Study on the sodium specific radioactivity in the second loop of pool-type sodium-cooled fast reactor

In pool-type sodium-cooled fast reactor,specific radioactivity of the secondary sodium, which is decided by the reactor block, has very important impact on radiation dose and subarea in relevant sodium rooms, environmental effect of the secondary sodium leakage and workers for maintenance. In the paper, the design and analysis method of specific radioactivity of secondary sodium was found out through studying the relations between the reactor block and the secondary loop in China Experimental Fast Reactor (CEFR). It was concluded that the upper limit of the specific radioactivity of the secondary loop was decided by the dose in the cold trap room, and the limit of specific radioactivity derived from irradiation damage of vessel's material and accident of secondary sodium leakage is highly larger than the upper limit, by right of which the design value of the specific radioactivity of the secondary loop in China Demonstration Fast Reactor (CDFR) can be determined. And the design value can be achieved through the shielding of reactor block. (authors)