Synchrotron radiation based XAFS analysis of the simulated nuclear waste glass samples prepared by bottom drain test in the full-scale mock-up melter (KMOC) (Contract research)

Okamoto, Yoshihiro; Nagai, Takayuki; Shiwaku, Hideaki; Kano, Shigeru; Himeno, Haruyuki*; Kobayashi, Hiroshi*; Nakatani, Mikio*

JAEA-Research 2018-013, 18 Pages, 2019/03

JAEA-Research-2018-013.pdf:1.98MB

The chemical state and local structure of some elements in the simulated nuclear waste glass samples (20 batches) prepared by bottom drain test in the full scale mock-up tests using KMOC melter were investigated by synchrotron radiation based X-ray absorption fine structure (XAFS) analysis. As a result of the analysis of cerium element, it was confirmed that the oxidation proceeds gently as the batch advanced. For manganese, iron, and zinc, there was almost no difference between batches, which seemed to be stabilized by getting into the frame structure of the borosilicate glass. There were no elements that seemed to be clearly crystalline except for platinum group elements. Remarkable precipitation was hardly observed in zirconium and molybdenum with the imaging analysis.

Contribution to upgrade of vitrification technology by synchrotron radiation analysis; From Chemical state analysis of waste glass to development of structural analysis to prove soundness

Okamoto, Yoshihiro; Nagai, Takayuki; Shiwaku, Hideaki

Yoyuen Oyobi Koon Kogaku, 62(1), p.11 - 17, 2019/01

The vitrified radioactive waste is a multicomponent material containing many kinds of elements. Synchrotron radiation XAFS with element selectivity is suitable for analysis of elements in the waste. From the XAFS analysis, the chemical state and the local structure of each element were clarified. Imaging XAFS technique was used as an analysis based on element distribution in the glass. The imaging XAFS is effective for analysis of elements that are less soluble in the glass like molybdenum and platinum group elements. It was clarified from the simultaneous imaging XAFS analyses of multiple elements that the chemical form of rhodium is strongly dominated by the distribution correlation with ruthenium. We proposed multi - scale structural analyses with wide angle scattering, PDF analysis, small angle scattering in order to evaluate the soundness of the vitrified waste.

Utilization of the knowledge of excavated archaeological artifacts for research and development of geological disposal

Mitsui, Seiichiro

Maizo Bunkazai Nyusu, (171), p.10 - 17, 2018/03

As part of research and development of geological disposal, "natural analogues" have been applied to validate concept of models and evaluation methodologies for performance assessment. By introducing domestic and overseas research results on natural analogues, this paper presents how we have utilized knowledge of excavated archaeological artifacts for geological disposal studies.

Local structure analysis of light elements included in simulated radioactive waste glasses by soft X-ray absorption fine structure

Okamoto, Yoshihiro; Nagai, Takayuki; Kaneko, Koji; Motokawa, Ryuhei; Haga, Yoshinori; Yamanaka, Keisuke*; Ota, Toshiaki*

2017-Nendo Seika Kokaigata Riyo Seika Hokokusho (Ritsumeikan Daigaku SR Senta), p.33 - 36, 2018/00

The high-level radioactive waste solution which generated from a spent nuclear fuel reprocessing process are mixed with a borosilicate glass frit in a vitrification process, and a chemical stable glass solidified body is produced. To understand local structure of light elements included in a glass solidified body, we carried out a B K-edge XANES measurement of raw glass frits and simulated radioactive waste glasses. As a result of this estimation of boron local structure in glass samples, it was found that the sp type boron (BO) percentage increases and the sp type (BO) percentage by increasing the sodium content in glass frits.

Vitrification technology for radioactive wastes

Amamoto, Ippei

Journal of the Society of Inorganic Materials, Japan, 24(391), p.393 - 401, 2017/11

Glass is a non-crystalline solid, as such, it is relatively easy to change its composition to control its characteristics. The borosilicate glass, which is produced by the addition of boron oxide into sodium-lime glass, possesses excellent heat-resistant properties and mechanical strength. It has a wide variety of uses. The borosilicate glass is applied as the vitrified medium for radioactive wastes to immobilize and stabilize them for long term. The glass form which is loaded with high-level radioactive waste is called the vitrified waste. This paper classified the radioactive waste and describes treatment and production methods of vitrified waste, its characteristics, disposal method and also introduces alternative vitrified medium.

