Iodine immobilization: Development of solidification process for spent silver-sorbent using hot isostatic press technique. (September 2016)

• Record Type: Journal Article
• Authors: Masuda, Kaoru; Kato, Osamu; Tanaka, Yoshiaki; Nakajima, Shingo; Okamoto, Shinya; Sakuragi, Tomofumi; Yoshida, Satoshi
• Is Part Of: Progress in nuclear energy. Volume 92(2016:Sep.)
• Page Start: 267
• Page End: 272
• Publication Date: 2016-09
• Subjects: Iodine -- Immobilization -- HIP (hot isostatic press) -- Process development -- Alumina -- Silver iodide; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 333.7924
• DOI: 10.1016/j.pnucene.2015.09.012
• Languages: English
• ISSNs: 0149-1970

Abstract

Abstract: The iodine filters which are used after nuclear fuel reprocessing contain radioactive iodine ( 129 I), almost all of which exists as silver iodide (AgI) adsorbed by the silver doped alumina base sorbents. In this work solidification of iodine contaminated silver-sorbent within alumina matrix is studied using a hot isostatic press (HIP). The product is treated to form a dense solidified material, where 129 I is physically confined in the form of AgI in the alumina based composite. This paper deals with the development of the production process. Silver-sorbents loaded with inactive iodine (I2 ) were prepared for HIP treatments. Although several types of alumina are originally present in the alumina based materials, they were found to be transformed to corundum after the HIP treatment. Optimization of the HIP process conditions was carried out. The effects of the major parameters on the process were investigated. Scanning electron microscope observations (SEM) confirmed that iodine was confined as AgI in the alumina matrix after the HIP treatments. A certain number of voids (void ratio: 10–15%) coexisted. Reduction of voids was further investigated and it was established that high temperature and vacuum pretreatment of iodine loaded silver-sorbents before the HIP treatment could significantly reduce void ratios to less than 5% in the solidified bodies. A simulation program for the HIP was developed to predict the size and relative density of the scale-up solidified body. Highlights: We developed solidification process of iodine using the HIP. Solidified body can be produced directly from silver-sorbent containing iodine. SEM and XRD showed that iodine was confined in alumina matrix as AgI. Simulation program of HIP process was developed and verified by experimental results.