Post on 21-Jan-2021
Purity and purification of argon in terms of 222Rn
Hardy Simgen / Grzegorz Zuzel
Max-Planck-Institut für Kernphysik Heidelberg
Introduction� 3 subprojects:� Measurement of 222Rn in commercially available Ar� Search for clean storage tanks� Design of a dedicated 222Rn purification column� GSTR-07-006 available on webpage� Summarizing results until April 07� In the talk (as usual): All gas volumes at Standard Temperature and Pressure (STP)
Status after Ringberg meeting: 222Rn in commercial Ar
Initial activties at time of LAr delivery:� Argon 5.0 (Westfalen AG): 8.4 mBq/m3� Argon 6.0 (Westfalen AG): 0.4 mBq/m3
⇒ Concentration depends on quality⇒ ~2 orders of magnitude worse than N2
Can it be understood?
Air separation plantBoilingpoints
Rn
O2
Ar
N2
New results on initial Ar purity� Argon 5.0 (LINDE) [Gran Sasso]:0.4 mBq/m3� Argon 4.8 (Air Liquide) [MPIK]:0.3 mBq/m3� Argon 4.6 (Westfalen AG) [MPIK]:0.7 mBq/m3� Better than expected (but still worse than N2)⇒ Storage time between production and
delivery must be taken into account.
222Rn emanation of storage tanks for cryogenic liquids
3.5 +- 0.2
1.8 +- 0.4
2.7 +- 0.3
65 +- 6
42 +- 2
177 +- 6
222Rn activity in saturation [mBq]
technical
technical
7.0
6.0
6.0
technical
Quality of stored gas
63 +- 30.67Westfalen
AG
4.1 +- 0.416SOL
0.9 +- 0.13LINDE
0.56 +- 0.036.3LINDE
2.7 +- 0.60.67Air Liquide
59 +- 23Westfalen
AG
specific 222Rn act. [mBq/m3]
Vol. [m3]
Tank from
Adsorption in pores
Column purification
Column purification
Column purification
Column purification
Column purification
Column purification
Expected breakthrough curve
0
0.2
0.4
0.6
0.8
1
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Volume of argon
rela
tive
222 R
n co
ncen
trat
ion Breakthrough
Small fractionleaks through
Low-level proportional counter
Background for 222Rn: ~1 count/day
Mobile Radon Extraction Unit
222Rn detection limit: ~0.3 µBq/m3
Results for gas phase adsorption (150 g carbon trap)
26000.70.278012.4.07
>2700<0.50.201414.11.04
Reduction factor [1/kg]
Final conc. [µBq/m3]
Initial conc. [mBq/m3]
Volume[m3]
Date
222Rn removal in gas phase is very efficient
Experimental setup for liquid phase adsorption tests
Results for liquid phase adsorption (60 g carbon trap)
3702.70.06776.6.07
7403.30.154824.4.07
4202.10.05674.6.07
3305.60.1110413.6.05
1706006.02008.6.05
6605.20.2114019.4.07
Reduction factor [1/kg]
Final conc. [µBq/m3]
Initial conc. [mBq/m3]
Volume[m3]
Date
Results for liquid phase adsorption (60 g carbon trap)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0 50 100 150 200 250
Volume of argon [m^3]
rela
tive
222
Rn
co
nce
ntr
atio
n
Expected breakthrough curve
0
0.2
0.4
0.6
0.8
1
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Volume of argon
rela
tive
222 R
n co
ncen
trat
ion Breakthrough
Small fractionleaks through
Results for liquid phase adsorption (60 g carbon trap)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0 50 100 150 200 250
Volume of argon [m^3]
rela
tive
222
Rn
co
nce
ntr
atio
n
Leakingthrough
Breakingthroughat 5 bar
(-166 °C)
at 1 bar(-178 °C)
Conclusions� Commercial Ar not as dirty as believed� still worse than N2� Very clean storage tank available at LNGS� Purification still necessary� Contamination due to oxygen removal� Next tests: Liquid phase adsorption with large adsorption column