Derivation of Dose-Based Detection Limits for Drinking Water and Effluent Compliance Ken Sejkora...

Derivation of Dose-Based Detection Limits for Drinking Water and Effluent Compliance

Ken SejkoraEntergy Nuclear Northeast – Pilgrim

Station

Presented at the 17th Annual RETS-REMP WorkshopPhiladelphia, PA / 25-27 June 2007

Reason for Concern NRC vs. EPA … different limits due to:

Age-specific differences Ingestion rates Dose models and dose factors – ICRP-2 vs. ICRP-

30 Total body vs. Critical Organ

Various limits exist governing effluent compliance, safe drinking water standards, and dose/risk assessment

Basis for Detection Limit Based on equal dose consequence??

Approach used by EPA for drinking water standard Based on argument of “reasonable survey”??

Loose basis of current ODCM LLD requirements What’s reasonable… 1 hour analysis?

8 hour analysis? Radiochemical separation? Dose is a common denominator

representative of risk, and should be used as basis, but reasonableness should be considered in cases of extremely low LLDs.

NRC Effluent Concentration Limits

Specified in Appendix B to Part 20--Annual Limits on Intake (ALIs) and Derived Air Concentrations (DACs) of Radionuclides for Occupational Exposure; Effluent Concentrations; Concentrations for Release to Sewerage

Derived from ICRP-30 dose models, adult age class

Committed dose of 100 mrem/yr for public Preamble to Effluent Concentration Limit

Tables“Consideration of non-stochastic limits has not been included in

deriving the air and water effluent concentration limits because non-stochastic effects are presumed not to occur at the dose levels established for individual members of the public.”

EPA Drinking Water Standard

Specified in 40 CFR 141.25 Refer to: www.epa.gov/safewater/rads/radfr.pdf

Committed dose of 4 mrem/yr Based on drinking water consumption

of 2 liters/day = 730 liters/yr H-3 = 20,000 pCi/L Sr-90 = 8 pCi/L

EPA Drinking Water Standard … where did it come from?

Roots in ICRP-2, circa late 1950s Based on NRC maximum permissible

concentration (MPC) value, where 1 MPC = 500 mrem/yr total body… “second generation derivative” Step 1: Dose Conversion Factor = mrem/pCi Step 2: Max perm. Intake = pCi to yield 4 mrem/yr Step 3: Max perm. Conc. = pCi/L to yield intake of

MPI, assuming ingestion rate of 730 L/yr

EPA Drinking Water Standard …why it’s important

Standard limit adopted by state regulatory agencies… often takes precedence over ODCM limits if groundwater is involved

Used as basis for tables in standard ODCM guidance – NUREG-1301/1302 Table 3.12-2, “Reporting Levels”… 20,000 pCi/L

for drinking water; 30,000 pCi/L for non-DW Table 4.12-1, “Lower Limit of Detection”… set at

1/10 of Reporting Level = 2,000 pCi/L for DW; 3,000 pCi/L for non-DW.

Other ICRP-2 based Factors Regulatory Guide 1.109, age-specific DCFs LADTAP Factors… refinement of RG-1.109

factors RG-1.109 and LADTAP dose conversion

factors are the de facto values used in most plants’ ODCMs, effluent control programs, and effluent dose calculation software

ICRP-30 based Factors Based on ICRP-26 “standard man”

approach, occupational exposure… circa early 1970s

Single age class = adult male Basis for current values in 10CFR20

Appendix B, and EPA Federal Guidance Report 11

ICRP-60/72 Factors Based on ICRP-60 metabolic models…

most modern, circa late 1990s Non-occupational exposure, latest

risk quality factors, multiple age classes

Standard among international community, but not widely adopted in USA, nor endorsed by NRC; however, adopted in EPA FGR-13

Deriving dose-based LLD: Body Step 1: Dose Factors

• Age-specific factors from LADTAP• Total Body Dose Factors = mrem/pCi Ingested

Nuclide Adult Teen Child Infant ICRP-30

H-3 5.99E-08 6.04E-08 1.16E-07 1.76E-07

6.40E-08

Mn-54 8.72E-07 1.17E-06 2.85E-06 4.51E-06

2.77E-06

Co-60 4.72E-06 6.33E-06 1.56E-05 2.55E-05

2.69E-05

Sr-90 1.75E-04 2.04E-04 5.15E-04 5.74E-04

1.43E-04

Cs-137 7.14E-05 5.19E-05 4.62E-05 4.33E-05 5.01E-05

Deriving dose-based LLD: Body Step 2: Maximum Permissible Intake

• pCi/yr intake to yield on 1 mrem/yr Total Body Dose• 25% of EPA “dose limit” of 4 mrem/yr; easy to scale


