Quality Assurance (QA) of OBT Quality Assurance (QA) of OBT - - PowerPoint PPT Presentation

Quality Assurance (QA) of OBT Measurement in Environmental Samples Quality Assurance (QA) of OBT Measurement in Environmental Samples

September 12, 2011 UNRESTRICTED / ILLIMITÉ

Sang Bog Kim, Ph.D. Research Scientist Environmental Technologies Branch Chalk River Laboratories Chalk River, Ontario Canada

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Outline

• 1. Background
• 2. Analytical Procedure
• 3. Previous OBT Inter-Laboratory Comparisons
• 4. CRL’s Experiments
• 5. Discussions

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• 1. Background
• Environmental tritium pathways
• Release and measurement
• Recent tritium conferences
• Lessons learned from Fukushima in Japan
• Difference between HTO and OBT
• HTO measurement
• OBT history and definition
• OBT classification
• OBT measurement

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Environmental Tritium Pathw ays

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CNSC (2010)

Tritium in the biological cycle of water

Release ≠ Measurement

• Environmental release forms are HT and HTO
• Environmental measureable forms are HTO and OBT
• HT → HTO → OBT
• HTO measurement is relatively simple and

straightforward

• OBT behaviour in the environment is relatively

complicated and has a higher uncertainty than HTO behaviour

• OBT measurement is useful for normal operations
• OBT prediction is useful for accidental situations

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Lessons Learned from Fukushima

• Earthquake: Natural disaster
• Tsunami: Natural disaster
• Radiation: Man-made disaster
• Are public very conservative or generous?
• It is a time to reinforce environmental safety!

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Recent Tritium Conferences

• EMRAS II in Vienna (2009 and 2010)
• “Tritium 2010” in Japan (2010)
• ICRER in Hamilton (2011)
• OBT is a rising topic!

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Differences betw een HTO and OBT

• Dose conversion factors (DCF) from ICRP

HTO = 1.4 x 10-11 Sv/Bq OBT = 4.2 x 10-11 Sv/Bq

• Retention time in biota
• Half-life in humans
• OBT/HTO ratios in environmental samples
• Chemical forms
• Dose contribution
• Regulation guideline

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HTO Measurement

• HTO and TFWT or THO (H2O form)
• IAEA’s Inter-Laboratory Comparison (TRIC2008)
• Certified Standard Material (Multi-Media RadCheMTM

Assessment Program (MRaD) by Environmental Resource Associates (ERA))

• Drinking Water Guideline (7,000 Bq/L for Canada)

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OBT History and Definition

• 70’s and 80’s : Tissue Bound Tritium (TBT)
• Health Physics (1993) Special Issue :
• Organically Bound Tritium (OBT)
• Exchangeable Tritium
• Non-exchangeable Tritium
• EMRAS I and II : On-going topic
• Carbon bound tritium (CBT)
• XBT (X=N,O,S)
• Buried Tritium
• USA : Soluble and non-soluble OBT

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OBT Classification

• Total OBT = Non-exchangeable OBT + Exchangeable OBT

(Diabate and Strack, 1993)

• OBT
• Soluble OBT: Dissolved organic tritium (DOT)

Tritiated organic (TO) Non-exchangeable OBT Exchangeable OBT

• Insoluble OBT: Non-exchangeable OBT

Exchangeable OBT

• Buried tritium: Exchangeable OBT

Non-exchangeable OBT

• Biogenic (early metabolism) and abiogenic (late metabolism)

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Exchangeable and Non-exchangeable OBT

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OBT Measurement

• Total tritium = Tissue free water tritium (TFWT) + OBT

(Canada, France) OBT

• OBT = Total Tritium – TFWT (UK)
• Wet combustion (?)

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TFWT OBT TFWT

• 2. Analytical Issues
• OBT measurement scheme
• HTO extraction
• OBT measurement methods
• Critical steps
• Where we are!

