NUREG/CR-6821

Solubility and Leaching of

Radionuclides in Site

Decommissioning Management

Plan (SDMP) Soil and

Ponded Wastes

Pacific Northwest National Laboratory

U.S. Nuclear Regulatory Commission

Office of Nuclear Regulatory Research

Washington, DC 20555-0001

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NUREG/CR-6821

Solubility and Leaching of

Radionuclides in Site

Decommissioning Management

Plan (SDMP) Soil and

Ponded Wastes

Manuscript Completed: May 2003

Date Published June 2003

Prepared by

A.R. Felmy, V.L. LeGore, S.A. Hartley

Pacific Northwest National Laboratory

P.O. Box 999

Richland, WA 99352

P. Reed, NRC Project Manager

Prepared for

Division of Systems Analysis and Regulatory Effectiveness

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

NRC Job Code W6409
NUREG/CR-6821, has been reproduced

from the best available copy.
ABSTRACT

Samples of disposed wastes from one former and two current U.S. Nuclear Regulatory

Commission Site Decommissioning Management Plan Sites, labeled Sites D, E, and F, were

studied to determine 1) the key radionuclides and their concentrations present in the waste, 2) the

solubility limits and solubility limiting phases for these radionuclides, 3) the rate of attainment of

solubility equilibrium, 4) the observed leaching rate for radionuclides that may or may not be

solubility controlled, and 5) identify, if possible, the potential for radiocolloid formation. To

achieve these goals, batch studies were conducted over ranges of solution pH values (2-12),

solid to solution ratio, and particle size. In addition, flow-through column studies were

conducted of selected samples to help verify the mechanisms and predictive relations identified

in the batch experiments. The results show that the major radionuclides present in the wastes

varied widely between the three sites.

At all three sites, comparisons of filtered and unfiltered analyses of samples from either flowthrough columns or well waters did not show any evidence of radiocolloids. At Site F, certain

well samples contained very high concentrations of iron oxide particles. However, these

particles did not show any clear evidence of high radionuclide content.

Maximum dissolved concentrations (solubility limits) and radionuclide-leaching rates have been

calculated for use in performance assessment calculations at all three sites. Observed Th

concentrations at Site D were quite low, the maximum Th solubility was 3.2 x 1o M. U

solubilities at Site D, 1.6 x 10 M, were the highest observed at any of the sites. The leaching

rates at Site D for Th and U were calculated to be 3.1 x 10-9 g U/hr and 1.4 x 106 g Ulhr,

respectively. At Site E the Th solubilities and leach rates were also quite low, 3.16 x 10-9 M, and

1.5 x 10-10 g Th/hr, respectively. The solubilities and leach rates for U at Site E were also quite

low, 3.16 x 10-9 M and 1.6 x 1010 g U/br, respectively. At Site F, the principal radionuclides

retained in the soil were Cs-137 and Ra-226. The maximum observed solubilities for these

radionuclides were 1.8 x 10-14 M and 8.5 x 10-12 M respectively. Maximum leach rates were 1.5

x 1017 g/hr and 2.2 x 10-.3 g/hr for Cs-137 and Ra-226 at Site F.

Statistical analysis of the observed solubilities was hampered by the generally very low

solubilities (at or below the analytical detection limit) found for the radionuclides. Only the

following means and standard deviations, assuming a normal distribution, were calculated:

Site D - U (8.9 x 10M± 6.9 x 10-6)

Site F - Cs-137 (1.6 x 10-14M ± 2.4 x 10-'), Ra-226 (3.0 x 10- 2M ± 3.9 x 102).

iii
CONTENTS

ABSTRACT................................................................................................................................. iii

EXECUTIVE SUMMARY .......................................... ix

ABBREVIATIONS .......................................... xi

1. INTRODUCTION ........................................... 1

2. SITE SAMPLING AND SAMPLE SELECTION .......................................... 3

3. METHODS AND MATERIALS .......................................... 7

3.1 Chemical Analysis Procedures .......................................... 7

3.2 Radiological Analysis .......................................... 7

3.3 Solubility and Batch Studies .......................................... 8

3.4 Colunn Studies .......................................... 9

3.5 Radiocolloids .......................................... 9

4. RESULTS AND DISCUSSION ......................................... 11

4.1 Chemical Analysis ......................................... . 11

4.2 Radiological Analysis .......................................... 17

4.2.1 Site D ......................................... 17

4.2.2 SiteE ......................................... 19

4.2.3 Site F ......................................... - 22

4.3 Solubility, and Leaching Studies .......................................... 26

4.3.1 Site D ......................................... 26

4.3.2 Site E ......................................... 31

4.3.3 Site F ......................................... 35

4.4 Calculations of Solubility Limits and Leaching Rates .................................. 40

4.4.1 Site D .......................................... 41

4.4.2 Site E ......................................... 41

4.4.3 Site F ......................................... 42

4.5 Radiocolloids ......................................... . 42

4.6. Statistical Analysis ......................................... . 43

5. REFERENCES ......................................... 45

APPENDIX

A TABLES OF EXPERIMENTAL DATA............................................................................. A-1

v
FIGURES

3-1. Schematic of Column Apparatus ............................................................... 10

4-1. Alpha Spectra of Highest Activity Site D Sample. Th-232 and Daughters Present Only at

Very Low Levels .............................................................. 1 9

4-2. Alpha Spectra of Sample K3 from Site E .............................................................. 22

4-3. Gamma Spectra of Soil Samples at Site F. a) Soil 2S, b) Soil 5S, and c) Soil 6S ............. 24

4-4. Total (T) Th Concentrations (moles/1) in Site D Solubility Studies ................................... 28

4-5. Total (T) U Concentrations (moles/I) in Site D Solubility Studies .................................... 29

4-6. Total (T) U Concentrations (moles/l) in Site D Batch Leaching Studies .......................... 30

4-7. Total (T) Thorium and U Concentrations (moles/I) in Site D Column Studies ................. 30

4-8. Total (T) Th Solubilities (moles/) in Site E Sample K2 .................................................... 32

4-9. Th-232 Daughters Solubilized in the Solubility Studies of Site E Sample K2 .................. 32

4-10. Cs-137 Activities in Site F Soil Sample Solubility Studies .. ............................................ 36

4-11. Measured Radium-226 and Bismuth-214 Activities and Uncertainties for all Solubility,

Batch Leaching, and Column Samples Between pH Values of 5 to 10 from Site F ...... 40

4-12. Statistically Simulated Distribution of Uranium Concentration at Site D Using Only the

Mean and Standard Deviation of the Four Column Data Points ..................................... 44

vi
TABLES

2-1. Description of Site Sampling and Well Locations at Site E ................................................. 3

2-2. Description of Soil Sample Locations at Site F ............................................................ 4

4-1. Chemical Composition of Samples at Sites E (see Table 2-1) and D ................................ 12

4-2. Chemical Composition with Depth for Core 46 (Location G) at Site E ............................ 13

4-3. Chemical Analysis of Water and Well Samples at Site E (see Table 2-1) ......................... 14

4-4a. Calculated Aqueous U(VI) Species in Surface and Well Waters at Site E . . 15

4-4b. Calculated Aqueous U(VI) Species in Surface and Well Waters at Site E .. 15

4-5. Chemical Analysis of Soils and Sediments Site F. (2 sheets) ........................................... 15

4-6. Inorganic Chemical Analysis of Well and Surface Waters at the Site F ........................... 16

4-7. Volatile Organic Carbon Analysis of the Water Samples at the Site F (ug/1) ................... 17

4-8. Radiological Analysis of the Highest Activity Soil Sample at Site D ............................... 18

4-9a. Radiological Analysis (Gamma Spectroscopy) of Wastes (Samples Kl-K5) at Site E. .20

4-9b. Radiological Analysis (Gamma Spectroscopy) of Wastes (Core 46) and Plant Material at

Site E ........................................................... 21

4-10. Radiological Analysis of Wastes at Site E . ........................................................... 21

4-11. Radiological Analysis of Soil and Vegetative Samples at Site F (pCi/g) ........................ 25

4-12. Radiological Analysis of the Water Samples at Site F (pCi/L) ........................................ 25

4-13. Calculated Aqueous Ni and U(VI) Species in Well Waters at Site F ............................. 26

4-14. Measured pH Values in Batch Leaching Studies at Site D as a Function of Time ......... 27

4-15. Thorium Concentrations in Batch Leaching Studies of Site D Sample in the Absence of

CO2 ........................................................... 27

4-16. Chemical Analysis of Batch Leaching Studies for Samples from Site E ........................ 34

4-17. Chemical Analysis of Column Studies for Site E Samples .............................................. 35

vii
4-18. Ra-226 and Daughter Activities in Site F Solubility Studies ........................................... 37

4-19. Ra-226 and Daughter Activities in Site F Batch Leaching Studies ................................. 38

4-20. The pH Values in Site F Batch Leaching Studies ............................................................ 39

4-21. Radionuclide Concentrations in Site F Column Studies .................................................. 39

4-22. Summary of Solubility and Leaching Rate Calculations at Each Site ............................. 42

4-23. Filtered and Unfiltered Thorium and Uranium Concentrations in Column Studies ........ 43

viii
EXECUTIVE SUMMARY

Each year the U.S. Nuclear Regulatory Commission (NRC) receives requests to discontinue Site

Decommissioning Management Plan (SDMP) Sites that involve the use of radioactive materials.

However, the termination of some licenses and the possible release of the site for unrestricted or

other uses are sometimes nonroutine owing to the level, volume, or complex nature of the

radiological contamination. In such cases, a clearer scientific understanding of the nature, both

physical and chemical, of the radiological contamination is required to make informed judgments

as to the level of site remediation that may be required. As part of such an overall effort, this

report summarizes the findings from solubility, batch, and soil/waste column studies conducted

on wastes from one former and two current NRC Site Decommissioning Management Plan

(SDMP) Sites. These studies were designed to determine 1) the key radionuclides and their

concentrations present in the waste, 2) the solubility limits and solubility limiting phases for

these radionuclides, 3) the rate of attainment of solubility equilibrium, 4) the observed leaching

rate for radionuclides that may or may not be solubility controlled, and 5) identify, if possible,

the potential for radiocolloid formation.

The results show that the major radionuclides present in the wastes varied widely between the

different sites depending upon the specific application and the disposal practices. At two of the

sites where radioactive slags or depleted U were disposed, the dominant radionuclides were Th

and U with their associated daughter products. At Site D, U and associated daughters were the

dominant radionuclides present. Th was present at only very low concentrations. At Site D, the

samples contain depleted U and no solubility-controlling phase was present. Adsorption or ion

exchange processes appear to control the leachable U concentrations in these samples. At Site E,

Th and associated daughters were the dominant radionuclides. Th daughters were in secular

equilibrium with the parent Th-232 in all samples. Analysis of data from solubility studies

indicated that aqueous Th concentrations are solubility controlled, most likely by amorphous

Th0 2(am). T02(am), sets upper limits on the dissolved Th concentrations.

At the third site, Site F, several different radionuclides were present owing to the wide range of

manufacturing activities conducted at the site. These varied activities resulted in the release of

several different radionuclides including: H-3, Sr-90, Cs-137, Ni-63, and Ra-226. H-3 and Sr-90

were the dominant radionuclides found in the groundwater and Cs-137 and Ra-226 (with

associated daughters) were the dominant radionuclides found in the soil samples. Ni-63 was

present at relatively low activity (< 12 pCi/g) in the soil samples.

Comparisons of filtered and unfiltered analyses of effluent samples from flow-through columns

from Site D did not show any evidence for the presence of radiocolloids, nor did analysis of

filtered and unfiltered well water samples at Sites E and F. Maximum dissolved concentrations

(solubility limits) and radionuclide-leaching rates have been determined for use in performance

assessment calculations for all three sites.

