PURPOSE: To display the number completion state allowing automatic insertion when the sequence number is unknown by providing sequence counter virtual position calculating/actual position extracting circuits and control rod operation detecting/judging means.

CONSTITUTION: A sequence counter virtual position calculating circuit 22 outputs the operation quantity of a control rod corresponding to the sequence number as the virtual control rod position signal. A sequence counter actual position extracting circuit 21 extracts and outputs the control rod position signal corresponding to the sequence number. The virtual control rod position signal and the control rod position signal are compared 23 in sequence for each sequence number of a sequence counter, and the operation completion state of the control rod corresponding to the sequence number of the sequence counter is detected 24, 25. The propriety of the control rod operation is judged 26 according to the planed execution sequence number based on this detection. If adequate, the execution sequence number is initially set 20 for the sequence number. The judged result and completion state are outputted 20 to the outside.