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