Engineering Aspects for Landfi lling Radioactively Contaminated Wastes Derived from the Fukushima DaiichiNuclear Power Plant Accident

摘要

Wastes contaminated with radiocesium released from the accident of the Fukushima Daiichi Nuclear Power Station are classified as low-concentration wastes with 8,000 Bq/kg or lower, and high-concentration wastes exceeding 8,000 Bq/kg. The former is called “specified municipal solid waste” or “specified industrial waste,” and the latter, “designated waste.” This paper introduces off-site management, such as landfilling; characteristics of these wastes; and the legal framework for their management. In their management, the key characteristics of these wastes are high leachability of radiocesium from incineration fly ash from specified municipal solid wastes, and low leachability from bottom ash and sewage sludge ash. The radiocesium leachability of cement-solidified designated waste decreases with increasing unconfined compression strength. The significant engineering aspects of landfilling are as follows: soil can inhibit migration of radiocesium in landfill sites, capping over a layer of the radioactively contaminated waste is an effective method of containing radiocesium in landfill sites, and no barrier layer should be installed beneath the waste layer to control migration of radiocesium. Installation of such a barrier would result in production of highly concentrated leachate.