Method of load following-up control operation for a BWR type reactor

Purpose: To eliminate complicated operation procedures under the operation control conditions imposed in view of the prevention for fuel rod injuries. Method: An envelope is prepared in the stationary operation before the start of the load following-up control operation (linear power density already experienced by the fuel rod) and an envelope is prepared in which the power for the lower part of the reactor core is sufficiently decreased relative to the above mentioned envelope by the insertion of control rods. Then, load following-up operation is started under the core flow rate control along a control rod pattern used for preparing the latter envelope, so that variations in the power distribution during the load following-up operation may be confined within a range of an envelope prepared by the synthesis of the former envelope and the latter envelope. (Sekiya, K.)