Monitoring and control system for reactor control rod

The present invention enables diagnosis of control rod position detector during reactor operation and a manual operation of other control rods during decomposing inspection of control rod dries. Namely, when an operator removes a control cable of a direction selection control valve upon decomposing inspection operation of the control rod drives during periodical inspection, diagnosis function of the direction selection control valve is overriden by a diagnosis override designation device for every objective control rod. This releases interlock and enables manual operation for the control rods. Control rod withdrawal operation required for decomposing inspection for the control rod drives, and control rod insertion/withdrawal operation required for fuel exchange are enabled by the function. With such procedures, since operation can be performed simultaneously with the decomposing inspection for the control rod drives, the period for the periodical inspection can be shortened. In addition, since the diagnosis device for the control rod position detector is operated during reactor operation, even if the control rod position detector should fail, it can be specified rapidly. (I.S.)