National Mining Association 

Experimental Determination 

of Radon Fluxes over Water 
Introduction 

This presentation will: 

 Discuss prior information regarding radon fluxes from water 

surfaces 

 Discuss laboratory research funded by the National Mining 

Association (NMA) regarding radon fluxes from water 

surfaces. 

 Compare the results of the research with previously 

reported data. 

Show that radon fluxes from most water surfaces at uranium 

recovery operations are insignificant and approximate 

background soil fluxes for most areas. 
Prior Work 

Information regarding radon fluxes from water 

surfaces has been presented on the following 

two (2) occasions: 

Radon Emissions From Tailings Ponds - Dr. 

Douglas B. Chambers - July 2, 2009 

Radon Flux from Evaporation Ponds – Dr. 

Kenneth R. Baker, Ph.D. Environmental 

Restoration Group, Inc and Alan D. Cox - 

Homestake Mining Company of California 
Prior Work - continued 

•Radon Emissions From Tailings Ponds - Dr. 

Douglas B. Chambers - July 2, 2009 

• Discussed Rn-222 gas exchange via diffusion from the 

surface of a small lake (Experimental lakes, Ontario) 

• Concluded that Radon-222 releases were low as shown in 

the table below: 
Prior Work - continued 

 Radon Flux from Evaporation Ponds – Dr. Kenneth R. Baker, Ph.D. 

Environmental Restoration Group, Inc and Alan D. Cox - Homestake 

Mining Company of California 

 Measured radon flux from an evaporation pond using modified floating Large Area 

Activated Charcoal Canisters (LAACCs) 

 Concluded that radon fluxes obeyed the Stagnant Film Model (SFM) and that flux rates in 

picoCuries per meter2-second were approximately 0.01 times the Radium-226 activity of 

the water. The Radon-222 activity of the water was not measured in this experiment and 

was assumed to be in equilibrium with the dissolved Radium-226.

 A picture of the floating Large Area Activated Charcoal Canister (LAACC) used is shown 

below: 
Discussion of Prior Work 

Both prior experiments were performed in 

outdoor environments specifically in 

experimental lakes or evaporation ponds 

under non-laboratory conditions. 

No specific data regarding actual Radon-222 

activity of the water was provided for either 

experiment. 
Purpose of this Research 

 This current research was performed to determine Radon-222 flux at the 

surface of water containing Radium-226 and Radon-222 under controlled 

laboratory conditions using an accepted method of determining Radon – 

222 flux, specifically using Large Area Activated Charcoal Canisters 

(LAACCs) as described in Radon Flux Measurements on Gardiner and 

Royster Phosphogypsum Piles Near Tampa and Mulberry, Florida since 

this is the currently accepted method of determining radon flux in Method 

115 referenced in 40 CFR Part 61.253 Determining compliance. 

 In this way, data gathered in the course of this study can be effectively 

compared with other data collected in prior compliance monitoring work 

using Large Area Activated Charcoal Canisters (LAACCs) since the 

measurement method is the same. 
Testing Protocol 

 Five (5) barrels containing deionized water with the following Radium-226 activities were 

created using a traceable Radium-226 standard: 

 0 picoCuries per liter (water with no added Radium-226)

 5,000 picoCuries per liter 

 10,000 picoCuries per liter 

 15,000 picoCuries per liter 

 20,000 picoCuries per liter 

The solutions were placed in barrels as shown below: 

The Radium – 226 in the solutions in the barrels was allowed to attain 

radiometric equilibrium with the Radon-222 by being allowed to sit 

covered for forty (40) days (slightly over ten (10) half lives for Radon222). 
Testing Protocol continued 

 Styrofoam floats were created to float the Large Area Activated Charcoal 

Canisters (LAACCs) over the water in the barrels as shown below: 
Testing Protocol continued 

 The Large Area Activated Charcoal Canisters (LAACCs) were installed in 

the floats as shown below: 

The Large Area Activated Charcoal Canisters (LAACCs) fit 

snugly in the float to create a seal. 

They are similar in appearance to the ones used by Dr. 

Kenneth R. Baker. 
Testing Protocol continued 

 The Large Area Activated Charcoal Canisters (LAACCs) 

were floated on top of the Radium-226/Radon-222 bearing 

water in the barrels as shown below: 

The weight of the Large Area Activated Charcoal Canister (LAACC) unit 

presses the float into the water creating a seal between the water and 

the float. 
Testing Protocol continued

 Barrels of Radium-226 solution were prepared. 

 The analysis results for the barrels were as follows: 

•The barrels were allowed to attain radiometric equilibrium for forty (40) days 

(slightly over ten (10) half lives for Radon-222). 

•A very high Radium-226 activity (higher than would be encountered in operations) 

was used to test relationships under extreme conditions. 

•Data reported to the number of significant figures provided in final report. 