Statistical analysis of the solubility and leaching data was hampered by low solubilities for the

majority of the radionuclides found at the sites. Only limited statistical analysis was for possible

for U at Site D and for Cs-137 and Ra-226 at Site F.

ix
These results provide experimental evidence on the nature of the contamination present at these

sites and the range of conditions under which the radionuclides are likely to be either soluble and

mobile in the groundwater or insoluble and immobile. Such results will likely assist in the

evaluation of effective remediation strategies for these sites.

x
ABBREVIATIONS

Ac actinium

Al aluminum

(am) amorphous

AS alpha spectroscopy

Bi bismuth

(c) crystalline

Ca calcium

Ci/ml curies per milliliter

DMG Dimethylglyoxime

Fe iron

g gram

GC gas chromatography

GM Gieger-Mf1ller

IC ion chromatograph

ICP inductively coupled plasma spectroscopy

ICP-MS inductively coupled plasma mass spectrometry

keV one thousand electron volts

KP kinetic phosphorescence

LSC liquid scintillation counting

m meter

mg magnesium

mg/l milligrams per liter

ml milliliter

Mo molybdenum

MS mass spectrometry

Nb niobium

NRC U.S. Nuclear Regulatory Commission

ORISE Oak Ridge Institute for Science and Education

Pb lead

pCi/g picocuries per gram

xi
-

pH negative log of the activity of If

PNNL Pacific Northwest National Laboratory

ppm parts per million

Ra radium

Rn radon

SDMP Site Decommissioning Management Plan

Si silicon

Ta tantalum

Th thorium

U uranium

VOC volatile organic compound

XRF x-ray fluorescence

Zr zirconium

xii
1. INTRODUCTION

The U.S. Nuclear Regulatory Commission (NRC) has identified 25 SDMP materials facilities

that are undergoing non-routine decommissioning (NRC 2002). All of these sites require some

degree of remediation before sites can be released for unrestricted use. As a result, the NRC is

currently in the process of conducting performance assessments of these sites to better ascertain

the potential for radionuclides solubilization, leaching, or migration offsite. As part of this

overall effort, the Pacific Northwest National Laboratory (PNNL) was contracted to obtain

selected samples from different Site Decommissioning Management Plan (SDMP) sites and

conduct batch and flow-through column leaching studies of these wastes to determine the

radionuclides present in the waste, the maximum leachable concentrations (solubility limits) for

important radionuclides, the time required for radionuclides to reach solubility equilibrium, the

overall radionuclide leaching rates, and, if possible, identify the potential impact of colloids in

transporting radionuclides.

This report presents detailed results of PNNL studies on one former and two current SDMP soil

or ponded waste sites labeled Sites D, E, and F.

The waste at Site D primarily consists of DU mixed with soil and other material. The facility at

Site E was used to smelt MglTh metal alloys from 1958 to about 1970. The Mg was recovered

and used for underground cathode protection. The Th containing slag was broken up, crushed,

and disposed (sluiced) into a 5-acre retention pond adjacent to a creek (no name creek). The

disposal site occupies approximately 10 acres and is comprised of an upgradient freshwater

pond, a 5-acre retention pond, and an old grass covered reserve pond. Previous site surveys

show approximately 2 million 3 of radioactive soil/sludge with >5OpCi/g radioactivity. The site

has been extensively sampled and contour plots of radioactivity levels have been determined and

were shown to the sampling team by site personnel.

The principal radionuclides released at Site F were H-3, Sr-90, Cs-137, and Ra-226. The site is

adjacent to a river, which has periodically flooded and redistributed the radionuclides. The

groundwater gradient is generally from the site toward the river. There is also an old, mostly

filled-in barge canal than ran between the main buildings at the site and the river. This canal

served as a partial disposal basin during site operations. One of the sampling sites, designated

S6, is located in the old canal and is labeled "East Lagoon" on previous maps of the site. There

are an extensive number of sampling wells that have been drilled at the site. The sampling team

utilized a subset of these wells to obtain current groundwater samples.

The following sections of this report describe site sampling and sample selection, chemical

analysis, radiological analysis, solubility and leaching studies, and investigations of

radiocolloids.

1
2. SITE SAMPLING AND SAMPLE SELECTION

The Oak Ridge Institute for Science and Education (ORISE) collected samples from Site D.

PNNL received five samples. All samples consisted of a fine brown clay material with a

consistent total U concentration (reported by ORISE)' varying from 14 to 39 pCi/g. A total of

18 samples from Site E were collected by PNNL and NRC staff on September 14 and 15, 1998.

These samples consisted of five surface slag/sludge samples (depth 0-2'), six samples from a

previously collected core (0-20'), four samples of pond/pore water, two stream samples, and one

sample of plant material. In addition, staff collected four well samples from A&M Engineering

and Environmental Services, Inc.2 from locations up gradient and down gradient of the retention

pond. The slag/sludge samples collected within the retention pond were from the locations

identified as 'hot spots" on the licensee map of site contamination. The sampling team verified

the location of these hot spots using a Gieger-Maller (GM) counter. Table 2-1 presents a

summary of the collected samples.

Table 2-1. Description of Site Sampling and Well Locations at Site E.

Sampling Location Material Sampling Sample

Collected Notes Labels

Site A Pond water Small pond next to peninsula KW-1

Site B Surface material Whitish coloration K1 and KI rock

Site C Slag/sludge, pore water, and plant - Depth 18 in. K2, KW-2, marsh

material collected pH 9.5, edge of hot spot grass

Site D Slag/sludge and pore water collected - Depth 18in. K3, KW-3

pH 9.7

Site E Outlet from freshwater pond pH 8.7 KWP-l

Site F Large pond in "retention pond" pH 8.8 KW-4

Site G Surface material Approximate location of K4

core 46 and

hot spot near fence line

Site H Surface material Gathered from highest GM K5 and K5 rock

reading at bare spot in

reserve pond

Site I Stream sample at weir pH 8.9 KWP-2

Site P10 Well sample pH(6.72-6.83) P-10

(WD = 8.44 ft)

Site MWD-4 Well sample pH(6.80-6.83) MWD-4

(WD = .53 ft)

Site MWD-5 Well sample pH(8.41-8.49) MWD-5

(WD = 11.94 ft)

Site MWD-8 Well sample pH(7.67-7.74) MWD-8

(WD= 5.29 ft)

IPersonal communication from Wade Adams (ORISE).

2 A&M Engineering and Environmental Services, Inc., Tulsa, Oklahoma.

3
- | |

Site Sampling and Sample Selection

At Site F, soil and water samples were collected on June 4, 2002. A total of seven soil samples,

eight water samples, and one vegetative sample were collected. In addition, aliquots of the water

samples were filtered in the field to obtain information on the dissolved versus particulate

fraction. Measurements of the pH, Eh (redox potential), and conductivity were also made at the

time of sampling whenever possible. A brief description of the samples is given in Tables 2-2

and 2-3.

Table 2-2. Description of Soil Sample Locations at Site F.

Sample Designation Location Sampling

Notes

Si Northwest corner of

plastics machine shop

S2 Adjacent to 8 x 8 block 2000 uR/hr - top of grass,

building 2600 uR/hr at soil level

S3 Old garage site 1000 uR/hr beta/gamma,

300 uR/hr beta

S4 Under main building 500 uRlbr beta/gamma,

loading dock 200 uR/hr beta

S5 Southwest comer of 2500 uR/hr beta/gamma,

lacquer storage site, same 800 uRihr beta

as State of PA site

S6 East Lagoon In dug hole contacting

.__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _w a te r

S7 Near licensee well 5, at

outfall

VI Same as S5 Strawberries

4
Site Sampling and Sample Selection

Table 2-3. Water Samnles Collected at Site F.

Sample Designation Location Sampling

Notes

IL East Lagoon, dug hole pH = 6.4

Conductivity = 493 uS

Eh (uncorrected) = -25mV

Eh (corrected) = 166 mV

2L East Lagoon, surface water pH = 7.4

Conductivity = 412 uS

Eh (uncorrected) = 21OmV

Eh (corrected) = 401 mV

3GW Licensee Well A pH = 7.7

Conductivity = 273 uS

Eh (uncorrected) = 27OmV

Eh (corrected) = 461 mV

4GW Licensee Well 3 pH = 6.35

Eh (uncorrected) = 317.5mV

Eh (corrected) = 509 mV

5RW River water pH = 7.33

Eh (uncorrected) = 273mV

Eh (corrected) = 464 mV

6GW Well M4 pH = 5.64

Eh (uncorrected) = 137.4mV

Eh (corrected) = 329 mV

Large amounts of red iron oxide

present in sample

7GW Well MIO pH = 6.44

Eh (uncorrected) = 71.5mV

Eh (corrected) = 263 mV

Large amounts of red iron oxide

present in sample

8GW Well G pH --6 (pH paper)

Eh (uncorrected) = 284.2mV

____________________ .____________ __ Eh . ...(corrected) = 476 mV

(a) Corrected Eh corresponds to the field Eh meter reading adjusted versus the normal hydrogen

electrode (NHE).

5
3. METHODS AND MATERIALS

The following discussion provides more details on the analysis procedures and sample

preparation for the solubility, batch, and column studies.

3.1 Chemical Analysis Procedures

The pH measurements were performed using a combination glass electrode (Ross) calibrated

with buffers at pH 4, 7, and 10. Conductivity was measured with a Pharmacia Bioteche

conductivity meter and compared to KCl standards with a range concentration, of 0.001 M to 1.0

M. The Eh was measured with a Bradley James" Eh electrode. Anion analysis was performed

using a Dionex DX6004 Chromatographic Systemo. Inorganic carbon analysis was performed

using a Dohrman Model D-890.- Alkalinity titrations were performed using a Denver

Instrument 295 titrater, titrated to a pH 4.5 end point (method 403 in Standard Methodsfor the

Examination of Water and Wastewater Clesceri et al. 1999]). Analysis of cations was

performed suing an inductively coupled plasma (1CP) unit. High-purity calibration standards

were used to calibrate and verify calibration (EPA Method 6010 B). A volatile organic carbon

(VOC) analysis was performed by Severn Trent Services3 using gas chromatography (GC)/mass

spectrometry (MS).

Total chemical analysis of solid materials was performed by energy dispersive x-ray

fluorescence (XRF) with low (parts per million ppm]) detection limits for most elements from

Al to Ce. Chemical analysis of solutions was performed by ICP analysis, except for samples

with low concentrations of Th, U, or Nb, which were determined by inductively coupled plasma

mass spectrometry (ICP-MS). Surface area analysis was conducted using a Micrometrics Model

2010 Brunauer-Emmett-Teller" analyzer.

All analysis was performed under guidelines provided in PNNL Quality Assurance good

practices procedures: ICPMS (PNNL-AGC-415), ICP (PNNL-AGG-ICP-AES); IC (EPA

Method 300, The Determination ofInorganic Anions in Water by Ion Chromatography); and

XRF (use of NBS standard reference materials).

3.2 Radiological Analysis

Gamma spectroscopy analysis of solid and solution samples was conducted using a

high-efficiency intrinsic germanium detector calibrated over the energy range 60 to 2000 keV.

The following energy peaks were used to determine the radionuclide concentrations: Ac-228,

911 keV; Bi-212, 727 keV; Pb-212, 239 keV; Ra-226, 186 keV; Bi-214, 609 keV; Pb-214, 352

keV; Th-234, 62.3 keV. All analyses were performed on duplicate or triplicate samples.

Selected samples were also submitted for analysis of isotopic ratios by alpha spectroscopy (AS)

(Th) and kinetic phosphorescence (KP) (U). To separate the U, the samples were dissolved in

HCI and passed through anion exchange columns. The columns were washed with concentrated

3 Severn Trent Services, St Louis, Missouri.

7
Methods and Materials

HCl, then 6M HCI + NH4I. U was then eluted with dilute nitric acid. Th samples required extra

fusions with KOH and K2S207 to assure all of the thorium minerals had dissolved. The Th from

the fusion solutions was collected on NdF3, then fumed with sulfuric acid to eliminate the

fluoride. The Nd (with Th) was re-precipitated with strong base to separate the sulfate and then

dissolved in nitric acid. Th was then separated on a nitrate anion exchange column. The product

solution was then measured for Th by AS.

In the case of samples from Site F, samples for H-3 were analyzed by distillation followed by

liquid scintillation counting (LSC) and samples for Sr-90 were analyzed by ion exchange,

elution, and LSC. Selected samples for Ra-226 were analyzed by BaSO4 precipitation,

separation onto membrane filters and subsequent counting by AS.

Ni-63 was determined in the soil samples by first treating the material with concentrated HNO3

to destroy the organics, evaporation to dryness, followed by redissolution in HCL.