REDOX state analysis of platinoid elements in simulated high-level radioactive waste glass by synchrotron radiation based EXAFS

Okamoto, Yoshihiro; Shiwaku, Hideaki; Nakada, Masami; Komamine, Satoshi*; Ochi, Eiji*; Akabori, Mitsuo

Journal of Nuclear Materials, 471, p.110 - 115, 2016/02

https://doi.org/10.1016/j.jnucmat.2016.01.008

Extended X-ray Absorption Fine Structure (EXAFS) analyses were performed to evaluate REDOX (REDuction and OXidation) state of platinoid elements in simulated high-level nuclear waste glass samples prepared under different conditions of temperature and atmosphere. At first, EXAFS functions were compared with those of standard materials such as RuO. Then structural parameters were obtained from a curve fitting analysis. In addition, a fitting analysis used a linear combination of the two standard EXAFS functions of a given elements metal and oxide was applied to determine ratio of metal/oxide in the simulated glass. The redox state of Ru was successfully evaluated from the linear combination fitting results of EXAFS functions. The ratio of metal increased at more reducing atmosphere and at higher temperatures. Chemical form of rhodium oxide in the simulated glass samples was RhO unlike expected RhO. It can be estimated rhodium behaves according with ruthenium when the chemical form is oxide.

Development of performance assessment models for glass dissolution

Goto, Takahiro*; Mitsui, Seiichiro; Takase, Hiroyasu*; Kurosawa, Susumu*; Inagaki, Manabu*; Shibata, Masahiro; Ishiguro, Katsuhiko*

MRS Advances (Internet), 1(63-64), p.4239 - 4245, 2016/00

https://doi.org/10.1557/adv.2017.215

NUMO and JAEA have conducted a joint research since FY2011, which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation stage for deep geological disposal of radioactive waste. As a part of this joint research, we have been developing glass dissolution models which consider various processes in EBS, such as precipitation of Fe-silicates associated with iron overpack corrosion, and Si transport through corrosion products in the cracked overpack. The objectives of the modeling work are to evaluate relative importance of relevant processes and to identify further R&D issues towards development of a convincing safety case. Sensitivity analyses suggested that predicted glass dissolution time ranges from 110 to 110 years or more due to uncertainties in the current understanding of the key processes, namely precipitation of Fe-silicates and transport characteristics of the altered glass layer.

Chemical stability of solidified products made from incombustible wastes by plasma melting

Kameo, Yutaka; Haraga, Tomoko; Nakashio, Nobuyuki; Hoshi, Akiko; Nakashima, Mikio

Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(4), p.354 - 362, 2004/12

https://doi.org/10.3327/taesj2002.3.354

In order to investigate chemical stability of solidified products made from Low Level Radioactive Wastes (LLW) by plasma melting, a leaching test based on the MCC (Material Characterization Center)-3S Agitated Powder Leach Test Method was performed to determine Normalized Elemental Mass Loss (NL) of both main components (Na, Al, Si, Ca, and Fe) of the solidified product and radioactive tracers (Co, Cs, and Eu) incorporated into it. The results of leaching test indicated that NLi value was greatly affected by basicity defined as weight ratio of CaO to SiO in the solidified product, while effect of FeO concentration on NL value was small. In the case of basicity less than 0.8, logarithm of NL linearly increased with the basicity, implying that NL value can be estimated by chemical composition of the solidified products.

Plasma melting treatment of low level radioactive waste

Nakashio, Nobuyuki; Nakashima, Mikio

Dekomisshoningu Giho, (26), p.45 - 55, 2002/11

http://www.randec.or.jp/publish/documents/gihou/Decommissioning%20gihou_26.pdf

Melting treatment of low-level radioactive wastes (LLW) is considered to be a promising technology for the preparation of a stable solid that will be disposed of in near surface repositories. This is because of large reduction of waste volume and production of a stable homogeneous solidified product. In the Japan Atomic Energy Research Institute (JAERI), the construction of the Waste Volume Reduction Facilities (WVRF) has been in progress since 1999. In advance of operation of the WVRF, we have been conducting melting tests of non-metallic solid wastes with the aim of establishing the optimum melting condition for preparation of a stable solid that is suitable for disposal. We have reviewed a part of the melting test conducted in our program.

Evaluation of operatinal condition in LWTF; Tests using technical scale equipment

; Murata, Eiichi*; Sawahata, Yoshikazu*; Saito, Akira*

JNC TN8430 2001-002, 43 Pages, 2001/02

JNC-TN8430-2001-002.pdf:1.98MB

Japan Nuclear Cycle Development Institute (JNC) is designing the Low level radioactive Waste Treatment Facility (LWTF) in the Tokai Reprocessing Plant (TRP). The low level liquid waste generated the TRP is separated salt (NaNO, etc) and radionuclide in liquid treatment process of LWTF. The process can get higher volume reduction than previous bituminization. Based on the engineering tests equal to the liquid treatment process of LWTF, the validity of operational condition in LWTF is evaluated. As the results, it is confirmed that all operational condition in the processes which is Iodine immobilization, Pre-filter filtration, Pre-treatment, Coprecipitation and Ultrafiltration are available.