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OBT Measurement Scheme

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TFWT Extraction

• Freeze-drying system (Lyophilization)

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Laboratory design Commercial brand

OBT Measurement Methods

• Parr Combustion (U.S.A.) : Only available for plant and

animal samples

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Detection limit is approximately 7-10 Bq/L

OBT Measurement Methods

• Tube furnace system: Soil samples for CRL

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OBT Measurement Methods

• Plasma combustion: Germany

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OBT Measurement Methods

• 3He Mass Spectrometer: University of Ottawa

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OBT Measurement Methods

• Oxidizer: Packard brand

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Critical Steps

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Critical Step Process Step 1

• Freeze-dry (water residue)
• Oven-dry (temperature, duration)
• Azo-distillation (old fashioned)

Step 2

• Rinse (volume, duration) or no rinse
• Combustion (Parr bomb, tube furnace)
• Distillation (remove impurities)

Step 3

• Liquid scintillation counter (Quantulus, Packard,

Aloka)

• Cocktail (Ultima Gold series)
• Counting condition (background, time)

Where w e are!

• No Certified Reference Materials (CRMs)
• No Standard OBT Procedures
• IAEA and National Institute of Standard and Technology

(NIST)

• Quality Assurance (QA)
• Quality Control (QC)

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• 3. Previous OBT Inter-Comparisons
• Canada (CRL)
• Canada (CRL, OPG, UO)
• France
• Japan
• UK

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Canada (CRL)

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• Fusion Science and Technology 48, 762-766 (2005) :1998-1999
• Sample : Lettuce (approximately 990 Bq/L) and Crabapple (approximately 37 Bq/L)
• Blank sample: Polyethylene beads (Alathon 1145, DuPont, USA)
• Seven labs (Canada, England, France, Romania, Russia)
• Parr combustion system (3 labs) and Quartz combustion tube system (5 labs)
• Better agreement at higher OBT concentrations than lower OBT concentrations

Canada (CRL, OPG, UO)

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• COG-09-3015 (2009)
• CRL and OPG; CRL and UO
• CRL ‘s measurement was lower than OPG and UO
• Rinsing process and 3He-ingrowth mass spectrometry

France (CEA)

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Grass sample (2009) Grass sample (2010)

Japan

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Swain liver sample Polished rice sample

• Radioisotopes, 39 (1990)
• 6 laboratories (5 use Quartz combustion and 1 uses plasma reactor)
• Aloka LSC-LB (Teflon 100 ml vial and quartz vial)
• Variation coefficients were 68% for the polished rice and 35% for the Swine liver

UK (NCAS)

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• National Compliance and Assessment Service, NCAS/TR/99/003 (1999)
• 7 Laboratories (Total tritium, tritiated water and OBT)
• Aliquot sample (added tritium labelled sucrose)
• This was not an environmental sample!

• 4. CRL’s Experiments
• Water residue
• Furnace temperature
• OBT in plants
• OBT in animals
• OBT in fish
• OBT in soil
• OBT/HTO ratio

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Water Residue (1)

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• From a commercial brand (Labconco)

Water Residue (2)

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Sample Fresh weight (g) % after Freeze- dry (3 days) % after Oven- dry (1 day) Tomato 212 198 98.3 98.8 99.8 100 Lettuce 205 210 99.8 100 99.9 100 Beet 209 203 98.2 95.6 99.9 99.9 Average 206±5.2 98.5±1.6 99.9±0.1 CRL’s procedure = Freeze-dry + Oven-dry (at 55ºC)

Furnace Temperature

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• Pickering soil (P-2)

OBT in Plants

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• Environmental Monitoring Results in 2009

HTO and OBT in Animals

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• CRL site and sites greater than 50 km from CRL

OBT in Fish

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• Yearly sampling
• In order to develop “Eco-metabolic tritium model”, MOU is being prepared

between CRL and Romania.

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Sampling Locations – Fish Study

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C C C

                        

• B02

B09 B08 B04 B03 B01 B10 B07 B06 To (Mackey) Petawawa Allumette Island Sheenboro Chichester To Waltham Demers Centre Pembroke T

• K

i l l a l

• e

Rapides des Joachims ORR BMC KMC PET ORF ORH ORD ORP BDO BHC CRH SHC LTH BTH SCB S-7 S-6 SOB OR5 DBC HIL Fort William

Chapeau

Balmer Bay Deep River Chalk River

CRL                                                   

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C

• Critical Group Location

CRL Environmental Monitoring Locations Outside CRL Boundary

Beach Sediment Fish Surface Water Farm Animals Produce River / Lake Highway 17 Road

Environmental Technologies Branch, CRL February 2008 Map-08-006

Map A-1b: CRL Liquid and Biological Environmental Monitoring Locations - Outside CRL Boundary

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Working on the Ottaw a River

Mackey 35 Rolphton 26 Sand Spit 36 Cotnam 26 TOTAL # of fish: 123

Todd Chaput

Total Fish Sampled (2010)

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OBT in Soils

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• Northern Ontario was higher than Ottawa and Saskatchewan
• What is OBT background in Canada?