Dimethylglyoxime (DMG) is then added to the sample to precipitate Ni(DMG)2, which is then

extracted into methylene chloride. The Ni (DMG)2 destroyed by HNO3 and the Ni-63 dissolved

into dilute HC1. This procedure should eliminate all other beta emitters. Ni-63 is then

determined using LSC.

3.3 Solubility and Batch Studies

Solubility studies were conducted for equilibration times extending from 32 days to a maximum

of 275 days at either 1:30 or 1:10 soil to solution ratios. Solubility studies were conducted either

in an atmosphere chamber under an atmosphere of ultrapure argon or on the bench top over a

broad range of pH values extending from approximately I to 12 depending upon the specific

samples examined. Batch studies were conducted both in an atmospheric chamber in the

absence of CO2 and on the bench top where CO2was allowed into the samples. The bench-top

studies were conducted as both "long-term" and "short-term" experiments. In the long-term

studies the samples were kept lightly capped but there was no forced equilibration with

atmospheric CO2. In the short-term studies the samples were vigorously bubbled with air over a

three-day period to ensure the equilibration with atmospheric CO2. The introduction of CO2 is

potentially important owing to the possible formation of either Th(IV) carbonate complexes

(Felny et al. 1997) or U carbonate complexes (Grenthe et al. 1992). All of the batch studies

were conducted at the "natural" pH of the sample, which varied with reaction time, and

conditions, as the samples dissolved. No pH adjustments were made by adding acid or base. All

of the batch and solubility suspensions were prepared in the following manner. For each site

sample a solid/solution suspension was prepared by placing approximately 1 gram of material in

30 ml of deionized water in each 50-ml centrifuge tube. Approximately 24 such suspensions

were prepared for each sample in the solubility studies. Each sample was independently

adjusted to a different pH value within the prescribed range using reagent grade HCI or NaOH.

The batch samples were prepared in the same manner but only two suspensions (duplicates) were

prepared for each site sample. All suspensions were then placed on an orbital shaker and shaken

until sampling. Sampling of the solubility and batch suspensions consisted of pH measurements

followed by centrifugation at 2000 x g for 7 to 10 min. A sample of the supernatant was then

filtered through an Amicon CentriCon-300 type filter with effective 30,000-molecular-weight

cutoff and average pore diameter of 3.6 nm. The membrane were pretreated by washing with

8
Methods and Materials

pH-adjusted deionized water (to the approximate pH of the sample) followed by filtration of a

0.5 ml to 1.0 ml aliquot of sample to saturate any adsorption sites. This first aliquot of the

sample was then discarded. This pretreatment process was then followed by filtration of

approximately 5 ml of sample. Approximately 1 ml of this sample was then withdrawn and

acidified for ICP or ICP-MS and radiological analysis. The remaining unacidified sample was

retained for anion analysis by IC.

3.4 Column Studies

Flow-through column experiments for determining the impact of flow rate on leaching behavior

were conducted using 32-ml Savelex0 Teflone columns (see Figure 3-1) connected to 3M

modular infusion pumps operating at a flow rate of 0.1 or 1.0 mllhr. Each 32-ml column was

then packed with 30 to 40 g of soil material depending upon the exact particle size. The final

solution volume in each column (pore volume) was then approximately 16 to 17 mis. Porous

frits were placed at the top and bottom of each column to prevent any fine suspended material

from passing through the column. The solutions entered the columns through the bottom and

passed out the top into a sealed collection bottle. Samples from the collection bottle were taken,

pH measurements made, and filtered as described for solubility and batch studies. Filtrates were

split into acidified and unacidified aliquots for analysis by ICP or ICP-MS and IC, respectively.

Radiological analysis was also performed on an acidified sample. Column experiments were

continued for times extending to 72 days depending upon the sample.

3.5 Radiocolloids

The potential for radiocolloid transport was assessed by comparisons between filtered and

unfiltered well water and column samples. The filters used to separate the particles from

solutions were Amicon CentriCon-30 type filter with effective 30,000-molecular-weight cutoff

and average pore diameter of 3.6 nm. The use of filters with such a small pore size means that

any suspended or colloidal material will be removed (with the possible exception of extremely

small nanoparticles). The difference between filtered and unfiltered analysis will therefore

represent a maximum potential for radiocolloid migration because a wide range of colloidal or

suspended particles would be removed by filtration. The designation "soir' represents soil or

slag material depending upon the specific sample. The pH port, which was present on only a few

columns, was not used. All pH measurements were made in the sample-collecting vessel.

9
Methods and Materials

0

U5: I=Y! _

la

:

0

A

aa

E

4

KC Teflon Screen U

SP98030148.1

Figure 3- 1. Schematic of Column Apparatus.

10
4. RESULTS AND DISCUSSION

4.1 Chemical Analysis

The total chemical analysis of the highest activity soil sample at Site D (see Table 4-1, last

column) shows a bulk composition dominated by Al, Si, and Ca characteristic of alumino-silicate

minerals or calcium alumino-silicate minerals with significant amounts of Fe. The element in

highest concentration with radioactive isotopes is U.

The total chemical analysis of the solid materials collected at Site E (Table 4-1) shows that the

principal constituent is Mg (as high as 36% by weight) with lesser amounts of Si, Al, Mn, Ca,

and Fe. The high Mg apparently resulting from the disposal of Mg/Th alloy slags. The total

chemical analysis also shows significant concentrations of Th (as high as 1600ppm) but total U

was undetectable by XRF (detection limit - lOppm). These same trends are evident in core 46

(Table 4-2), except there is less Mg and Th in the upper section of core 46 and more Al and Si

than in the samples from the retention pond. The higher Al and Si readings are indicative of a

higher alumina-silicate mineral content (more natural sediment proportions).

Chemical analysis of the pore waters within the retention pond (sampling Site C, sample KW-2,

and Site D, sample KW-3) showed exceptionally high pH values (pH 9.5 - 9.7) (Table 4-3).

Such high pH readings are indicative of chemical equilibrium with brucite (Mg(OH) 2(c)). These

high pH readings indicate that the Th present on the site is most likely very insoluble (Felmy et

al. 1991), either as hydrous thorium oxide or crystalline thoranite (ThO2(c)). This is supported

by the chemical analysis of the collected water samples (Table 4-3), which show Th

concentrations at or below the analytical detection limit (-0.2ugfl). The dissolved U

concentrations in all samples were also quite low, either at or below the analytical detection limit

(0 .2ug/1). It is also interesting to note that there is apparently some naturally occurring U in

the drainage of no-name creek since detectable U was found in the outlet from the freshwater

pond (sample KWP-1). No other radionuclides, with the exception of 5pCi/ml of 210Pb in the

sample from the up-gradient freshwater pond, were present at concentrations >lpCi/ml in any

water sample taken at the site, data not shown.

The well water analysis shown in Table 4-3 for Site E was used as input for geochemical

modeling calculations using the MINTEQ-A2 equilibrium model (Allison et al. 1991). These

results, for U (Table 4-4a), using the original MINTEQ-A2 database, show that the predominant

aqueous species in solution should be anionic uranium-carbonate complexes. However, there

have been considerable changes in the available thermodynamic data for aqueous complexes

published since the compilation of the MNTEQ-A2 database. These efforts include the

extensive NEA review of the thermodynamics of U (Grenthe et al. 1992) and the work on mixed

metal-uranyl-carbonates (Kalmykov and Choppin 2000). The authors have therefore revised the

thermodynamic data for aqueous complexes of uranium in the MINTEQ-A2 database with these

more recent data. The results (Table 4-4b) show quite a dramatic difference in the computed

aqueous speciation. Most significantly, the aqueous species of U are now dominated by a

neutral (Ca2 U02 (C03 )3 (aq)) complex. How such differences in chemistry affect the migration

of U(VI) species in groundwater is still unknown.

11
Results and Discussion

Table 4-1. Chemical Composition of Samples at Sites E (see Table 2-1) and D.

Element Sample K1 Sample K2 Sample 1(3 Sample K4 Sample KS Site D

(ppm) Highest

Activity

Sample

Al 31800±3000 28400+3500 19500±3300 38500*4100 33800+3700 56100*6200

Si 98800±7100 92200*6900 38200*3200 125600*9200 16500*12000 258000*1,000

K 4380*310 860*80 340*40 6390*460 7150+510 20000+1400

Ca 8330±520 13390*950 3120±230 24800*1800 10360±740 13970*1000

Mg 194900 300400 364300 157600 164800

Ba 2307±121 4990+250 3550*180 6620*340 3410±180 -

Mn 21600*1519 10060*710 8190±580 8550*610 4050+290 460±71

TI 1650±120 1790+1300 1230±90 3370±240 2670*190 -

Fe 11200*7800 26300+1900 17500*1200 51600*3600 15700*1100 42700±3000

Ni 382*31 125*14 118*13 206*20 66.4*9.5 608*52

Cu 508*38 260*21 450*33 665±50 163+14 177*20

Zn 2418*179 1790+130 2230*160 1710±120 1114*79 241+22

Pb 128*12 128*12 78.1*8.1 18616 90.9*8.9 -

Cr 324*24 <20 <17 157±16 <17

As 104±9 <23 <22 <27 <21

Se 5.56±2.14 11.6*2.9 13.9+2.9 10.8*3.3 <4.5+2.3 <5.5*5.5

P 910*470 1730*550 1920*460 <1300 2400*530

S <300 1400*260 1500*250 <480 <400

Rb 20*2.1 <3 <2.8 24.8*2.9 38.1*3.4 100.9-*9.1

U <5 <5.3 <4.8 <7.5 <6.8 65.28.5

Sr 40.3+3.3 48.1*4.2 22.9*2.5 119*9 84.5*6.5 118.4*9A

Y 25*2.5 59.6*4.8 61.2+4.8 60±5 44.2*3.8 31*3.9

Nb 5.9+1.5 4.1+2 <3.6 7*2.2 6.8*1.8 75.6*6.5

Mo 25*4.3 <14 <12 <13 <9.4 21.5*4.1

Zr 2923*205 7160±500 6200±430 5460380 2740*190 -

Th 513±37 1290*92 1600*110 1277*91 632*46 28*10

Hg _ <7.3*7.3

Br <5.7±5.7

Ga _ _ _ _ _ 21.4±5.7

12
Results and Discussion

Table 4-2. Chemical Composition with Depth for Core 46 (Location G) at Site E.

Element Depth (1-2 ft) Depth (2-3 ft) Depth (4-5 ft) Depth (5-6 ft) Depth (6-9 ft)

(ppm)

Al 52500±4800 41900±4400 34000±4100 49000±5500 59400±6500

Si 303000±21000 147000*11000 70300±5400 46000±4000 37900±3600

K 15100±1100 8190±590 4020±300 2500+200 1630±150

Ca 8620±620 24200±1700 21700*1500 13450*960 14100±1000

Mg 25800 173170 258000 291000 286000

Ba 1128±63 5680±290 7650±390 6140±310 4910±250

Mn 1031±88 8340±600 15300±1100 28700+2000 43100+3000

Ti 3800±270 3360±240 3180±230 3040±220 2800±200

Fe 23000±1600 33100±2300 57600±4000 32000±2300 40000±2800

Ni 82±11 110±14 247±24 210±23 387±37

Cu 119±11 503±38 686±51 1088±80 1520±110

Zn 244±19 1430±100 2330±170 3480±250 4560±320

Pb 47.8±6.2 159±14 175±16 661±50 1269±93

Cr 58±9.6 91±13 170+18 374+32 649±51

As <20 <25 <31 <44 <55

Se <3.2 12.1±3.1 19.9±4.1 28±5.8 34.7±7.2

P 1860±620 2840±700 1880±670 1500±690 <1600

S <400 840+260 1330±290 <700 <860

Rb 75.6t5.8 37.7±3.5 <4.4 <5.6 <6.6

U <7.3 <7.3 <7.2 <9.4 <11

Sr 94.7±7.1 124.6±9.3 -114.1±8.7 86.4±7.3 772±7.1

Y 36.3±3.2 62.8±5.1 82.6+6.4 126.9±9.9 158±12

Nb 9.2±1.6 7. 12 5.5±2.3 8.6+3.6 11.8±4.1

Mo <5.4 <13 <15 <24 <28

Zr 910±64 5980±420 8200±570 13220±930 17700±1200

Th 104.3±9.7 1177±84 2010±140 3480±250 4500±320

13
Results and Discussion

Table 4-3. Chemical Analysis of Water and Well Samples at Site E (see Table 2-1).

