C-14 Calculations Concerns and Caveats. Jim Key Key Solutions, Inc.

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1 C-14 Calculations Concerns and Caveats Jim Key Key Solutions, Inc.

2 C-14 Dose Methodology Killough, G. G., & Rohwer, P. S. (1978). A new look at the dosimetry of 14 C released to the atmosphere as carbon dioxide. Health Physics Journal. The Seminal Publication for C-14 Environmental Impact Referenced in most all subsequent technical publications.

3 C-14 Pathway Considerations Only C-14 in CO 2 form is of dosimetric interest. Inhalation and Liquid Pathways are insignificant. Carbon is transported through the environment without significant biomagnification. Human Food Chain Inhalation uptake by animals is negligible. Only viable dose pathways: Vegetation Ingestion OR Products from Animals Feeding on Contaminated Vegetation

4 C-14 in the Food Chain C-14 incorporated into vegetation only in the form of CO 2. Essentially 100% of carbon in vegetation comes from the atmosphere. Occurs as a result of photosynthesis process. Only that C-14 released in the form of CO 2 during the daylight growing season will be incorporated into the animal/human food chain.

5 Growing Season Meteorology [Killough & Rohwer 1978] Killough Suggests Renormalization of Met Data to Account for Daylight Growing Season Meteorology. Growing Season Meteorology Will Differ Significantly From Annual Average Wind Speed / Direction Pasquill Stability Class Summer meteorology results in higher frequency of unstable atmospheric conditions (Pasquill categories A and B)

6 Growing Season Meteorology Renormalization of met data to calculate dispersion for growing season is nothing new. For calculations of doses through ingestion pathways, particularly through the cow-milk pathway, meteorological data for only the grazing or growing season should be used. (Reg Guide 1.111)

7 Atmospheric Dispersion C-14 Inhalation Pathway Should Be Modeled Using Long Term Averaged Dispersion (Annual average /Q) C-14 Ingestion Pathways Should Be Modeled Using Meteorology During Daytime Growing Season

8 Calculation of Daylight Growing Season X/Q X/Q calculated using Joint Frequency Distribution (JFD) constructed from met data only for those hours of daylight during the growing season.

9 Calculation of Daylight Growing Season X/Q Growing season depends on: Location Crops Grown Use local agricultural authorities for reference. Use NOAA Sunrise/Sunset Algorithm Predicts Sunrise and Sunset Times based on date and latitude Use meteorology from 1 hour after sunrise to 1 hour before sunset. Meteorology during sunrise and sunset is not typical of meteorology during daytime (Mark Abrams, TES)

10 Growing Season Meteorology [Killough 1978] Killough s results based on data taken in Knoxville, TN exhibited a 3 increase in ground level daytime growing season /Q over annual average /Q. This result is quoted in numerous articles that reference Killough. This is misleading and not necessarily correct.

11 Growing Season Meteorology [Killough 1978] /Q was calculated assuming a 100 meter release elevation. For 100% elevated releases : Expect increased X/Q Due to increased vertical mixing plume touchdown occurs at nearer locations For mixed mode or ground level release X/Q: Will decrease due to increased vertical mixing causing great dispersion at nearer locations.

12 Growing Season Meteorology Summer daytime meteorology results in higher frequency of unstable atmospheric conditions (Pasquill categories A and B). Can Result in Higher or Lower average ground level concentrations as compared to annual average data set. Results are dependant on receptor location as well as release point characteristics.

13 Annual vs Daylight/Growing Season /Q Site Annual /Q sec/m 3 Day-Seasonal /Q sec/m 3 Day-Season to Annual Ratio

14 C-14 Dose Pathway Animal Products YUM! C-14 Moo Burgers Milk Shakes!

15 Parameters Needed SET Intake SET

16 Stable Element Transfer Coefficient Reg Guide 1.109, Tables E-1 and E-2 provide stable element transfer coefficients (SET) for: Cow Milk - (F m ) Cow Meat - (F f ) Goat Milk - (F m ) Concentration ratios (CR) between animal intake and animal food product. Less variability between CR values for similar animals and similar animal products. H-3 and C-14 in Table E-1 - Meat and milk coefficients are based on specific activity considerations.

