Establishing an evaluation method for the aging phenomenon by physical force in fuel debris

Suzuki, Seiya; Arai, Yoichi; Okamura, Nobuo; Watanabe, Masayuki

Journal of Nuclear Science and Technology, 60(7), p.839 - 848, 2023/07

https://doi.org/10.1080/00223131.2022.2159559

The fuel debris, consisting of nuclear fuel materials and reactor structural materials, generated in the accident of Fukushima Daiichi Nuclear Power Plant can become deteriorated like rocks under the changes of environmental temperature. Although the fuel debris have been cooled by water for 10 years, they are affected by seasonal and/or day-and-night temperature changes. Therefore, in evaluating the aging behavior of the fuel debris, it is essential to consider the changes in environmental temperature. Assuming that the fuel debris are deteriorated, radioactive substances that have recently undergone micronization could be eluted into the cooling water, and such condition may affect defueling methods. We focused on the effect of repeated changes in environmental temperature on the occurrence of cracks, and an accelerated test using simulated fuel debris was carried out. The length of the crack increases with increasing number of heat cycle; therefore, the fuel debris become brittle by stress caused by thermal expansion and contraction. In conclusion, it was confirmed that the mechanical deterioration of the fuel debris is similar to that of rocks or minerals, and it became possible to predict changes in the length of the crack in the simulated fuel debris and environmental model.

Evaluation of crack growth rates and microstructures near the crack tip of neutron-irradiated austenitic stainless steels in simulated BWR environment

Chimi, Yasuhiro; Kasahara, Shigeki; Seto, Hitoshi*; Kitsunai, Yuji*; Koshiishi, Masato*; Nishiyama, Yutaka

Proceedings of the 18th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, Vol.2, p.1039 - 1054, 2018/00

https://doi.org/10.1007/978-3-319-68454-3_76

In order to understand irradiation-assisted stress corrosion cracking (IASCC) growth behavior, crack growth rate (CGR) tests have been performed in simulated Boiling Water Reactor water conditions at 288C on neutron-irradiated 316L stainless steels (SSs) at 12-14 dpa. After the tests, the microstructures near the crack tip of the specimens are examined with scanning transmission electron microscope (FE-STEM). In comparison with a previous study at 2 dpa, this result shows a less benefit of low electrochemical corrosion potential (ECP) conditions on CGR. A crack tip immersed over 1000 hours was filled with oxides, while almost no oxide film was observed near the crack front in the low-ECP conditions. In addition, a high density of deformation twins and dislocations were found near the fracture surface of the crack front. It is considered that both localized deformation and oxidation are possible dominant factors for the SCC growth in highly irradiated SSs.

Bayesian nonparametric analysis of crack growth rates in irradiated austenitic stainless steels in simulated BWR environments

Chimi, Yasuhiro; Takamizawa, Hisashi; Kasahara, Shigeki*; Iwata, Keiko; Nishiyama, Yutaka

Nuclear Engineering and Design, 307, p.411 - 417, 2016/10

https://doi.org/10.1016/j.nucengdes.2016.07.015

To investigate influential parameters for irradiation-assisted stress corrosion cracking (IASCC) growth behavior, we attempt to analyze statistically existing data on the crack growth rate (CGR) in irradiated austenitic stainless steels (SSs) in boiling water reactor (BWR) environments using the Bayesian nonparametric (BNP) method. From the probability distribution of CGR and some input parameters, such as yield stress of irradiated material (), stress intensity factor (), electrochemical corrosion potential (ECP), and fast neutron fluence, the mean CGR is estimated and compared with the measured CGR. The analytical results show good reproducibility of the measured CGR. The results also indicate the possible neutron fluence effects on CGR in high CGR region (i.e., high neutron fluence condition) by radiation-induced segregation (RIS), localized deformation, and/or other mechanisms than radiation hardening.

Present status of in-pile IASCC growth tests at JMTR

Kaji, Yoshiyuki; Ugachi, Hirokazu; Nakano, Junichi*; Matsui, Yoshinori; Kawamata, Kazuo; Tsukada, Takashi; Nagata, Nobuaki*; Dozaki, Koji*; Takiguchi, Hideki*

HPR-364, Vol.1 (CD-ROM), 10 Pages, 2005/10

Irradiation assisted stress corrosion cracking (IASCC) is one of the critical concerns when stainless steel components have been in service in light water reactors (LWRs) for a long period. In the research field of IASCC, mainly PIEs for irradiated materials have been carried out, because there are many difficulties on SCC tests under neutron irradiation. Hence as a part of the key techniques for in-pile SCC tests, we have embarked on a development of the test technique to obtain information concerning effects of applied stress level, water chemistry, irradiation conditions, etc. In this paper, we describe the developed several techniques, especially control of loading on specimens, monitoring technique of crack propagation and so on, and the present status of in-pile IASCC growth tests using pre-irradiated materials at JMTR.

Effect of sensitizing heat treatment on fatigue crack growth properties at liquid helium temperature

*; *; O.Ivano*; Nunoya, Yoshihiko; Nakajima, Hideo; Tsuji, Hiroshi

Fatigue & Fracture of Engineering Materials & Structures, 18(6), p.671 - 678, 1995/00

https://doi.org/10.1111/j.1460-2695.1995.tb00891.x

no abstracts in English

Description of code system PLES/PTS for evaluation of pressure vessel integrity during PTS events

Hirano, Masashi; Kosaka, Atsuo

JAERI-M 92-006, 76 Pages, 1992/02

JAERI-M-92-006.pdf:1.53MB

no abstracts in English

Preparation of ThO sols having colloid-size distribution suitable for gelation into microspheres

; ; Shiba, Koreyuki

Journal of Nuclear Science and Technology, 21(7), p.528 - 537, 1984/00

https://doi.org/10.3327/jnst.21.528

no abstracts in English

Cyclic Crack Growth Typical Weld HAZ Microstructures of SA 533gr.B Steel in Simulated BWR Environment

; ; Shindo, Masami; ; ; ; ; ; *; *; et al.

JAERI-M 82-062, 23 Pages, 1982/06

JAERI-M-82-062.pdf:1.31MB

no abstracts in English

Fatigue behavior of pipes containing multiple flaws in inner surface

; ; ; ;

Nucl.Eng.Des., 74(2), p.199 - 213, 1982/00

https://doi.org/10.1016/0029-5493(83)90057-2

no abstracts in English

Creep Test of Type 304 Stainless Steel Cylindrical Tube Subjected to Internal Pressure

Ueda, Shuzo; ;

JAERI-M 9647, 22 Pages, 1981/08

JAERI-M-9647.pdf:0.77MB

no abstracts in English