Field deployable radioanalytical platform for unattended near-well monitoring of radioactive groundwater plumes

Matthew J. O’Hara1, Jay W. Grate2,

Scott R. Burge3, Robert C. Harding3

1 Energy & Environment Directorate, 2 Fundamental Science Directorate,

Pacific Northwest National Lab., Richland, WA3 Burge Environmental, Inc., Tempe, AZ

Presentation Outline

Need for monitoring radionuclides in groundwater

Radiochemical sensingEquilibrium-based mini-column sensors

Sensor & detector hardware

Sensor performance & behavior (focus on 99Tc)

“Plug & Play” analytical platform for field monitoring

Operational scheme & primary components

Field deployable formats:

Pump & Treat process monitor (99Tc)

Remote autonomous instrumentation (90Sr)

Future path

Select U.S. Drinking Water Limits (DWLs) for radionuclides

Radionuclide

EPA Regulatory Limits (Max. Contaminant Level, MCL*)

pCi/L Bq/L µg/L

Tc-99 900 33.3 5.3 x 10-2

Uranium (nat’l) 20.5 0.76** 30

Sr-90 8 0.3 6 x 10-8

I-129 1 0.04 6 x 10-3

* Equivalent dose of 4 mrem/year for β-emitters

** Based on nat’l U specific activity of 25,280 Bq/g

The Hanford Site & its Subsurface Contamination

Hanford Area: ~1600 km2

Original mission: Pu production; Current mission: Restoration!

1.7 T liters of radioactive waste water discharged to the groundCreated 4 M m3 of contaminated soil

1 B m3 of groundwater exceeding Drinking Water Limits (DWL) for radionuclides

Covering an area ~200 km2

DOE Richland Operations Office Soils & Groundwater Remediation Project website:http://www.hanford.gov/rl/?page=1333&parent=0

Contaminant Plume Distribution

Hartman, M.J., V.S. Richie, J.A. Rediker, Hanford Site Groundwater Monitoring for FY2008, March, 2009

Contaminant Plume Distribution

Hartman, M.J., V.S. Richie, J.A. Rediker, Hanford Site Groundwater Monitoring for FY2008, March, 2009

Reactor disassembly/cocooning;

Pump & treat;

In-situ remediation;

Facility D&D;

Pump & treat

Waste

Vitrification

RADIOCHEMICAL SENSING

Basic Radiochemical Sensor

Dense homogeneous packing of sorbent & scintillating particles is ideal for moderate to high energy β-emissions

Concentration of analyte places β-decay events within range of scintillator particles

Column viewable by dual PMTs

Using SENS-TECH PMTs w/ TTL output

Coincidence counting logic reduces background ~15x

Stainless Steel (SS) shielding reduces background ~10x

Equilibrium Sensing Approach

1. Sorbent in equilibrium w/ GW

2. β-emitter/GW delivered to sensor column

3. Sorbent in chemical equilibrium w/ β-emitter/GW

4. Reversible analyte-sorbent interaction in GW

5. Sorbent in equilibrium w/ GW

1 2 3 4 5

0

5

10

15

20

25

30

35

0 50 100 150 200

Time, min

Re

sp

on

se

, cp

s

3

42

15

Minicolumn equilibrium sensor: reagentless & reversible

Equilibration Sensing—Calibration; 99Tc

Calibration range ½ to 5x the Drinking Water Limit (0.033 Bq/mL)

150 mL each standard delivered at ~1 mL/min syringe flow rate

Performed 60min. static counts

Measurement Efficiency, Em = 16.6 cps/(Bq/mL)

0.0

1.0

2.0

3.0

4.0

0 200 400 600 800 1000 1200

Time, min

Co

un

t R

ate,

cp

s

B B

0.017

0.37

0.033

0.73

y = 16.644x + 0.0131

R2 = 0.9998

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.00 0.05 0.10 0.15 0.20

Tc-99 Activity, Bq/mLC

ou

nt

Rat

e, c

ps

Tc-99 DWL

(0.033 Bq/mL)

Minimum Detectable Activity (MDA) of the Minicolumn Sensor: 99Tc

MDA allows one to determine the analytical limit of the sensor

1. Count time, t [Vary from <1 to 8 hours]

2. Background cnt rate, Cb [0.47 cps]

3. Measurement Effic., Em [16.6 cps/(Bq/mL)]

* L. A. Currie, Anal. Chem. 40,

586-593 (1968).

