1. Comparison of MCNP and ERICA results in two different marine areas
F.K. Pappa1,2, D.L. Patiris1 , C. Tsabaris1, G. Eleftheriou1
E.G. Androulakaki1,2, M. Kokkoris2, R. Vlastou2
Collaboration of:
1. Institute of Oceanography, Hellenic Centre for Marine Research
2. Department of Physics, National Technical University of Athens
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Outline
Motivation
Study areas
Methodology
Results
Discussion
Future plans
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Problems and motivation
Problems:
Determination of the radiation dose is a complicated procedure for the marine environment due to biodiversity and to radiation interactions in the water
Poor literature data for marine key parameters (e.g. concentration factors , radiation dose biological effects, biokinetic models)
ERICA Assessment Tool :
Specialized software system to assess the radiological risk to biota
Based on the combination of exposure/dose/effect assessment with risk characterization
Motivation:
To compare the external dose rate of ERICA with results of a generalized code (MCNP5)
To identify sources of discrepancies for various radionuclides and improve the input parameters by providing experimental ones related to the area of study
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The idea
To run MCNP code for estimating the external dose for one specific marine organism (benthic fish) taking into account specific radionuclides (e.g. 40K, 137Cs, 210Pb)
To estimate the dose rates of MCNP (MeV/g) in units of ERICA (μGy/h) using the same study area
To optimize conversion parameters for MCNP (effective volume, wet density)
To estimate the quality of input activity for both matrices (seawater and sediment) using ERICA and MCNP tools
MCNP
External dose rates in agreement?
Same organism and area
Simple case (monenergistic radionuclides (e.g.40K, 137Cs)
Yes No
ERICA
Optimaze the input data in the code
Proceed in internal and total dose rate
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5. (Stratoni port, Shatt al-Arab estuary)
Study areas
(Stratoni port, Shatt al-Arab estuary)
Location: North Greece, Ierissos Gulf
History: Mining activities form ancient times until today
Sampling: Surficial (sediment) samples at Stratoni port
Location: Persian Gulf
History: two wars and other non-military anthropogenic pressures (production and transportation of oil, irrigation, wastes (urban, power plant, industry)
Sampling: surficial (sediment) samples
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Methodology (ERICA)
Tier 2 (site specific)
Mean values of activity concentrations at the areas of study
Selected organism → benthic fish
40K → added →insert important parameters (CR and Kd)
Problem: Not available Kd values for 40K in the literature
Solution: Conversion salinity to 40K activity concentration (Tsabaris and Ballas, 2005)
Problem: Not available CR values for K in the literature
Solution: Use the ones from Na (IAEA, 2004).
Tsabaris, C., Ballas, D., On line gamma-ray spectrometry at open sea. Appl. Radiat. Isot. 62 (1), 83-89
International Atomic Energy Agency (IAEA), Sediment Distribution Coefficients and Concentration Factors for Biota in the Marine Environment. Technical Reports Series No.422 (Vienna).
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7. Geometry Approximation
Methodology (MCNP)
Approximations: Preserve volume and mass of benthic organism
Different effective volume for each radionuclide
Insert:
The characteristic photon energy of each radionuclide (take into account photons and secondary electrons).
The effects of beta emissions have not yet been simulated.
b. Sediment composition in both areas
Reality
Geometry Approximation 3D
Flounder
Bluespotted ribbontail rays
ell
rpp
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What is the effective volume?
Effective Radius (R)
40K
210Pb
157cm
115cm
9.5 cm
38cm
water
sediment
First order approach → ignore the impact of beta decay emissions → justified
40K→ 1460 keV
137Cs →662 keV
210Pb →45 keV
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Results (Shatt al-Arab estuary)
ERICA
mcnp
Relative Difference
Benthic
rpp
ell
(μGy/hr)
(%)
40K
1.59·10-2
1.15 ·10-2
1.04·10-2 28 35
137Cs
2.10·10-4
1.55 ·10-4
1.60·10-4 26 24
210Pb
not measured
Shatt al-Arab
The external dose rate of 40K estimated by ERICA and MCNP tools was 1.59·10-2 (μGy/hr) and 1.15 ·10-2 (μGy/hr), respectively. The difference between the two codes ranged from 28 to 35%.
