Characterization and storage of radioactive zeolite waste

Abstract

For the safe storage of zeolite wastes generated by the treatment of radioactive saline water at the Fukushima Daiichi Nuclear Power Station, this study investigated the fundamental properties of herschelite adsorbent and evaluated its adsorption vessel for hydrogen production and corrosion. The hydrogen produced by the herschelite sample is oxidized by radicals as it diffuses to the water surface and thus depends on the sample's water level and dissolved species. The hydrogen production rate of herschelite submerged in seawater or pure water may be evaluated by accounting for the water depth. From the obtained fundamental properties, the hydrogen concentration of a reference vessel (decay heat = 504 W) with or without residual pure water was evaluated by thermal-hydraulic analysis. The maximum hydrogen concentration was below the lower explosive limit (4%). The steady-state corrosion potential of a stainless steel 316L increased with the absorbed dose rate, but the increase was repressed in the presence of herschelite. The temperature and absorbed dose at the bottom of the 504 W vessel were determined as 60• C and 750 Gy/h, respectively. Under these conditions, localized corrosion of a herschelite-contacted 316L vessel would not immediately occur at Cl − concentrations of 20,000 ppm.

Defect Sites in Zeolites: Origin and Healing

“…They are used as catalysts in gas exhaust systems, as sorbents in gas separation, as water softeners in solid detergents, remediation of municipal water, capturing radioactive nuclides, etc. [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ] The zeolite applications stem from their unique properties (shape‐selectivity, ion‐exchange capability, acidity/basicity, hydrophobicity/hydrophilicity, adsorption capacity) that are governed by their crystal structure (framework type) and chemical composition. [ 10 ] Further, the size and morphology of the zeolite crystals substantially affect their performance in these applications.…”

Recent activities in the field of nuclear waste management

“…Based on the experimental results and computer simulations, 99.9% of radioactive cesium removal was achieved in the first three months after the accident [4]. For the safe storage of zeolite wastes generated by the Cs removal activity, fundamental properties of the zeolite adsorbent used in Fukushima Daiichi Nuclear Power Station were studied [5]. Furthermore, hydrogen production and corrosion of the spent zeolite vessels were investigated in the same paper.…”

Thermal treatment of Cs-exchanged chabazite by hot isostatic pressing to support decommissioning of Fukushima Daiichi Nuclear Power Plant

“…Spent ion exchange materials pose a particular challenge, due to: potential dispersal in the event of a loss of containment, as a result of their granular nature; very high dose rates and radiogenic heating, as a result of their selectivity for short-lived radionuclides (e.g. 90 Sr, 137 Cs); and production of hydrogen from the radiolysis of entrained water, which poses a potential explosion risk [8]. Since spent ion exchange materials are generated not only at Fukushima, but also at other nuclear licenced sites as described above, there is a clear need to develop suitable conditioning routes to minimise the risk associated with these highly radioactive and dispersible materials, whilst producing passively safe waste packages of minimal volume, to reduce storage and disposal costs.…”