NSSS control systems are key to the daily operation of the plant. They are designed to be automatic wherever possible, with manual override options for operator control if needed. In a traditional PWR there are over 100 NSSS control loops that provide everything from the monitoring of temperatures and automatic alarms to the full automatic control of the feedwater and main steam systems. In the iPWR world, the number of control loops will be much less than the 100 plus loops mentioned above. This is partly due to the small nature of the design: fewer tanks, less piping, fewer valves, less peripheral equipment. And it is partly due to the incorporation of gravity-fed or passive cooling systems. New iPWR designs have made use of the 50 plus years of existing operating experience and have improved and simplified the steam system architecture where possible, making for much simpler control systems. The following sections will discuss the unique nature of iPWR NSSS control instrumentation.

iPWR NSSS control systems will most likely use some of the same isolated safety related instrumentation signals as found in current PWRs, but some of the instrumentation will be unique to NSSS control, like feedwater pressure and boron tank measurements, and will not require the same nuclear pedigree as safety system measurements. These measurements may likely be accomplished with the same devices that are used in traditional PWRs. The constraint in the non-safety category instruments is primarily a size constraint. The need for smaller instruments may drive an evolution in the secondary side, non-safety instrumentation.

On the other hand, the fact that NSSS instrumentation does not have the strict class 1E qualification that safety related applications demand, may make transitions to state-of-the-art technological advances a natural evolution. Definition of the non-safety I&C requirements has only just begun in most iPWR designs, so how the instrumentation is going to be developed to meet these requirements is still uncertain.