0.0001

0.0010

0.0100

0.1000

0 1 2 3 4 5 6 7 8

Count Time, hr

MD

A,

Bq

/mL

99Tc DWL = 0.033 Bq/mL

1/10th 99Tc DWL = 0.0033 Bq/mL

Ld = 4.653 Cbt + 2.706

MDA(Bq / mL ) =Ld

tEm

−1

*

0

20

40

60

80

100

120

140

160

180

0 1000 2000 3000 4000 5000 6000 7000

Co

un

ts /

Up

da

te

Time, min

313 Bq/L

157

0

3116 7.8

0

Equilibration Sensing—Calibration; 90Sr

Change sorbent chemistry: crown ether

Measurement Efficiency, Em = 0.0239 cps/(Bq/L)

y = 0.0239x + 0.0541

R² = 0.998

0

1

2

3

4

5

6

7

8

0 100 200 300 400S

en

sor

Re

spo

nse

, cp

sSr-90 Conc., Bq/L

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 2 4 6 8 10 12 14 16 18 20 22 24

MD

A,

Bq

/L

Count Time, hrs

Minimum Detectable Activity (MDA) of the Minicolumn Sensor: 90Sr

MDA allows one to determine the analytical limit of the sensor

1. Count time, t [Vary from 1 to 24 hours]

2. Background cnt rate, Cb [0.27 cps]

3. Measurement Effic., Em [0.0239 cps/(Bq/L)]

* L. A. Currie, Anal. Chem. 40,

586-593 (1968).

90Sr DWL = 0.3 Bq/L

Ld = 4.653 Cbt + 2.706

MDA(Bq / mL ) =Ld

tEm

−1

*[Plume site typically runs

~70 – 120x greater than DWL]

Contamination Plume Data: Well 299-W22-83

99Tc migration does not happen in isolation

Other major anions that track 99Tc migration:

Nitrate

Chloride

Chromate

Sensor must function in this dynamic environment!

0.01

0.10

1.00

10.00

100.00

1,000.00

10,000.00

100,000.00

2001 2002 2003 2004 2005 2006

Sampling Date

Co

ncen

trati

on

(µ

g/L

)

NitrateSulfateChlorideChromateTc-99

0

2

4

6

8

10

0 100 200 300 400 500 600

Time, min

Co

un

t R

ate,

cp

s

Co-Contaminant Effects on 99Tc Sensor

1) Pristine groundwater + 99Tc Anion

Pristine GW

(ppm)

Elevated Anions

(ppm)

Elevated Anions

+ Cr(VI)

(ppm)

Nitrate 1.7

Chloride 3.9

Sulfate 13.5

Chromate ---Em = 16.5 cps/(Bq/mL)

Blank

0.5 Bq/mL

0.17 Bq/mL

Co-Contaminant Effects: Chemical Selectivity

2) Anionic co-contaminants in groundwater + 99Tc

0

2

4

6

8

10

0 100 200 300 400 500 600

Time, min

Co

un

t R

ate,

cp

s

Em = 11.8 cps/(Bq/mL)

(28.5% loss)

Anion

Pristine GW

(ppm)

Elevated Anions

(ppm)

Elevated Anions

+ Cr(VI)

(ppm)

Nitrate 1.7 71.9

Chloride 3.9 8.0

Sulfate 13.5 20.5

Chromate --- ---

Co-Contaminant Effects: Color Quench

3) Anionic co-contaminants + color quench agent + 99Tc

0

2

4

6

8

10

0 100 200 300 400 500 600

Time, min

Co

un

t R

ate,

cp

s

Em = 7.9 cps/(Bq/mL)

(52.1% loss)

Anion

Pristine GW

(ppm)

Elevated Anions

(ppm)

Elevated Anions

+ Cr(VI)

(ppm)

Nitrate 1.7 71.9 71.9

Chloride 3.9 8.0 8.0

Sulfate 13.5 20.5 20.5

Chromate --- --- 0.3

Co-Contaminant Effects: Color Quench

3) Anionic co-contaminants + color quench agent + 99Tc

0

2

4

6

8

10

0 100 200 300 400 500 600

Time, min

Co

un

t R

ate,

cp

s

Em = 7.9 cps/(Bq/mL)

(52.1% loss)

Anion

Pristine GW

(ppm)

Elevated Anions

(ppm)

Elevated Anions

+ Cr(VI)

(ppm)

Nitrate 1.7 71.9 71.9

Chloride 3.9 8.0 8.0

Sulfate 13.5 20.5 20.5

Chromate --- --- 0.3

Matrix Spike Addition Analysis

Analysis of Hanford groundwater samples (HGW) with increasing levels of co-contaminants

Use matrix spike addition to calibrate

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 900 1800 2700 3600Time, min

Cou

nt

Rat

e, c

ps

a dcb

Anion HGW a

(ppm)

HGW b

(ppm)

HGW c

(ppm)

HGW d

(ppm)

