derivation of dose-based detection limits for drinking water and effluent compliance ken sejkora...
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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
Nuclide Adult Teen Child Infant ICRP-30
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
Nuclide Adult Teen Child Infant ICRP-30
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
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 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
Nuclide Adult Teen Child Infant ICRP-30
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
Nuclide Adult Teen Child Infant ICRP-30
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
Pathway H-3 Mn-54 Co-60 Sr-90 Cs-137
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
Aquatic Food 1.08E-06
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
Pathway H-3 Mn-54 Co-60 Sr-90 Cs-137
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
Aquatic Food 8.98E-07
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
Pathway H-3 Mn-54 Co-60 Sr-90 Cs-137
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
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 4.67E-05 2.02E-03 1.96E-02 1.04E-01 3.66E-02
Aquatic Food 1.50E-06
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
Nuclide Adult Teen Child Infant ICRP-30
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
Nuclide Adult Teen Child Infant ICRP-30
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