Barrel 

Number 

Prepared 

Radium-226 

Activity 

Measured 

Radium-226 

Activity 

Measured 

Radon-222 

Activity 

 pCi/L pCi/L pCi/L 

 

1 0.0 -0.5 32. 4 

2 5,000. 4,580. 5500.

3 10,000. 9,450. 11000. 

4 15,000. 13,900. 16600.

5 20,000. 19,200. 21500.
Testing Results 

 Test Summary 

 

Date Canister 

Set 

Date Canister 

Removed 

Radium-226 

Activity 

Reported 

Radium-226 

Activity 

Used 

Radon-222 

Activity 

Reported 

Flux Rate 

Flux rate 

Used 

 pCi/L pCi/L pCi/L pCi/M2-sec pCi/M2-sec

Day 1 7/31/11 8/1/11 -0.5 0.0 32. 4 <0.5 0.0

Day 1 7/31/11 8/1/11 4,580. 4,580. 5500. 2.8 2.8 

Day 1 7/31/11 8/1/11 9,450. 9,450. 11000. 5.6 5.6 

Day 1 7/31/11 8/1/11 13,900. 13,900. 16600. 8.8 8.8 

Day 1 7/31/11 8/1/11 19,200. 19,200. 21500. 12. 12. 

Day 2 8/1/11 8/2/11 -0.5 0.0 32. 4 <0.5 0.0

Day 2 8/1/11 8/2/11 4,580. 4,580. 5500. 2.4 2.4 

Day 2 8/1/11 8/2/11 9,450. 9,450. 11000. 4.3 4.3 

Day 2 8/1/11 8/2/11 13,900. 13,900. 16600. 6.8 6.8 

Day 2 8/1/11 8/2/11 19,200. 19,200. 21500. 8.3 8.3 

Day 3 8/2/11 8/3/11 -0.5 0.0 32. 4 <0.5 0.0 

Day 3 8/2/11 8/3/11 4,580. 4,580. 5500. 2.2 2.2 

Day 3 8/2/11 8/3/11 9,450. 9,450. 11000. 4.6 4.6 

Day 3 8/2/11 8/3/11 13,900. 13,900. 16600. 6.8 6.8 

Day 3 8/2/11 8/3/11 19,200. 19,200. 21500. 8.9 8.9 

Day 4 8/3/11 8/4/11 -0.5 0.0 32. 4 <0.5 0.0 

Day 4 8/3/11 8/4/11 4,580. 4,580. 5500. 1.9 1.9 

Day 4 8/3/11 8/4/11 9,450. 9,450. 11000. 3.7 3.7 

Day 4 8/3/11 8/4/11 13,900. 13,900. 16600. 5.5 5.5 

Day 4 8/3/11 8/4/11 19,200. 19,200. 21500. 7.3 7.3 

Day 5 8/4/11 8/5/11 -0.5 0.0 32. 4 <0.5 0.0 

Day 5 8/4/11 8/5/11 4,580. 4,580. 5500. 2.0 2.0 

Day 5 8/4/11 8/5/11 9,450. 9,450. 11000. 3.5 3.5 

Day 5 8/4/11 8/5/11 13,900. 13,900. 16600. 4.8 4.8 

Day 5 8/4/11 8/5/11 19,200. 19,200. 21500. 7.9 7.9 

Day 6 8/5/11 8/6/11 -0.5 0.0 32. 4 <0.5 0.0

Day 6 8/5/11 8/6/11 4,580. 4,580. 5500. 2.0 2.0 

Day 6 8/5/11 8/6/11 9,450. 9,450. 11000. 3.5 3.5 

Day 6 8/5/11 8/6/11 13,900. 13,900. 16600. 5.0 5.0 

Day 6 8/5/11 8/6/11 19,200. 19,200. 21500. 6.6 6.6 

Notes: 

•Reported Radium-226 

activity of -0.51 set to zero 

for calculation purposes. 

•Reported Radon-222 flux 

of <0.5 set to zero for 

calculation purposes 

•Data reported to the 

number of significant 

figures provided in final 

report. 
Radium-226 Activity versus Radon-222 Flux Rate 

y = 0.0004x

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0 5000 10000 15000 20000 25000

Radon-222 Flux (pCi/M2-sec)

Radium-226 Activity (pCi/L)

Radium-226 Activity versus Radon-222 Flux

Radon-222 Flux - Y Value

Predicted Flux

Linear (Predicted Flux )

Note: The R2 (correlation coefficient squared) value is 0.96, 

showing good linear correlation. 
Radon-222 Activity versus Radon-222 Flux Rate 

y = 0.0004x

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0 5000 10000 15000 20000 25000

Radon Flux (pCi/M2-sec)

Radon-222 Activity (pCi/L)

