Resolution of Generic Safety Issues: Issue 39: Potential for Unacceptable Interaction Between the CRD System and Non-Essential Control Air System (Rev. 1) ( NUREG-0933, Main Report with Supplements 1–34 )
This issue was identified in a 1980 AEOD memorandum107 and concerned the slow loss of control air pressure in the pneumatic control system of BWR scram systems. Air pressure loss at certain low rates can allow a sufficient discharge of water from the scram outlet valves to fill or almost fill the scram discharge header before a scram can be initiated and the rods inserted either by manual or automatic scram initiation. A full or almost full header would prevent scram of the control rods.
The safety concern of this issue was addressed in Issue 25, "Automatic Header Dump on BWR Scram System," which was resolved with requirements. Therefore, consideration of the impact of a license renewal period of 20 years was not necessary.1564