Emissão de 14C pelas unidades I e II da Central Nuclear Almirante Álvaro Alberto (CNAAA) e seu efeito local nos níveis ambientais

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

14 C is a is a long-lived beta-emitting nuclide (T = 5730 years) produced naturally 1/2 14 14 14 in the upper atmosphere as a result of reactions between neutrons and stable N( N(n,p) C). 14 C as well during their routine Although in a lesser extent, nuclear power plants produce 14 operation. Since it is converted in CO and mixed throughout the atmosphere, it is 2 incorporated into plant tissues, via photosynthesis process, and hence in food chain. Because 14 of the biological importance of C and long half-life, it is of interest to quantify the amounts released by nuclear industry. The Brazilian nuclear central named Nuclear Central Admiral Álvaro Alberto (CNAAA) has two nuclear reactors of PWR type in operation, Angra I (657 MWe) and Angra II (1350 MWe), and one under construction, Angra III (1309 MWe PWR). The aim of this 14 C content in the environment study was to determine the strength of the sources and the through analyses of air, vegetation and soils taken within 5 km (the influenced area) of CNAAA. The thesis consists of an extensive review about the subject (part one) and of four papers (part two). 14 The first paper is about the determination of C concentrations released by reactors (source strength). For Angra I, a device was developed in order to sample the gaseous effluents and for Angra II, a commercial monitoring system had already been implemented 14 since its initial operation (2001). The C can be emitted as hydrocarbons, CO or CO , 2 depending on the type of reactor. For PWRs, the main chemical form released is hydrocarbons (80 %). The monitoring system of Angra I was planned to determine both CO 2 and hydrocarbon fractions but in Angra II, all hydrocarbons are converted to CO by using a 2 Pd/Al O catalyst at 450 C. The liquid scintillation was the method employed to measure the 2 3 samples. The second one concerns the atmospheric dispersion of the released radiocarbon through measurements of air samples taken with 3 km from power plants, in five different wind directions. The sampling system consisted of a pump connected to a trapping column filled with 3 M NaOH solution. The trapped CO was, then, precipitated as BaCO using a 2 3 solution. For the measurements, the single stage accelerator mass espectrometry system BaCl 2 (SSAMS) was used. This system belongs to the Radiocarbon Laboratory located in Geology Department of Lund University, in Sweden. 14 C content in vegetation samples. Since food The third paper is the investigation of chain starts with plants, these measurements are useful to estimate radiation exposure to local population. Grass samples were taken up to five km from power plants, in seven different wind directions. The SSAMS was employed for the analyses. The last paper involves the study of soils taken just close to power plants (within 1 14 km) and at 50 km far from them, in a reference area. Not only C content was determined but 13 137 14 analyzes of C, total C and Cs were also made. SSAMS was used for the C measurements.

ASSUNTO(S)

carbono - impacto ambiental geologia geociências solos processamento de dados- geologia ar atmosférico ams usinas nucleares pwr 14c vegetação

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