H-3 1.7E+07 1.7E+07 8.6E+06 5.7E+06 1.6E+07

Mn-54 1.1E+06 8.5E+05 3.5E+05 2.2E+05 3.6E+05

Co-60 2.1E+05 1.6E+05 6.4E+04 3.9E+04 3.7E+04

Sr-90 5.7E+03 4.9E+03 1.9E+03 1.7E+03 7.0E+03

Cs-137 1.4E+04 1.9E+04 2.2E+04 2.3E+04 2.0E+04

Deriving dose-based LLD: Body Step 3: Drinking Water Concentration

• Adult=730 L/yr; Teen/Child=510 L/yr; Infant=330 L/yr• pCi/L to yield 1 mrem/yr Total Body Dose


H-3 2.3E+04 3.2E+04 1.7E+04 1.7E+04 2.1E+04

Mn-54 1.6E+03 1.7E+03 6.9E+02 6.7E+02 4.9E+02

Co-60 2.9E+02 3.1E+02 1.3E+02 1.2E+02 5.1E+01

Sr-90 7.8E+00 9.6E+00 3.8E+00 5.3E+00 9.6E+00

Cs-137 1.9E+01 3.8E+01 4.2E+01 7.0E+01 2.7E+01

Deriving dose-based LLD: Organ Step 1: Dose Factors

• Age-specific factors from LADTAP• Maximum Organ Dose Factors = mrem/pCi Ingested


H-3 5.99E-08 6.04E-08 1.16E-07 1.76E-07

6.40E-08

Mn-54 1.40E-05 1.21E-05 1.07E-05 1.99E-05

8.14E-06

Co-60 4.02E-05 3.66E-05 2.93E-05 2.57E-05 4.99E-05

Sr-90 8.71E-03 1.02E-02 2.56E-02 2.83E-02

1.55E-03

Cs-137 1.09E-04 1.49E-04 3.27E-04 6.11E-04

5.55E-05

Deriving dose-based LLD: Organ Step 2: Maximum Permissible Intake

• pCi/yr intake to yield 1 mrem/yr Maximum Organ Dose• 25% of EPA “dose limit” of 4 mrem/yr; easy to scale


H-3 1.7E+07 1.7E+07 8.6E+06 5.7E+06 1.6E+07

Mn-54 7.1E+04 8.3E+04 9.3E+04 5.0E+04 1.2E+05

Co-60 2.5E+04 2.7E+04 3.4E+04 3.9E+04 2.0E+04

Sr-90 1.1E+02 9.8E+01 3.9E+01 3.5E+01 6.5E+02

Cs-137 9.2E+03 6.7E+03 3.1E+03 1.6E+03 1.8E+04

Deriving dose-based LLD: Organ Step 3: Drinking Water Concentration

• Adult=730 L/yr; Teen/Child=510 L/yr; Infant=330 L/yr• pCi/L to yield 1 mrem/yr Maximum Organ Dose


H-3 2.3E+04 3.2E+04 1.7E+04 1.7E+04 2.1E+04

Mn-54 9.8E+01 1.6E+02 1.8E+02 1.5E+02 1.7E+02

Co-60 3.4E+01 5.4E+01 6.7E+01 1.2E+02 2.7E+01

Sr-90 1.6E-01 1.9E-01 7.7E-02 1.1E-01 8.8E-01

Cs-137 1.3E+01 1.3E+01 6.0E+00 5.0E+00 2.5E+01

Comparison of Derived Concentrations Total Body vs. Maximum Organ

• pCi/L to yield 1 mrem/yr Dose Consequence• Most-limiting concentration based on LADTAP DCFs

Nuclide Total Body Maximum Organ Ratio

H-3 1.7E+04 1.7E+04 1.0E+00

Mn-54 6.7E+02 9.8E+01 6.9E+00

Co-60 1.2E+02 3.4E+01 3.5E+00

Sr-90 3.8E+00 7.7E-02 5.0E+01

Cs-137 1.9E+01 5.0E+00 3.9E+00

Comparison of Derived Concentrations Total Body vs. Maximum Organ

• pCi/L to yield 1 mrem/yr Dose Consequence• Most-limiting concentration based on ICRP-30 DCFs

Nuclide Total Body Maximum Organ Ratio

H-3 2.1E+04 2.1E+04 1.0E+00

Mn-54 4.9E+02 1.7E+02 2.9E+00

Co-60 5.1E+01 2.7E+01 1.9E+00

Sr-90 9.6E+00 8.8E-01 1.1E+01

Cs-137 2.7E+01 2.5E+01 1.1E+00

EPA vs. NRC Approach EPA drinking water approach only addresses

intake and dose from drinking water ingestion NRC RG-1.109 approach assumes multiple

pathways: Drinking water ingestion Fish and shellfish ingestion Shoreline sediment Food crop ingestion from irrigated plants Animal product ingestion… milk, meat

Far-field dilution… dose consequence based on concentrations at location of exposed receptor, instead of concentrations at point of discharge

How much dose are we missing?