KW?- P-10 KWP-2 KW-1 KW-2 KW-3 MWD-4 MWD-5 MWD-8 KW-4

pH 8.7 7.29 8.9 8.3 9.5 9.7 7.04 8.15 7.62 8.8

Na II 21 11 52 14 39 48 44 31 34

K 4.2 0.8 7.2 128 12 18 34 190 200 67

Ca 30 39 35 127 3.2 4.5 110 63 58 23

Mg 4.3 11 6.3 288 88 55 59 35 110 ISO

CI 6 19 10 310 40 53 290 410 450 310

F 0.3 0.53 0.3 4 1.6 0.9 0.64 2.3 2.5 4

IC 18 42.9 22.4 89.5 54.1 60 40.8 15.8 59.8 61.7

S04 35 4.6 12 230 20 14 69 11 4.8 73

Th < 0.2 <0.2 < 0.2 < 0.2 < 0.2 < 0.2 <02 <02 <0.2 < 0.2

(ug)L 1.021 (.021 [.02] [.021 [.021 [021 .i21 (.021 [.021 [.021

U 0.24 0.86 0.36 0.92 < 0.2 < 0.2 1.14 0.1 0.14 < 0.2

(ug/1) [.0791 [.281 [.12] [.301 [.0661 [.0661 [381 [.033] (4 61 .06

(a) Concentrations in mg/I, pH in units. Inorganic carbon (IC) in mg/i as C. Numbers in brackets are in pCi/I.

Three soil samples with the highest radiological activity at Site F were selected for chemical

analysis (Table 4-5). The results showed that the soils were predominately alunminosilicates with

significant amounts of Ca and Fe. The Fe most likely being present as an oxide/hydroxide. In

contrast to the other sites, no detectable concentrations of Th or U were found in these high

activity soils. This absence of Th and U is a direct consequence of the differing manufacturing

activities at the Site F.

Chemical analysis of the water samples (see Table 4-6) show that the waters are predominately

calcium bicarbonate-sulfate waters with near circumneutral pH values. The measured redox

potentials varied widely among the samples and were correlated with the dissolved Fe

concentration. The lower the redox potential (Eh), the higher the concentration of dissolved Fe.

The high-dissolved Fe being most likely present as ferrous Fe (Fe(ll)). Detectable

concentrations of VOC compounds (see Table 4-7) were also found in two of the water samples

that exhibited reducing conditions, samples 6GW and 7GW, suggesting a link between disposal

of solvents or other organic containing solutions and the onset of reducing conditions. The VOC

results are lower than the earlier analysis based upon the 1996 Monserco study (Monserco 1996).

The only other water sample with high Fe and reducing conditions was the single sample taken

from the hole dug in the East Lagoon (sample L). This sample exhibited the lowest redox

potential and the highest dissolved iron content, but no detectable VOCs were found. The reason

for the lower redox potential is obvious from the physical setting. Sample L was taken from the

bottom of the marshy lagoon where the soils undoubtedly contained a high-organic content

resulting from vegetative decay.

14
Results and Discussion

Table 44a. Calculated Aqueous U(VI) Species in Surface and Well Waters at Site E.

Sample UO2 (OH) UO2 C0 3(a) UO2(CO3 )21 UOxC03 )t

KWP-1 1.8 _ 26.5 71.5

P-10 - 2.6 76.5 20.9

KWP-2 1.2 _ 15.8 83.0

KW-I __ 5.1 94.9

MWD-4 4.4 76.4 19.2

MWD-5 __42.3 56.2

MWD-8 _ _ 35.0 64.6

(a) Use of the U(VI) thermodynamic data in Allison et al. (1991). All values in percent of total soluble U.

Table 4-4b. Calculated Aqueous U(VI) Species in Surface and

Well Waters at Site E.

Sample UOd(COS), U0 2 (C0 3 ) Ca2UO2 (C03 )3 (aq)

KWP-1 2.2 5.8 92.0

P-10 13.9 3.8 81.9

KWP-2 __4.7 94.4

KW-l _ 6.5 93.1

MWD-4 8.3 2.1 89.1

MWD-5 3.9 5.2 90.9

MWD-8 SA 10.0 84.5

(a) Use of more recent thermodynamic data (see text). All values in percent of total soluble U.

Table 4-5. Chemical Analysis of Soils and

Sediments Site F. (2 sheets)

Element Sample S2 Sample S5 Sample S6

(ppm)

Al 52300*3900 43300±3300 65400*4800

Si 243000*17000 269000*19000 207000*15000

K 14400*1000 118001840 13720*960

Ca 41800+2900 10820*770 10060+720

mg 9080 5640 6360

Ba 374*28 379±33 434*32

Mn 1341*99 885*67 133±24

TI 4870*340 5370±390 7110*510

Fe 26200+1800 25100*1800 24500*1700

Ni 40t6 23*5 120*10

Cu 45*5 76*7 507*36

Zn 1004*71 823*58 666*47

Pb 124*10 181*13 239*17

15
Results and Discussion

Table 4-5. Chemical Analysis of Soils and

Sediments Site F. (2 sheets)

Cr 75*7 124*10 741±52

As 12*2 7+2 7+2

P 2560*420 2120*320 5610±480

S 1760±170 1510+160 8640*640

Rb 64*5 57*4 85*6

U <5 (1.6) <4 (1.3) <9 (3.0)

Sr 92*7 95+7 125*9

Y 25+2 26*2 36*3

Nb 9*1 12*1 18±2

MO <2 3*1 8*1

Zr 281*14 293*15 216*11

Th <7 (.77) <5 (.55) <13 (1.3)

Pb 139*8 194*10 253+13

Cd 140 150 68

(a) Numbers in parenthesis are in pCi/g.

Table 4-6. Inorganic Chemical Analysis of Well and Surface

Waters at the Site F.

| IL 2L 3GW 4GW 5RW 6GW 7GW 8GW

pH(units) 6.4 7.4 7.7 6.35 7.33 5.64 6.44 6

Eh(mv) 166 401 461 509 464 329 263 476

Na 6 17 10 10 15 6 5 12

K 6 11 3 2 2 4 8 2

Ca 67 51 27 38 22 43 53 31

Mg 3 3 6 7 5 4 10 7

Cl 13 24 26 22 23 3 3 18

F 0.49 0.10 0.04 0.05 0.07 0.10 0.05 0.39

IC(b) 36 50 17 21 17 <10 45 26

Alkalinity 34 43 17 24 14 7 40 22

(mg/I C) I

SO4 67 13 24 24 21 119 35 23

Mn 0.30 -- 3.78 - 0.29 4.09 1.07 1.33

Sr 0.23 0.14 0.14 0.45 0.10 0.23 0.25 0.50

Zn 0.19 0.15 _ - - 0.24 - -

Fe 30.8 - - - 0.36 4.35 4.33 -

U (ugh/) 0.232 0.191 <0.05 <0.01 0.068 <0.05 <0.01 <0.01

_ _ [.076] [.0631 [.022] _ I

(a) All values are mg/l, unless denoted otherwise. Numbers in brackets are in pCi/.

(b) Inorganic carbon (mg/I as C).

16
Results and Discussion

Table 4-7. Volatile Organic Carbon Analysis of the Water

Samples at the Site F (ug/).

Organic 4GW 6GW 7GW

1,1 Dichloroethane 3.0 .27 .76 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _(1.3 ) (3 .2 )

Cis-1, 2 Dichloroethene 2.3 26 .65 .___ __ __ __ __ _ _ _(0 .8)

1, 1, 1 Trichloroethane 4.8 - .48

.62 Trichloroethene 31 _ .8)

Tetrachoroethene 2 1.1

(a) Values in parenthesis were take_ _ _ _ _ _ _ _ _ (0 2 ) (1 .8 ) (a) Values in parenthesis were taken from Monserco (1996).

4.2 Radiological Analysis

Radiological analyses of site materials yield the isotopic composition of the radioactive

elements. Such analyses are important not only for more detailed analyses of possible health

effects but also because the relative ratios of the various isotopes yields important information on

isotopic separation processes that may have occurred at the site. This information is key to

understanding the site history, waste disposal practices, and migration fate of each isotope at the

site.

4.2.1 Site D

Radiological analysis of the highest activity Site D sample (Table 4-8 and Figure 4-1) showed

principally total U (by KP) and the first U-238 daughter (Th-234). Other daughter products of

the U-238 decay chain may be detectable (see Th-230 peak in Figure 4-1) but present only at

very low levels. Thus, this sample indicates that U was very cleanly separated from its daughters

at some time in the past and only the U ended up getting mixed with the waste. This is in

agreement with the site characterization, which shows that much of the U originates from

depleted uranium disposed at the site. There were no signs of natural Th-232 or its daughters in

this sample.

17
i

Results and Discussion

Table 4-8. Radiological Analysis of the Highest

Activity Soil Sample at Site D.

Nuclide Gamma Spectroscopy AS/KP

Th-Series (3)

232-Th _10.2

228-Ac _

228-ih 2 0.4

224-Ra _

212-Pb

212-Bi

238-U Series (20) - 23±0.5

238-U --

234-Th 30+10

234-U _ 

230-Th 1±0.2

226-Ra _

214-Pb _

214-Ri

235-U Series _

235-U

(a) Gamma spectroscopy analyses represent the average of three subsamples of each slag. AS/KP

represent Th isotopic analysis by AS and total U by KP. All values in pCitg.

(b) Uranium values are close to detection limit and because of interferences are hard to quantify

with the counting system. Values in parenthesis are calculated from the XRF data for thorium and

uranium assuming all of the Th is Th-232 (.lxl 7Ci/g) and all of the U is U-238 (3.3x107Ci/g).

18
Results and Discussion

ah-230

I'I . . . .. .. . . .. ... lb-228

a

U

4 ~ .......

2 ...........

I

Th-232

............ .

...............

ILLLI

0o 4500

.i

...........

Ra-224

..............

.........................

I I

W _ 

Ill . u .

R .II

_

Awl

3500

-

400 5000 5500 6000 6500

Energy (keV)

Figure 4-1. Alpha Spectra of Highest Activity Site D Sample. Th-232 and Daughters

Present Only at Very Low Levels.

4.2.2 Site E

The radiological analysis of the solid materials at the Site E by gamma spectroscopy (Tables 4-

9a and 4-9b) and AS and KP (Table 4-10) show that the 232Th daughters appear to be in secular

equilibrium. The single analysis of 232Th by AS also indicates that the 232Th is in secular

equilibrium with the ' 8Th daughter (Figure 4-2). However, the AS analysis of 232Th for sample

K3 is less than half the analysis of the daughters by gamma spectroscopy. This is most likely the

result of sample heterogenity combined with a small sample size (-0.lg) for the AS analysis. As

expected all 8U daughters detectable by gamma spectroscopy are near background levels owing

to the low concentrations of U in the samples. Interestingly the AS of these samples shows

significant concentrations of the 238U daughter 23 0T& Apparently natural 23 3

U was present in the

materials at one time. The U being removed in processing the Mg/Th alloy. The insoluble Th

daughter remained in the waste.

Radiological analysis of the deep core obtained by Site E staff showed fairly uniform distribution

of radiological components with depth. It is also interesting to note that the sample of plant

material (grasses) collected near the K2 "hot spot" contained very low levels of 32Th daughters.

It is possible that even these low values could have been the result of small amounts of inorganic

19
Results and Discussion

waste associated with this material. There does not appear to be any indication of a bioconcentration effect, at least in this vegetative sarnple.

In the case of the surface and well waters at Site E, radiological analysis of all of the samples

collected at the site did not reveal the presence of any radionuclides at activities greater than

I pCi/l. This analysis included all of the Th-232 daughters. Apparently, the daughters of Th232 are retained in the insoluble ThO2(am) as will be indicated later in the section on solubilities.

Table 4-9a. Radiological Analysis (Gamma Spectroscopy) of

Wastes (Samples K1-K5) at Site E.

