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

https://doi.org/10.1016/j.jnucmat.2004.08.032

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. 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.

Structual design study of a proton beam window for a 1-MW spallation neutron source

Teraoku, Takuji*; Terada, Atsuhiko*; Maekawa, Fujio; Meigo, Shinichiro; Kaminaga, Masanori; Ishikura, Shuichi*; Hino, Ryutaro

JAERI-Tech 2003-026, 77 Pages, 2003/03

JAERI-Tech-2003-026.pdf:19.78MB

A 1-MW spallation neutron source aiming at materials and life science researches will be constructed under the JAERI-KEK Proton Accelerator Project(J-PARC). The proton beam window functions as a boundary wall between a high vacuum area and a helium atmosphere and it is cooled by light water because high heat-density is generated in the window material by interactions with the proton beam. Then, uniformity of the water flow is requested at the window to suppress a hot-spot that causes excessive thermal stress and cooling water boiling. Also, the window has to be strong enough in its structure for inner stress due to water pressure and thermal stress due to heat generation. In this report, we propose two types of proton beam windows, flat-type and curved-type. We evaluated the strength of structure and thermal hydraulic analysis. As a result, it was found that sufficient heat removal was assured with uniform water flow at the window, and the stress could be maintained below allowable stress values. Accordingly, it was confirmed that the proton beam window designs were feasible.