Radon Reduced Air and SNOLAB

Aksel Hallin

Queen’s University

August, 2006

Radon is a major issue for low background experiments

• SNO Acrylic vessel and NCD’s• Kamland Scintillator• Borexino purification system• SNO Cover gas• Majorana, DEAP internal parts

• Average air in Canada 20 Bq/m3; u/g 130 Bq/m3

• More serious problem as detectors get bigger

There is a significant effort in the community (See LRT proceedings and theses)

Radon daughters are electrically charged,and drift in electrical fields. They plate out on various surfaces. Also have physical and chemical adsorbtion of radon and its daughters. (See Michael Leung’s thesis)

Four aspects of radon

• Monitoring

• Radon reduced environments

• Desorption of daughters into detector volumes

• Cleaning surfaces

MonitoringTechniques typically involve concentrating radon into an active volume cryogenically or using electrostatics to concentrate the daughters and then counting alphas.

Technology is well developed

Radon reduced environments

• SNO covergas system

• SNO water system• Highest purity, low

flow• Limited by radon

ingress• Excludes

personnel

Andrea Pocar, PhD Thesis, Princeton, 2003

Radon Clean Laboratory Concept

Radon scrubber

HEPA

LabEquipment

20 Bq/m3

9.4x106 222Rn/m3

30 m3/min

(100 cfm)

People/processes

.0002 Bq/m3

94 222Rn/m3

8460 222Rn totalClass 1000 Clean Room?

.00002 Bq/m3

9.4 222Rn/m3

.02 Bq/m3

9,400 222Rn/m3

2 Bq/m3

940,000 222Rn/m3

3m x 10m x 10m90 m3 room140 m2 area

emanation23 Rn/min

If walls 10 Rn/m2hr

Air Lock#1

Air Lock#2

3 m3/min

80 Rn/min80 Rn/min48 Rn/min

Leaks/diffusion23 Rn/min

28 Rn/min

Tolerable Rn load = Rn scrubber flow rate timesAcceptable Rn concentration= 3 m3/min x 94 Rn/m3

= 282 Rn/min

Electrostaticdeposition plates

ChemicalBaths?

Lights

Cooler

Radon scrubber

(1 cfm)

K. McFarlaneMay 16, 2006

Ba

ffle

9,400 222Rn in lungs

125,000 222Rn dissolved

o o

Continuous radon monitoring

Cleaning contaminated acrylic

Cleaning quartz and other materials discussed in Michael Leung’s thesis