Assessment of liquid disposal originated by uranium enrichment at Aramar Experimental Center São Paulo—Brazil
Marli Gerenutti, Marcos Moisés Gonçalves, Sandra Regina Rissato, José Martins de Oliveira, Marco Antonio dos Santos Reigota, et al. Environmental Monitoring and Assessment An International Journal Devoted to Progress in the Use of Monitoring Data in Assessing Environmental Risks to Man and the Environment ISSN 0167-6369 Environ Monit Assess DOI 10.1007/ s10661-011-2274-5
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Author's personal copy Environ Monit Assess DOI 10.1007/s10661-011-2274-5
Assessment of liquid disposal originated by uranium enrichment at Aramar Experimental Center São Paulo—Brazil Marli Gerenutti & Marcos Moisés Gonçalves & Sandra Regina Rissato & José Martins de Oliveira Jr & Marco Antonio dos Santos Reigota & Mário Sergio Galhiane
Received: 30 June 2010 / Accepted: 19 July 2011 # Springer Science+Business Media B.V. 2011
Abstract This work presents a liquid disposal monitoring originated from uranium enrichment process at Aramar Experimental Center from 1990 to 1998. Assessment of uranium, fluorides, ammoniacal nitrogen, chemical oxygen demand, and pH measurements were made in water samples and compared with results achieved in other countries, as North America and India. The liquid disposal evaluation, generated by uranium enrichment process, showed low levels, considering most parameters established by Federal and State Legislation, aiming environmental pollution control. However, uranium levels were above the limits established by Conselho Nacional do Meio Ambiente, Environment Protection Agency and mainly by the World Health Organization. Keywords Uranium . Environmental contamination . Water analysis
M. M. Gonçalves School of Chemistry, Universidade Estadual de Campinas, Campinas, Brazil M. Gerenutti (*) : J. M. de Oliveira Jr : M. A. dos Santos Reigota School of Pharmacy, Universidade de Sorocaba, Av Dr Eugênio Salerrno, 100/140, 18035-430 Sorocaba, Brazil e-mail: [email protected]
S. R. Rissato : M. S. Galhiane School of Chemistry, Universidade Estadual Paulista, Bauru, Brazil
Introduction Among the Brazilian alternatives to large-scale energy generation, nuclear power is very expensive, considering the investments required by emergency systems security, radioactive waste storage, and decommissioning of nuclear power plant that has expired its lifetime (Valdović and Bošković 2000). There are several elements for estimating decommissioning cost such as pre-actions, facility shutdown activities, procurement of general equipment and material, dismantling activities, waste processing, packaging, transportation, storage and disposal, site security, surveillance and maintenance, site restoration, cleanup and landscaping, project management, engineering, site support, social measures, research and development, and fuel and nuclear material management (OECD/NEA 2006). Uranium enrichment process gives rise to a large amount of nearly pure U-238 that is useless as fuel in nuclear reactors. For each kilogram of enriched uranium produced, 200 kg of low-enriched uranium are generated, mainly U-238, a radionuclide that emits a less harmful type of radiation but with a half-life of about 4.5 billion years. It is considered 40% less radioactive than natural uranium, but its chemical toxicity is similar (Valdović and Bošković 2000). Uranium has both radioactive and chemical toxicity that mainly affect two vital organs: kidneys and lungs (Silva et al. 2000). The uptake of uranium in the kidneys has been attributed to the complexes formed with proteins and phospholipids, which are considered
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major sites of damage in this organ. Uranium can also affect the brain, changing neurological and pathological signs specially in cerebral cortex, such changes have been observed in rats subjected to tests using uranium salts. The tolerable daily uptake of uranium established by World Health Organization is 0.6 μg kg−1 bodyweight−1 (Gilman et al. 1998; WHO 1998; WHO 2003). WHO, Health Canada and CONAMA (Conselho Nacional do Meio Ambiente—Brazil) set the maximum concentration of uranium in water respectively less than 9, 20, and 20 μg kg−1 (Gilman et al. 1998; WHO 1998). The main danger inherent to the disposal of atomic waste is basically the environmental contamination. Water contamination is generally the most likely form of pollution related to atomic waste disposal. Groundwater can get in contact with radioactive elements that have percolated from atomic waste, contaminating water supplies from local or distant communities (ASTDR 1999). Industries involved in the nuclear fuel cycle, including the uranium ore mining, milling, refining, conversion, fuel production, nuclear power generation, and nuclear waste management are subjected to licensing and control processes. The waste generated by these activities require appropriate procedures for its treatment, before disposing them in the environment (IAEA 1995). Unsuspected before, human activities have been increasing environmental radioactivity levels, being, nowadays, a potential source of exposure. Therefore, papers have been published on this topic, looking for the development of technologies for remediation and disposal treatment (Anderson et al. 2003; Wu et al. 2006; Landa 2004). Considering the environment, especially in areas close to nuclear fuel cycle industries, complex rejects give rise to a dynamic equilibrium with large fluctuations in water quality. These fluctuations can be fast or slow and are usually associated with the weather, including precipitation and hydrological phenomena, reflecting the toxicity of mine effluents (Antunes et al. 2007a; Carvalho et al. 2007a, b). Sediments accumulate radionuclides by water sorption or by sedimentation of suspended radioactive solids. The radionuclides that remain associated with sediments are strongly influenced by chemical, biochemical, and microbiological changes that occur in the environment (Valdović and Bošković 2000).
