Comparison of MCNP and ERICA results in two

Comparison of MCNP and ERICA results in two different marine areas F. K. Pappa 1, 2, D. L. Patiris 1 , C. Tsabaris 1, G. Eleftheriou 1 E. G. Androulakaki 1, 2, M. Kokkoris 2, R. Vlastou 2 Collaboration of: 1. Institute of Oceanography, Hellenic Centre for Marine Research 2. Department of Physics, National Technical University of Athens 25 th Symposium of Hellenic Nuclear Physics Society

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

Problems and motivation Problems: a. Determination of the radiation dose is a complicated procedure for the marine environment due to biodiversity and to radiation interactions in the water b. Poor literature data for marine key parameters (e. g. concentration factors , radiation dose biological effects, biokinetic models) ERICA Assessment Tool : a. Specialized software system to assess the radiological risk to biota b. 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 (MCNP 5) • To identify sources of discrepancies for various radionuclides and improve the input parameters by providing experimental ones related to the area of study 25 th Symposium of Hellenic Nuclear Physics Society 2

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. 40 K, 137 Cs, 210 Pb) • To estimate the dose rates of MCNP (Me. V/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 ERICA MCNP Same organism and area Simple case (monenergistic radionuclides (e. g. 40 K, 137 Cs) External dose rates in agreement? Yes No Proceed in internal and total dose rate Optimaze the input data in the code 25 th Symposium of Hellenic Nuclear Physics Society 3

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 25 th Symposium of Hellenic Nuclear Physics Society 5 4

Methodology (ERICA) § Tier 2 (site specific) § Mean values of activity concentrations at the areas of study § Selected organism → benthic fish § 40 K → added →insert important parameters (C and K ) R d Problem: Not available Kd values for 40 K in the literature Solution: Conversion salinity to 40 K 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). 25 th Symposium of Hellenic Nuclear Physics Society 5

Methodology (MCNP) Reality Bluespotted ribbontail rays • Approximations: Preserve volume and mass of benthic organism Geometry Approximation 3 D • Different effective volume for each radionuclide Flounder • Insert: a. 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 ell rpp 25 th Symposium of Hellenic Nuclear Physics Society 6

What is the effective volume? Effective Radius (R) water 40 K 1460 ke. V 137 Cs → 662 ke. V 210 Pb → 45 ke. V 15 7 c m 40 K→ 210 Pb 38 cm m 5 c 11 9. 5 cm First order approach → ignore the impact of beta decay emissions → justified sediment 25 th Symposium of Hellenic Nuclear Physics Society 7

Results (Shatt al-Arab estuary) ERICA Benthic 40 K 137 Cs Shatt al-Arab 210 Pb Relative Difference mcnp rpp (μGy/hr) ell 1. 59· 10 -2 1. 15 · 10 -2 1. 04· 10 -2 2. 10· 10 -4 1. 55 · 10 -4 1. 60· 10 -4 rpp ell (%) 28 26 35 24 not measured 137 • The external dose rate of C estimated by ERICA and 40 K estimated by ERICA and MCNP tools was 2. 10· 10 -4 MCNP tools was 1. 59· 10 -2 (μGy/hr) and 1. 55 · 10 -4 (μGy/hr) and 1. 15 · 10 -2 (μGy/hr), respectively. The (μGy/hr), respectively. The difference between the two difference between the codes ranged from 24 to 26%. two codes ranged from 28 to 35%. • The simulation results for different geometries were in good agreement 25 th Symposium of Hellenic Nuclear Physics Society 8

Results (Stratoni port) 2. 90· 10 -2 2. 15 · 10 -2 2. 05 · 10 -2 137 Cs 3. 90· 10 -4 2. 99 · 10 -4 3. 04 · 10 -4 3. 39· 10 -4 4. 16 · 10 -7 3. 04 · 10 -7 210 Pb • The external dose rate of 40 K 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%. 26 29 23 9. 5 cm ? • The external dose rate of 137 C 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%. 22 ? m 40 K m ell 7 c rpp (μGy/hr) 5 c 11 Stratoni mcnp water 15 ERICA Benthic 40 K Relative 210 Pb Difference rpp ell (%) 38 cm sediment • The simulation results for different geometries were in good agreement 25 th Symposium of Hellenic Nuclear Physics Society 9

Discussion ü The calculated results using the two tools in the cases of 40 K and 137 Cs were in satisfactory agreement. In the case of 210 Pb we confirmed the impact of the electron emission on the absorbed dose rates. ü The different simulated (benthic) geometries contribute only slightly (40 K, 137 Cs) to the dose rates results ü MCNP is widely used in the marine environment – MCNP-CP would be preferable (TCS effects, full decay scheme simulations). ü The input data in the MCNP code have to be harmonized with the ERICA processing module (210 Pb problem) ü 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). 25 th Symposium of Hellenic Nuclear Physics Society 10

Future plans ü Defining input parameters for Naturally Occurring Radionuclides (NOR) ü Estimating external dose rates in other matrices (e. g. pelagic fish, etc) ü To assume radioactivity equilibrium in MCNP calculations as in the ERICA runs ü 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). 25 th Symposium of Hellenic Nuclear Physics Society 11

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

Methodology (MCNP) Reality • Approximations: Preserve volume and mass of benthic organism • Different effective volume for each radionuclide Bluespotted ribbontail rays Flounder • Insert: a. The characteristic photon energy of each radionuclide (take into account photons and electrons) b. Sediment composition in both areas 24 th Symposium of Hellenic Nuclear Physics Society Geometry Approximation 2 D 3 D ell rpp 14

• 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) 24 th Symposium of Hellenic Nuclear Physics Society 15

210 Pb 137 Cs discrepancy Eb endpoint (ke. V) Ib (%) Decay mode 16, 96 84 b- 63, 50 16 b- 513, 97 94. 4 b- 892, 22 0. 00058 b- 1175, 63 5. 6 b- 44, 04 10. 67 e 482, 9 0. 00104 b+ 1504, 9 0. 047 e Erica default radiation weighting factors: x 10 for alpha x 3 for low energy (<10 ke. V) beta x 1 for other beta and gammas 1311 40 K MCNP does NOT differentiate the electrons due to their energy Info: Table of Isotopes (http: //nucleardata. nuclear. lu. se) 24 th Symposium of Hellenic Nuclear Physics Society 16