# URANIUM MILL TAILING S RADON FLUX CALCULATIONS

PI Ñ ON RIDGE PROJECT MONTROSE COUNTY, COLORADO

Submitted To: Energy Fuels Resources Corporation 44 Union Boulevard, Suite 600 Lakewood, Colorado 80228

Submitted By: Golder Associates In c. 44 Union Boulevard, Suite 300 Lakewood, Colorado 80228

August 2010 Pro ject No. 073

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### EXECUTIVE SUMMARY Energy Fuels Resources Corporation (EFRC) proposes to license, construct, and operate a conventional
acid leach uranium and vanad ium mill at the Piñon Ridge Property in western Montrose County, Colorado. The Piñon Ridge Mill includes an administration building, a 17

- acre mill, a 30.5

- acre tailings
cell with phased expansion capacity to 91.5 acres, a 40

- acre evaporation pond area wi th an expansion capacity to 80 acres, an approximately 6

- acre ore storage pad, and access roads. The mill is designed to process ore containing uranium and vanadium produced from mines located within a reasonable haul
distance on the Colorado Plateau.

G older Associates Inc. (Golder) was commissioned by EFRC to evaluate the operations of the uranium mill tailings storage facility at the Piñon Ridge Mill in terms of the 20 pCi/m2s radon (Rn

- 222) flux standard that applies to uranium tailings facilities con structed prior to 1989

. Although this flux standard does not apply to new facilities such as the Pi ñon Ridge Mill, it did play an inherent role in establish ing the tailings disposal practices and maximum areas specified for new facilities u nder the U.S. E nvironmental Protection Agency (EPA) regulations found in 40 CFR 61 Subpart W, “National Emission Standards for
Radon Emissions from Operating Mill Tailings” (EPA, 1998). EFRC had expressed a desire to maintain radon flux levels from the tailings to “ As L ow A s Reasonably Achievable ” (ALARA) levels
, as required by
State of Colorado and U.S. Nuclear Regulatory Commission (NRC) regulations

. To achieve this goal
, EFRC requested that Golder evaluate radon flux levels under a range of potential operating condit ions.

The radon flux calculations presented in this report were conducted using the WISE Uranium Mill Tailings Radon Flux Calculator, as updated on November 23, 2009 (WISE, 2009). The results of these
calculations show that the radon flux levels of the p roposed uranium mill tailings facility at the Piñon Ridge
Mill site will be less than 20 pCi/m2s under normal operating procedures whereby the tailings are
maintained in a saturated state

. Golder also assessed various unsaturated scenarios that could occu r in the event of temporary equipment failure or during pre
- closure operations when the water cover will be
eliminated , and found that the radon flux remained less than 20 pCi/m2s under drying conditions with up to 20 percent of the tailings surface being unsaturated.August 2010 i 073

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# Table of Contents

EXECUTIVE SUMMARY

................................ ................................ ................................ ........................ ES

- 1 1.0 INTRODUCTION

................................ ................................ ................................ ................................ ..... 1
2. 0 SITE DESCRIPTION

................................ ................................ ................................ ............................... 2 3.0 MILL TAILINGS RA DON FLUX EVALUATION

................................ ................................ ....................... 3 3.1 Description of the Uranium Mill Tailings Radon Flux Calculato r

................................ ......................... 3 3.2 Input Data

................................ ................................ ................................ ................................ ............ 3 3.2.1 General Tailings Properties

................................ ................................ ................................ ......... 4
3.2.1.1 Ra

- 226 Activity Concentration in the Uranium Tailings [pCi/g]

................................ ............. 4 3.2.1.2 Ra

- 226 Activity Ratio in Slimes vs. Sand

................................ ................................ .............. 4 3.2.1.3 Rn

- 2 22 Emanation Fraction in Slimes

................................ ................................ .................. 4 3.2.1.4 Rn

- 222 Emanation Fraction in Sand

................................ ................................ ..................... 4 3.2.1.5 Fraction Passing #200 Mesh (75 μm)

................................ ................................ ................... 5 3.2.1.6 Fraction of Pond Area with less than 1 m depth

................................ ................................ ... 5 3.2.1.7 Average Pond Depth for Areas greater than 1 m deep

................................ ........................ 5 3.2.1.8 Ra

- 226 Activity Concentration in Impounded Water [pCi/L]

................................ ................. 5
3.2.1.9 Effective Stagnant Water Transport Coefficient [m 2 / s]

................................ ........................ 5
3.2.2 Zone

- Specific Tailings Properties

................................ ................................ ................................ 6 3.2.2.1 Surface Area [m2]

................................ ................................ ................................ .................. 6
3.2.2. 2 Bulk Density [g/cm 3 ]

................................ ................................ ................................ .............. 6 3.2.2.3 Porosity

................................ ................................ ................................ ................................ . 6 3.2.2.4 Moisture Content [dry wt %]

................................ ................................ ................................ .. 7 3.2.2.5 Fraction Passing No. 200 Mesh (75 μ m)

................................ ................................ .............. 7
3.2.2.6 Rn

- 222 Effective Diffusion Coefficient [m2/s]

................................ ................................ ........ 8 4.0 RA DON FLUX MODELING RE SULTS

................................ ................................ ................................ . 10 4.1 Mill Tailings Operational Scenarios

................................ ................................ ................................ ... 10 4.2 Radon Flux Model Calculation Results

................................ ................................ ............................. 11 4.3 Atmospheric Radon Concentrations

................................ ................................ ................................ . 12 5.0 CONCLUSIONS

................................ ................................ ................................ ................................ .... 13 6.0 USE OF THIS R EPORT

................................ ................................ ................................ ........................ 14 7.0 REFERENCES

................................ ................................ ................................ ................................ ...... 15August 2010 ii 073

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### List of Tables

Table 1 Results of Radon Flux Model Table 2 Radon Flux with Unsaturated Tailings Exposure



### List of Figures Figure 1 S ite Location Map Figure 2 Site Facilities Map Full Build

- Out Figure 3 Proposed Piñon Ridge Tailings Cell Zones Figure 4 Radon Flux vs. Percent Water Cover



### List of Appendices Appendix A Details of Radon Flux Calculations for Saturated and Submerged Tailing s Appendix B Details of Radon Flux Calculations for Allowable Unsaturated Tailings ExposureAugust 2010 1 073

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### 1.0 INTRODUCTION This report was prepared by Golder Associates Inc. (Golder) to assist Energy Fuels Resources Corporation (EFRC) in developing its operating plan for the Pi ñ on Ridge tailings cells and evaporation ponds (EFRC, 2010)

. T he average radon (Rn

- 222) flux levels for its proposed tailings cells were evaluated under normal operating conditions and under drying conditions where a portion of the tailings may los e saturation

