NSSS temperature instrumentation is an open field for both new tech and older devices. The typical NSSS temperature measurements in large PWRs are:

• boric acid tank temperature;

• let-down heat exchanger outlet temperature;

• let-down orifice safety valve temperature;

• residual heat removal (RHR) loop return temperature;

• pressurizer liquid temperature;

• pressurizer vapor temperature;

• pressurizer surge line temperature;

• pressurizer spray line temperature;

• volume control tank temperature;

• seal water injection temperature;

• chiller related temperatures;

• charging temperature;

• pressurizer relief tank temperature;

• reactor vessel flange leak-off temperature.

Depending on design, iPWRs may require some of the same measurements. Some of these temperature measurements will originate inside the reactor vessel and will need to have a very reliable and verified temperature device pedigree. This need would tend to indicate the traditional RTD and thermocouple devices, although new technology solutions should not be abandoned, even for the harsher environments.

Some of the temperature measurements will be made away from the harsh environment that exists in or near the reactor vessel, and could be an application for new technologies such as MEMs and/or fiber technology. These technologies may offer additional benefits such as easy maintainability, use-and-throw-away devices, better accuracy, more and distributed measurements, and diagnostic capabilities. The new technology is likely to be cheaper, easier to purchase, and more accurate. These economic and engineering benefits may outweigh the pedigree of the traditional

RTD, but will have to be evaluated on a case-by-case basis. Section 6.2.4 identifies some of the new technology options for temperature measurements.