Deriving Total Pathway Dose Factors

Use Reg Guide 1.109 approach and pathways, assuming freshwater lake

Assume irrigation 50% of year Assume concentration of 1 pCi/L in water,

derive corresponding concentration in each pathway media type

Apply age-specific usage factors to each pathway media type

Determine age-specific dose from each pathway media type

Combined Pathway Dose Adult Total Body

Adult Dose Factor - mrem/yr/pCi/L

Pathway H-3 Mn-54 Co-60 Sr-90 Cs-137

Sediment 0.00E+00 6.53E-04 1.02E-02 0.00E+00 4.86E-03

Water 4.37E-05 6.37E-04 3.45E-03 1.28E-01 5.21E-02

Aquatic Food 1.40E-06

4.00E-01 9.68E-03 1.98E-01

3.36E+00

Crops 3.50E-05 8.56E-034.82E-

021.88E+0

0 7.47E-01

Milk 1.86E-05 1.37E-04 3.04E-03 9.23E-02 5.58E-01

Meat 6.59E-06 1.56E-04 1.40E-02 2.46E-02 6.60E-02

Total 1.05E-04 4.10E-01 8.85E-02 2.32E+00 4.78E+00

Total/Water 2.4 643.9 25.7 18.2 91.8

Combined Pathway Dose Teen Total Body

Teen Dose Factor - mrem/yr/pCi/L


Sediment 0.00E+00 3.65E-03 5.67E-02 0.00E+00 2.71E-02

Water 3.08E-05 5.97E-04 3.23E-03 1.04E-01 2.65E-02


4.08E-01 9.87E-03 1.75E-01

1.86E+00

Crops 4.06E-05 1.32E-027.43E-

022.52E+0

0 6.25E-01

Milk 2.42E-05 2.37E-04 5.26E-03 1.39E-01 5.24E-01

Meat 3.93E-06 1.23E-04 1.11E-02 1.69E-02 2.84E-02

Total 1.01E-04 4.25E-01 1.60E-01 2.96E+00 3.09E+00

Total/Water 3.3 713.0 49.7 28.4 116.7

Combined Pathway Dose Child Total Body

Child Dose Factor - mrem/yr/pCi/L


Sediment 0.00E+00 7.62E-04 1.18E-02 0.00E+00 5.67E-03

Water 5.92E-05 1.45E-03 7.96E-03 2.63E-01 2.36E-02


4.44E-01 1.07E-02 1.94E-01 7.16E-01

Crops 6.33E-05 2.62E-021.49E-

015.17E+0

0 4.52E-01

Milk 3.83E-05 4.77E-04 1.07E-02 2.89E-01 3.85E-01

Meat 4.76E-06 1.90E-04 1.73E-02 2.69E-02 1.59E-02

Total 1.66E-04 4.73E-01 2.07E-01 5.95E+00 1.60E+00

Total/Water 2.8 325.4 26.1 22.6 67.8

Combined Pathway Dose Infant Total Body

Infant Dose Factor - mrem/yr/pCi/L


Sediment 0.00E+000.00E+0

00.00E+0

0 0.00E+00 0.00E+00

Water 5.81E-051.49E-

03 8.42E-03 1.89E-01 1.43E-02

Aquatic Food 0.00E+00

0.00E+00

0.00E+00 0.00E+00 0.00E+00

Crops 0.00E+000.00E+0

00.00E+0

0 0.00E+00 0.00E+00

Milk 5.81E-05 7.55E-041.75E-

02 3.22E-01 3.60E-01

Meat 0.00E+000.00E+0

00.00E+0

0 0.00E+00 0.00E+00

Total 1.16E-04 2.24E-03 2.59E-02 5.12E-01 3.75E-01

Total/Water 2.0 1.5 3.1 2.7 26.2

Combined Pathway Dose ICRP-30 Adult Total Body

ICRP-30 Adult Dose Factor - mrem/yr/pCi/L


Sediment 0.00E+00 6.53E-04 1.02E-02 0.00E+00 4.86E-03

Water 4.67E-05 2.02E-03 1.96E-02 1.04E-01 3.66E-02


1.27E+00 5.51E-02 1.62E-01

2.35E+00

Crops 3.74E-05 2.72E-022.75E-

011.54E+0

0 5.24E-01

Milk 1.98E-05 4.36E-04 1.73E-02 7.54E-02 3.92E-01

Meat 7.04E-06 4.95E-04 7.99E-02 2.01E-02 4.63E-02

Total 1.12E-041.30E+0

0 4.57E-01 1.90E+00 3.36E+00

Total/Water 2.4 643.2 23.3 18.2 91.8

Combined Pathway LLD: Body Step 1: Dose per Unit Concentration

• Combined Total Body pathway dose – mrem/yr/pCi/L