Nitrate 1.7 72.6 144 231

Chloride 3.9 8.4 13.0 19.2

Sulfate 13.5 20.7 27.8 37.0

Matrix Spike Addition Analysis: Results99Tc in each sample = 0.033 Bq/mL99Tc injected during spike run = 0.126 Bq/mL

Sample

Sensor

Response,

Pre-Spike

(cps)

Sensor

Response,

Post-Spike

(cps)

Measured Em

(cps/(Bq/mL))

Calculated

Activity,

(Bq/mL)

Actual

Activity,

(Bq/mL)

% Bias

HGW a 0.520 2.411 15.6 0.0333 0.0335 -0.49%

HGW b 0.352 1.748 11.7 0.0302 0.0335 -9.9%

HGW c 0.269 1.285 8.3 0.0326 0.0335 -2.6%

matrixsp

eq

s

sps

speq

mA

RV

VVR

E

)(,

−

−

= Amatrixsp =

AspVsp

Vs

Where:

m

eq

SampleE

RA =

Activity Conc.

of sample:

And:

“PLUG & PLAY” ANALYTICAL PLATFORM

“Plug & Play” Analytical Platform Schematic

Wells / Aquifer Tubes

Detection

Module

Syringe Pump

Waste

Sampling

Chamber

Purge

Water

Reagent &

Spike Inlet

Detection Module

H2O Quality

Sensors

Configuration 1: 99Tc Platform for Pump & Treat Plant

Panel configurationDimensions 2.5’ x 2’ x 0.5’

Conducive to wall-mount

4 sample input lines

Multiple waste pathways

Configuration 1: 99Tc Platform for Pump & Treat Plant

Flat panel configurationDimensions 2.5’ x 2’ x 0.5’

Conducive to wall-mount

4 sample input lines

3 waste water paths

Communications:Platform ↔ Laptop via 2-way radio

User ↔ Laptop via wireless internet

Software:Laptop runs Visual Basic

Platform has EEPROM chips onboard

Sensor & Shielding

Calib. Std.

Reagent

Computer boards;

fluid routing

& peripheral sensors

Syringe

Pump

Sampling

Chamber4 Sample Inlet lines

Configuration 1: 99Tc Platform for Pump & Treat Plant

Flat panel configurationDimensions 2.5’ x 2’ x 0.5’

Conducive to wall-mount

4 sample input lines

3 waste water paths

Communications:Platform ↔ Laptop via 2-way radio

User ↔ Laptop via wireless internet

Software:Laptop runs Visual Basic

Platform has EEPROM chips onboard

Hanford 200 West Area: ZP-1 Pump & Treat Plant

Post-CCl4Treatment

To

Injection

Well

CCl4extraction

process

99Tc

extraction

process

CCl4-Bearing Extraction Wells

99Tc present

Pre-CCl4Treatment

< DWL

Column

Break-

throughMonitoring

Location

Configuration 2: Field Deployable Remote Analytical System

90Sr analytical system connected to well near Columbia River

Support structure deployed; analytical system scheduled for June, 2010 deployment

System capable of connecting to 4 well sources

Design:

“Off-the-grid” operation

365 day/yr operation

>5000 pCi/L

contour line

Sr-90

Plume Apatite Barrier

Evaluation of 2- and 3-Dimensional Computer Modeling

Daily uploads of most recent analytical data would provide near-real time information:

Plume movement

Flux calculations across horizontal / vertical transects

Remediation efficacy

Conclusions

Need exists for remote groundwater monitoring of radioactive contamination plumes

More resolved transport / migration data

Low cost

Analytical results interlinked to plume migration database

Measurement of radionuclides is possible via the equilibrium sensing approach

Detection modules for Tc-99; Sr-90;

I-129 being developed currently (x-rays)

(plus uranium via spectrophotometry)

Versatile “Plug & Play” platform allows multiple detection scenarios on one chassis

Substantially reduces platform development cost

AcknowledgementsU.S. Department of Energy Office of Science Small Business Technology Transfer (STTR) program

U.S. DOE’s Environmental Management Science Program (EMSP)

U.S. DOE’s Environmental Remediation Science Program (ERSP)

O’Hara, M.J., S.R. Burge, J.W. Grate, Anal Chem, 2009, 81(3): 1228-1237.

O’Hara, M.J., S.R. Burge, J.W. Grate, Anal Chem, 2009, 81(3): 1068-1078.

Grate, J.W., O.B. Egorov, M.J. O’Hara, T.A. DeVol, Chem Reviews, 2008, 108(2):543-562.

Egorov, O.B., M.J. O’Hara, J.W. Grate, Anal Chem, 2006.78(15):5480-5490.

Further Reading