Both the sensitivity and the temperature range depend on the iron concentration. The sensitivity is typically around 15 µV/K at low temperatures, and the lowest usable temperature varies between 1.2 and 4.2 K.  Type P (55%Pd/31%Pt/14%Au–65%Au/35%Pd, by weight) thermocouples give a thermoelectric voltage that mimics the type K over the range 500 °C to 1400 °C, however they are constructed purely of noble metals and so shows enhanced corrosion resistance. This combination is also known as Platinel II. Thermocouples of platinum/molybdenum-alloy (95%Pt/5%Mo–99.9%Pt/0.1%Mo, by weight) are sometimes used in nuclear reactors, since they show a low drift from nuclear transmutation induced by neutron irradiation, compared to the platinum/rhodium-alloy types. The use of two wires of iridium/rhodium alloys can provide a thermocouple that can be used up to about 2000 °C in inert atmospheres. Thermocouples made from two different, high-purity noble metals can show high accuracy even when uncalibrated, as well as low levels of drift. Two combinations in use are gold–platinum and platinum–palladium. Their main limitations are the low melting points of the metals involved (1064 °C for gold and 1555 °C for palladium). These thermocouples tend to be more accurate than type S, and due to their economy and simplicity are even regarded as competitive alternatives to the platinum resistance thermometers that are normally used as standard thermometers. HTIR-TC offers a breakthrough in measuring high-temperature processes. Its characteristics are: durable and reliable at high temperatures, up to at least 1700°C; resistant to irradiation; moderately priced; available in a variety of configurations - adaptable to each application; easily installed. Originally developed for use in nuclear test reactors, HTIR-TC may enhance the safety of operations in future reactors. This thermocouple was developed by researchers at the Idaho National Laboratory (INL)    The table below describes properties of several different thermocouple types. Within the tolerance columns, "T" represents the temperature of the hot junction, in degrees Celsius. For example, a thermocouple with a tolerance of ±0.0025×"T" would have a tolerance of ±2.5 °C at 1000 °C.