OBT in Soil (HT release site)

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CRL Boundary Decontamination Loop Old Port Hope Road Plant Road

1986/7 Experiment 1994 Experiment C B A 1986/7 Experiment 1994 Experiment C B A

CRL

Sample Locations Cranberry Lake Sample Locations Cranberry Lake

100 200 metres

Map-11-10

LEGEND LEGEND

Sample Location Historic Experiment Road CRL Property Boundary

Soil depth HTO concentration (kBq/L) Percent 0 - 2 cm 2 - 4 cm 2,000 1,500 50.0 % 4 - 6 cm 6 - 8 cm 8 - 10 cm 1,200 1,000 700 41.5% 10 - 12 cm 12 - 14 cm 14 -16 cm 16 -18 cm 18 -20 cm 350 110 80 30 17 8.5 % Total 6,987 100 % Davis et al., (1995)

OBT in Soil (15 years later)

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OBT is still there, but HTO is not!

OBT in Soil (Darlington)

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                                                                           Lake O n tario

D arlington P rov incial P ark

Darlington N uclear

H igh w ay 401 Martin Rd. Holt Rd. Rundle Rd. Maple Grove Rd. Green Rd. C

• u

r t i c e R d . B ase line R d. O s b

• u

r n e B l

• r

S t . Solina Rd.

D -1 D -2 D -3

Martin Rd. H

• l

t R d . Rundle Rd. Maple Grove Rd. Green Rd. Courtice Rd. B ase line R d. O s b

• u

r n e B l

• r

S t . Solina Rd. Solina Rd

D AR LIN G T O N                          S a m plin g S ite S a m plin g S ite W o o dla n d W e tla nd R o a d

D-1: Approximately 5 km from the reactors D-2: Approximately 2.1 km from the reactors D-3: Approximately 5 km from the reactors

OBT in Soil (Darlington)

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OBT/HTO Ratios

• Rvalue = OBTconcentration / HTOconcentration
• Interpretation the exposure conditions (dynamic or

equilibrium)

• If Rvalue is consistent, we can estimate the OBT

concentration by the HTO concentration

• CRL has analyzed more than 2,000 non-human biota

samples in Canada

• No single value and only a range
• OBT activity concentration unit (Bq/L combustion water,

Bq/kg-fresh)

• CRL uses “Bq/L” for the specific activity model

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OBT/HTO ratio example

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Sample HTO (Bq/kg-f) OBT (Bq/kg-f) Ratio HTO (Bq/L) OBT (Bq/L) Ratio

Leaves 1 2.9 2.6 0.897 3.6 26 7.172 Leaves 2 7.4 7.4 1.000 9.3 74 8.000 Leaves 3 55.2 2.3 0.042 69.0 23 0.333 Leaves 4 105.3 1.3 0.012 131.6 13 0.099 Assumptions: water content is 80% and water equivalent factor (WEF) is 0.5

8 times

Discussions

• CRL has analysed OBT in more than 2,000

environmental samples since the 1980’s.

• CRL is very confident in the analysis of any

environmental samples

• The OBT/HTO ratio around the CRL site is not

consistent

• Requires a site-specific environmental tritium study
• OBT activity unit (Bq/L or Bq/kg-fresh)
• CRL has many tritium measurement sites
• Aquatic ecosystem: Perch Lake, Ottawa River
• Wetland ecosystem: Duke Swamp
• Terrestrial ecosystem: Acid Rain Site, HT release site

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Aquatic and w etland ecosystems

Perch Lake Duke Swamp

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Terrestrial ecosystem

Perch Lake garden Acid Rain Site garden

International OBT inter-comparison

• In May (3 days), 2012 France will be hosted the first

OBT workshop

• Organized by CEA (France) and AECL (Canada)
• Candidate : France, Canada, Romania, Germany,

Japan, Korea, India, US, Belgium, UK, Swiss, Russia etc.

• Three inter-comparison exercise (2012-2015)
• Dry sample, exchangeable and non-exchangeable OBT
• Three-days workshop
• Tritium environmental monitoring
• OBT in environmental samples
• Inter comparison exercise

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Thanks!