In order to evaluate the possible risks from radioactivity uptake by humans through the food chain, studies have been done on the absorption, concentration, retention, and release of radioactive materials by aquatic organisms (Antunes et al. 2007b; Gudkov et al. 2008; Markich 2002). Aiming to analyze the intensity and quantity of chemical waste in Ipanema and Sorocaba rivers from disposal of atomic wastewater generated by enrichment of uranium in Aramar Experimental Center (AEC), this paper presents a monitoring assessment of liquid disposal from uranium enrichment process, from 1990 to 1998.
Experimental methods Identification of AEC facilities The Production Department named Centro Tecnológico da Marinha in AEC—São Paulo had three divisions: manufacturing, assembly and enrichment. The enrichment division was composed by: operation of Isotopic Enrichment Laboratory (LEI), planning and control of the process, maintenance, decontamination, and stripping operation of pilot plants for isotopic enrichment (USIDE) and sectors to support the process. LEI and USIDE were the enrichment division units chosen to be studied. LEI may be considered responsible for the enrichment through the uranium hexafluoride ultracentrifugation process. The operation scale is related to the development and process demonstration, and it has also been used for testing equipment associated with these procedures. This facility has been operating since 1988, producing UF6 enriched to the level of 20% (by weight) of U-235 (CNEN 1985). Samples The evaluation of wastewater samples generated in the AEC was performed by the Radioprotection Laboratory (LARE), from 1990 to 1998. For operational purposes, LEI monitoring for liquid disposal, began in 1989 with the measurement of fluoride and pH, in 1990 with uranium and biochemical oxygen demand (BOD) analysis, in 1993 with measurement of ammonia nitrogen and sporadic monitoring of iron and nickel (ARAMAR 1997).
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The liquid waste generated in LEI, consisted of citric solutions from decontamination operations, potassium hydroxide solutions from gas scrubbers, liquid Fomblin® from decontamination processes and washing floor waters. Figure 1 shows the sequence for the decontamination of ultracentrifuge parts and plastic containers. The waste generated in these cases was accumulated in the tanks 5 and 6. Citric solutions with large amount of uranium were stored and transported in plastic containers to thermo solar evaporator and other solutions were delivered through specific pipes to the collection, storage, and reject processing systems (ARAMAR 1997). The liquid streams generated during normal operation of USIDE were originated by the fan coils condensed waters, water from washbasins, showers and drains of restricted areas, and solutions from gas scrubbers.
Whereas the main contaminant was uranium, the waste was transported to the tanks, and rejects with radiation levels higher than 2.6×10−6 Bq g−1 should be transferred to the LEI thermo solar evaporators. Monitoring of the USIDE effluents has started in the second half of 1996 with uranium, fluorides, ammonia nitrogen and BOD analysis, as well as pH measurement. To determine physical and chemical parameters, all samples were collected and stored in a refrigerator in glass bottles at 4°C until analysis. Thus, all samples were submitted to specific analysis, in order to obtain authorization to release the disposal contained in the collection and storage tanks. According to AEC procedure, whenever the disposal condition was unsatisfactory, its subsequent disposal occurred after appropriate treatment.
Fig. 1 Decontamination sequence for ultracentrifuges and bombs
2. Gas scrubber.
2.1. Mechanic devices.
• • • •
Two hot cycles without drainage with Sun; • Drainage in plastic cilinder; • Hot water washing; • Drainage in plastic cilinder;
Citric acid ultrasound immersion; Water washing; Acetone drying; Monitoring and packaging.
3. Immersion in ultrasound with citric acid; 4. Washing and oxidation removal; 5. Drying, monitoring and packaging. B. LIQUID EFFLUENTS (TANKS 5 AND 6)
⇓ 2.2. Stators and other electronics.
