This specification covers the requirements for sheathed, Type K and N thermocouples for nuclear service. This specification can be used for sheathed thermocouples which are required for laboratory or general commercial applications where the environmental conditions exceed normal service requirements. The measuring junction styles for thermocouples are as follows: Style G2 (grounded) in which measuring junction is electrically connected to conductive sheaths and Style U2 (ungrounded) in which measuring junctions are electrically isolated from conductive sheaths and from reference ground. Different properties of the sheath such as integrity, cracks, voids, inclusions, surface finish, surface defect, and metallurgical structure shall be determined by performing different tests. Insulation resistance between thermoelements and the sheath shall be measured as well.

1.1 This specification covers the requirements for sheathed, Type K and N thermocouples for nuclear service. Depending on size, these thermocouples are normally suitable for operating temperatures to 1652 °F (900 °C); special conditions of environment and life expectancy may permit their use at temperatures in excess of 2012 °F (1100 °C). This specification was prepared specifically to detail requirements for using this type of sheathed thermocouple in nuclear environments. This specification can be used for sheathed thermocouples which are required for laboratory or general commercial applications where the environmental conditions exceed normal service requirements. The intended use of a sheathed thermocouple in a specific nuclear application will require evaluation by the purchaser of the compatibility of the thermocouple, including the effect of the temperature, atmosphere, and integrated neutron flux on the materials and accuracy of the thermoelements in the proposed application. This specification does not attempt to include all possible specifications, standards, etc., for materials that may be used as sheathing, insulation, and thermocouple wires for sheathed-type construction. The requirements of this specification include only the austenitic stainless steels and other alloys as allowed with Specification E 585/E 585M for sheathing, magnesium oxide or aluminum oxide as insulation, and Type K and N thermocouple wires for thermoelements (see Note 1).

1.2 General Design Nominal sizes of the finished thermocouples shall be 0.0400 in. (1.016 mm), 0.0625 in. (1.588 mm), 0.125 in. (3.175 mm), 0.1875 in. (4.763 mm), or 0.250 in. (6.350 mm). Sheath dimensions and tolerances for each nominal size shall be in accordance with and . The measuring junction styles for thermocouples covered by this specification are as follows:

1.2.1 Style G (grounded) Measuring junction electrically connected to conductive sheaths, and

1.2.2 Style U (ungrounded) Measuring junctions are electrically isolated from conductive sheaths and from reference ground.

1.3 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.