. The resulting flux levels were compared to the 20 pCi/m2s flux limit adopted for the much larger pre

- 1989 tailings facilities in 40 CFR 61 Subpart W, “National Emission Standards for Radon Emissions from Operating Mill Tailings” (EPA, 1998). This standard does not apply to the Pi ñ on Ridge Mill per se , as the mill tailings facility meets the standard found in 40 CFR Subpart W 61.252 (b) (1) for facilities constructed after December 15, 1989 for phased disposal

. This standard limits phased di sposal to no more than two tailings impoundments in operation at any one time and limits the maximum size of the impoundme nts to 40 acres

. However, EFRC plans to reduce radon flux levels to “As Low As Reasonably Achievable” (ALARA) levels
, as defined in t he Colorado Department of Public Health and Environment (CDPHE) and U.S. Nuclear Regulatory Commission (NRC) regulations by implementing tailings operating practices designed to limit radon flux

. The 20 pCi/m2s flux level represents a convenient yardstick for evaluating tailings operating practices, as this flux rate was used by the U.S. Environmental Protection Agency (EPA) in its previous Subpart W rulemaking in assessing the associated health risk s of
both pre
- and post

- 1989 tailings facilities.

The ra don flux calculations in this report were conducted using the WISE Uranium Mill Tailings Radon Flux Calculator, as updated on November 23, 2009 (WISE, 2009). The results of these calculations show that the proposed uranium mill tailings facilit ies at the Piñon Ridge Mill site will produce substantially less than 20 pCi/m2s radon flux under normal operating conditions and procedures whereby the tailings are
maintained in a saturated state

. This report also assessed various unsaturated scenarios that could occur in the event of temporary equipment failure or during standby or pre

- closure periods when water
cover would be reduced and found that the 20 pCi/m2s flux level was not exceeded under drying conditions with up to 20 percent of the tailings surface bei ng unsaturated.August 2010 2 073

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### 2.0 SITE DESCRIPTION EFRC proposes to license, construct, and operate a conventional acid leach uranium and vanadium mill at the Piñon Ridge Property in western Montrose County, Colorado. The property covers approximately
880 acres in the sou theastern portion of Paradox Valley. The proposed Piñon Ridge Mill is located at 16910 Highway 90, approximately 7 miles east of Bedrock, Colorado, and 12 miles west of Naturita, Colorado. Figure 1 shows the location of the proposed project site.

The Pi ñ on Ridge Mill is designed to process ore containing uranium and vanadium produced from mines
located within a reasonable haul distance on the Colorado Plateau

. The facility includes an administration building, a 17

- acre mill, a 30.5

- acre tailings cell wit h phased expansion capacity to 91.5 acres, a 40

- acre evaporation pond area with an expansion capacity to 80 acres, an approximately 6

- acre ore storage pad,
and access roads. The phased expansion plan is designed to meet the standard found in 40 CFR Subpar t W 61.252 (b) (1), as only two 30.5

- acre tailings cells would be in operation at any one time

. This would only occur for a relatively short transition period when the first cell is reaching its full capacity and a second cell is being put into service

. The proposed uranium mill and tailings facilities at full build

- out are shown in Figure 2.

The mill will initially process 500 tons of ore per day (tpd), but is designed to accommodate future expansion of production capacity to 1,000 tpd. The projected op erating life of the facility is 40 years, operating 24 hours per day, 350 days per year at 500 tpd.

The ore to be processed at the mill contains elevated concentrations of natural uranium and its decay products. The average uranium content in the blended ore is 0.23 percent U 3 O 8

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### 3.0 MILL TAILINGS RADON FLUX EVALUATION

3.1 Description of the Uranium Mill Tailings Radon Flux Calculator

The Uranium Mill Tailings Radon Flux Calculator evaluat es the radon flux from a bare and/or water

covered uranium mill tailings sto rage area. The calculator is based on the modeling work of Nielson (Nielson and Rogers, 1986).

The model performs one

- dimensional, steady

- state radon diffusion calculations for various areas of the tailings deposit. For the submerged area, the model ca lculates the radon transport from the tailings through the impounded water to the top of the surface, and radon released from radium dissolved in the impounded water that covers the submerged tailings. It assumes that all radon reaching the top 1

- meter (3 .28 foot) layer of the water is released into the air, as well as all radon produced from dissolved radium in this top layer. The following areas are calculated in the model:

 Submerged Tailings U nder Impounded Water. This area is primarily comprised of t he smaller particle size material in the tailings (“slimes”) which are preferentially accumulated in the center of the tailings storage facility as tailings are deposited. The submerged tailings consider two separate areas in the calculation:

 Submerged a rea at a depth of 1 meter or less; and

 Submerged area at greater than 1 meter.

 Saturated Beach . This area is located on the perimeter of the tailings storage facility and represents a mixture of particle size material (“slimes and sands”) which deposits o n the perimeter beaches. This area, while not covered with tailings water, will be wetted with recycled raffinate solution or tailings water to keep the tailings fully saturated. Keeping the tailings saturated in this manner minimizes the radon flux from the beach areas of the tailings cell.

 Unsaturated Z one

. While it is the intent of EFRC to keep all beaches fully saturated, there may be some interim period where small areas of the tailings surface may become temporarily unsaturated due to mechanical fa ilure of the water recycle system, or due to reduction in water cover during standby or pre

- closure periods. Hence, calculations were performed to evaluate the maximum percentage of unsaturated tailings exposure that would still result in a radon flux lev el below 20 pCi/ m2 s

.
The various areas used for the radon flux calculations are shown in Figure 3.



### 3.2 Input Data The physical and radiological properties of the uranium mill tailings that were input into the model are
defined below. While the model allows for default parameters to be used, the most meaningful results for
actual site conditions are obtained if site

- specific data is used

. Since the tailings facility has not been built and no actual tailings have been processed, data from other representativ e uranium mill sites has been used wherever possible together with sampling data for typical Salt Wash ores that will comprise the proposed feed to the Piñon Mill

. The effective radon diffusion coefficients were obtained using methods developed by Nielson and Rogers (1986) and Rogers and Nielson (1991).August 2010 4 073

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### 3.2.1 **General Tailings Properties** This section provides discussion of the general tailings properties used in the radon flux modeling and the specific values used for the Piñon Ridge project.