6. Plastic barrel gathered material to
• 7.5% citric acid wet paper cleaning; be conducted to thermo solar • 10% (NH4)2CO3 wet tissue paper cleaning; evaporator. • Acetone wet tissue or paper cleaning (drying step). 3. Drying, monitoring and packaging. C. SOLID RESIDUE
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Liquid disposal analysis
Chemical oxygen demand
For monitoring the chosen parameters, LARE has used internationally recognized methods, which are described below:
Was performed by potassium dichromate reflux (titrimetric analysis), which is the most suitable, due to its high oxidant capacity. The analysis of liquid disposal was performed by closed reflux method (titrimetric and colorimetric methods), due to economic advantages.
Uranium The determination of uranium in liquid or gas disposals was achieved by using gravimetric or fluorimetric analysis. In LARE, from 1990 to 1998, the monitoring of uranium in the liquid disposal was made through fluorimetric analysis and the results were expressed in μg L−1 or μg g−1. Fluorides Among the methods suggested for determining fluoride ions in water, the most satisfactory were the potentiometric and colorimetric ones. In LARE, fluoride monitoring in liquids was performed by potentiometric analysis and the results were expressed in μg g−1 or μg L−1. Ammonia nitrogen In general, ammonia nitrogen determination was directly and manually made in drinking water, surface water, from lakes and rivers. However, when high precision determination was required, there was a need for preconcentration. Colorimetric with Nessler reagent and gravimetric methods were used (CNEN 1985; ARAMAR 1997). For ammonia detection the following methods have been used: titrimetric (concentrations higher than 5 mg L−1), ammonia-selective electrode method (NH3 concentrations of 0.03 to 1 400 mg L−1), phenate method (NH3 linear concentrations of 0.6 mg L−1), and automated phenate method (NH3 concentrations between 0.02 and 2.0 mg L−1). pH The method for pH measurement was the electrometric one, using potentiometric determination which employed standard hydrogen electrode and reference electrode. In LARE, AEC liquid disposal measurement was performed by potentiometric analysis.
Results and discussion The quality of water and wastewater can be represented by various parameters, which reflect the main physical, chemical and biological features of the environment. The liquid disposal generated in the uranium enrichment process has acquired features accordingly to the procedure employed. The requirements to be met for the liquid disposal are subject to specific legislation, which provides quality standards for the liquid disposal and the environment involved. The removal of pollutants in treatment was made in order to reach a desired quality or quality standard, and it is linked to current concepts of level and treatment efficiency (APHA 1998). Patterns of effluent release become increasingly restricted, and there is the need to recycle water, thus preserving water sources and, at the same time, providing an effective use of that resource. Therefore, the treatment degree required for a reject always depends on the environment, the features of the downstream water from its releasing point, the self purification features and the environmental water dilution (Valdović and Bošković 2000; IAEA 1995). The use of polymer materials showed positive results in effluent treatment generated by nuclear reactors (Preetha et al. 2006). This paper presents a monitoring of liquid disposal released in Ipanema and Sorocaba rivers, generated by uranium enrichment process at Aramar Experimental Center, from 1990 to 1998. Ipanema and Sorocaba (Fig. 2) rivers are classified as class 2, with water intended, after conventional treatment, to domestic supply, vegetable and tree fruit irrigation, and primary contact recreation (São Paulo 1976; CONAMA 2005a; CONAMA 2005b; CONAMA 2008). According to Table 1, the results showed that the semestral volume of liquid released by LEI and
Author's personal copy Environ Monit Assess Fig. 2 Sorocaba and Ipanema rivers (Smith 2003)
USIDE were considered lesser than the amounts allowed by Federal and State laws, considering the features of Sorocaba River is thus in accordance with the legislation (São Paulo 1991). Table 2 shows the semestral average concentration of fluorides and ammonia nitrogen released in LEI's liquid disposal, and the values of pH and COD from 1990 to 1998. Considering the quality standard in Class 2 rivers and the liquid disposal release standard, CONAMA 357/2005 (Article 34, Fluent Release Patterns) (CONAMA 2008), the maximum concentration of fluoride released in USIDE and LEI liquid effluents did not exceed the concentration limit recommended (Table 2), i.e., 10 mg L−1. However, according to the World Health Organization, the fluoride level established as optimal for drinking water ranges from 0.7 to 1.2 mg L−1, according to the mean annual temperature (18°C=1.2, 19–26°C= 0.9, 27°C=0.7 mg L−1). The maximum levels of Table 1 7Q10 values considering Sorocaba river
7Q10 estimation of minimum 7-day, 10-year discharge