17 CR From RG Carbon SET for Cow Milk (F m ) = 1.2E-2 da/l Cow Consumption Rate (Q F ) = 50 kg/da Gives a Concentration Ratio (CR) CR F m da kg feed Q kg meat da l milk / da Activity in Milk kg feed / da Activity in Feed 1.2E F

18 CR From Specific Activity Assuming Specific Activity Equilibrium Concentration Ratio = Specific Activity Ratio Cow Milk Carbon Fraction (CF m ) = kg-c/kg-milk Cow Feed Carbon Fraction (CF f ) = kg-c/kg-feed (1.109 default value) CR Milk Feed CF CF

19 SET Definition The Stable Element Transfer Coefficient is Defined as: Activity in Produce[uCi / kg] SET Activity in Feed[uCi / kg] Feed Intake [kg / da] Assuming Specific Activity Equilibrium: SET Produce Carbon Fraction [uci / kg] Feed Carbon Fraction [uci / kg] Feed Intake[kg / da]

20 C-14 SET SA Derivation Cow Milk CF milk = kg-carbon / kg-milk CF forage = kg-carbon / kg-forage Consumption Rate = 50 kg/da kg.067kg C liter milk C kg forage50kg / da da kg RG Table E-1 = da/kg

21 C-14 SETs Derived from Specific Activity Approach Product Reg Guide Derived SET Cow Milk Cow Meat Goat Milk Goat Meat Sheep Meat Egg 2.9

22 Reg Guide C-14 Model Parameters Equilibrium Fraction (P-factor) C-14 Release Rate Atmospheric Dispersion Plant Carbon Fraction Atmospheric Carbon Concentration

23 Equilibrium Fraction (P-factor) Ratio of the total annual release time to the total annual time during which photosynthesis occurs assumes photosynthesis time of ½ yr or 4400 hours. For continuous C-14 releases this is assumed to be unity. Incorrectly defined and pretty much worthless. Should redefine P-factor as fraction of C-14 released during daylight growing season. Recall is an engineering design bases document and contains conservatism inappropriate for reporting of actual doses to the public.

24 AIR Reg Guide Compartment Model MEAT C Food = f(sa Veg, Q m, SET) VEGETATION SA Veg = SA Air HUMAN A human = f(c food,u a ) Dose = f(sa Air, Q m, SET, U a )

25 Problems With Reg Guide and NUREG 0133 C-14 Methodology IAEA TECDOC Series No Quantification of Radionuclide Transfer in terrestrial and Freshwater Environments for Radiological Assessments Section recommends Stable Element Transfer Coefficients should not be used for C-14 and H-3. Section 3.1 states specific activity model be used for all aquatic foods.

26 Some Parameters Are Difficult to Document or Have a Large Associated Uncertainty Stable Element Transfer Coefficient Available Only For a Few Species Cannot Address Differences Between Species Cannot Address Differences Among the Same Species Animal Consumption Rates Can Vary Widely Cow Producing ~ 5 liters/day consumes 32 Kg/da. Cow Producing ~ 40 liters/day consumes 100 Kg/da. Yet SA in Milk from both animals will reach equilibrium ~ 1 year. No difference in dose to human between the two cows.

27 AIR Specific Activity Compartment Model MEAT SA Food = SA Veg HUMAN SA Human = SA food VEGETATION SA Veg = SA Air Dose = f(sa Air )

28 Specific Activity Model Specific Activity Model Conservative Assumes specific activity has reached equilibrium in all environmental compartments. Provides an absolute upper limit on food chain concentrations.

29 Modified Specific Activity Compartment Model AIR MEAT SA M = SA Veg C M = f(cf M, SA Air ) HUMAN A Ing = f(c M, U a ) VEGETATION SA Veg = SA Air Dose = f(sa Air, CF M, U a )

30 Why Use Such A Model? Reasonable To Assume No SA Equilibrium in Humans Due To Wide Variation Among Individuals In: Food Sources Age Group Consumption Habits Individual Consumption Habits Allows Site Specific Adjustments For Such Variations

31 RG vs. Specific Activity Model Advantages We already know how to use it. Explicit methodology provided. Disadvantages Not correctly implemented in NUREG Criticized for significant underestimate of carbon content for vegetation. See NUREG Depends on being able to find Stable Element Transfer Coefficients. Should not be dependant on animal ingestion rates. Would be difficult to defend technically as more recent guidance (NUREG 3332, NCRP and IAEA) uses Specific Activity approach.

32 Reg Guide Dose Factors Can I Use Them for SA Approach? Assumes Chronic Rather Than Acute Exposure Based On Continuous Exposure Over a One-Year Environmental Exposure Period Dose Factors Appropriate to Apply to a Specific Activity Model

33 Specific Activity Model Advantages Fewer parameters less uncertainty No need for stable element transfer coefficients. Is not dependant on animal ingestion rate. Depends only on feed and food carbon fractions Common information easily found and documented. Not dependant on animal species Disadvantages New methodology Not 1.109

34 Specific Activity Model De-facto methodology found in: IAEA Safety Report Series No. 19 Technical Reports Series No. 472 NCRP Report No. 76 NUREG 3332 Current Technical Periodicals

35 Why Use Specific a Activity Model? Concentration of Vegetated C-14 Highly Dynamic Varies seasonally and diurnally. Dependant on stage and rate of plant growth. Affected by short term meteorology. Drought Conditions Cloud Cover and Heat Stress SA models compare favorably with more sophisticated models which suffer from increased parameter uncertainty.