### 3.2.1.1 Ra

- 226 Activity Con centration in the Uranium Tailings [pCi/g] This input parameter is the overall activity concentration of radium

- 226 in the bulk tailings material

. The value for the equilibrium concentration of radium

- 226 was calculated based on the average grade of the

o re that will be processed

. The average uranium content in the blended ore is expected to be 0.23 percent U 3 O 8 .
The activity of U

- 238 in the Piñon Ridge uranium tailings was evaluated as follows:



### EQUATION 1

) ( ) ( 647 ) ( ) ( 000
, 330 ) ( )

( 85

. 0 ) ( ) ( 0023

. 0 238

238 238 238

8 3 8 3

ore U

U U

O U U

ore O U 

### g pCi
g pCi
g g g g Activity

**−**

**− −**  **−** 

### = ** **  ** **  ** ** 

**⋅ **  ** **  ** **  ** **  ****

**⋅ **  ** **  ** **  ****

**=**

Assuming secular equilibrium in the ore between uranium

- 238 and radium

- 226, and that all radium goes into the tailings, the activity of radium

- 226 will be 647pCi/g.



### 3.2.1.2 Ra

- 226 Activity Ratio in Slimes vs. Sand This input parameter estimates the ratio of ra dium

- 226 activity concentrations in the slimes fraction vs. the sand fraction of the tailings material

. The radium

- 226 activity concentrations typically increase with decreasing particle size and the slimes will contain a higher concentration of radium

- 22 6. A ratio of 4 has been used in the calculations, which corresponds to the value used by Nielson and Rogers (1986) in the development of the model.



### 3.2.1.3 Rn

- 222 Emanation Fraction in Slimes This input parameter is the fraction of the total amount of radon

- 222 produced by radium decay that escapes from the solid fraction of the slimes tailings particles and gets into the pores of the material. The value depends on the tailings material and the moisture content. It varies over a range of 0.1 to 0.4 with typical values in the range of 0.2 to 0.3. Nielson and Rogers (1986) uses a value of 0.22 for the tailings slimes, and this value was used in the calculation for the Piñon Ridge project.



### 3.2.1.4 Rn

- 222 Emanation Fraction in Sand This input parameter is the fraction of t he total amount of radon

- 222 produced by radium decay that escapes from the solid fraction of the sand tailings particles and gets into the pores of the material. The value depends on the tailings material and the moisture content. This parameter typical ly varies over a range of 0.1 to 0.4

. Nielson and Rogers (1986) uses a value of 0.15 for the tailings sands, and this value was used in the calculation for the Piñon Ridge project.August 2010 5 073

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### 3.2.1.5 Fraction Passing #200 Mesh (75 μm) This input parameter is the fraction by weight of the overall bulk tailings material passing a No. 200 mesh, corresponding to a particle diameter of 75 μm or less. Since a 75

- μm particle diameter typically marks the sand/silt dividing line, this figure denominates the fraction that is not sand , or the fraction of combined silt and clay contents ("slimes").

The value used for this parameter is taken from data as reported in Golder (2008a). The fraction for the bulk tailings material passing the #200 mesh is 0.379 (i.e., 37.9 percent). This gra dation is based on data obtained from processing of Salt Wash ores at the Whi te Mesa Mill in Blanding, Utah.



### 3.2.1.6 Fraction of Pond Area with less than 1 m depth This input parameter is the fraction of the pond area that has less than 1 meter of water cover

. Th is fraction was determined graphically for various percentages of total water cover based on the projected slope of the underly ing coarse and fine tailings. The tailings with less than 1 meter of water cover contribute to the radon flux of the facility.



### 3.2.1.7 A verage Pond Depth for Areas greater than 1 m deep This input parameter is the depth of the pond area that has greater than 1 meter of water cover

. This depth was determined graphically for various percentages of total water cover based on the projected
sl ope of the underlying coarse and fine tailings. Th e tailings with greater than 1 meter of water cover do not contribute to the radon flux of the facility.



### 3.2.1.8 Ra

- 226 Activity Concentration in Impounded Water [pCi/L] This input parameter is the activity concen tration of dissolved radium

- 226 in the impounded water covering the deposited tailings material. As previously discussed, the uranium content of the projected ore to be processed at the Piñon Ridge Mill has been determined to be 0.23 percent U 3 O 8 , which leads to a radium activity of 647 pCi/g (refer to Section 3.2.1.1 ). The specific Ra

- 226 content of the impounded water in equilibrium with the tailings material was estimated using the values previously established for a
model mill in the U.S. Nuclear Regulatory Commission (NRC) NUREG

- 0706 “Final Generic EIS on Uranium Milling” (NRC, 1980; Table 5.3). This document lists an activity level of 250 pCi/L Ra

- 226 for tailings solution at the model mill based on an activity level of 280 pCi/g Ra

- 226 in the ore. Scaling up to the expected higher uranium and radium activity levels in the Piñon Ridge ore of 647 pCi/g, the calculated radium activity level of the tailings solution in equilibrium with the tailings is 581 pCi/L.



### 3.2.1.9 Effective Stagnant Water Transport Coefficient [m 2 / 

### s ] This parameter describes radon transport in water. The established value for this parameter is 3x10 - 7

m2 / s, as determined by Nielson and Rogers (1986).August 2010 6 073

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### 3.2.2 **Zone**

**- Specific Tailings Properties**  The following parameter s describe the specific properties of each tailings area: (i) the area submerged under impounded water; (ii) the saturated beach area; and (iii) the unsaturated area.



### 3.2.2.1 Surface Area [ m2 ] This parameter is the surface area for a given type of tailings. A cal culation was made for each of the three areas in the tailings cell: the submerged area, the saturated area, and the unsaturated area

. If no tailings exist in any particular area, then a value of zero (0) is entered and the area is discarded. The
calculat ions were based on a tailings cell area of approximately 30.5 acres (120,365 m2 )

.



### 3.2.2.2 Bulk Density [g/cm 3 ] Each area of the tailing cell will have specific bulk density properties due to the nature of the deposition of tailings in the tailings cell. As repor ted in the tailings settlement report (Golder, 2010), the average dry density of tailings after initial settlement with release of water to the tailings pool is expected to be 79.2 pounds per cubic foot (pcf) , or 1.27 grams per cubic centimeters (g/cm 3 )

. The submerged, saturated, and
unsaturated areas in the tailings cell will each have different dry densities depending on the amount of
slimes and sands in these areas

.
For the submerged area, which is mostly comprised of finer particle material (“slimes”), a bulk density value of 70 pcf was used. This corresponds to the expected average density for the material that will collect in the central part of the tailings cell, which will be submerged for most of the time while the tailings cell is being filled. This corresponds to a dry bulk density of 1.12 g/cm 3

. For the saturated transition area, which is comprised mostly of sandy material with some amount of slimes, an average bulk density value of 80 pcf was used

. This corresponded to a dry bulk density of 1.28 g/cm 3 . For the sandy beach material, a bulk density of 90 pcf was used, which corresponds to a dry bulk density of 1.44 g/cm 3

.
These dry density determinations were made after reviewing the available physical parameter information
for the Atlas Moab tailings area (Golder, 2005), which indicated that the tailings density ranged from 50.2 pcf to 88.6 pcf for the slimes to a range of 81 to 106 pcf for the sand materials

. The Piñon Ridge Mill tailings facility is expected to achieve higher densities bec ause dewatering will be facilitated by the barge

mounted pump

- back system and the tailings cell underdrain system

. It is important to note that the dry density of 70 to 90 pcf for the Piñon Ridge tailings applies only to the near

- surface tailings that are contributing to the radon flux

. Tailings at depth will have substantially higher densities due to
consolidation

. The tailings density will also increase further after placement of the soil cover during cell
closure.



