A Comparison of Doses from 137 Cs and 210 Po in Surroundings Of

IAEA-SM-354/111P XA9952008 A COMPARISON OF DOSES FROM 137Cs AND 210Po IN SURROUNDINGS OF NUCLEAR POWER PLANT JURAGUA DUE TO INGESTION OF MARINE FOOD ALONSO HERNANDEZ, C. M., R. AVILA MORENO M. DIAZ ASENCIO, A. MUNOZ CARAVACA, E. SUAREZ MORELL, Laboratorio de Vigilancia Radiologica Ambiental del Centro, Cienfuegos, Cuba Between 1991 and 1995 The Environmental Radiological Surveillance Laboratory of Cienfuegos carried out a Radiological Monitoring Program in the central area of Cuba, with the purpose of evaluation of the site of the first Nuclear Power Plant in construction in our country. As a part of this program natural and artificial background radionuclide levels in the marine environment were determined. From these results, two radionuclides caught our attention, 210 Po by his share to the internal irradiation dose and 137 Cs due to this possible increase when the plant operates. The purpose of this work was the evaluation of the individual doses by ingestion of marine organisms in two residential areas with a great radiological interest: Cienfuegos city and Castillo de Jagua. Our work covered Cienfuegos City, the s^ u. ''...< main residential focus of the province with an ingestion of marine organism near to the national "''"'"" ' average and the residential area of Castillo de Jagua, ••••"•' h-> ••?•=•. where is found a high ingestion rate because of his fishing habits. --•^•-" „ The dose determinations were carried out .•-ijrj- „- ' "*x • from concentration levels in marine organisms T."S-— . 1_. edible parts, determined experimentally, and from ^ i...... ... - • ' ~j . the local ingestion rates in both areas. In our analysis : ; --~— *&•' - -•-- v'-=-" were used the metabolic and Dosimetric models ^- - .. .—.-..SL- recommended by ICRP[1] . Samples from 23 species of fish, mollusk - - • — and crustaceans were collected in Cienfuegos FIG. 1 Map of the studied areas. Fishing Port, taken to our Laboratory where the edible parts were separated and later analyzed. The 210 Po was determined by alpha radiometry after the spontaneous electrodeposition of the radionuclide in silver discs, from a clorhidric solution of the digested sample. [2] The 137 Cs analyses were carried out by gamma spectrometry in a system with a pure Ge detector and a passive lead shield after the radiochemical separation of the radionuclide. Both essays are validated with OIEA reference materials and certified in compliance with ISO IEC- 25. The commercial network defined the Ingestion rate of Cienfuegos City, and the Statistic Province Direction and The Marine Products Distribution Company supplied the data.[3] In The Castillo de Jagua area was done a direct survey with a representative residential sample about their ingestion habits. The concentration levels of 210 Po and I37 Cs are shown in Table No. 1 The concentration levels of 2I0Po in Cienfuegos Bay marine organisms are high in comparison with levels reported in literature [4]: 0.7 and 20 Bq/Kg in muscular tissues of fish and mollusk respectively. The 210Po levels in the white shrimp reach values of 156 Bq/Kg. The levels of 137Cs are normal for a zone affected only by global fallout and are similar to other data observed by Baxter et al and Silva et al in 1987 for the Caribbean region. [5],[6] In Castillo de Jagua the fish ingestion rate follows a lognormal distribution. The geometrical mean value was 51.1 Kg/year and the average 103 kg/year. The 95% percentile was 351 Kg/year and the 440 representative interval from 21.4 to 116 Kg/year. The 1.6 % of population doesn't eat fish. The ingestion of mollusk and crustaceans is not significant. TABLE I. CONCENTRATION LEVELS OF TABLE II. COMMITTED EFFECTIVE DOSES 210PoANDI37Cs. FOR BOTH POPULATION GROUPS. Organism 210po 137Cs Ingestion Committed Committed Bq/Kg fresh Bq/kg fresh Value Effective Effective weight weight Kg Dose Po- Dose Cs-137 Fish 19.5 0.1 210 (jxSv) (M-Sv) [5.2-89] [0.09-0.3] Cienfuegos 4.45 44.6 0.005 Mollusk 25 0.9 51.1 516 0.06 [20-33] [0.1-0.11] Castillo de 351 3500 0.42 Crustacean 125 0.1 Jagua [0.06-0.2] [50-156] 21.4-116 200-1200 0.02-0.13 The fish ingestion rate in Cienfuegos City was 4.45 Kg/ year, similar to the national mean. The dose, according to all written above, takes into consideration only the fish ingestion. In Table 2 are shown the doses for the two populations after all calculations including for The Castillo de Jagua area the 95% percentile value and the representative interval. The dose from I37Cs is the 0.01 % of doses due to 210Po. The 95% percentile in Castillo de Jagua reaches a dose of 3.5 mSv for 210Po. This value is close to the ones reported for populations from the artic and subartic areas in north hemisphere which dietary habits are based on caribou and reindeer meat. [7] The Representative Interval dose is higher than the reported for the rest of the world due to food ingestion of 0.2 mSv. [4] The mean individual dose from 137Cs in seafood for Cienfuegos City corresponds to 12 minutes Effective dose of total food consumption for this population according to Suarez et al [8] (0.2 mSv per year) and 1 minute Effective dose from all natural sources (2.4 mSv per year) [4]. For The Castillo de Jagua population the geometrical mean dose from 210Po corresponds to 251 days Effective dose of total food consumption for this population (0.7 mSv per year) [8] and 77 days Effective dose from all natural sources. The 210Po dose for The Castillo de Jagua population, due to its high ingestion rates and the slightly high levels of 210Po, represents a significant contribution to the dose of total food consumption. It's necessary a further analysis about the possible sources of 210Po in Cienfuegos Bay. References [1] International Commission of radiological Protection. "Limits for intake of Radionuclides by workers". ICRP-30. 1982. Pergamon Press. Oxford. [2] HASL-300. Procedure Manual of Environmental Measurements Laboratory. USA. 1990. [3] CEE. Reporte Interne Comite Estatal de Estadisticas. Dpto. Demografico. Cienfuegos 1991 [4] UNSCEAR (1993). Ionizing Radiation : Sources and Biological Effects. United Nations. New York. [5] BAXTER, M. S. et al. A Comparison of Doses from 137Cs and 210Po in Marine food: A Major International Study. J. Environ. Radioact. 34(1), 69-90 (1997) [6] SJJLVA, A., et al. Radioactividad Ambiental Alrededor de la Central Laguna Verde. Informe de Impacto Ambiental (Comision Federal de Electricidad, Veracruz, Mexico)(1992). [7] PERSOON, B. R. "Radiolead (210Pb, 210Po) and stable lead in the lichen, reindeer and man". P 347- 367 in The Natural Radiation Environment II. Conf- 720805-P2 1972. [8] SUAREZ M, E. ALONSO H, C. DIAZ A, M. MUNOZ C, A. Evaluaciones y Calculos Orientativos de las Dosis de Irradiacion de la poblacion residente debida al consumo de productos alimenticios. Informe de Seguridad CEN Juragua. Cap. 2.6 1992. 441.

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