Table 2.

${}^{222}$Rn emanation results of various stainless steel (SS) samples. Where relevant, the normalization to surface area and to weld seam length is also given

ID	Sample	Supplier	Description	Treatment	${}^{222}$Rn emanation rate
#4	Plates with welds (304 or 316L)	CRIOTEC Impianti S.p.A.	5 plates w. 8.25 m TIG-weld seam 17.9 cm $\times$ 17.6 cm $\times$ 1 cm Total: 0.33 m${}^2$/12.9 kg	Untreated	(190 ± 30) $\mathrm{\mu }$Bq (560 ± 100) $\mathrm{\mu }$Bq/m${}^2$ (23 ± 4) $\mathrm{\mu }$Bq/m
#5	Tubes with welds (316L)	ALCA Technology S.r.l.	3 tubes w. 4.8 m TIG-weld seam Outer diameter: 10.18 cm Thickness of wall: 0.34 cm Length: 30 cm Total: 0.56 m${}^2$/7.2 kg	Untreated	(214 ± 26) $\mathrm{\mu }$Bq (380 ± 50) $\mathrm{\mu }$Bq/m${}^2$ (45 ± 5) $\mathrm{\mu }$Bq/m
#5a	Tubes with welds (316L)	ALCA Technology S.r.l.	Same as sample #5	Electro-polished	(47 ± 19) $\mathrm{\mu }$Bq (80 ± 30) $\mathrm{\mu }$Bq/m${}^2$ (10 ± 4) $\mathrm{\mu }$Bq/m
#6	Tubes (316L)	ALCA Technology S.r.l.	3 tubes Outer diameter: 10.18 cm Thickness of wall: 0.34 cm Length: 30 cm Total: 0.56 m${}^2$/7.2 kg	Untreated	(160 ± 50) $\mathrm{\mu }$Bq (290 ± 90) $\mathrm{\mu }$Bq/m${}^2$
#7	Tube with welds (304L)	Lamm’s machine Inc.	Tube with 3.6 m TIG-weld seam Outer diameter: 10.16 cm Thickness of wall: 0.2 cm Length: 34 cm Total: 0.19 m${}^2$/1.5 kg	Untreated	$\le$ 38 $\mathrm{\mu }$Bq $\le$ 200 $\mathrm{\mu }$Bq/m ${}^2$ $\le$ 11 $\mathrm{\mu }$Bq/m
#8	Tube with welds (304L)	Lamm’s machine Inc.	Tube with 3.6 m TIG-weld seam Outer diameter: 10.16 cm Thickness of wall: 0.2 cm Length: 34 cm Total: 0.19 m${}^2$/1.5 kg	Electro-polished	(52 ± 23) $\mathrm{\mu }$Bq (270 ± 120) $\mathrm{\mu }$Bq/m${}^2$ (14 ± 6) $\mathrm{\mu }$Bq/m
#9	Tube with welds (304L)	Lamm’s machine Inc.	Tube with 3.6 m TIG-weld seam Outer diameter: 10.16 cm Thickness of wall: 0.2 cm Length: 34 cm Total: 0.19 m${}^2$/1.5 kg	Etched and electro-polished	(57 ± 17) $\mathrm{\mu }$Bq (300 ± 90) $\mathrm{\mu }$Bq/m${}^2$ (16 ± 4) $\mathrm{\mu }$Bq/m
#10	Stainless steel bellow	Streas S.r.l.	Bellow with one CF40 flange 1 m long, inner diameter 35 mm	Untreated	(130 ± 40) $\mathrm{\mu }$Bq
#11	Stainless steel bellow	Streas S.r.l.	Bellow with one CF100 flange 0.4 m long, inner diameter 100 mm	Electro-polished	$\le$160 $\mathrm{\mu }$Bq
#12	Large heat exchanger	GEA Group	Type FG5X12-60: 60 SS plates (338 mm $\times$ 130 mm) brazed with copper alloy	Untreated	(510 ± 50) $\mathrm{\mu }$Bq
#13	Small heat exchanger combined with large heat exchanger	GEA Group	Type FG3X8-20: 20 SS plates (226 mm $\times$ 86 mm) brazed with copper alloy plus type FG5X12-60 (see above)	Etched for $\sim 12$h with 1.8% HNO${}_3$	(134 ± 24) $\mathrm{\mu }$Bq
#14	High-purity electrical heater with large heat transfer surface	D.A.T.E. (Developpement et Applications des Techniques de L’Energie)	Custom-designed heater complying with very high purity standards	Etched for $\sim 15$min with 2% HNO${}_3$	(70 ± 27) $\mathrm{\mu }$Bq
#15	Stainless steel packing material	Sulzer Ltd.	55 structured packings, type EX 0.095 m${}^2$/piece, total surface: 5.2 m${}^2$	Untreated	(48 ± 20) $\mathrm{\mu }$Bq (9 ± 4) $\mathrm{\mu }$Bq/m${}^2$