Basic concept for construction of final disposal sites for incineration fly ashes contaminated with radioactive Cs (over 100,000 Bq/kg)

The incineration fly ashes made from combustible waste contaminated with radioactive Cs derived from the accident at the Fukushima Daiichi Nuclear Power Station contain radioactive Cs as well as stable Cs contained mostly as soluble salts, in addition to about 30% of salts (CaCl₂, NaCl, KCl). This study summarizes the basic concept for multiple defenses that take into account the characteristics of the objects to be disposed of, which is necessary in face of construction of a final disposal site made of reinforced concrete for incineration fly ashes contaminated with over 100,000 Bq/kg of radioactivity. The durability of concrete should be taken into consideration when selecting a candidate site and designing the structure. Comprehensive measures should be applied based on the latest technologies that take into account management during both normal times and severe accident times, service life, required performance during earthquakes, cracking (temperature stress and drying), and acceleration of ASR, salt damage, salt deterioration due to saturated salts. (A.O.)