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 25th Symposium of Hellenic Nuclear Physics Society

25th Symposium of Hellenic Nuclear Physics Society Outline Motivation Study areas Methodology Results Discussion Future plans 25th Symposium of Hellenic Nuclear Physics Society 1

25th Symposium of Hellenic Nuclear Physics Society 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 25th Symposium of Hellenic Nuclear Physics Society 2

25th Symposium of Hellenic Nuclear Physics Society 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 25th Symposium of Hellenic Nuclear Physics Society 3

(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 25th Symposium of Hellenic Nuclear Physics Society 4

25th Symposium of Hellenic Nuclear Physics Society 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., 2005. On line gamma-ray spectrometry at open sea. Appl. Radiat. Isot. 62 (1), 83-89 International Atomic Energy Agency (IAEA), 2004. Sediment Distribution Coefficients and Concentration Factors for Biota in the Marine Environment. Technical Reports Series No.422 (Vienna). 25th Symposium of Hellenic Nuclear Physics Society 5

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 25th Symposium of Hellenic Nuclear Physics Society 6

25th Symposium of Hellenic Nuclear Physics Society 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 25th Symposium of Hellenic Nuclear Physics Society 7

25th Symposium of Hellenic Nuclear Physics Society 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 25th Symposium of Hellenic Nuclear Physics Society 8

25th Symposium of Hellenic Nuclear Physics Society 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 2.99 ·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 25th Symposium of Hellenic Nuclear Physics Society 9

25th Symposium of Hellenic Nuclear Physics Society 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). 25th Symposium of Hellenic Nuclear Physics Society 10

25th Symposium of Hellenic Nuclear Physics Society 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). 25th Symposium of Hellenic Nuclear Physics Society 11

25th Symposium of Hellenic Nuclear Physics Society Thank you for your attention 25th Symposium of Hellenic Nuclear Physics Society 13

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 24th Symposium of Hellenic Nuclear Physics Society

24th Symposium of Hellenic Nuclear Physics Society 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) 24th Symposium of Hellenic Nuclear Physics Society

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  0.00058  1175,63  5.6 b- 1311 40K 44,04  10.67 e  482,9  0.00104 b+  1504,9  0.047 Info: Table of Isotopes (http://nucleardata.nuclear.lu.se) 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 24th Symposium of Hellenic Nuclear Physics Society