Ken Sejkora

1

• Ken Sejkora
• Entergy Nuclear Northeast Pilgrim Station
• Presented at the 18th Annual RETS-REMP Workshop
• Charlotte, NC / 23-25 June 2008

2
Reason for Concern

• Regulatory Guide 1.109 accounts for buildup of
  radioactivity for the following exposure
  pathways
• Waterborne Nuclides in Shoreline Deposits
• Waterborne Nuclides in Irrigated Foods
• Deposition of Airborne Nuclides on Ground Plane
• Deposition of Airborne Nuclides on Soil and
  Crops forage, produce, vegetables, milk, meat

3
Reason for Concern (continued)

• Regulatory Guide 1.109 assumes buildup period
  (tb) of 15 years
• approximate midpoint of facility operating
  life per Equations A-4 and C-1
• Many facilities have operated for well beyond 15
  years, and many are pursuing license extension
  for an additional 20 years of operation total
  span of up to 60 years

4
Reason for Concern (continued)

• What is the impact on dose calculations of
  assuming buildup during entire duration of
  40-year license?
• What is the impact on dose calculations of
  assuming 20 years of additional operation?

5
Buildup Equation

• Used in RG-1.109 equations 3, 4, A-4, A-6, A-7,
  A-8, A-13, C-1, and C-5
• General form of equation