### 3.2.2.3 Porosity The porosity (n) of the tai lings material is the ratio of the pore volume (air

- and water

- filled) to the total volume of the tailings. This value was calculated using the following relationship:August 2010 7 073

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### EQUATION 2

e e n **+**

**=** 1

where e is the void ratio

. Limited data on void ratio is available for existing tailings facilities. The data from the Moab tailings area showed that the void ratio for the finer particle material (“slimes”) was 1.35 using the same criteria for densification modifications that we re used for the determination of the dry bulk
densities

. This corresponds to a porosity of 0.57 for the slimes. This value, which was input into the model, is higher than the default value used in the model and is considerably more conservative (i.e., a higher porosity results in a higher radon flux).

For the average tailings material in the saturated area and unsaturated area of the tailings cell, a void ratio of 0.65 was used based on data from the Moab tailings area, which resulted in a porosity of 0.3 9

. The model uses a default value of porosity of 0.4 for all areas of the tailings cell.



### 3.2.2.4 Moisture Content [dry wt %] During the majority of operations, the tailings will either be submerged or fully saturated. The only area where percent moisture needs to be specified in the model is the unsaturated area. The moisture content of unsaturated tailings was assumed to be 15 percent, which is a relatively conservative estimate

. By comparison, the moisture content in the unsaturated Atlas tailings ranged fr om approximately 21 percent to 28 percent when measured in the early 1980s (Golder, 2005).



### 3.2.2.5 Fraction Passing No. 200 Mesh (75 μ m) The fraction of material passing the No. 200 mesh provides an indication of the particle size of the
material. Since 75 **μ** m (th e opening size of the No. 200 mesh) typically marks the dividing line between silts/clays (“slimes”) and sands, each of the zones in the tailings cell will have different characteristics for this parameter. The average amount of fines passing a No. 200 me sh in the tailings discharge has been estimated to be 0.379 (Golder, 2008a). An estimate of the distribution of these fines through the various areas of the tailings cell was made based on a material balance calculation. Assuming that the tailings
cell c onsists of 33.3% submerged fines, 33.3% transitional sands/fines and 33.3% sandy material, the fraction passing through the No. 200 mesh would be 0.72, 0.36 and 0.05 respectively. These proportions are roughly based on the percentages of fines observed in the Atlas Tailings Impoundment of 0.95, 0.45, and 0.21 for slimes, sand/slimes, and sands, respectively (Golder, 2005)

. However, the Atlas Mill processed ores from several different formations (using both acid and alkaline leach processes) and the
result ant tailings contained more fines than the proposed Salt Wash ores.

The model uses a default distribution for minus No. 200 mesh tailings of 0.5, 0.3 and 0.0 for the three areas. Because the model has a higher default value for fines passing a No. 200 me sh in all of the tailings (i.e., 0.40) than the Salt Wash ores (0.379), it is apparent that the model assumes aAugust 2010 8 073

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. This large slime area was common at historic tailings impoundments, which were typically 100 acres or mo re in size and the tailings were discharged from only a few points

. This resulted in greater segregation between finer and coarser particles and a larger slime

area

. The smaller Piñon Ridge tailings cells will have multiple discharge points around the pe rimeter of each cell that is expected to result in the concentration of finer tailings within the center of each cell and in the development of a larger and more uniform transitional area between the slimes and sands.



### 3.2.2.6 Rn

- 222 Effective Diffusion Coefficient [ m2 /s] The effective diffusion coefficient (De) for radon

- 222 is defined from Fick's equation as the ratio of the diffusive flux density of radon activity across the pore area to the gradient of the radon activity concentration in the pore or interstitial space. The diffusion coefficient in porous media is a property of the diffusing species, the pore structure, the type of fluids present in the pores, the adsorption properties of the solid matrix, the fluid saturations, and temperature. The Radon Flux C alculator Model calculates this value from the correlations from Nielson and Rogers (1986) using porosity and moisture content. The model also allows the input of experimental radon diffusion coefficients or coefficients obtained from more
reliable source s.

The effective radon diffusivity values in porous media can vary over a wide range of values depending on the porosity of the material and particularly on its degree of water saturation. In a fully saturated soil material, the radon diffusion coefficien t may be as low as 10 - 10 m2 /s and, at the upper limit, the diffusion
coefficient for air of 1.1x10 - 5 m2 /s. Typically, the effective diffusion coefficient of radon in unconsolidated soil material with varying moisture content ranges from 10 - 6 m2 /s to 10 - 10 m2 /s

. While the radon flux model uses an existing correlation to determine the effective radon diffusion coefficient, the user is encouraged to input experimentally determined effective diffusion coefficients or other more reliable diffusion coefficient
i nformation to increase the accuracy of the calculation.

Subsequent to the correlations that were used in developing the radon flux model, Rogers and Nielson (1991) have conducted additional correlations and proposed an updated correlation for the effecti ve diffusion coefficient, D e , as follows:



### EQUATION 3 

### ) 6 6 exp( 14 t p

s s t t o e 

### R R p p D D

**− −**  **=**

where D o (equal to 1.1×10 - 5 m2 /s ) is the radon diffusivity in open air, p t is the total soil porosity, and R s is the water saturation in the soil (or the fraction of the pore space filled with water, also called the saturation ratio).