Nuclide Kl | K2 | K3 K4 KS

232-ih Series - - - - -

228-Ac - 108±3 96±3 187+0.5 39±1

212-Bi - - 111*3 46±1

212-Pb 43+2 115±4 106±4 199±0.7 47+2

224-Ra 42+1 - 107+2 201±0.5 48±1

228-lb 37±5 129±22 101+32 31*5

238-U Series - -- -

226-Ra 2±0.2 1±0.5 3±0.8 1±0.3 3±0.3

214-Bi - 3±1 3±0.3 1±0.2 2±1

214-Pb 1±0.05 3±0.2 3±0.6 1+0.05 2±0.08

234-Th 8±3

(a) Values in pCi/g.

20
Results and Discussion

Table 4-9b. Radiological Analysis (Gamma Spectroscopy) of Wastes

(Core 46) and Plant Material at Site E.

Nuclide (2-3) ft (4-5) ft (5-6) ft (6-9) ft Plant Material

232-Th Series - - -- -

228-Ac 81*2 96t2 151 4 6t0.2

212-Bi - 110*3 176*5 - 8tOA

212-Pb 87*4 104±4 169*6 194±8 70.3

224-Ra 107t2 180+3 197*6 7+0.4

228-lh 83*6 105t34 161415 221±13 -

238-U Series - - - - -

226-Ra 6*1 4+0.6 7±1 10±0.6 2±0.3

214-Bi - 5*0.3 7tOA 8*02 <1

214-Pb 5t0.7 8t0.2 9*0.3 <1

234-Th _ -

(a) Values in pCilg.

Table 4-10. Radiological Analysis of

Wastes at Site E.

Nuclide K3 (Sample 1)

232-Th Series

232-Th 36*2

228-lb 39*3

238-U Series <I

238-U _

234-U _

230-Th 66*3

(a) Values in pCi/g.

(b)Thorium isotopes were analyzed by AS and uranium by KP.

21
Results and Discussion

U

30 ..................

Th-232

20 .

10 ..................

10.

: d1AV

. . . . . . . . ..

.............

: Th-228

,.............

Ra-224

.:

.. ... ... ... .... .. .

....... ......... .

Po-212:

0

3500 4000 4500 5000 5500 6000 6500 7000

Energy (keV)

Figure 4-2. Alpha Spectra of Sample K3 from Site E.

4.2.3 Site F

Radiological analysis of the soils and vegetative samples collected at Site F (see Table 4-11 and

Figure 4-3) show that the dominant radionuclides are Cs-137 and Ra-226 with associated

daughters (Bi-214), along with small amounts of Ni-63. Am-241 was detected only in the soil

sample from the East Lagoon (6S) and possibly at site 4S, although the concentrations are close

to the detection limits. Also of note is that Ra-226 was found in the vegetative sample

(strawberries) collected at the site. Therefore, the possibility of vegetative uptake of

radionuclides does exist. A far more exhaustive study than that conducted here, including

complete washing of samples to remove any accumulated dust, would be required to verify this

concern/issue. The concentrations of H-3 and Sr-90 were very low in the solid materials.

Certainly, the small concentrations of H-3 could be due to small amounts of adsorbed water.

In contrast to the results for the soils, the radionuclides found in the water samples were H-3, Sr90, and one sample with Ra-226 and Ni-63 (see Table 4-12). So the Cs-137, though present in

high concentration in the soils, is apparently in a nonleachable fraction. When the H-3 and Sr-90

analyses are compared against the earlier Monserco (1996) data for the same wells (see the

22
Results and Discussion

values in parenthesis in Table 4-12), it is apparent that the concentrations in the groundwater

have decreased significantly. The results in this study are based upon filtered samples, so the Sr90 values are soluble concentrations. It is not clear from earlier reports if some fraction of

particulate matter might have been included in the reported measurements. Several of these

wells had very high concentrations of particulates (predominately iron oxides), which could have

adsorbed some of the Sr-90. However, only very low concentrations of Sr-90 were found in the

soil samples, which supports the conclusion that the Sr-90 is principally in solution. The single

sample with detectable Ra-226 was found in the hole dug in the mud at the bottom of the East

Lagoon (IL). It is not entirely clear why the Ra-226 is the highest in this sample. The

associated soil (sample 6S, Table 4-11) does not contain a high concentration of Ra-226. It is

possible that the Ra-226 is related to the reducing conditions that exist in the sample and the high

dissolved Fe content Reducing conditions could have resulted in the dissolution of iron oxides

and the release of Ra2+ into solution. The presence of the high concentrations of Fe2+ could have

then prevented removal via ion exchange or other processes. In any event, the measured Ra-226

concentrations are consistent with estimates of Ra-226 in the well samples (10-100 pCi/L)

provided by site personnel based upon total alpha analysis. It is not clear if there is any dissolved

Am-241 in the water samples, since results are all at or very close to the analytical detection

limits.

Geochemical modeling of the well water analysis shown in Table 4-6 and Table 4-11 shows that

the Ni is present primarily as the uncomplexed Ni2+ ion and U is present either as anionic

uranium carbonate complexes or as the neutral Ca2 U02 (CO3)3 (aq) complex (Table 4-13). If

present as a cationic species, the Ni may be less mobile than if complexed and present as an

anion.

23
Results and Discussion

IEVY

I.EiS 

aIE+41

1.4

I.E+2

LE+2 

1140.-

I.E+6

1.E+35

1144 

I I.E+3

I.E+2-

1.E+1

1.E+ -

Eney (keV)

400 S00 1200 1600 200D 2400 2000 3200

Emra (eV)

L.E+6

L.E+5

ILE44

21

I.E+3

L.E+2

I.E+Il

7 t -5~ 

(C)

an..Gt 1

0 400 t00 12C0 160 200 2400 20O0 320

EnVy (keV)

Figure 4-3. Gamma Spectra of Soil Samples at Site F. a) Soil 2S, b) Soil 5S, and c) Soil 6S.

24
Results and Discussion

Table 4-11. Radiological Analysis of Soil and Vegetative Samples at Site F (pCi/g).

iS 2S 3S 4S 5S 6S 7S V1

133±3 244±5 21±0.4 112±2 4600±90 61±1 69±1 8±02

H-3 9±03 69±1 18±0.5 10±0.3 5±0.2 125±4 13±0.4 14+0.7

3±0.1 5920±180 2500±100 25±1 4±0.4 89±4 23±0.7 <9

9JSr 0.3±0.04 0.8±0.08 12.141.2 16.7+3.3 8.7±0.9 2.8±0.3 0.5±0.05 3.6±0.1

23F <0.5 <2 0.8±0.2 <0.6 <4 2±0.2 10.1 <31

<3 <10 <5 3±0.5 <10 5±0.6 <3 <70

0.7±0.05 .38±0.04 1.6±0.06 1.2±0.06 - 12±0.02 3.4±0.1 -

Table 4-12. Radiological Analysis of the Water Samples at Site F (pCilL).

IL 2L 3GW 4GW SRW 6GW 6GW 7GW 7GW 8GW

Rust Rust

*f6Ra 37±7 ND <14 <15 <13 <8 6±0.6 <8 <2 <8

H-3 3120±250 1630±230 3040±240 18,000+7 ND 4440+270 7690±380 603+200

37 (12,702) (49,200) (1280)

1Cs <90 <100 <80 <70 <70 <70 1.4*0.4 <70 <0.9 <100

Sr <20 <20 <20 490±108 <20 890±160 8630±1200 <20

(3823) (89,000) (6)

241 Am <0.2 0.210.07 <0.5 <0.3 <0.3 0.52±0.16 <7 <0.2 <8 <0.2

63N; 40*4 6*4 7*4 10+4 5*4 19*4 - 7*4 - 13

ND = Not determined, insufficient sample for AS.

(a) The term "Rust" indicates the reddish precipitate present in the well samples that were removed by filtration and

counted. Values in parenthesis are average values from Monserco (1996).

25
Results and Discussion

Table 4-13. Calculated Aqueous Ni and U(VI) Species in Well

Waters at Site F.

IL 2L 3GW 4GW 5RW 6GW 7GW 8GW

Ni2+ 79.9 53.7 68.6 87.9 - 802 77.8 90.0

NiSQ4 (aq) 4.8 - 1.8 2.2 - 9.2 2.5 2.2

NiHCO3

4 14.5 22.9 11.0 9.3 - 10.5 18.7 7.5

NiCO3 (aq) - 10.8 10.5 - - _ _ _

Ni(CO3)22- - 11.8 7.7 - - _

U02 CO3 (aq) 20.0 - - - - - _

UO2(C0 3) 39.5 6.3 - - 20.0 _ _ _

UO2(COA - 2.7 - 11.0 _ _ _

Ca2UO2(C0 3 (aq) 39.3 90.9 - _ 68.6 _ _

(a) All values in percent of total soluble nickel or uranium. Only samples with detectable nickel or

uranium were included.

4.3 Solubility, and Leaching Studies

4.3.1 Site D

The pH values for the "long-term" samples exposed to CO2 (see Table 4-14) show very similar

values to those in the absence of C02, indicating that the light capping of these samples

prevented influx of sufficient C02 to equilibrate the solutions, with the possible exception of the

longest-term (45 day) samples. However, the "short-term" studies with vigorous bubbling did

show lower pH values more typical of equilibration with atmospheric C02. The pH values in the

column experiments (see Table 4-14) are also in line with this trend.

4.3.1.1 Thorium

The total Th concentrations in the Site D sample (see Table 4-1) were very low relative to the

other sites sampled. This very low Th concentration is reflected in very low observed Th

solubilities (see Figure 4-4)' which seldom exceeded 1 0-8M even at very low pH values. This

result agrees with the batch leaching data that shows maximum Th concentrations of 1 0 7 5M (see

Table 4-15). Finally, all dissolved Th concentrations in the batch studies in the presence of CO2

and in the column studies were at or below the analytical detection limit of approximately 10-

"3M (data not shown).

26
Results and Discussion

Table 4-14. Measured pH Values in Batch Leaching Studies at

Site D as a Function of Time.

Leaching Batch Study No Batch Study CO2 Batch Study C0 2 Column

Time CO2 - "Long Term" - "Short Term" Experiments

2 hr 8.57 8.88

6br 8.57 _ 8

.75 days - 8.06

3 days 8.53 8.56 8.13 _

5 days - -- 8.23

7 days 8.81 8.50 _ _

8 days - 8.21

14 days - 8.34 _ _

30 days - 8.43

45 days - 8.22 _

78 days 8.29

Table 4-15. Thorium Concentrations in Batch

Leaching Studies of Site D Sample in the Absence

of CO2 .

Leaching Time -log [Thi

2 hr -8.29

6 hr < -8.50

3 days -7A5

7 days < -8.50

15 days < -8.50

37 days -7.54

27
Results and Discussion

-4

4 | * 4Days X 31 Days

iI-.

-7

X 0

. .3.a.U.. . ..... a* 0 * 0 .. 

Detection Limit

.9. 0......|......................................... ... 0 1 2 3 4 x 6 7 8 9 10 11 12 13

pH

Figure 4-4. Total (') Th Concentrations (molesA) in Site D Solubility Studies.

43.1.2 Uranium

The total U concentration in the Site D sample (see Table 4-1) is significantly different than that

at Site E. The Site D process resulted in the conversion of depleted UF6 to depleted U 30s. This

difference in chemical form results in quite different observed U solubilities (see Figure 4-5).

The U in Site D samples is relatively easily solubilized by acid with essentially 100% of the U

soluble at low pH values. The observed U concentrations in solution also do not appear to

correspond to any known solubility controlling solid phase for a U(VI) solid. The dramatically

reduced soluble U concentrations over the pH range 3 to 5 seem to correspond more to

adsorption edges for U(VI) on aluminum oxide or silica oxide surfaces (McKinley et al. 1995)

than to expected solubility trends. This is also reasonable given the clayey nature of Site D

samples. The observed U concentrations in the batch leaching studies (see Figure 4-6) were

similar both in the presence and absence of CO2 and show very similar trends to the solubility

studies at the same pH values. This is expected. Site D samples were all a fine clayey soil.