36 f - Factors Used to distinguish different food categories. Fraction of ingestion by human or animal that is from local contaminated source. Fraction of stored (decayed) versus fresh (undecayed) food substance. Fraction of pasture versus feed to distinguish between vegetation types and associated agricultural yield.

37 f - Factors f Factors have the highest impact on dose. Reduces dose for long and short lived nuclides equally. Site specific values are easily determined, documented and defended.

38 R ai(cowmilk) j D Q f - Factors K Q i fpf Y P F s U ap w F m r it h 1 fpfs e itf Y S DFL aij e Pasture grass consumption fraction No Decay Agricultural productivity Y P = 0.7 kg/m 2 Feed consumption fraction Decayed Agricultural productivity Y P = 2.0 kg/m 2

39 Usage and Consumption R ai(cowmilk) j D Q K Q i fpf Y P F s U ap w F m r it h 1 fpfs e itf Y S DFL aij e Pasture grass consumption fraction No Decay Agricultural productivity Y P = 0.7 kg/m 2 Feed consumption fraction Decayed Agricultural productivity Y P = 2.0 kg/m 2

40 Human Usage Factors U ap Human consumption for maximum individual as defined in RG Maximum Individual consumption represents reasonable deviation from the average population (~ percentile). Reasonable to adjust U ap to account for fraction of ingested food produced locally.

41 Animal Consumption Factor - Q F Taken from RG 1.109, Table E-3. Provides average animal consumption rates. Also appropriate to adjust for fraction of animal feed provided from local sources.

42 C-14 Changes Some Things For Atmospheric Particulate and H-3 Direct deposition and integrating compartments make leafy vegetation highest potential dose pathway. For Atmospheric C-14 Highest dose driven by local dietary carbon. Food stuffs other than leafy vegetation can become significant.

43 RG Table E-5 Lists Fruits, Vegetables and Grain food pathway. Footnote ** breaks this down as: 22% Fruits 54% Vegetables (including leafy vegetables) 24% Grain WRONG

44 RG Table E-5 Correction Vegetable grouping of footnote ** is incorrect. Should read NON-LEAFY App C.4 makes this clear in the definitions of U av and U al. U av defined as: non-leafy vegetables, fruit and grains. U al defined as leafy vegetables.

45 Milk Products Carbon Fraction ~ gm-c / kg MILK (65-110) CHEESE (350) BUTTER (620)

46 Meat Carbon Fraction ~ gm-c / kg (Fresh Weight) BEEF (200) HEN (240) PORK (300)

47 Broad Leaf Vegetation Carbon Fraction ~ 30 gm-c / kg (Fresh Weight) CABBAGE & LETTUICE TURNIP GREENS CELLERY

48 Fruits Carbon Fraction ~ 62 gm-c / kg (Fresh Weight)

49 Root Vegetables Carbon Fraction ~ 46 gm-c / kg (Fresh Weight) CARROT TURNIP RADISH

50 Tubers Carbon Fraction ~ 103 gm-c / kg (Fresh Weight) POTATOES YAMS SWEET POTATOES

51 Grain and Cereals Carbon Fraction ~ 390 gm-c / kg (Fresh Weight) San Jose Police Dept CORN WHEAT BARLEY

52 Food Group Dose Contributions Adult % of child dose Teen Fruits 43% of child dose Meat Leafy Vegetables Child Grain Non-Leafy Milk

53 Concerns H-3 and C-14 Are Now The Greatest Contributors to Offsite Dose. Highest Dose Impact From Airborne Releases Highest Dose Is From Terrestrial Food Chain

54 The Requirement for the Radiological Environmental Program is Driven by 10 CFR 50, Appendix I, Section IV, B.2 Provide data on measurable levels of radiation and radioactive materials in the environment to evaluate the relationship between quantities of radioactive material released in effluents and resultant radiation doses to individuals from principal pathways of exposure.

55 Environmental Monitoring Program Bases NUREGs 0472, 0473, 1301 & Bases 3/ Purpose is to provide: representative measurements of radiation and of radioactive materials in those exposure pathways and for those radionuclides that lead to the highest potential radiation exposures to MEMBERS OF THE PUBLIC resulting from station operation.