This correlation has also been used in the latest User’s Manual for RESRAD modeling (Yu et al., 2001) and in the support documentation for the modeling impacts on radioactive soils (Yu et al. , 2003).August 2010 9 073

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correlation. For example, the calculation of D e for the case of saturated tailings (i.e., R s = 1) having a total porosity ( p t ) of 0 .39 is as follows:



### EQUATION 4

s m x s m x D
e 2 9 ) 39

. 0 14 ( 2 5 

### 10 03

. 1 ) ) 1 ( ) 6 ( ) 1 ( ) 39

. 0 ( ) 6 exp(( ) 10 1

. 1 ( **− ⋅**  **−** 

### = **⋅ −**  **⋅ ⋅**  **− =** August 2010 10 073

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### 4.0 RADON FLUX MODELING RESULTS

4.1 Mill Tailings Operational Scenarios Details of the design and operation of the proposed 30.5

- acre tailings facility are given in Golder (2008b).
Th e evaluation of radon flux from various operational scenarios from initial filling of the tailings cell to full capacity has been calculated for the following cases:

 Case 1: Initial Fill

- 100% water cover;

 Case 2: Partial Fill

- 80% water cover;

 Case 3: Partial Fill

- 50% water cover;

 Case 4: Partial Fill

- 20% water cover; and

 Case 5: Final Fill

- 0% water cover

.
Typically, the tailings cell will operate with 20 to 80 percent water cover with the smaller water cover occurring during the summer evapor ation season and the larger water cover occurring in the winter

. One hundred percent water cover would normally occur only during the initial filling of the cell when the area of tailings deposition is much smaller, or after a very large precipitation eve nt

. Zero percent water cover would normally occur only during the pre

- closure period when the tailings solution is removed to achieve
final deposition grades and allow for the start of closure activities (EFRC, 2010).

For each of the scenarios, it is ass umed that the tailings will be deposited uniformly on the tailings beaches around the tailings cell perimeter, and that all of the surface area of the tailings cell will contain tailings

. This represents a point in the operation of the tailings facility w hen the cell is nearing full capacity.

The proposed operating procedures for the filling and maintenance of the tailings facility dictates that the tailings will be kept saturated by applying tailings or raffinate solutions on the deposited tailings materi al

. The raffinate is the barren process solution that is pumped to the evaporation ponds for disposal. Since water saturation will aid in the retardation of radon release, the normal mode of operation will be to keep the tailings wet at all times

. The t ailings facility will be considered to be in an operational mode from initial filling through the pre

- closure steps described in the “Operating Plan, Tailings Cells and Evaporation Ponds” (EFRC, 2010)

. Once full, the tailings cell will be considered in cl osure mode and a radon and evapotranspiration cover will be placed over the tailings to permanently suppress radon flux in accordance with plans approved by the Radiation Control Program of the Colorado Department of Public Health and Environment (CDPHE).

Although EFRC plans to continuously keep the beach areas on the perimeter saturated during operations, there may be some interim period where a limited amount of the tailings surface may temporarily become
unsaturated due to mechanical failure of the wate r recycle system, other unforeseen circumstances, or during the transition from operational to closure mode. While it is not the intent of EFRC to allow areas ofAugust 2010 11 073

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i: \ 07 \ 81694 \ 0400 \ 0406 fnlradonfluxcalcs 17aug10 \ 07381694 fnlrpt radfluxcalcs 17aug10.doc unsaturated tailings to be exposed for any significant length of time, a series of model runs were performed which evaluated how much unsaturated tailings material could be allowed on an interim basis
while still staying below 20 pCi/ m2 s of radon flux

.



### 4.2 Radon Flux Model Calculation Results
The radon model was run for the various water cover scenar ios outlined in Section 4.1 . The results of these calculations are presented in Table 1 and Figure 4

. The results indicate that the radon flux will be below 20 pCi/ m2 s for all scenarios

. The radon flux generated for the case with 100 percent water cover is primarily attributable to the area with less than 1 meter of water cover

. The model input parameters and data output are provided in Appendix A.



### TABLE 1 RESULTS OF RADON FLU X MODEL

Case Water Cover (%) Radon Flux (pCi/ m2 s) 1 100 2.62 2 80 3.27 3 50 5.05 4 20 6.79 5 0 7.44

Modeling of unsaturated tailings was also performed to determine how much unsaturated material could be exposed during operations should the solution application system be temporarily shut down for r epairs
or other reasons

. These results are shown in Table 2 for the worst case of zero percent water cover

. Other percentages of water cover of course would show allowable unsaturated tailings areas in excess of
the values in Table 2. The percentages ca lculated were of the saturated material rather than the whole of the tailings area. As can be seen from this table, the radon flux for all cases shows that some degree of unsaturated tailings can be allowed while still remaining below 20 pCi/m2s of radon flux.



### TABLE 2 RADON FLUX WITH UNSA TURATED TAILINGS EXP OSURE

Case Water Cover (%) Unsaturated Tailings (%) Radon Flux (pCi/ m2 s) 1 0 5 10.57 2 0 10 13.70 3 0 20 19.95

The details of these calculations are provided in Appendix B.August 2010 12 073

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### 4.3 Atmospheric Radon Concent rations The results of radon flux values for the tailings facility cannot readily be converted to airborne radon concentrations due to the need for meteorological modeling and determination of where the airborne
concentrations would be measured. EPA has e stimated the maximum radon air concentration at the edge of a uranium tailings cell ( WISE, 2009; EPA, 1983). Based on these estimates, and assuming a maximum radon flux at the surface of the tailings cell of 20 pCi/m 2 sec, the maximum radon in the air
woul d be approximately 0.28 pCi/l. Since the tailings cells will typically have a radon flux well below
20 pCi/m 2 sec, the air concentration of radon near the Pi ñ on Ridge tailings cell s is expected to be proportionately lower.

The report “Estimates of Radiatio n Doses to Members of the Public from the Piñon Ridge Mill” (Two Lines, 2009) also provides insight on the potential radon doses resulting from the ore stockpile, tailings cells, and mill emissions

. This report is included in EFRC’s Radioactive Materials License Application to the Radiation Control Program of CDPHE

. This study was conducted using the MILDOS Area model, which includes material properties, emission rates, and site

- specific meteorological data as model inputs

. The study projected that radon doses at the property’s fence line from all sources would range from 1.2 to 9.0 millirems per year (mrem/yr)
, and the nearest residents to the mill would receive a dose of less than
1 mrem/year

. The study conservatively assumed that one tailings cell had reached capacity and a second tailings cell was in the initial stages of operation.August 2010 13 073

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### 5.0 CONCLUSIONS Golder was commissioned by EFRC to evaluate the operations of the uranium mill tailings storage facility at the Piñon Ridge Mill in terms of radon flux

. The evaluation focused on identifying the flux levels produced during normal operations whereby tailings would be maintained in a saturated state with varying levels of water cover depending on the season and stage of operations

. Operating flux levels were

co mpared to the 20 pCi/m2s flux limit established by the U.S. Environmental Protection Agency (EPA) in 40 CFR 61 Subpart W, “National Emission Standards for Radon Emissions from Operating Mill Tailings” (EPA, 1998) for pre

- 1989 tailings impoundments

. The ev aluation also looked at the flux levels that would occur as tailings lose some level of saturation due to drying conditions

.
The radon flux calculations presented in this report were conducted using the WISE Uranium Mill Tailings Radon Flux Calculator, as updated on November 23, 2009 (WISE, 2009). The results of the radon flux modeling calculations demonstrate that the proposed normal mode of operation will maintain radon flux
levels well below 20 pCi/m2s. The modeling has also shown that some fraction o f the tailings deposition
can be unsaturated while still maintaining flux levels below 20 pCi/m2s. This situation could occur as a result of equipment breakdown or during the transition from operational to closure mode.August 2010 14 073

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### 6.0 USE OF THIS REPORT This report has been prepared exclusively for the use of Energy Fuels Resources Corporation (EFRC) for specific application to the Pi ñ on Ridge Project. The analyses reported herein were performed in accordance with accepted practices. No third

- party engineer or consult ant shall be entitled to rely on any of the information, conclusions, or opinions contained in this report without the written approval of Golder
and EFRC.