Where ?i nuclide decay constant, yr -1
tb buildup period, yr
6
Buildup Factor by Nuclide
Nuclide Half-life years Lambda Buildup Factor by Buildup Period Buildup Factor by Buildup Period Buildup Factor by Buildup Period
Nuclide Half-life years Lambda 15-yr 40-yr 60-yr
Mn-54 0.856 8.10E-01 1.24E00 1.24E00 1.24E00
Fe-59 0.122 5.67E00 1.76E-01 1.76E-01 1.76E-01
Co-60 5.271 1.32E-01 6.55E00 7.56E00 7.60E00
Zn-65 0.669 1.04E00 9.65E-01 9.65E-01 9.65E-01
Sr-90 28.600 2.42E-02 1.26E01 2.56E01 3.16E01
I-131 0.022 3.15E01 3.18E-02 3.18E-02 3.18E-02
Cs-134 2.062 3.36E-01 2.96E00 2.97E00 2.97E00
Cs-137 30.170 2.30E-02 1.27E01 2.62E01 3.26E01
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Buildup Factor Ratio by Nuclide
Nuclide Ratio to 15-yr Buildup Factor Ratio to 15-yr Buildup Factor Ratio to 15-yr Buildup Factor
Nuclide 15-yr 40-yr 60-yr
Mn-54 1.00 1.00 1.00
Fe-59 1.00 1.00 1.00
Co-60 1.00 1.16 1.16
Zn-65 1.00 1.00 1.00
Sr-90 1.00 2.04 2.51
I-131 1.00 1.00 1.00
Cs-134 1.00 1.01 1.01
Cs-137 1.00 2.06 2.57
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Clarification of Buildup Equation for Vegetation
Pathways
Equation for Buildup in Vegetation
External Surface Contamination Term Short-term
weathering
Internal Plant-Soil Uptake Term Long-term
metabolism
Affects equations for irrigated crops, produce,
vegetables, and forage (which in turn affects
milk and meat)
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Vegetation External Contamination Term
Where r fraction of deposited activity
retained on leaf/plant surface ?Ei
weathering removal rate constant, 14-day
half-life nuclide half-life te exposure
time to deposition fallout forage 30d, crops
60d Yv vegetation yield forage 0.7 kg/m2,
crops 2 kg/m2 The external contamination term
from deposition fallout typically accounts for 75
to 100 of the total radionuclide activity in and
on vegetation. Not dependent on duration of
buildup period.
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Vegetation Internal Plant-Soil Uptake Term
Where fI fraction of year forage/crops are
growing or irrigated (exposed) Biv
soil-to-plant uptake factor for nuclide i P
effective surface soil density, 240 kg/m2 The
metabolic uptake term from soil typically
accounts for less than 10 of the total
radionuclide activity in and on forage (cow-milk
pathway), and less than 20 in the crop pathway.
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Forage Concentration Terms
Nuclide Deposition Term Uptake Term Uptake Term Uptake Term
Nuclide Deposition Term 15-yr 40-yr 60-yr
Mn-54 1.04E02 1.31E00 1.31E00 1.31E00
Fe-59 9.04E01 4.25E-03 4.25E-03 4.25E-03
Co-60 1.07E02 2.25E00 2.60E00 2.61E00
Zn-65 1.04E02 1.41E01 1.41E01 1.41E01
Sr-90 1.07E02 7.80E00 1.59E01 1.96E01
I-131 2.48E02 2.32E-02 2.32E-02 2.32E-02
Cs-134 1.06E02 1.08E00 1.09E00 1.09E00
Cs-137 1.07E02 4.63E00 9.55E00 1.19E01
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Forage ConcentrationBuildup Factor Ratio by
Nuclide
Nuclide Ratio to 15-yr Buildup Factor Ratio to 15-yr Buildup Factor Ratio to 15-yr Buildup Factor
Nuclide 15-yr 40-yr 60-yr
Mn-54 1.00 1.00 1.00
Fe-59 1.00 1.00 1.00
Co-60 1.00 1.00 1.00
Zn-65 1.00 1.00 1.00
Sr-90 1.00 1.07 1.10
I-131 1.00 1.00 1.00
Cs-134 1.00 1.00 1.00
Cs-137 1.00 1.04 1.06
13
Crop Concentration Terms
Nuclide Deposition Term Uptake Term Uptake Term Uptake Term
Nuclide Deposition Term 15-yr 40-yr 60-yr
Mn-54 4.43E01 1.31E00 1.31E00 1.31E00
Fe-59 3.61E01 4.25E-03 4.25E-03 4.25E-03
Co-60 4.57E01 2.25E00 2.60E00 2.61E00
Zn-65 4.39E01 1.41E01 1.41E01 1.41E01
Sr-90 4.59E01 7.80E00 1.59E01 1.96E01
I-131 8.84E01 2.32E-02 2.32E-02 2.32E-02
Cs-134 4.53E01 1.08E00 1.09E00 1.09E00
Cs-137 4.59E01 4.63E00 9.55E00 1.19E01
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Crop ConcentrationBuildup Factor Ratio by Nuclide
Nuclide Ratio to 15-yr Buildup Factor Ratio to 15-yr Buildup Factor Ratio to 15-yr Buildup Factor
Nuclide 15-yr 40-yr 60-yr
Mn-54 1.00 1.00 1.00
Fe-59 1.00 1.00 1.00
Co-60 1.00 1.01 1.01
Zn-65 1.00 1.00 1.00
Sr-90 1.00 1.15 1.22
I-131 1.00 1.00 1.00
Cs-134 1.00 1.00 1.00
Cs-137 1.00 1.10 1.14
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Summary

• Extended buildup period has negligible impact on
  ingestion pathway concentrations and doses from
  irrigated crops, produce, vegetables, milk, and
  meat less than 25 increase for worst-case
  nuclide (Sr-90) for 60-year buildup period most
  nuclides exhibit lt1 increase

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Summary (continued)

• Ground plane or sediment exposure can be affected
  up to 2-times the 15-year assumption, but these
  exposure pathways typically contribute less than
  0.05 of the total dose
• Buildup equations assume uniform release rates
  (Ci/yr) over duration of buildup period. Current
  and future release rates are likely much lower
  than those when plants began operation

17
Conclusion

• Increased buildup time posed by license extension
  carries negligible impact for affecting effluent
  dose calculations.
• There is no need to modify RG-1.109 equations or
  buildup assumptions to account for additional
  buildup from additional years of operation.