Resolution of Generic Safety Issues: Item A-25: Non-Safety Loads on Class 1E Power Sources ( NUREG-0933, Main Report with Supplements 1–34 )
The Class 1E power sources provide the electric power for the plant systems that are essential to reactor shutdown, containment isolation, reactor core cooling, containment heat removal or are otherwise essential in preventing significant release of radioactive material to the environment. This NUREG-03712 item addresses the issue of whether or not non-safety loads should also be allowed to share these sources.
If non-safety loads are allowed to be connected to the Class 1E power system, it is possible that they may cause degradation by introducing loss of redundancy or other failure mechanisms.
Possible solutions include prohibiting the connection of non-safety loads or requiring special precautions for cases where a nonsafety load is connected to the 1E source.
This issue has been addressed by Revision 2 to Regulatory Guide 1.75144 which was issued in September 1978 and includes special requirements for connection of non-safety loads to a Class 1E source. As an alternate to the Regulatory Guide requirements, current licensing practice permits the use of periodically-tested, redundant Class 1E fault-interrupting devices as an acceptable isolation device between the Class 1E power source and the connected non-Class 1E load. This current practice is being formalized as a BTP for incorporation into the SRP.11 Therefore, this issue has been RESOLVED.