Golder sincerely appreciates the opportunity to support EFRC on the Pi ñ on Ridge Project. Please

con tact the undersigned with any questions or comments on the information contained in this report.

Respectfully submitted,

GOLDER ASSOCIATES INC.

Kimberly F. Morrison, P.E., R.G. Erich Tiepel, PhD., P.E. Associate

- Senior Project Manager PrincipalAugust 2010 15 073

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### 7.0 REFEREN CES Energy Fuels Resources Corporation (EFRC)

. 2010. “Operating Plan, Tailings Cells and Evaporation Ponds.”
Golder Associates Inc. (Golder)

. 2005. “Materials Handling Evaluation Study for the Moab Tailings Impoundment, Moab, Utah. ” Submitted to S.M. St oller

. Reference No. 053

- 2269. 21 September 2005.
Golder Associates Inc. (Golder)

. 2008a. “Project Design Criteria, Piñon Ridge Geotechnical Services. ” Revision C. 5 May 2008.
Golder Associates Inc. (Golder)

. 2008b. “Tailings Cell Design Report, Piño n Ridge Project, Montrose County, Colorado. ” Prepared for Energy Fuels Resources Corporation

. Reference No. 073

- 81694

. October.
Golder Associates Inc. (Golder)

. 2010. “Tailings Cell Foundation and Closure Cover System Settlement Analyses Addendum, Piño n Ridge Project, Montrose County, Colorado,” Letter report to Mr. Frank Filas, Energy Fuels Resources Corporation, April.

Nielson, K.K., and V.C. Rogers

. 1986

. “Surface Water Hydrology Considerations in Predicting Radon Releases from Water

- Covered Areas of Uranium Tailings Ponds,” Geotechnical & Geohydrological Aspects of Waste Management, Fort Collins, Colorado, pp. 215

- 222.
Rogers, V.C., and K.K. Nielson. 1991. "Multiphase Radon Generation and Transport in Porous Materials," Health Physics, No. 60, pp . 807

- 815.
U.S. Environmental Protection Agency (EPA). 1983. “Final Environmental Impact Statement for Standards for the Control of Byproduct Materials from Uranium Ore Processing (40 CFR 1092),” Vol. 1, Report No

. EPA/520/1

- 83

- 008

- 1, September.

U.S. En vironmental Protection Agency (EPA)

. 1998. Regulations as found in 40 CFR 61 Subpart W, National Emission Standards for Radon Emissions from Operating Mill Tailings, April.
U.S. Nuclear Regulatory Commission (NRC)

. 1980. NUREG

- 0706, “Final Generic EIS on Uranium Milling. ” Office of Nuclear Material, Safety and Safeguards, Washington, D.C., September

. 850 pp.
WISE Uranium Project (WISE)

. 2009. Uranium Mill Tailings Radon Flux Calculator, November. http://www.wise

- uranium.org/ctb.html?unit=c

Yu, C., C

. Loureiro, J.J. Cheng, L.G. Jones, Y.Y. Wang, Y.P. Chia, and E. Faillace. 1993. Data Collection Handbook to Support Modeling Impacts of Radioactive Material in Soil

. Environmental Assessment and Information Sciences Division, Argonne National Laborator y, Argonne, Illinois, April.
Yu, C., A.J. Zielen, J.J. Cheng, D.J. LePoire, E. Gnanapragasam, S. Kamboj, J. Arnish, A. Wallo III, W.A. Williams, and H. Peterson. 2001. Users’ Manual for RESRAD Version 6, Environmental Assessment Division, ANL/EAD

- 4, Argo nne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois. EPA regulations as found in 40 CFR 61 Subpart W, National Emission Standards for Radon Emissions from Operating Mill Tailings, April 1998.

### FIGURES

### Piñon Ridge Project Area Uncompahgre NF Grand Mesa NF Gunnison NF

Manti-Lasal NF Gunnison NF

Uncompahgre NF Colorado Natl Mon

Black Canyon of Gunnison CO

Curecanti Natl Rec Area 

### Mesa

Montrose Delta

Ouray

Gunnison

San Miguel Hinsdale Grand COLORADO

UTAH

Delta Paonia

Olathe

Ridgway Norwood Crawford Redlands Palisade

Hotchkiss Cedaredge Fruitvale

Orchard City Orchard Mesa

Loghill Village Clifton

Montrose Grand Junction

Nucla Bedrock Gateway

Naturita 70

50

550 6

141 65

92

90 25 133

62 145 348

347

97

141 141

90 D i v

i d

e D

N u c l a D

e l t a F f 7

0 2 6 5

133

D i v i d e

107°30’0"W 107°30’0"W

107°45’0"W 107°45’0"W

108°0’0"W 108°0’0"W

108°15’0"W 108°15’0"W

108°30’0"W 108°30’0"W

108°45’0"W 108°45’0"W

109°0’0"W 109°0’0"W39°0’0"N39°0’0"N38°45’0"N38°45’0"N38°30’0"N38°30’0"N38°15’0"N38°15’0"N 10 0 10 5 MILES 1:500,000

Denver, Colorado DESIGN

GIS
CHECK

REVIEW PROJECT No. 073-81694

08/04/2010 FILE No. 11x17_SiteLoc.mxd

SCALE AS SHOWN REV 0 

### FIGURE 1 SITE LOCATION MAP MONTROSE COUNTY, COLORADO

AJR TITLE PROJECT SCALE 

### LEGEND

REFERENCES Base Data: ESRI, 2009. Imagery: ESRI API, Assorted Dates. Projection: StatePlane, Colorado South, NAD83, Feet.