Radon-222 Activity versus Radon-222 Flux

Radon-222 Flux - Y Value

Predicted Flux

Linear (Predicted Flux )

Note: The R2 (correlation coefficient squared) value is 0.96, 

showing good linear correlation. 
Maximum and Minimum Radon-222 Fluxes versus Radium226 Activity of the Water 

Maximum Slope = 0.00064 

 Minimum Slope = 0.00034 

Average Slope = 0.0004 (previous slide) 

Maximum and Minimum Radon-222 Fluxes versus Radium226 Activity

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0 4,580 9,450 13,900 19,200

Radium-226 Activity (pCi/L)

Radon-222 Flux (pCi/M2-sec)

Maximum Radon-222 Flux (pCi/M2-sec) 

Minimum Radon-222 Flux (pCi/M2-sec) 
Maximum and Minimum Radon-222 Fluxes versus Radon222 Activity of the Water 

Maximum Slope = 0. 00057 

 Minimum Slope = 0.00031 

Average Slope = 0.0004 (previous slide) 

Maximum and Minimum Radon-222 Fluxes versus 

Radon-222 Activity

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

32 5500 11000 16600 21500

Radon-222 Activity (pCi/L)

Radon-222 Flux (pCi/M2-sec)

Maximum Radon-222 Flux (pCi/M2-

sec)

Minimum Radon-222 Flux (pci/M2-

sec)
Standard Deviation of Radon-222 Flux versus Radium-226 

Activity of the Water 

Standard deviation of the Radon-222 flux equals approximately 

0.0001 times the Radium-226 activity of the fluid. 

Standard Deviation of Radon-222

 Flux versus Radium-226 Activity of the Fluid

0.00

0.50

1.00

1.50

2.00

2.50

0 4,580 9,450 13,900 19,200

Radium-226 Activity of the Fluid Standard Deviation of Radon-222 Flux

Standard Deviation of Flux Rate

(picoCuries per meter2-second)
 Standard Deviation of Radon-222 Flux versus Radon-222 

Activity of the Water 

Standard deviation of the Radon-222 flux equals approximately 

0.0001 times the Radon-222 activity of the fluid. 

Standard Deviation of Radon-222

 Flux versus Radon-222 Activity of the Fluid 

0.00

0.50

1.00

1.50

2.00

2.50

32.40 5500 11000 16600 21500

Radon-222 Activity of the Fluid Standard Deviation of Radon-222 Flux

Standard Deviation of Flux Rate

(picoCuries per meter2-second)
•Radon-222 flux is linearly dependent upon Radon-222 activity of the fluid even 

at high fluid Radon-222 activities. 

•Standard deviation of the flux rate is also linearly dependent upon the Radon222 activity of the fluid approximating 0.0001 times the Radon-222 activity. 

•In a normal distribution, 95.4% of the measurements will lie within two (2) 

standard deviations from the mean. 

•The mean of the flux rate is related linearly to the Radon-222 activity of the fluid 

approximating 0.0004 times the Radon-222 activity. 

•For the measured Radon-222 activities of the fluid in the barrels, 95.4% of the 

measured flux rates at the fluid surface can be calculated by the following 

equation: 

•Radon-222 Flux = 0.0004*(Radon-222 Activity) +/- 2*(0.0001)*(Radon-222 

Activity) which simplifies to: 

•Radon-222 Flux = 0.0004*(Radon-222 Activity) +/-0.0002(Radon-222 

Activity) 

•This equates well with the relationship between the maximum flux rates and 

Radon-222 activity of 0.00057*(Radon-222 Activity) 

Conclusions 
Conclusions continued 

•This experimental data does not correlate well with fluxes derived from 

application of the Stagnant Film Model (SFM). The Stagnant Film Model (SFM) 

appears to be too conservative, over estimating fluxes by at least an order of 

magnitude. 

•This data however correlates fairly well with data presented by Dr. Douglas 

Chambers regarding the experimental lake, shown again below: 

The experimental data lies between the Radon-222 fluxes 

from turbulent mixing depths of 10 and 50 centimeters. 
Conclusions continued

 The above discussed experimental data fits well with the Radon-222 flux 

data obtained by another uranium recovery licensee in tests conducted 

in its tailings impoundment in August 2010 that was recently submitted 

to the Environmental Protection Agency (EPA). 

 Radon-222 fluxes from water surfaces even in the case of high Radium226 and Radon-222 activities are minimal and in the case of fluid 

Radium-226 activities up to 5,000 pCi/L are within the range and 

variability of natural background assuming a typical planet wide 

background flux of 1 ‐ 2 pCi/m2‐ sec (Steven H Brown, CHP, SENES 

Consultants Limited – November 7, 2010). 

 Construction of a fluid retention impoundment and filling it with water 

containing up to 5,000 pCi/L Radium-226 would just displace normal 

background surface flux in most areas.