These studies therefore closely mimic the solubility studies except that no pH adjustments were

made in the batch studies. However, the results for the column studies were dramatically

different (see Figure 4-7). These data show very high dissolved U concentrations. These

increases in concentration are clearly related to the much higher solid/solution ratio in the

column studies as opposed to the solubility or batch studies. This dependence on solid/solution

ratio is a clear indication that the U in Site D samples is highly reactive and not controlled by

solubility phenomena. It appears likely that the observed U concentrations in solution are

controlled by adsorption or ion exchange processes on the soil minerals.

28
Results and Discussion

.4-

E

-7.

* 4 Days

a 31 Days

Total U present

l 0 

X

0

if *0 *I

0

0

It

0

.11 4

2 3 4 6 .1 6 7 8 9 10 I 12 13

pH

Figure 4-5. Total (I) U Concentrations (moles/I) in Site D Solubility Studies.

The dashed line labeled "Total U present" represents the U concentration in solution if all of the

U in the sample dissolved.

29
Results and Discussion

* No C02

-5 o Introduced C02

-7

0

6

.

,_ ~~~~~~~~~~~Uranium Concentrations in

...... ,................ .

o 5 10 15 20 25 30 3S 40 45

Days

* Total (T) U Concentrations (moles/l) in Site D Batch Leaching Studies.

-a

Figure 4-6.

-4.

-5.

-6-

0

-7

-8.

Th XU

U Batch Concentration - Corrected for Solid/Solution Ratio - - -- - -- M- ---- ----

NUN

2~~~~~~~

U Batch Concentration

Detection Limit

-A -

... .I... .. -............ . . .- .t- . . -- . [. -

O 10 20 30 40 50 60 70 80

Days

Figure 4-7. Total (T) Thorium and U Concentrations (moles/I) in Site D Column Studies.

M represents either Th or U. The dashed line labeled "U Batch Concentration - Corrected for

30
Results and Discussion

Solid/Solution Ratio" represents the soluble U in the batch experiments multiplied by the higher

solid/solution ratio in the column experiments.

4.3.1.3 Other Radionuclides

The radiological analysis of the solubility and column data did not show significant

concentrations of any Th-232 or U-238 daughter. Bi-212 and Pb-212 were detected in a few

samples, but the concentrations were so low and the uncertainty of the analysis so high that any

quantification of concentration was impossible. Such low concentrations are consistent with the

radiological analysis of the solid Site D sample, shown in Table 4-1.

4.3.2 Site E

The solubility of one of the highest activity samples (K2) from the freshwater pond was studied

over a range of pH values (1-12) to help identify the solubility controlling phases for the

radionuclides. The results of these studies for Th (see Figure 4-8) show the Th solubilities are

apparently being controlled by hydrous thorium oxide. This fact explains the very low (i.e.,

-undetectable) dissolved Th concentrations in the retention pond even though significant Th

exists in the solid phase. Also of interest are the observed amounts of 232Th daughters that were

solubilized in these solubility experiments (Figure 4-9). The amounts of released daughters quite

closely follow the hydrous thorium oxide solubility curve. At low pH where the hydrous

thorium oxide dissolves, the daughter concentrations increase rapidly. At higher pH there were

no measurable daughters in solution. Given the differences in chemical behavior between the

daughters (Pb, Bi, and Ra isotopes) is seems highly unlikely that isotopes of these elements

would coincidently follow the hydrous thorium oxide solubility curve. Apparently the daughter

products from the decay of 232Th are trapped inside the insoluble thorium oxide particles and are

only released when this parent thorium compound dissolves. This hypothesis would also explain

the absence of daughters in the water samples at the site. The solubility data for U (data not

shown) show only very low dissolved U even at the lowest pH values, owing to the very small

concentrations of U in the samples.

31
Results and Discussion

-3-

-4-

-5-

i --

.-

-7-

x3%b

0 a

O1 0(amn)

* 6 Days

X 32 Days

a

xt

I

U.

46

S1

I61

................ .10...... IM.. .......... A.s .... ,o s ...s...... $0 Z ... ".4 .6,.... 

4%etecton Limiit

-2

0 ~ h a....a..-.I .. .............................

1 2 3 4 5 6 7 a 9 10 11 12 13

Figure 4-8.

pH

Total (1) Th Solubilities (moles/l) in Site E Sample K2.

100-

Q0-

80-

* Pb-212

X Bi-212

* Ra-224

0 T1-208

- - Leachable Th

0

.3

0

a

S01

-a

'S70-

60-

50-

40-

30-

N

*

0

i

20-

10-

I

I

[i -,

0 1 a 1 12 13

pH

Figure 4-9. Th-232 Daughters Solubilized in the Solubility Studies of

Site E Sample K2.

Batch leaching and column studies were also conducted on the two samples from the "hot spot"

32
Results and Discussion

(K2 and K3). The batch studies were conducted in contact with atmospheric CO2. These studies

therefore monitor not only the observed changes in elemental and radionuclide concentrations

with time, but also allow the introduction of CO2. This introduction of CO2 is especially

important given the fact that aqueous carbonate complexes are potentially strong enough to

solubilize the hydrous thorium oxide (Felmy et al. 1997) and potentially liberate any 232Th

daughters entrained in the solids. The effect of carbonate was not evaluated in the previously

described solubility studies. The solubility studies focused on the identification of solubility

controlling phases and on the effects of changes in pH. The column studies focused on the

effects of water flow on radionuclide solubility and leaching. As water flows through the waste,

the more soluble Mg and Ca compounds are leached from the waste and the pH decreases. The

batch leaching and column studies therefore provide information on the response of the waste to

changes in environmental factors (i.e., introduced water and infiltrating atmospheric gases).

The results of the batch leaching studies (see Table 4-16) show initially high pH values that

decrease as CO2 is introduced over time. The introduced CO2 is evident in the increasing

inorganic carbon concentrations. It is important to note that the dramatic decrease in Ca

concentration in the 35-day sampling of the batch studies corresponds to the appearance of a

"white precipitate" or coating on the sample container, presumably containing some calcite

(CaC0 3). The precipitate began as a white floc and continued to increase with time, eventually

effectively cementing together many of the remaining waste particles. The introduction of CO2

therefore results in decreases in pH and transformation of the waste material from what appears

to be predominant hydroxide compounds to predominantly carbonate compounds. Interestingly,

this increase in carbonate content has not solubilized any of the Th or other radionuclides in the

waste, as all radionuclide concentrations remained at or below the detection limits.

The results of the column studies (see Table 4-17) show different but predictable trends. The

solution flowing through the column does not allow the carbonate content to build up as was

seen in the batch tests. In fact, the carbonate content actually decreases during the column

studies. This suppresses the formation and precipitation of carbonate containing solids. The

major elements therefore follow a somewhat more predictable trend of initial dissolution

followed by washout in the column. The pH values decrease with time as more and more of the

initial basic solid components of the waste are removed in the column effluent. However, the

radionuclides present in the column effluent remain at the detection limit. This is also expected

from the solubility studies at the corresponding pH values.

33
Results and Discussion

Table 4-16. Chemical Analysis of Batch Leaching Studies

for Samples from Site E.

Sample pH (units) Ca (mg/l) Mg (mg/) Inorganic

l ~~~~~~~~~~~Carbon

l__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (m g/ as C )

K2_

2 hr 9.96 2.2 14

6hr 10.13 33 32

3 days 9.96 94 83 _

7 days 9.93 82 130 92

14 days 9.87 88 195 146

35 days 9.56 1.9 318 199

99 days 9.30 0.73 150

K3

2 hr 9.96 0.64 19

6hr 10.14 34 41

3 days 9.95 4.6* 73 _

7 days 9.97 4.4* 120 109

14 days 9.88 110 160 148

35 days 9.61 1.5 280 183

99 days 9.19 0.64 190

34
Results and Discussion

Table 4-17. Chemical Analysis of Column Studies for Site E Samples.

Sample pH (units) Ca (mg/I) Mg (mg/I) Cl (mg/I) Inorganic Carbon

I(mg" as C)

K2

0.72(5 days) f 9.46 J 110 | 120 50 64

2.60(11 days) J 9.47 7.8 J 89 34 62

6.11(24 days) 9.21 83 80 4.5 48

249 (66 days) 8.53 1.5 34

K3

1.05 (5 days) f 9.14 6.9 58 55 _ _47

2.87(11 days) 9.12 73 84 46 40

6.27 (24 days) 8.92 5.3 52 15 38

24.8 (66 days) 8.83 1.1 37 - _

(a) Numbers in the left-hand column represent cumulative pore volumes of solution through the column.

Numbers in parenthesis represent the actual time of leaching.

433 Site F

Three of the soil samples obtained at Site F were examined in the initial solubility studies. These

samples include soil sample 2, which had the highest concentration of Cs-137, soil sample 5,

which had the highest concentration of Ra-226, and soil sample 6, which was taken from the

bottom of the East Lagoon. This latter sample was selected since it was the only sample where

the soils were in direct contact with the analyzed water.

The only radionuclides detected in the solubility studies were Cs-137 and Ra-226 with

associated daughters. This fact is expected from the solids characterization data (see Table 4-10)

which shows very low, or no detectable concentrations, of H-3, Sr-90, Th-232, and Am-241. The

addition of significant amounts of solution to these samples in the solubility studies only results

in a further dilution of these already low values. As a result, only the results for Cs-137 and Ra226 have meaning.

The solubility data for Cs-137 in these samples (see Figure 4-10) shows a consistent trend for all

samples. At pH values greater than four, all samples show Cs-137 concentrations in solution

that were at or near the analytical detection limit. Cs-137 in detectable concentration was

evident only under the most acidic conditions when significant dissolution of the soils was

occurring as a result of added acid. As expected, the Cs-137 concentrations in the acid region

were directly correlated with the total Cs-137 present in the soil (see Table 4-11). The absence

of Cs-137 from solution in the solubility studies at pH values near those found at the site is also

in agreement with the absence of Cs-137 from the groundwater (Table 4-12).

The solubility data for Ra-226 and/or its daughter Bi-214, is provided in Table 4-18. These

analyses were done primarily by gamma spectroscopy. This fact, combined with the small

35
Results and Discussion

amounts of solution available for analysis, means that the analytical detection limits are higher

than for the groundwater. The limited analysis done by AS is, in general, good agreement with

the gamma spectroscopy results except for the lower-activity samples. In the lower-activity

samples, the gamma spectroscopy appears to overestimate the Ra-226 owing to the high

associated uncertainty. The results do show significant increases in Ra-226 or Bi-214 in solution

in the more acid pH region. In fact, if the observed Ra-226 concentrations in the solubility

studies are corrected for the solid/solution ratio in the experiments (a factor of 30 or 10) it can be

seen that the Ra-226 is essentially 100% removed from the solids under the most acidic

conditions. This is in contrast to the results for Cs-137 where only a fraction of the Cs was

removed even under the most acid conditions. Clearly, the Ra-226 is in a different chemical

form in the soils than the Cs-137. At pH values near those found at the site, the observed

solubilities of Ra-226 are greatly reduced over their acid values and are close to the detection

limits. The low observed concentrations are in at least qualitative agreement with the low

observed concentration of Ra-226 found in the groundwater at the site (Table 4-12).

The results for the batch leaching studies (Table 4-19) are also consistent with the solubility

results in that the Cs-137 concentrations are at or below the detection limit (-0.lpCi/ml) in all

samples and the Ra-226 or Bi-214 concentrations (Table 4-19) are similar to the results of the

solubility studies at the same pH values. The pH values in the batch studies were all found to be

in the range 7 to 9 (Table 4-20).

30 

25 -

20 -

.. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... ....... .....

-

U

0

0

0

0

a

A~~f n A ELv !!

* Soil 2 - 4 days

O Soil 2 - 31 days

* Soil 5 - 4 days

1 Soil 5 - 31 days

A Soil 6 - 4 days

A Soil 6 - 31 days

- Detection Umit

15 -

10 -

5-

U - .. in- II

..... ... I.... .... .... .... .... .... .... .... .... ....

1 2 3 4 5 6 7 8 9 10 11 12 13

pH

Figure 4-10. Cs-137 Activities in Site F Soil Sample Solubility Studies.

36
Results and Discussion

Table 4-18. Ra-226 and Daughter Activities in Site F Solubility Studies.

