Containment Design and Study for the Fast Critical Assembly of JAERI

The Fast Critical Assembly of the Japan Atomic Energy Research Institute (FCA) at the Tokai site is used to obtain the reactor physics data as the first step of the fast breeder reactor development schedule in Japan. The containment of FCA must meet the Japanese site criteria for the hypothetical accident, which is assumed as the gross-meltdown and resulting critical power excursion. A nuclear energy of 1020 fissions and a chemical energy of 3 x 107 ca l resulting from the rapid metal-air reaction are estimated to be released at the hypothetical accident. The FCA containment consists of the primary containment to absorb the explosive energy equivalent to a TNT 100-kg explosion, and the secondary containment which withstands the internal static pressure of 1.6 kg/cm2 and is gas-tight, less than 2%/24 h at the design pressure. It is also equipped with the argon ejection system to extinguish the metal fire within the containment area at the accident. The primary containment is a reinforced concrete structure (14 m x 14 m x 13.5 m high and 1.1m thick), of which the strain energy is designed to be more than the impulsive energy caused by a TNT 100-kg explosion. Tests were performed with scaled models to obtain the data on the dynamic pressure and impulse distribution and the response of structures due to the TNT explosion. A reinforced concrete cylinder with a hemispherical cap (24 m diam., 21.4 m high and 40 cm thick, lined with 6-mm-thick steel plate) was selected as the secondary containment, as it was considered to be more advantageous than a steel vessel in economy, shielding, and also anti-missile protection. This paper describes the design philosophy of the FCA containment necessary to meet the given criteria and also the data of the model for anti-blast design. (author)