Determination of natural radionuclides 40K, eu and eth in environmental samples from the vicinity of Aramar Experimental Center, Brazil

Transcription

1 Determination of natural radionuclides 40K, eu and eth in environmental samples from the vicinity of Aramar Experimental Center, Brazil André Luis Lima de Araújo Marco Antônio Proença de Moraes Bruno Robles Arine Rosane Fagundes Raquel M. da Silva Radioecological Laboratory Aramar Experimental Center September 18th, 2014

2 Introduction CTMSP Centro Tecnológico da Marinha em São Paulo (Navy Technology Center in São Paulo) development in the field of naval nuclear propulsion Two nucleus: SEDE (São Paulo city, located in the campus of São Paulo University) Centro Experimental Aramar - CEA (Iperó city) CEA: started in 1986 in an area donated by the Ipanema National Forest, a conservation unit allocated the main laboratories for the development of the nuclear fuel cycle September 18th, 2014

3 Introduction Exploration, mining and processing Conversion Enrichment CEA Nuclear submarine Generation of electricity Reconversion and fabrication of fuel element September 18th, 2014

4 Introduction Laboratório Radioecológico (LARE) Radioecological Laboratory Main attributions: 1. Check the effluents and gas emissions 2. Environmental Monitoring Radiological analysis, non-radiological analysis, ecotoxicity Biological matrices fishes, agricultural products, milk, eggs, pasture Geological matrices soil and sediments Water river, groundwater, rain Air particulate matter, gases 60 sampling points in 10 km radius September 18th, 2014

5 Introduction Natural Radioactivity (background radiation) Radionuclides found in: Atmosphere: 7 Be, 14 C, 3 H - interaction with cosmic radiation, 222 Rn ( 238 U series) Soils and Rocks: Series of 238 U and 232 Th, and 40 K September 18th, 2014

6 Introduction Radioactivity in soils and sediments by gamma-spectrometry: 232 Th assessed measuring daughters 238 U assessed measuring daughters 40 K direct measurement Indirect estimation: equivalent thorium (eth) and equivalent uranium (eu) September 18th, 2014

7 Introduction 238 U Series 214 Bi (609 kev) Bq kq -1 x = eu mg kg Pb (351 kev) Bq kg -1 x = eu mg kg -1

8 Introduction 232 Th Series 228 Ac (911 kev) Bq kg -1 x = eth mg kg Pb (238 kev) Bq kg -1 x = eth mg kg Tl (583 kev) Bq kg -1 x = eth mg kg -1

9 Introduction 40 K 40 K (1460 kev) Bq kg -1 x 31.3 = K mg kg -1 Considering 40 K = % of the total K

10 Introduction Baseline data on the level of radionuclides in soil and sediments - 40 K, eth and eu - Reference for documenting changes of the environmental radioactivity - Estimating the radiation dose for assessing the population health risk 40 K

11 Introduction Estimating the Anual Radiation Dose (ARD) in µsv year -1 ARD = [(K 1.505) + (eu 0.625) + (eth 0.310) ] K mass fraction in %, and eth and eu in mg kg -1

12 Objective Investigating changes on the natural radioactivity in soil and sediments at CEA Evaluate the applicability of the ARD equation to access the background dose values September 18th, 2012

13 Experimental Soil Sampling: 0-5 cm depth Bi-annualy 3 kg 12 sampling points 8 with dosimeters (TLD s) Sediment river Sampling: Petersen Dredge Bi-annualy 3 kg 3 points at Ipanema stream, 3 points at Ferro stream and 2 points at Sorocaba river September 18th, 2012

14 Experimental Sample Preparation Oven-drying at 125 C for 16 hours Sieve shaker g separated from 120 mesh fraction Sealed and stored for 1 month September 18th, 2012

15 Experimental Radioactivity measuring: High resolution gamma-ray spectroscopy Germanium detector Counting time = 12 hours Genie 2000, Canberra September 18th, 2012

16 Results and Discussion Detection limit for different matrices Samples Thorium series Uranium series Water 3000 ml Bq L Soil Bq g Sediment Bq g Ash Bq g Orange Juice Bq L Milk Bq LMilk Particle matter Bq m 3 x September 18th, 2012

17 Results and Discussion Average and standard deviation of K, eu and eth mass fraction (mg kg -1 ) in soil Period 1992 to ,00E+05 1,00E+04 mg kg -1 1,00E+03 1,00E+02 1,00E+01 K 6500 ± 2250 mg kg -1 eth 10.3 ± 3.6 mg kg -1 eu 3.2 ± 1.0 mg kg -1 1,00E Th U K September 18th, 2012

18 Results and Discussion Average and standard deviation of K, eu and eth mass fraction (mg kg -1 ) in sediment river Period 1992 to ,00E+05 1,00E+04 mg kg -1 1,00E+03 1,00E+02 K 9300 ± 3900 mg kg -1 eth 9.8 ± 3.7 mg kg -1 eu 4.0 ± 0.9mg kg -1 1,00E+01 1,00E Th U K September 18th, 2012

19 Results and Discussion Average and standard deviation of annual radiation dose (ARD) and average annual dose obtained by thermolluminescent dosimeter (TLD), period 2000 to 2012 ARD in soil 660 ± 65 µsv y -1 TLD in soil 620 ± 70 µsv y -1 µsv y ARD TLD September 18th, 2012

20 Results and Discussion Comparison Annual radiation dose (ARD) calculated from the K, eth and eu mass fractions in soils and average annual dose obtained by thermoluminescent dosimeter. Sampling points monitored in the years of 2011 and B September 18th, 2012

21 Results and Discussion Average and standard deviation of annual radiation dose (ARD) calculated from the K, eth and eu mass fractions in soils - Period 1992 to µsv y Year ARD 660 ± 65 µsv y -1 ANOVA: no significant differences of ARD in soil among the years (p > 0,05).

22 Results and Discussion Average and standard deviation of annual radiation dose (ARD) calculated from the K, eth and eu mass fractions in sediments - Period 1992 to µsv y ± 90 µsv y ARD ANOVA: no significant differences of ARD in sediments among the years (p > 0,05)

23 Conclusions Dose below the annual limit of 1,000 µsv y -1 Internation Comission on Radiological Protection ARD equation suitable to access the background radiation, since results demonstrated a good agreement with TLD measurements September 18th, 2012

24 September 18th, 2012