fluoride in drinking water are set according to the consumer age, and the daily amount of water intake. In tropical countries, where the daily water intake is higher, the fluoride control should be more rigorous concerning public water supply. However, when the fluoride concentration exceeds the limits established by existing laws, drinking water must be defluorinated, due to the possibility of causing dental and skeletal fluorosis, in both humans and animals (Bucher et al. 1991). Evaluation of ammonia nitrogen is very important, because at high concentrations, it exhibits high toxicity for fish, in general. The average concentrations of ammonia nitrogen, released in liquid disposal of LEI and USIDE, have had values below the maximum concentration of 20 mg L−1 (Table 2) (CONAMA 2008). Similarly, the pH measurement is one of most relevant analysis often used for chemical water
7Q10 monthly (m3 s−1)
7Q10 estimated (m3 h−1)
7Q10 excellent (m3 h−1)
Sorocaba river higher (851 km2)
Sorocaba river lower (3,109 km2)
Author's personal copy Environ Monit Assess Table 2 Semestral monitoring of LEI liquid effluent, tanks 5 and 6 Fluorides (mg L−1)
Ammonia nitrogen (mg L−1)
COD (mg L−1 O2)
1998 1st sem 1997
1996 2nd sem
1995 2nd sem
1994 2nd sem
1993 2nd sem
1991 2nd sem
1990 2nd sem
Means and standard deviations of fluorides and ammonia nitrogen concentrations, chemical oxygen demand (COD), and their respective pH range variations
testing. Virtually, in all reservoirs or water treatment plants, the acid–base balance, filtration, precipitation, coagulation, disinfection and corrosion control are pH dependent. The pH influences the physicochemical equilibrium, driving it to more or less toxic chemical species. Fish life becomes almost impossible if the pH is below 6.0 or above 9.0. At a pH lower than 6.0, the balance bicarbonate/carbon dioxide is shifted towards carbon dioxide, which becomes toxic to fish, from 100 mg L−1. At pH greater than 8.0 there is a release of molecular ammonia, more toxic than its ion, and the limit for fish death lies between 0.2 and 2.0 mg L−1 (Rand and Petrocelli 1985). In this context, practically all the pH values in LEI liquid
disposal between 1990 and 1998 were within the allowed ones (Table 2) (CONAMA 2008). Determination of uranium is vital for assessing environmental pollution, not only by its presence in water (especially water springs) and soil, but also because of its decay, which generates considerable levels of radioactivity in the environment (Dong et al. 2006) (this type of contamination is considered persistent, because uranium-238 has a half-life of ∼4.5 billion years, while uranium-235 has a half-life of approximately 0.7 billion years). However, information on uranium toxicity is limited and some studies have shown that its toxicity mainly depends on many variables, mostly pH and carbonates (Shepard et al. 2005; ICRP 1993). Several international
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agencies on health and environmental protection have recommended maximum concentration limits for uranium in drinking water or water springs for consumption. The International Commission on Radiological Protection (ICRP 1993) recommended the maximum limit in water of 0.0019 mg L−1 and WHO (2004) the maximum of 0.015 mg L−1 used for water springs for consumption. However, according to CONAMA Resolution no. 357/05, Article 15 (freshwater class 2) (CONAMA 2005b), the standard uranium emissions was set at 0.002 mg L−1. Table 3 shows the monitored uranium presented concentrations from 1990 to 1998, assessed in LEI for liquid disposals. The amounts of uranium ranged from 0.105 to 0.635 mg L−1 for liquid disposals. These results indicate that uranium concentrations were discovered to be above the limit of 0.020 mg L−1
Table 3 Semestral uranium monitoring from LEI liquid effluents
recommended by CONAMA (2005b) and 0.030 mg L−1 by US EPA (2003) and specially 0.015 mg L−1 by WHO (2004). However, when compared with values obtained in international literature, the results appear to be close to values of 0.973 mg L−1 obtained both in North America's (US EPA 1990; 1991) and 0.471 mg L−1 in the India's spring waters (Bansal et al. 1988).
Conclusions Liquid disposal effluent evaluation generated by uranium enrichment processes at AEC, for most parameters, showed results below the limits prescribed by Brazilian Federal and State legislation to control environmental pollution. The results for uranium in liquid were above
Uranium Concentrations (mg L-1) in Liquid Effluents Tank 5
1998 1st sem
1993 2nd sem
1991 Means and standard deviations of uranium concentrations and the total semestral amount of uranium delivered
1990 2nd sem
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the limits recommended by CONAMA (0.020 mg L−1) and EPA (0.030 mg L−1), and mainly by WHO (0.015 mg L−1), but were close to the values obtained in international literature for spring waters. This paper gives evidence to the importance of monitoring the effluent generated by the uranium enrichment and suggests the need to expand its monitoring through environmental samples as fountainheads, sediments, soil, and biota next to nuclear facilities, in order to create real parameters for the population health as well as the environmental protection. Acknowledgment The authors are grateful to CNPq-Conselho Nacional de Desenvolvimento Científico e Tecnológico, for financial support.
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