08/04/2010 AJR WHEN PRODUCED AT SIZE 11X17IN

08/04/2010 SS

08/04/2010 KFM ENERGY FUELS RESOURCES CORPORATION PIÑON RIDGE PROJECTMap Document: M:\Pinonridge\ArcMap\RadonFluxCalc\11x17_SiteLoc.mxd / Modified 8/4/2010 3:12:01 PM / Plotted 8/4/2010 3:12:01 PMby AReither Property Boundary
Town
Interstate Highway Major Road
Local Road
National Park or Forest
State County
Stream
Intermittent Stream

Dam
ReservoirSaturatedUnsaturatedSubmergedd>1md<1mKFM Jul-10 073-81694.0002ET NTS N/AET TailingsZonationFigure.xls 3ENERGY FUELS RESOURCES CORP.PIÑON RIDGE PROJECTTailings Zonation Model AssumptionsSaturatedUnsaturatedSubmergedd>1md<1m2345678 Radon Flux (pCi/m 2 s)ET Aug-10 073-81694.0023KFM NTS N/AET07381694 RadonFluxCalc Fig4.xls4Radon Flux vs. Percent Water CoverENERGY FUELS RESOURCES CORP.PIÑON RIDGE PROJECT0123456780 10 20 30 40 50 60 70 80 90 100

Radon Flux (pCi/m 2 s)% Water Cover

### APPENDIX A DETAILS OF RADON FLU X CALC ULATIONS FOR SATURATED AND SUBMERGED TAILINGSAugust 2010Uranium Mill Tailings Radon Flux Calculations073-81694.23I:\07\81694\0400\0406 FNLRadonFluxCalcs 17AUG10\AppA\07381694 AppA EF RadFluxCalcs 0%Water 0%Unsatd ErichTiepel 06AUG10.xlsx647 4 0.22 0.15 0.379 1 0 578 3.00E-07Tailings ZoneSurface Area(m2)Bulk Density(g/cm3)PorosityMoisture Contents(dry wt_%)Fraction Passing#200 Mesh(75μm)Rn - 222Effective DiffusionCoefficient (m2/s)Submerged 0 1.12 0.57 Saturated 0.72 5.08E-10Saturated 120365 1.28 0.39 Saturated 0.36 1.03E-09Unsaturated 0 1.44 0.39 15 0.05 3.53E-05Ra - 226 ActivityConcentrationin Ponding Water(pCi/l)Ra - 226 ActivityConcentrationsin Tailings(pCi/g)Effective StagnantWater Transportcoefficient(m2/s)Input Data / 0% Water Cover / 0% UnsaturatedTailings DataRadon Flux ResultspCi/m2s7.44Zone - Specific Tailings PropertiesFractionPassing #200 Mesh(75 μm)Fraction of PondAreawith less than1 m deepAverage Pond Depthfor Areas Greater than1 m deepRa - 226 ActivityRatio inslimes vs. sandRa - 222 EmanationFractionin slimesRa - 222 EmanationFractionin sandAugust 2010Uranium Mill Tailings Radon Flux Calculations073-81694.23I:\07\81694\0400\0406 FNLRadonFluxCalcs 17AUG10\AppA\07381694 AppA EF RadFluxCalcs 20%Water 0%Unsatd Erich Tiepel 06AUG10.xlsx647 4 0.22 0.15 0.379 0.358 1.83 578 3.00E-07Tailings ZoneSurface Area(m2)Bulk Density(g/cm3)PorosityMoisture Contents(dry wt_%)Fraction Passing#200 Mesh(75μm)Rn - 222Effective DiffusionCoefficient (m2/s)Submerged 24073 1.12 0.57 Saturated 0.72 5.08E-10Saturated 96292 1.28 0.39 Saturated 0.36 1.03E-09Unsaturated 0 1.44 0.39 15 0.05 3.53E-05Ra - 226 ActivityConcentrationin Ponding Water(pCi/l)Ra - 226 ActivityConcentrationsin Tailings(pCi/g)Effective StagnantWater Transportcoefficient(m2/s)Input Data / 20% Water Cover / 0% UnsaturatedTailings DataRadon Flux ResultspCi/m2s6.79Zone - Specific Tailings PropertiesFractionPassing #200 Mesh(75 μm)Fraction of PondAreawith less than1 m deepAverage Pond Depthfor Areas Greater than1 m deepRa - 226 ActivityRatio inslimes vs. sandRa - 222 EmanationFractionin slimesRa - 222 EmanationFractionin sandAugust 2010Uranium Mill Tailings Radon Flux Calculations073-81694.23I:\07\81694\0400\0406 FNLRadonFluxCalcs 17AUG10\AppA\07381694 AppA EF RadFluxCalcs 50%Water 0%Unsatd Erich Tiepel 06AUG10.xlsx647 4 0.22 0.15 0.379 0.19 2.43 578 3.00E-07Tailings ZoneSurface Area(m2)Bulk Density(g/cm3)PorosityMoisture Contents(dry wt_%)Fraction Passing#200 Mesh(75μm)Rn - 222Effective DiffusionCoefficient (m2/s)Submerged 60182 1.12 0.57 Saturated 0.72 5.08E-10Saturated 60182 1.28 0.39 Saturated 0.36 1.03E-09Unsaturated 0 1.44 0.39 15 0.05 3.53E-05Ra - 226 ActivityConcentrationin Ponding Water(pCi/l)Ra - 226 ActivityConcentrationsin Tailings(pCi/g)Effective StagnantWater Transportcoefficient(m2/s)Input Data / 50% Water Cover / 0% UnsaturatedTailings DataRadon Flux ResultspCi/m2s5.05Zone - Specific Tailings PropertiesFractionPassing #200 Mesh(75 μm)Fraction of PondAreawith less than1 m deepAverage Pond Depthfor Areas Greater than1 m deepRa - 226 ActivityRatio inslimes vs. sandRa - 222 EmanationFractionin slimesRa - 222 EmanationFractionin sandAugust 2010Uranium Mill Tailings Radon Flux Calculations073-81694.23I:\07\81694\0400\0406 FNLRadonFluxCalcs 17AUG10\AppA\07381694 AppA EF RadFluxCalcs 80%Water 0%Unsatd Erich Tiepel 06AUG10.xlsx647 4 0.22 0.15 0.379 0.142 2.9 578 3.00E-07Tailings ZoneSurface Area(m2)Bulk Density(g/cm3)PorosityMoisture Contents(dry wt_%)Fraction Passing#200 Mesh(75μm)Rn - 222Effective DiffusionCoefficient (m2/s)Submerged 96292 1.12 0.57 Saturated 0.72 5.08E-10Saturated 24073 1.28 0.39 Saturated 0.36 1.03E-09Unsaturated 0 1.44 0.39 15 0.05 3.53E-05Effective StagnantWater Transportcoefficient(m2/s)Input Data / 80% Water Cover / 0% UnsaturatedTailings DataRadon Flux ResultspCi/m2sRa - 226 ActivityRatio inslimes vs. sandRa - 222 EmanationFractionin slimesRa - 222 EmanationFractionin sandRa - 226 ActivityConcentrationin Ponding Water(pCi/l)Ra - 226 ActivityConcentrationsin Tailings(pCi/g)3.27Zone - Specific Tailings PropertiesFractionPassing #200 Mesh(75 μm)Fraction of PondAreawith less than1 m deepAverage Pond Depthfor Areas Greater than1 m deepAugust 2010Uranium Mill Tailings Radon Flux Calculations073-8164.23I:\07\81694\0400\0406 FNLRadonFluxCalcs 17AUG10\AppA\07381694 AppA EF RadFluxCalcs 100%Water 0%Unsatd Erich Tiepel 06AUG10.xlsx647 4 0.22 0.15 0.379 0.2 3.05 578 3.00E-07Tailings ZoneSurface Area(m2)Bulk Density(g/cm3)PorosityMoisture Contents(dry wt_%)Fraction Passing#200 Mesh(75μm)Rn - 222Effective DiffusionCoefficient (m2/s)Submerged 120365 1.12 0.57 Saturated 0.72 5.08E-10Saturated 0 1.28 0.39 Saturated 0.36 1.03E-09Unsaturated 0 1.44 0.39 15 0.05 3.53E-05Radon Flux ResultspCi/m2s2.62Zone - Specific Tailings PropertiesFractionPassing #200 Mesh(75 μm)Fraction of PondAreawith less than1 m deepAverage Pond Depthfor Areas Greater than1 m deepRa - 226 ActivityRatio inslimes vs. sandRa - 222 EmanationFractionin slimesRa - 222 EmanationFractionin sandRa - 226 ActivityConcentrationin Ponding Water(pCi/l)Ra - 226 ActivityConcentrationsin Tailings(pCi/g)Effective StagnantWater Transportcoefficient(m2/s)Input Data / 100% Water Cover / 0% UnsaturatedTailings Data

