor and materials was held in Tokyo on July 16, 2001. In the committee, a review of the development programs and the present status on the blanket technology, materials and IFMIF(International Fusion Materials Irradiation Facility) in JAERI and Japanese Universities was reported, and the direction of these R&D was discussed. Moreover, the progress of the collaboration between JAERI and Japanese Universities was discussed. This report consists of the summaries of the presentations and the viewgraphs which were used at the committee.

Orbital angular momentum and interpretation of core-absorption magnetic circular dichroism on the band picture in Co-based Heusler alloys CoSn (=Ti, Zr, and Nb)

Yamasaki, Atsushi*; Imada, Shin*; Arai, Ryuji*; Utsunomiya, Hiroshi*; Suga, Shigemasa*; Muro, Takayuki*; Saito, Yuji; Kanomata, Takeshi*; Ishida, Shoji*

Physical Review B, 65(10), p.104410_1 - 104410_6, 2002/03

https://doi.org/10.1103/PhysRevB.65.104410

The magnetic circular dichroism (MCD) of core-level absorption [x-ray absorption spectroscopy (XAS)] spectra in the soft x-ray region has been measured for the ferromagnetic Heusler alloys CoTiSn, CoZrSn, and CoNbSn. The many-peak structures which are clearly observed in the Co 2p-3d XAS-MCD spectra cannot be well explained by atomic multiplet calculations but are better explained by the Co 3d unoccupied states predicted by linear muffin-tin orbital atomic sphere approximation band structure calculations. The MCD spectra show an obvious contribution of the orbital angular momentum component to the magnetic moment in these alloys. The ratio between the orbital angular momentum and spin derived from the MCD spectra varies by more than a factor of 2 within these alloys. The mechanism of this variation is discussed in comparison with the band structure calculations.