Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific program for fiscal year 2023)

Niwa, Masakazu; Shimada, Koji; Sueoka, Shigeru; Fujita, Natsuko; Yokoyama, Tatsunori; Ogita, Yasuhiro; Fukuda, Shoma; Nakajima, Toru; Kagami, Saya; Ogata, Manabu; et al.

JAEA-Review 2023-017, 27 Pages, 2023/10

JAEA-Review-2023-017.pdf:0.94MB

This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency (JAEA), in fiscal year 2023. The objectives and contents in fiscal year 2023 are described in detail based on the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. The plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques.

Measurement of angular dependent neutron production from thick target bombarded with 140-MeV protons

Iwamoto, Yosuke; Satoh, Daiki; Hagiwara, Masayuki*; Iwase, Hiroshi*; Kirihara, Yoichi*; Yashima, Hiroshi*; Nakane, Yoshihiro; Nakashima, Hiroshi; Nakamura, Takashi*; Tamii, Atsushi*; et al.

Nuclear Technology, 168(2), p.340 - 344, 2009/11

https://doi.org/10.13182/NT09-A9205

It is important to calculate neutron production from thick targets at forward angle near 0 degree and backward angle near 180 degree for the shielding design of proton accelerator facilities, and the accuracy should be determined by experimental data. There are, however, few experimental data near 0 degree, and no data near 180 degree in the energy region above 100 MeV. Neutron energy spectra at 0, 90 and 180 degrees produced from thick graphite and iron targets by 140 MeV protons were measured. It was found that the calculation with JENDL-HE was more suitable for the shielding design of proton accelerator facilities in the forward direction.

Supporting the surface charging mechanism of seismic-electromagnetic phenomena by the direct measurements of the electron and hole trapping centers

Tanaka, Kiriha*; Nagahama, Hiroyuki*; Muto, Jun*; Oka, Toshitaka; Yabe, Yasuo*

no journal, , 

The mechanisms of the seismic-electromagnetic phenomena attracted as precursors of short-term earthquake forecast have been suggested, however, it is still incompletely understood. Our results showed that the fracture by fault motions could produce the surface charges on the fault. It proves that the electromagnetic abnormalities by the fault motions may also be observed through the surface charging mechanism. Therefore, our study supports that the surface charging mechanism is plausible.

Effect of seismic fault slips at various depths on the E center in Quartz

Tanaka, Kiriha*; Muto, Jun*; Takahashi, Miki*; Jayawickrama, E.*; Sasaki, Osamu*; Oka, Toshitaka; Nagahama, Hiroyuki*

no journal, , 

A fault dating using electron spin resonance (ESR) is a developing direct method to estimate the age of the last fault movement. This method hypothesizes that natural radiation-induced ESR intensity, which is proportional to the concentration of charges trapped in defects accumulated in the interseismic period, is completely reset due to fracture, stress, and frictional heating by a seismic fault slip. The incomplete zeroing can result in age overestimation, hence, the understanding of its detailed conditions and mechanism is required. We have performed high-velocity friction experiments under various normal stresses to investigate the possibility for the signal zeroing by seismic fault slips at various depths. We infer that the degrees of grain fracture and frictional heating associated with the seismic fault slip originating from fault heterogeneity yield the complicated zeroing mechanism of the E center.

Potential for ESR signal zeroing of the E' center by experimental fault slips

Tanaka, Kiriha; Ohashi, Kiyokazu*; Muto, Jun*; Oka, Toshitaka

no journal, , 

Electron spin resonance (ESR) dating of a fault assumes that charge trapping centers in quartz in a fault material have been completely annihilated by the seismic fault slip (ESR signal zeroing). There is little understanding of the relationship between the signal zeroing and fault parameters. The previous high-velocity friction (HVF) experiments have implied that the E' center in quartz could be correlated with frictional power density and begin to decrease at a power density of 0.60.9 MW/m. However, the data was lacking to confirm the signal zeroing at higher power density. We performed HVF experiments for simulated quartz gouges with a slip rate of 1 m/s, a displacement of 10 m, and normal stresses of 1.02.5 MPa. ESR measurements were conducted for gouges before and after experiments. The peak-to-peak height of the E' center calibrated by that of the standard material was calculated as the ESR intensity (ESR intensity ratio) of the E' center. The ESR intensity ratio of the E' center decreased with increasing frictional power density of 0.961.4 MW/m. The maximum temperatures near the sliding surface were 260C at 0.96 MW/m, 600C at 1.0 MW/m, and 480C at 1.6 MW/m. The E' center is thermally unstable at 300C and more unstable at higher temperatures. Hence, the ESR intensity ratio might decrease due to larger frictional heating with increasing power density. Comparing our results with those in the previous study, the ESR intensity ratio clearly decreased with increasing power densities of 0.61.4 MW/m. HVF experiments mimic seismic fault slips of earthquakes with a moment magnitude of 89 at shallow depths of 100 m. Seismic fault slip of an earthquake at a depth of at least one hundred meters under the earth's surface can be required for ESR signal zeroing of the E' center.