### APPENDIX B DETAILS OF RADON FLU X CALCULATIONS FOR ALLOWABLE UNSATURATED TAILINGS EXPOSURE

Caption TextAugust 2010Uranium Mill Tailings Radon Flux Calculations073-81694.23I:\07\81694\0400\0406 FNLRadonFluxCalcs 17AUG10\AppB\07381694 AppB EF RadFluxCalcs 0%Water 5%Unsatd Erich Tiepel 06AUG10.xlsx647 4 0.22 0.15 0.379 1 0 578 3.00E-07Tailings ZoneSurface Area(m2)Bulk Density(g/cm3)PorosityMoisture Contents(dry wt_%)Fraction Passing#200 Mesh(75μm)Rn - 222Effective DiffusionCoefficient (m2/s)Submerged 0 1.12 0.57 Saturated 0.72 5.08E-10Saturated 114347 1.28 0.39 Saturated 0.36 1.03E-09Unsaturated 6018 1.44 0.39 15 0.05 3.53E-05Radon Flux ResultspCi/m2s10.57Zone - Specific Tailings PropertiesFractionPassing #200 Mesh(75 μm)Fraction of PondAreawith less than1 m deepAverage Pond Depthfor Areas Greater than1 m deepRa - 226 ActivityRatio inslimes vs. sandRa - 222 EmanationFractionin slimesRa - 222 EmanationFractionin sandRa - 226 ActivityConcentrationin Ponding Water(pCi/l)Ra - 226 ActivityConcentrationsin Tailings(pCi/g)Effective StagnantWater Transportcoefficient(m2/s)Input Data / 0% Water Cover / 5% UnsaturatedTailings DataAugust 2010Uranium Mill Tailings Radon Flux Calculations073-81694.23I:\07\81694\0400\0406 FNLRadonFluxCalcs 17AUG10\AppB\07381694 AppB EF RadFluxCalcs 0%Water 10%Unsatd Erich Tiepel 06AUG10.xlsx647 4 0.22 0.15 0.379 1 0 578 3.00E-07Tailings ZoneSurface Area(m2)Bulk Density(g/cm3)PorosityMoisture Contents(dry wt_%)Fraction Passing#200 Mesh(75μm)Rn - 222Effective DiffusionCoefficient (m2/s)Submerged 0 1.12 0.57 Saturated 0.72 5.08E-10Saturated 108329 1.28 0.39 Saturated 0.36 1.03E-09Unsaturated 12036 1.44 0.39 15 0.05 3.53E-05Radon Flux ResultspCi/m2s13.7Zone - Specific Tailings PropertiesFractionPassing #200 Mesh(75 μm)Fraction of PondAreawith less than1 m deepAverage Pond Depthfor Areas Greater than1 m deepRa - 226 ActivityRatio inslimes vs. sandRa - 222 EmanationFractionin slimesRa - 222 EmanationFractionin sandRa - 226 ActivityConcentrationin Ponding Water(pCi/l)Ra - 226 ActivityConcentrationsin Tailings(pCi/g)Effective StagnantWater Transportcoefficient(m2/s)Input Data / 0% Water Cover / 10% UnsaturatedTailings DataAugust 2010Uranium Mill Tailings Radon Flux Calculations073-81694.23I:\07\81694\0400\0406 FNLRadonFluxCalcs 17AUG10\AppB\07381694 AppB EF RadFluxCalcs 0%Water 20%Unsatd Erich Tiepel 06AUG10.xlsx647 4 0.22 0.15 0.379 1 0 578 3.00E-07Tailings ZoneSurface Area(m2)Bulk Density(g/cm3)PorosityMoisture Contents(dry wt_%)Fraction Passing#200 Mesh(75μm)Rn - 222Effective DiffusionCoefficient (m2/s)Submerged 0 1.12 0.57 Saturated 0.72 5.08E-10Saturated 96292 1.28 0.39 Saturated 0.36 1.03E-09Unsaturated 24073 1.44 0.39 15 0.05 3.53E-05Radon Flux ResultspCi/m2s19.95Zone - Specific Tailings PropertiesFractionPassing #200 Mesh(75 μm)Fraction of PondAreawith less than1 m deepAverage Pond Depthfor Areas Greater than1 m deepRa - 226 ActivityRatio inslimes vs. sandRa - 222 EmanationFractionin slimesRa - 222 EmanationFractionin sandRa - 226 ActivityConcentrationin Ponding Water(pCi/l)Ra - 226 ActivityConcentrationsin Tailings(pCi/g)Effective StagnantWater Transportcoefficient(m2/s)Input Data / 0% Water Cover / 20% UnsaturatedTailings Data