Sample pH Bi-214 Ra-226 pH (units) Bi-214 Ra-226

(units)

_-_ - 31 days - - -

Soil 2 - 30:1 1.40 9.3 1.8 15.9 ±4.4 - -

(11±0.2)

- 3.81 11.0±4.5 10.2±6.3 - - _

- 6A5 4.9±1.5 4.9 ±3.0 - -

- 6.91 4.5± 1.5 - - - _

- 7.53 3.3±1.3 - - -

- 11.79 6.6 4A - - -

__________ 4 days - - 32 days -

Soil2- 10:1 1.55 60± 16 32±7 1.94 20±7 30±5

(31 ±0.62)

- 5.62 9.8 ± 5.6 - 6.01 6.0 ± 1.7 _

- 7.29 4.1 ± A 6.88 8.7 ±4.7 _

- 9.95 7.0 ± 6A 8.01 4.6 ± 3.5 _

______ _____4 days -- 32 days -

Soil 3 -10:1 2.06 9.7 ±6.0 - 3.83 11.0±4

(1.4 .07)

- 6.03 6.8 ± 3.4 - 6.29 6.0±4.1

- 7.17 6.3 ±6.0 - 7.22 6.1 ± 1.5 10.9±4.3

- 9.58 2.2± 13 - 8.11 3.6± 1.1

_ 31 days - - -

Soil 5 - 30:1 1.34 325 59 298 ±13 _ _

(290 ± 5.8)

- 3.16 38 11 146±73 _

- 6.34 11 ±7.5 -

- 6.93 7.0±2.4 _ _

- 9.51 4.9 ±4.2 _ _ _

- 12.80 13 ±7.5 _ _

_ 31 days . _ _

Soil 6-30:1 1.85 12 ±7.1 14 4A _

(0.52±.04)

- 4.32 4.6 ± 1.8 -

- 5.97 14±5.5 - - _

- 6.96 7.1 ± 3.9 - _

- 10.56 2.1 ± 1.2 - _ _

(a) All values in pCi/il. analysis by gamma spectroscopy. Values in parenthesis were determined by AS.

37
Results and Discussion

Table 4-19. Ra-226 and Daughter Activities in Site F

Batch Leaching Studies.

Sample Bi-214 Ra-226

Soil 2 - 30:1

2hr 8.1 3.8

6hr 3.2± 0.8

3 days 4.3 ± 3.0

7 days 4.2 ± 1.5

14 days 5.9 ± 4.6

36 days 7.2 ± 4.5

Soil 2 - 10:1

2 hr

6hr 4.0± 1.3 -

3days 19±10

7 days 14±6.4

14days 8.1±3.9 _

35 days

Soil 3 - 10:1

2hr 5.4±1.3 _

6hr 10±5.3

3 days 3.9 1.5

7 days 9.8 5.5 

14 days

35 days

Soil 5 - 30:1

2hr 5.6±2.6

6 hr 4.7 1.4

3 days 6.1 1.3

7days 5.7±3.3

14 days 6.5 1.4

36 days 5.0± 1.6

Soil 6 - 30:1

2 hr 4.6± 3.3

6hr 11 5.7

3days 8.8±5.4

7 days 6.5 5.3

14 days 11 4.3

36 days 3.4 ± 1.3

(a) All values in pCi/lm. Data are shown for two different solution to solid

ratios (30:1 and 10:1). Analysis via gamma spectroscopy.

38
Results and Discussion

Table 4-20. The pH Values in Site F Batch Leaching Studies.

Leaching Soil 2-30:1 Soil 2- 10:1 Soil 3-10:1 Soil 5-30:1 Soil 6-30:1

Time

2 hr 7.63 7.77 7.71 7.26 7.39

6 hr 7.53 7.78 7.90 7.40 7.44

3 days 7.84 8.02 7.98 7.75 6.72

7 days 7.92 7.77 7.62 7.91 7.18

14 days - 7.78 7.78 - -

15 days 8.01 7.81 7.01

35 days - 7.80 7.80 - -

36 days 8.07 _ _ 8.05 7.72

Also, as was true in the solubility studies, the concentrations of the other potential radionuclides (H3, Sr-90, Th-232, and Am-241) were at or below the detection limits as a result of their initially very

low values in the soil materials.

The results from the column studies (see Table 4-21) show very similar trends to the solubility and

batch experiments. Cs-13 7 concentrations are at or below the detection limits and Ra-226 is also very

near the detection limits for the gamma spectroscopy. The AS measurements of Ra-226 are

significantly lower than the gamma spectroscopy measurements for two of the soil columns. Again,

this is consistent with the solubility results and indicates that the gamma spectroscopy values should

be treated as upper limits. Further evidence for this conclusion comes from a statistical analysis that

includes all of the solubility data for Ra-226 and Bi-214 in the solubility studies, batch leaching

studies, and columns studies (Figure 4-11). These results show that if the lower limits of the error

bars are accepted from the gamma spectroscopy analysis of these samples, then almost half of the

analysis could be either at zero or show negative concentrations. The analysis of Ra-226 by AS also

shows low concentrations (the three circled points in Figure 4-11) but have very much smaller

associated errors and therefore appear to be more reliable.

Table 4-21. Radionuclide Concentrations in Site F Column Studies.

Sample Pore Volumes Cs-137 Ra-226 Sr-90

Soil 2 - fast column 14.18 3.2 ±1.1

Soil 2 - slow column(' 6.04 0.21 0.06 0.10±0.02 <.02

11.80 - 3.9±1.0 -

Soil 5 - fast column 11.25 0.20 ± 0.06 -

Soil 5-slow cokun(") 3.37 <.2 1.9 ± 0.2 0.14 ± 0.01

8.18 0.15 ±0.04 3.9±2.1 

Soil 6 - fast column 13.20 - 8.2 1.5

Soil 6 - slow column(a) 3.16 <.2 0.02 ± 0.006 <.04

7.76 0.18±0.05 6.8± 12 -

(a) The designation "fast column" refers to a flow rate of lml/hr. The designation "slow column" refers to a flow

39
Results and Discussion

I rate of O.lmIl/hr. All values in nCi/ml. The asterisk designation refers to analysis of Ra-226 via AS. i

I

0-

-J 

.5

I I I I I I I III I I 11I I I1 I l 0-

---- r -rr-r -+--t-'t- F tv-~~~

0 10 20 30 40 50 60

Sample Number

Figure 4-11. Measured Radium-226 and Bismuth-214 Activities and Uncertainties for all

Solubility, Batch Leaching, and Column Samples Between pH Values of

S to 10 from Site F.

This pH range covers the entire range of values found at the site. All analysis is by gamma

spectroscopy, except the three circled points that were determined by AS.

4.4 Calculations of Solubility Limits and Leaching Rates

This section presents calculations of the equilibration mass transfer (leaching) rates of Th and U

from samples at Sites D and E. Leaching rates for radionuclides at Site F were performed only

for Cs-137 and Ra-226 because the other radionuclides were either soluble (H-3 and Sr-90) or

the measured concentrations were at or near the analytical detection limits (Ni-63, Am-241). For

the radionuclides, these leaching rates were calculated using the highest observed dissolved

concentration at the shortest equilibration time. This yielded the highest mass transfer rate for

equilibration that can be calculated from the data. It is certainly possible that a higher transfer

rate could have been calculated if samples were taken at earlier times (earliest times were 2 hr

for batch data). Nevertheless, all of the samples reached equilibrium or at least steady state

concentrations extremely rapidly since so little mass needed to be transferred to reach the steady

state concentration. These calculations numerically demonstrate this fact.

40
Results and Discussion

4.4.1 Site D

Solubility was controlled for Th and not U. Th - data from the coarse batch study were used

(Table 4-5). The highest solubility observed was 0- 5M Th after 3 days contact time. The

solution volume was 30 ml. This yields the following:

- Maximum solubility = 3.2xl04-M

- Leaching rate = 3.lxlO'9gTh/hr

U - data from the column study (Figure 4-5) were used to define a "solubility" limit owing to the

high solid/solution ratio and U concentration. Data from the batch study (see Figure 4-4) were

used to give a maximum leaching rate. The highest U concentration observed in the column

study was 1048M U after 4.7 days of leaching and this was selected as the solubility limit. The

leaching rate was calculated from the batch data at 2 hr of leaching (steady state already

obtained). The solution volume was 30 ml and the specific surface area was 19 m2/g.

This yields the following:

- Maximum solubility = 1.6x10' 5M

- Leaching rate = 1.4xlO6gU/hr. or 7.5xlO4gU/M2.hr 4

4A.2 Site E

The extremely insoluble nature of the radionuclide containing phases in Site E waste makes it

possible to calculate only a maximum leach rate based upon the authors' best estimate of the

analytical detection limit for each nuclide. In the case of Th and U this detection limit is

approximately 10 M. Although we cannot determine a time for dissolution from the batch or

column data, it does appear from the solubility studies that the dissolved Th and U is in

equilibrium with the solids by the first sampling period (6 days). The maximum leach rates can

be calculated as follows:

1045M = (3.16 x -9 moles/I) x (0.03 L of solution) = 9.5 x 1011 moles dissolved into

the solution.

This dissolution occurred in at most 6 days. This yields a leach rate of: 1.5 x 10-10 g T/h/r and

1.6 x 10'1 g U/hr. The rate for U being an obvious high maximum given the low to undetectable

concentration of U in the waste. Those calculated "solubility limits" obviously are controlled by

the analytical detection limits as opposed to physical processes.

4The leaching rates are calculated as follows:

(4xl 07 moles U/lX.031X238gU/moley((2hrs.Xl 9m2/gsoilXl gsoil))

= 7.5xlO sgU/m2.hr.

41
---------------- JResults and Discussion

4.4.3 Site F

The principal radionuclides present in the soils at Site F were Cs-i 37 and Ra-226. The other

radionuclides were either present mostly in the groundwater, H-3 and Sr-90, or were present in

the soils at only very low concentration (Ni-63, Am-241, Th-232). In the latter case, the

calculation of solubilities or leaching rates is either irrelevant or too low to be measurable.

In the case of Cs-137 and Ra-226 the best data for calculating maximum solubilities and leaching

rates is the column data (Table 4-20) analyzed by AS. These data show the maximum leachable

Cs-137 concentration was 0.21 pCi/ml (1.8 x 10-'4 M) and the maximum Ra-226 concentration

was 1.9 pCi/ml (8.5 x 1012 M). Higher concentrations are reported by gamma spectroscopy but

the uncertainties are too high for any definitive use (see Figure 4-10). Although these

concentrations are probably not controlled by specific precipitation/dissolution reactions

involving discrete solid phase, they do represent upper limits on the possible radionuclide

concentration in solution. As such, in computer models such as RESRAD (Yu et al. 2000), their

use as maximum "solubilities" has merit. Using these data, the maximum leaching rates would

be 1.5 x 10 7 g Cs-1371hr and 2.2 x 10-13 g Ra-2261hr.

The solubility and leaching data from all three sites is summarized in Table 4-22.

Table 4-22. Summary of Solubility and Leaching Rate Calculations at Each Site.

U Th Cs a

Site Solubility Leaching Solubility Leaching Solubility Leaching Solubility Leaching

Limit Rate Limit Rate Limit Rate Limit Rate

(g/cc) (ityr) (pcc) (pCilyr) (gicc) (pci/yr) (glcc) (pci/yr)

Site D I7.4xio-9 3.0 3.&x04 4000 -- - -- -

Site E 7.4xiO- 0.1 7.6x I O- 0.5 -- - - -

Site F - - - -- I2.5x 10 1.9XIO-I 1900

4.5 Radiocolloids

The best evidence for the presence of radiocolloids is direct analysis of such particles in the

groundwater at the site. Unfortunately, this was not possible for Site D since PNNL received

only soil samples. In the absence of direct determination, analysis of filtered and unfiltered

samples from flow-through column experiments are the only source of information on Site D

radiocolloids.

In the case of Site D, comparison of filtered and unfiltered Th and U concentrations in the

column studies (Table 4-23) showed high dissolved U concentrations that are identical with or

without filtration. Thus, the uranium in Site D leachates appears to be present in the dissolved

form.

42
Results and Discussion

Table 4-23. Filtered and Unfiltered

Thorium and Uranium Concentrations in

Column Studies.

Analysis Site D

lb - UF < 10 4 .M

in-F < Io'M

U-UF lo -60M

U-F 10-1-12M

UF = Unfiltered

F = Filtered at Site D.

