Power control systems and limiters in pressurized and boiling water reactors

Different plant control concepts have evolved for boiling water and pressurized water reactors as a consequence of the different inherent plant characteristics of the two lines. One essential precondition of the correct functioning of a control concept and the prevention, through its action, of inadmissible core conditions due to failures outside the control system is a core protection system ensuring that no actuation of a control element will give rise to unduly high power densities in the core. The core protection system consists of limiting functions designed with fourfold redundancy, which will be activated only in situations involving major malfunctions and will not affect the normal operation of a plant. (orig.)