The external dose rate of 137C estimated by ERICA and MCNP tools was 2.10·10-4 (μGy/hr) and 1.55 ·10-4 (μGy/hr), respectively. The difference between the two codes ranged from 24 to 26%.
The simulation results for different geometries were in good agreement
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Results (Stratoni port)
ERICA
mcnp
Relative Difference
Benthic
rpp
ell
(μGy/hr)
(%)
40K
2.90·10-2
2.15 ·10-2
2.05 ·10-2 26 29
137Cs
3.90·10-4
2.99 ·10-4
3.04 ·10-4 23 22
210Pb
3.39·10-4
4.16 ·10-7
3.04 ·10-7 ?
40K
210Pb
157cm
115cm
9.5 cm
38cm
water
sediment
Stratoni
The external dose rate of 40K estimated by ERICA and MCNP tools was 2.90·10-2 (μGy/hr) and 2.15 ·10-2 (μGy/hr), respectively. The difference between the two codes ranged from 26 to 29%.
The external dose rate of 137C estimated by ERICA and MCNP tools was 3.90·10-4 (μGy/hr) and ·10-4 (μGy/hr), respectively. The difference between the two codes ranged from 22 to 23%.
The simulation results for different geometries were in good agreement
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Discussion
The calculated results using the two tools in the cases of 40K and 137Cs were in satisfactory agreement. In the case of 210Pb we confirmed the impact of the electron emission on the absorbed dose rates.
The different simulated (benthic) geometries contribute only slightly (40K, 137Cs) to the dose rates results
MCNP is widely used in the marine environment – MCNP-CP would be preferable (TCS effects, full decay scheme simulations).
The input data in the MCNP code have to be harmonized with the ERICA processing module (210Pb problem)
The comparison between ERICA and MCNP would contribute to the optimization of the input parameters for other types of dose rates (e.g. internal ones).
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Future plans
Defining input parameters for Naturally Occurring Radionuclides (NOR)
Estimating external dose rates in other matrices (e.g. pelagic fish, etc)
To assume radioactivity equilibrium in MCNP calculations as in the ERICA runs
To improve comparison using harmonized assumptions for both tools (e.g. MCNP or MCNP-CP do not differentiate the low beta radiation biological effects from the high beta ones).
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Thank you for your attention
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14. Geometry Approximation
Methodology (MCNP)
Reality
Approximations: Preserve volume and mass of benthic organism
Different effective volume for each radionuclide
Insert:
The characteristic photon energy of each radionuclide (take into account photons and electrons)
b. Sediment composition in both areas
Geometry Approximation 2D 3D
ell
Flounder
Bluespotted ribbontail rays
rpp
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To support national agencies for risk assessment of the radiological impact to humans
To protect humans via environmental protection (e.g. non-human species live in the most contaminated environments)
To investigate potential effects induced by contaminants and radiation on environment (non human species)
The biological effects of relevance are:
Early mortality;
Some forms of morbidity;
Impairment of reproductive capacity by either reduced fertility or fecundity; and
Induction of chromosomal damage.
ICRP (2003) A framework for assessing the impact of ionising radiation on non-human species. ICRP Publication 91. Ann ICRP 33(3)
ICRP (2007) The 2007 recommendations of the international commission on radiological protection. ICRP Publication 103. Ann ICRP 37(2–4)
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16. 210Pb discrepancy Eb endpoint (keV) Ib (%) Decay mode 210Pb 16,96 84
16,96 
84 
b- 
63,50 
16 
137Cs
513,97 
94.4 
892,22   
1175,63 
5.6 b-
1311
40K
44,04 
10.67 e 
482,9 
b+ 
1504,9 
0.047
Info: Table of Isotopes (
Erica default radiation weighting factors:
x 10 for alpha
x 3 for low energy (<10 keV) beta
x 1 for other beta and gammas
MCNP does NOT differentiate the electrons due to their energy
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