What grades of stainless steel are used for nuclear power pipe fittings?

Q: What grades of stainless steel are used for nuclear power pipe fittings?

Nuclear power plant pipe fittings are primarily 316L (EN W.Nr. 1.4404, X2CrNiMo17-12-2) and 304L (EN W.Nr. 1.4307, X2CrNi18-9) stainless steel, depending on the circuit: 316L is the preferred nuclear-grade stainless steel for primary coolant circuit (PWR), auxiliary cooling systems, and any service with elevated Cl⁻ or boric acid (in PWR primary coolant). 304L is used for secondary circuit, steam generator secondary side, and auxiliary systems where lower Cl⁻ concentration makes 304L adequate. Low cobalt content limits are specified for nuclear-grade materials to minimise Co-60 activation in the reactor environment. Nuclear-grade heats require pre-approval, traceability through EN 10204 3.2 with witnessed inspection, and nuclear quality assurance programme compliance.

Nuclear Power Pipe Fittings | 316L 304L RCC-M ASME III EN 10253

Material Selection by Nuclear Power Circuit

Circuit / Service	Grade	EN W.Nr.	Special Req.	Standard
PWR primary coolant (auxiliary/RHR)	316L	1.4404	Low Co (≤0.10%), 3.2 cert with TPI	RCC-M or ASME III
PWR secondary circuit (steam generator)	304L or 316L	1.4307 / 1.4404	3.2 cert with TPI	RCC-M Class 2/3
BWR reactor coolant auxiliary	304L or 316L	1.4307 / 1.4404	Low Co, delta ferrite control, 3.2 cert	ASME III Cl. 1/2
Spent fuel storage / transfer pools	316L	1.4404	Boric acid compatibility, 3.1 cert min	RCC-M Class 3 / ASME III
Radioactive waste treatment	316L	1.4404	EN 10204 3.1 acceptable for non-safety circuits	EN 13480 / ASME
Cooling water (non-nuclear)	316L or CS	1.4404 / —	Standard EN 10204 3.1	EN 13480
Compressed air / nitrogen (non-nuclear)	CS or 316L	— / 1.4404	Standard	EN 13480

Nuclear Quality Assurance — Documentation Requirements

Material certification:

EN 10204 3.2 with TPI-witnessed inspection — mandatory for Safety Class 1/2
TPI bodies accepted: TUV, Bureau Veritas, SGS, APAVE, Intertek
Heat number traceability — continuous from melt to finished fitting
Low cobalt content (≤0.10%) on heat chemistry — limits Co-60 activation
Delta ferrite content (ASME III weld ferrite control) on welded fittings

Additional nuclear requirements:

RCC-M (French nuclear code) or ASME Section III — specify which code governs
NQA-1 or ISO 9001 nuclear QA programme compliance
PMI (positive material identification) on all fittings
Pressure-tested per applicable code (RCC-M, ASME B16.9)
Packaging with inert gas blanket or desiccant for corrosion prevention in storage

Please specify the applicable nuclear code (RCC-M Class, ASME III Class), safety classification, and required TPI body in your RFQ. Nuclear procurement timelines require early engagement — contact us as early as possible.

Key Grades for Nuclear Power

316L / 1.4404

X2CrNiMo17-12-2

★ PWR Standard

Primary-side auxiliary and RHR circuit fittings. Mo-bearing for boric acid and Cl⁻ resistance in PWR coolant. Low cobalt heats (≤0.10% Co) available. EN 10204 3.2 TPI as standard for nuclear supply.

304L / 1.4307

X2CrNi18-9

Secondary Circuit

Secondary circuit, steam generator secondary side, and non-safety nuclear auxiliary systems where Cl⁻ is low and Mo is not required. Lower cost than 316L for secondary-side systems.

FAQ — Nuclear Power Pipe Fittings

Nuclear power plant pipe fittings are primarily 316L (EN 1.4404, X2CrNiMo17-12-2) and 304L (EN 1.4307, X2CrNi18-9) stainless steel. 316L is the preferred grade for PWR primary coolant auxiliary circuits and service with boric acid or elevated Cl⁻. 304L is used for secondary circuit, steam generator secondary side, and auxiliary systems where lower Cl⁻ makes 304L adequate. Nuclear-grade heats require controlled low cobalt content (≤0.10% Co) to minimise Co-60 activation in the reactor environment. Full heat traceability via EN 10204 3.2 with TPI-witnessed inspection is mandatory for Safety Class 1 and 2 piping. RCC-M (French nuclear code) or ASME III documentation packages are available on request.