In the case of Site E, no radionuclides at concentrations greater than 1 pCi/l were found in either

filter or unfiltered samples at the site. Thus there was no evidence for radiocolloid migration at

Site E.

At Site F, analysis of particulate material (labeled rust in Table 4-12) collected in the well water

samples showed only very low activities indicating that the radionuclides in these wells were

predominantly in solution. In addition, analysis of filtered and unfiltered column samples by

LSC for total beta and alpha showed newly identical activities (data not shown). Thus, no clear

evidence was found for radiocolloid migration at Site F.

4.6. Statistical Analysis

Statistical analysis of the solubility and leaching data proved very difficult at all three sites

owing to the generally very low concentrations (at or below the detection limit).

In the case of Site D, all observed Th concentrations were at or below the detection limit so no

statistical analysis of the Th data was possible. In the case of U, the concentrations were quite

high but varied with solid-to-solution ratio. Therefore, the U did not appear to be solubility

controlled and the best data that would be representative of the expected groundwater

concentrations would be the column studies. However, there are only four data points in the

column experiments (see Figure 4-7). With only four data points, there is no way to determine

the uniqueness of the statistical distribution (normal, lognormal, etc.); therefore, there was

insufficient information to refute the hypothesis that the data are normally distributed. If a

normal distribution is assumed, the mean is 8.9 x 106 M and the standard deviation is 6.9 x 106.

If an overall distribution of possible U concentrations is simulated using this mean and standard

deviation, the resulting distribution is quite broad (Figure 4-12). This broad distribution is not

supported by the solubility or batch leaching data which also indicate high U concentrations in

solution. The broadness is solely statistical fact given the small number of data points from the

column studies.

43
Results and Discussion

a

Cr

2,

LL

-10A-5 0 10-5 2*1VA-5 3*10A5

U (M)

Figure 412. Statistically Simulated Distribution of Uranium Concentration at Site D

Using Only the Mean and Standard Deviation of the Four Column Data Points.

In the case of Site E, Th was the only major radionuclide present in the waste material.

However, the dissolved concentrations of Th never exceeded the analytical detection limit in any

of the solubility or leaching studies. Therefore, no statistical analysis was possible.

In the case of Site F, the predominant radionuclides in the soils were Cs-137 and Ra-226. In the

case of these radionuclides, most of the analytical data from the solubility and leaching

experiments was at or below the analytical detection limit. The only really reliable data for

statistical analysis was therefore the column data (Table 4-20) for Cs-137 and the AS analysis of

Ra-226. Use of these data yielded a mean and standard deviation for Cs-137 of 1.6x10-14 M ±

2.4xl0'15 and for Ra-226, 3.0xl -02 M ± 3.9x1 0-12. In the case of Ra-226, there are only three

points (two quite low and one considerably higher). As a result, the standard deviation for Ra226 is quite high and use of these results in performance assessment would also be questionable.

44
5. REFERENCES

Allison, J.D., D.S. Brown, and K.J. Novo-Gradac. EPA/600/3-91/021,

'"M1NTEQA2/PRODEFA2, A Geochemical Assessment Model for Environmental Systems

(Version 3)." U.S. Environmental Protection Agency, Environmental Research Laboratory:

Athens, Georgia. 1991.

Clescer, L.S., A.E. Greenberg, and A.D. Eaton. Standard Methods for the Examination of Water

and Wastewater, 2(fh Edition. American Public Health Association: Washington, D.C. 1999.

Felmy, A.R., D. Rai, S.M. Sterner, M.J. Mason, NJ. Hess, and S.D. Conradson.

"Thermodynamic Models for Highly Charged Aqueous Species: Solubility of Th(IV) Hydrous

Oxide in Concentrated NaHCO3 and Na2CO3 Solutions." Journal of Solution Chemistry.

Vol. 26, No. 3, pp: 233-248. 1997.

Felmy, A.R., D. Rai, and MJ. Mason. The Solubility of Hydrous Thorium (IV) Oxide in

Chloride Media: Development of an Aqueous Ion-interaction Model." Radiochimica Acta.

Vol. 55, pp: 177-185. 1991.

Grenthe, I., J. Fuger, RJ.M. Konings, R.J. LeMire, A.B. Muller, C. Nguyen-Trung and H.

Wanner. Chemical Thermodynamics of Uranium. North Holland, Elsevier Science Publishers:

Amsterdam, The Netherlands. 1992.

Kalmykov, S.N. and G.R. Choppin. "Mixed Ca2+U02

2+/C 32 -Complex Formation at Different

Ionic Strengths." Radiochimica Acta. Vol. 88, pp: 603-606. 2000.

McKinley, J.P., J.M. Zachara, S.C. Smith, and G.D. Turner. "The Influence of Uranyl

Hydrolysis and Multiple Site-Binding Reactions on Adsorption of U(VI) to Montmorillonite."

Clays and Clay Minerals. Vol. 43, No. 5, pp: 586-598. 1995.

Monserco(1996). ReportNo. Monsercol96/NB/1821.

U.S. Nuclear Regulatory Commission. (2002). "2002 ANNUAL UPDATE - STATUS OF

DECOMMISSIONING PROGRAM-, SECY-02-0169, U.S. Nuclear Regulatory Commission,

Washington D.C. 20555-0001, September 18, 2002.

Yu, C., D. LePoire, E. Gnanapragasam, J. Amish, S. Kamboj, B.M. Biwer, J.-J. Cheng, and S.Y.

Chen. "Probabilistic Modules for the RESRAD 6.0 and RESRAD-BUILD 3.0 Computer

Codes." NUREG/CR-6697 (ANLIEAD/TM-98). U.S. Nuclear Regulatory Commission:

Washington, D.C. 2000.

45
APPENDIX A

TABLES OF EXPERIMENTAL DATA.
Appendix A

Table Al. Data Supporting Fi re 44.

log Th log Th

pH 4 days 31 days

0.76 _ -7.82

1.79 -8.09

2.64 -7.69

3.06 _ -8.5

4.13 . -8.47

5.04 _ -8.5

7.04 -8.01 _

7.95 -8.5

8.73 -8.5

9A3 -8.5

9.84 -8.5 

9.9 _ -7.16

10.61 -8.5

11.14 _ -8.5

12.02 -8.5

12.33 -8.5

Table A2. Data Supporting Figure 4-5. (2 sheets)

10g UM log U(T)

pH 4 days 31 days

1.2 -5.12

1.3 -5.15

1.73 _-4.99

1.79 -5.13 _

2.33 -5.1

2.28 -5.17 _

2.64 -5.21

3.83 -6.09 _

4.13 _ -6.52

4.9 -7.05

5.04 -7.13

6.19 -7.29 

6.96 -6.99

7.04 -6.47 _

7.27 -6.45 _

7.67 -6.24 _

A-I
I

Appendix A

Table A2. Data Supporting Figure 4-5. (2 sheets)

log U(T) 10g UM

pH 4 days 31 days

7.95 -6.4

8.64 -- -6.48

8.67 -6.36

8.96 -6.15

9.43 -6.45

9.84 -6.4 --

9.9 -- -6.31

10.61 -6.65 _

11.14 -6.82

11.42 -6.59

12.33 -5.74

Table A3. Data Supporting Figure 4-6.

Log U(T) log U(T)

Days No C02 Short Term (CO2)

0.08 -6.39

0.25 -6.16 --

3 - -6.06

7 -6.25

14

15 -6.35

37 -5.64

Table A4. Data Supporting Figure 4-7.

log Th log U

Days Log(moleslL) Log(moles/L)

4.7 -8.5 -4.83

7.3 -8.5 -4.86

30.3 -8.5 -5.44

77.5 -8.5 -5.62

A-2
Appendix A

Table AS. Data Supporting Figure 4-8.

log Th(T) log ThT)

pH 6 days 32 days

0.34 -3.82

0.56 -3.86

0.88 -3.88

1.02 -3.93

3.02 -4.22

3.97 -5.97

4.23 -6.53

5.85 <-8.5

6.05 <-8.5

6.82 <-8.5

8.46 <-8.5

8.73 <-8.5

9.06 <-8.5

9.17 <-8.5

9.53 <-8.5

9.88 <-8.5

10.26 <-8.5

10.36 <-8.5

11.32 <-8.5 <-8.5

11 Al <-8.5

12.03 <-8.5

12.19 <-8.5

Table A6. Data Supporting Figure 4-9.

Pb-212 BI-212 | La-224 | T-208

pH__ _ _ _ _ _ _

3.02 49 60 51 -

3.62 48 62 65 15

4.23 7.6 12 - 8

6.05 0.1 0.1 - 2

11.32 0.1 0.1 0.1 -

A-3
NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER

(249) . . tAulwod b NRC. Add Vol.. Supp. Rev, NRCM 1102. and Addendum Number if any.)

3201,3202 BIBLIOGRAPHIC DATA SHEET NUREG/CR-6821

(See instnictions on the reverse)

2. TITLE AND SUBTITLE

Solubility and Leaching of Radionuclides in Site Decommissioning 3. DATE REPORT PUBLISHED

Management Plan (SDMP) Soil and Ponded Wastes MONTH I YEAR

June 2003

4. FIN OR GRANT NUMBER

.____________ ____________ _____________ _____________ _________ _ W6409

5. AUTHORES) 6. TYPE OF REPORT

TECHN ICAL

A. R. Felmy, V. L. LeGore, and S. A. Hartley 7. PERIOD COVERED lfrncusiveDatesl

& PER FORMING ORGANIZATION -NAME AND ADDR ESSftf NC. pay iDik bn ficorfiRgon, U.S Nlar Regulatry Commission ad 1ibi9 Byref rnrractorparve ine and mnaling addmn) 

Pacific Northwest National Laboratory

P.O. Box 999

Richland, WA 99352

9. S'ONSORING ORGANIZATION - NAME AND ADDRESS (if NRC. type 'Same ae aIoe"Jf contractor. provide NRC Diveston. Oflice or Region. U.S Nuclear Reguiatoiv Commission.

and mailing ddess)

Division of Systems Analysis and Regulatory Effectiveness

Office-of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC- 20555-0001

10. SUPPLEMENTARY NOTES

P. Reed, NRC Project Manager

11. ABSTRACT 200 words or kiu

Samples of disposed wastes at one former and two current U.S. Nuclear Regulatory Commission

(NRC) Site Decommissioning Management Plan (SDMP) Sites were studied to determine 1) the

key radionuclides present in the waste, 2) the solubility limits for these radionuclides, 3) the

observed leaching rate for radionuclides,and 4) identify the potential for radiocolloid formation.

The results show that the major radionuclides present in the wastes were U at Site D and Th at

Site E. The final concentrations of U at Site D were apparently controlled by adsorption/ion

exchange reactions with the host soil material. At Site E, the thorium was found to be very

insoluble at the pH values of the ground and surface waters at Site E. At Site F, H-3 and Sr-90

were the dominant radionuclides present in the groundwater (activities as high as 18,000 and

8600 pCiIL respectively) and Cs-137 and Ra-226 were the predominant radionuclides in the soil

samples (concentrations as high as 5900 and 4600 pCi/g, respectively). No evidence was found

for radiocolloid formation at any of the sites. Maximum dissolved concentrations (solubility

limits) and radionuclide-leaching rates have been calculated for use in performance assessment

calculations.

12. KEY WORDS/DESCRIPTORS List od orphrtes that will assist reseachers in locating the ePort.) 13. AVAI LABILITY STATEMENT

n imited 14. SECURITY CLASSIFICATION

Leaching, radionuclides, SDMP, solubility, slag, thorium, uranium, radium, cesium, (This PaW

tritium, strontium, waste Unclassified

(rhis Report)

Uncl assi fi ed

15. NUMBER OF PAGES

16. PRICE

NRC FORM 335 (289)
Federal Recycling Program
NUREG/CR-6821 SOLUBILITY AND LEACHING OF RADIONUCLIDES IN SITE DECOMMISSIONING

MANAGEMENT PLAN (SDMP) SOIL AND PONDED WASTES

JUNE 2003

UNITED STATES

NUCLEAR REGULATORY COMMISSION

WASHINGTON, DC 20555-0001

OFFICIAL BUSINESS