Thirty-year prediction of Cs supply from rivers to coastal waters off Fukushima considering human activities

Ikenoue, Tsubasa; Shimadera, Hikari*; Nakanishi, Takahiro; Kondo, Akira*

Water (Internet), 15(15), p.2734_1 - 2734_18, 2023/08

https://doi.org/10.3390/w15152734

The Fukushima Daiichi Nuclear Power Plant accident caused an accumulation of Cs in coastal sediment. The Cs supply from rivers to the ocean can affect the long-term fate of Cs in coastal sediment. Since the Fukushima coastal river basins include large decontaminated and evacuation order areas, considering the decontamination work and resumption of agriculture is important for predicting the Cs supply. We conducted a 30-year prediction of the Cs supply from the Fukushima coastal rivers to the ocean using a distributed radiocesium prediction model, considering the effects of human activities. In river basins with decontaminated and evacuation order areas, human activities reduced the total Cs outflow from agricultural lands, urban lands, and forest areas to the rivers and the Cs supply to the ocean by 5.0% and 6.0%, respectively. These results indicated that human activities slightly impacted the Cs outflow and supply. The Cs supply from rivers impacted by the accident to the coastal sediment was estimated to correspond to 11-36% of the total Cs in the coastal sediment in the early phase of the accident. Therefore, the Cs supply from rivers to the ocean is important for the long-term behavior of Cs in coastal sediment.

Insights into boron removal from water using Mg-Al-LDH; Reaction parameters optimization & 3D-RSM modeling

Eljamal, O.*; Maamoun, I.; Alkhudhayri, S.*; Eljamal, R.*; Falyouna, O.*; Tanaka, Kazuya; Kozai, Naofumi; Sugihara, Yuji*

Journal of Water Process Engineering (Internet), 46, p.102608_1 - 102608_13, 2022/04

https://doi.org/10.1016/j.jwpe.2022.102608

Empirical equations of crack growth rates based on data fitting of neutron irradiated stainless steel under high temperature water simulating boiling water reactor core conditions

Kasahara, Shigeki; Chimi, Yasuhiro; Hata, Kuniki; Fukuya, Koji*; Fujii, Katsuhiko*

Proceedings of 19th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors (Internet), p.1345 - 1355, 2019/08

This paper describes empirical equation development of crack growth rates (CGR) in consideration of IASCC of neutron irradiated stainless steel to contribute to structural integrity assessment of BWR reactor internals. Empirical equations of CGR (da/dt) were developed based on a formula of da/dt = MK, assuming that "M" and "n" tend to be saturated with increasing neutron fluence. To obtain the empirical equations for normal water chemistry (NWC) and hydrogen water chemistry (HWC) of BWR, a data fitting with least square method was applied to the datasets consisting of F, K and CGR from post irradiation examinations of neutron irradiated stainless steel under simulated NWC and HWC conditions from open literature. As a result, calculated results by the equation for NWC showed good agreement with measured CGR data, meanwhile those for HWC did not. The above difference was seemed to be attributed that CGR data obtained under HWC conditions were scattered extensively.

Influence of Zn injection on PWSCC crack growth rates and oxide film properties of Alloy 600

Chimi, Yasuhiro; Sato, Kenji*; Kasahara, Shigeki; Umehara, Ryuji*; Hanawa, Satoshi

Proceedings of Contribution of Materials Investigations and Operating Experience to Light Water NPPs' Safety, Performance and Reliability (FONTEVRAUD-9) (Internet), 10 Pages, 2018/09

To investigate the influence of Zinc (Zn) injection on primary water stress corrosion cracking (PWSCC) growth behavior, crack growth tests of 10% cold-worked Alloy 600 were performed in simulated primary water environment of pressurized water reactor (PWR) at 320C with a low-concentration (5-10 ppb) Zn injection under dissolved hydrogen (DH) conditions of 5, 30, and 50 cc/kgHO. As a result of the crack growth tests, DH-dependence of crack growth rate (CGR) showed a similar tendency to the predicted CGR based on the CGR data without Zn injection, indicating almost no effect of a low-concentration Zn injection on the crack growth behavior. Moreover, the microstructural analyses of oxide films formed inside the crack and on the specimen surface were conducted, and the intake of Zn in the oxides was detected on the specimen surface, but not detected inside the crack. This result was considered to be the cause of no Zn injection effect on the crack growth behavior.

An Integrated simulation system of meteorological and hydrological models for predicting dam water availability

Oba, Ryoji*; Bushnak, A.*; Kojiri, Toshiharu*; Matsuura, Tomonori*; Nagai, Haruyasu

Proceedings of the 3rd International Conference on Water Resources and Arid Environments 2008 and the 1st Arab Water Forum (Internet), 12 Pages, 2008/11

no abstracts in English

Isotope hydrograph separation for modeling of runoff mechanisms of atmospherically derived chemical and radioactive pollutants

Matsunaga, Takeshi; Yanase, Nobuyuki; Hanzawa, Yukiko; Tsuzuki, Katsunori; Naganawa, Hirochika

Journal of Water and Environment Technology (Internet), 3(2), p.243 - 252, 2005/00

https://doi.org/10.2965/jwet.2005.243

In a tributary watershed of the Kuji River of Japan, the hydrological components of runoff associated with a rain storm event were investigated using isotope tracers of hydrogen (H) and oxygen (O) in precipitations and stream water. The runoff was separated into either "old water" (pre-existing in the ground before the storm) and "new water"(from the storm precipitation). It was found that the discharge of several hazardous trace elements (Sb, Cu, Cr) was largely (24-54%) attributable to that of the new water in spite of its small contribution to the total water discharge. These investigations suggest that the new water may play an important role in the migration of atmospherically derived, hazardous trace elements to streams during rain storms.