56 Regulatory Guidance NUREG 1301 & 1302, App A, Radiological Assessment Branch Technical Position, Rev 1, Nov Position Sets Forth an acceptable minimum radiological monitoring program. Program requirements defined by Table

57 NRC Environmental Reporting Levels Nuclide Water Airborne Fish Milk Food pci/l pci/m 3 pci/kg pci/l pci/kg H-3 20,000 Mn-54 1,000 30,000 Fe ,000 Co-58 1,000 30,000 Co ,000 Zn ,000 Nb Zr I Cs , ,000 Cs , ,000 Ba La

58 Regulatory Guidance Obvious that branch technical position considered Mn, Co, Zn, I, and Cs to be the major dose contributors. Position focused on those nuclides and those pathways thought to have the largest radiological impact to the public. REMP program must continue to focus on the nuclides and pathways that have the largest radiological impact to the public.

59 Regulatory Guidance - Problems Current Regulatory Guidance Contains No Environmental Sampling Requirements for H-3 or C-14 in the Terrestrial Food Chain. A Minimum Acceptable Program is Not a Maximum Effective Program A Minimum Acceptable Program is Not Necessarily a Minimum Effective Program

60 C-14 ODCM Problems NUREG 0133 fails completely to address C-14 dose calculation. Methodology of RG is not a reasonable technical position and does not reflect current scientific practice.

61 C-14 REMP Problems NUREGs 0472, 0473, 1301, 1302 and the Branch Technical Position fail to address appropriate environmental monitoring of the two most significant dose contributors: H-3 and C-14. Also fail to address monitoring of ingestion pathways with highest dose impact to the public. Focus on leafy vegetation. C-14 dose impact comes though non-leafy vegetation. Higher Consumption of Non-Leafy ( 520 vs 64 kg/yr- adult) Non-Leafy Vegetation has higher carbon fraction and therefore is more sensitive environmental indicator.

62 C-14 Dose Calculation Mistakes X/Q Errors Use of D/Q rather than X/Q Use of Daytime Growing Season X/Q to Calculate Inhalation Pathway Dose Use of NUREG 0133 equations to calculate R apji site specific dose factors. Use of Imaginary Dose Pathways. Use of Imaginary Receptor Location

63 D/Q vs. X/Q C-14 enters food chain as CO2 and therefore must be modeled as a gas. Must model C-14 using X/Q! No significant deposotion, D/Q (1/m 2 ) applies to ground plane deposition X/Q (sec/m 3 ) x Deposition Velocity (m/sec) Can easily calculated R aipj for C-14 from NUREG 0133 methodology for all ingestion pathways. But R aipj units are wrong (m 2 mrem/yr per uci/sec)

64 Incorrect R aipj Site Dose Factors Can easily calculated R aipj for C-14 from NUREG 0133 methodology for all ingestion pathways. But R aipj units are wrong: m 2 mrem/yr per uci/sec Units must be: mrem/yr per uci/m 3 Take The Hint From NUREG 0133 H-3 Methodology

65 Incorrect R aipj Site Dose Factors Calculating R aipj using the equation of NUREG 0133, section R aipj = 8.9E+08 mrem/yr per uci/m 3 (child bone) Correct R aipj = 3.8E+06 and is given by: R aipj K' K" L S U f U f DFL a L a G aij

66 Imaginary Dose Pathways NUREG 0133 Section radioiodine and particulate [dose] is applicable to the location in the unrestricted area where the combination of existing pathways and receptor age groups indicates the maximum [dose] Purpose of land use survey is to identify actual local existing pathways. Calculate dose only for those exposure pathways determined as present by the land use census.

67 Imaginary Receptor Location Highly unlikely (or unfortunate) that all existing ingestion exposure pathways are present at the site boundary in the direction of the highest D/Q. Even more unlikely that all imaginary ingestion exposure pathways are present at the site boundary in the direction of the highest D/Q. NUREG 0133 Section radioiodine and particulate [dose] is applicable to the location in the unrestricted area where the combination of existing pathways and receptor age groups indicates the maximum [dose]

68 Question What Do You Get When Wrong Wrong DispersionValue Imaginary Imaginary Dose Factor Pathway Location

69 The Wrong Answer!!! Look at the Bright Side. This Can t Be All Bad, Can It?

70 Your Supervisor Will Finally Appreciate the Importance of What You Do

71 You Will Be Provided With Technical Assistance You Should Have Used X/Q!!! It Wasn t Clear in the ODCM!!!

72 And Upper Management Now Knows What You Do and Who You Are

73 Anyone Have Any Questions?

Preliminary Results of Modelling Radionuclide Depositions in Agricultural and Forest Environments Using the CHERPAC Code

Preliminary Results of Modelling Radionuclide Depositions in Agricultural and Forest Environments Using the CHERPAC Code 1. Introduction Draft 153-112320-CONF-001 S.L. Chouhan Environmental Technologies