H-3 1.1E-04 1.0E-04 1.7E-04 1.2E-04 1.1E-04

Mn-54 4.1E-01 4.3E-01 4.7E-01 2.2E-03 1.3E+00

Co-60 8.9E-02 1.6E-01 2.1E-01 2.6E-02 4.6E-01

Sr-90 2.3E+00 3.0E+00 5.9E+00 5.1E-01 1.9E+00

Cs-137 4.8E+00 3.1E+00 1.6E+00 3.7E-01 3.4E+00

Combined Pathway LLD: Body Step 2: Pathway Water Concentration

• pCi/L to yield 1 mrem/yr Total Body Dose Consequence


H-3 9.5E+03 9.9E+03 6.0E+03 8.6E+03 8.9E+03

Mn-54 2.4E+00 2.4E+00 2.1E+00 4.5E+02 7.7E-01

Co-60 1.1E+01 6.2E+00 4.8E+00 3.9E+01 2.2E+00

Sr-90 4.3E-01 3.4E-01 1.7E-01 2.0E+00 5.3E-01

Cs-137 2.1E-01 3.2E-01 6.3E-01 2.7E+00 3.0E-01

Comparison of Derived Concentrations Drinking Water vs. Combined Pathway

• pCi/L to yield 1 mrem/yr Total Body Dose Consequence• Most-limiting concentration based on LADTAP DCFs

Nuclide Drinking Water Combined Pathway

Ratio

H-3 1.7E+04 6.0E+03 2.8E+00

Mn-54 6.7E+02 2.1E+00 3.2E+02

Co-60 1.2E+02 4.8E+00 2.5E+01

Sr-90 3.8E+00 1.7E-01 2.3E+01

Cs-137 1.9E+01 2.1E-01 9.2E+01

Comparison of Derived Concentrations Drinking Water vs. Combined Pathway

• pCi/L to yield 1 mrem/yr Total Body Dose Consequence• Most-limiting concentration based on ICRP-30 DCFs

Nuclide Drinking Water Combined Pathway

Ratio

H-3 2.1E+04 8.9E+03 2.4E+00

Mn-54 4.9E+02 7.7E-01 6.4E+02

Co-60 5.1E+01 2.2E+00 2.3E+01

Sr-90 9.6E+00 5.3E-01 1.8E+01

Cs-137 2.7E+01 3.0E-01 9.2E+01

Which LLDs to Use? RG-1.109/LADTAP pathway approach includes

exposure “missed” by drinking water standard Maximum organ values are not applicable…

10CFR20 Appendix B basis for discounting non-stochastic effects at low doses involved

Age-specific dose factors and use factors Beyond scope of ICRP-30… ICRP-2 or ICRP-72?

When dealing with deriving new concentration limits and LLDs, one could argue we should use the most up-to-date methodology and science available… ICRP-72

Summary Current EPA approach outlined in

40CFR141 only addresses dose from drinking water ingestion Overlooks dose from other pathways,

which can contribute significantly more dose than water ingestion alone

Considers single age class, overlooks age-specific variability in dose factors and consumption rates

Summary (continued)

Use of organ-specific dose factors yields lower concentration limits Based on NRC approach in Appendix B to

10CFR20, non-stochastic dose effects are not applicable at the low dose levels assumed to occur from environmental exposure

Concentration limits and LLDs should be derived from effective total body doses

Summary (continued)

A consistent methodology should be used to derive water concentrations based on dose, but some LLDs may be difficult to achieve, and may necessitate a “reasonable survey” approach

Consideration should be given to deriving stochastic dose-based concentrations using the most modern standard… ICRP-72

Derivation of Dose-Based Detection Limits for Drinking Water and Effluent Compliance Ken Sejkora...

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