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Assessment of Tritium Accidents in Brazil

EMRAS II PROJECT – WORKING GROUP 7. Assessment of Tritium Accidents in Brazil. Nuclear Reactors in Brazil (present and future) Hydrological Modelling with the Database System for Environmental Hydrodinamics (SisBAHIA) Data gaps and special features in tropical sites.

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Assessment of Tritium Accidents in Brazil

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  1. EMRAS II PROJECT – WORKING GROUP 7 Assessment of Tritium Accidents in Brazil Nuclear Reactors in Brazil (present and future) Hydrological Modelling with the Database System for Environmental Hydrodinamics (SisBAHIA) Data gaps and special features in tropical sites

  2. Brazilian Nuclear Facilities WHAT WE HAVE NOW: • Two nuclear power plants and a new one under construction (all of them are PWR) • Two uranium mining and milling plants (one operating and other in phase of decommissioning plan). A third one is under commissioning • Three fuel cycle factories • Military facilities: R&D on the brazilian nuclear reactor for submarines and fuel cycle

  3. Brazilian Nuclear Facilities WHAT IS PLANNED FOR THIS DECADE: • Four new Nuclear Power Plants (the two first in the northeast and the others in the southeast of the country) • One Multipurpose Reactor to provide radionuclide for health (radiopharmacy) and industrial applications • Spent fuel storage plants outside reactor pools • National Repository for radioactive wastes with low and intermediary activity level

  4. Brazilian Nuclear Power Plants at Angra dos Reis (Rio de Janeiro) owned by Eletronuclear (ETN), subsidiary of Eletrobrás a mixed economy and open capital stock corporation (Shares are traded at São Paulo, NY and Madrid). Brazilian federal government is the majority stockholder

  5. The Ilha Grande Bay supplies water to nuclear plants, afterward the liquid effluents are discharged in another place of the bay

  6. SITE SELECTION IN THE NORTHEAST REGION FOCUSED AREA Eletronuclear Northeast Nuclear Power Plants

  7. BENCHMARK FOR SITE SELECTION IN THE NORTHEAST REGION • Business decision as the economical feasibility of new nuclear reactors was based on the National Energy Plan (PNE-2030) • Energy market (Population of São Francisco River Basin are on the edge with 50 million people with repressed demand) • There are no previous impediments from public organizations and regulatory authorities • Public Hearings and Stakeholder Involvement since the early stages Eletronuclear Northeast Nuclear Power Plants

  8. SITE SELECTION PROCESS AND CRITERIA The process must consider site characteristics that interfer in all phases of the plant: • Build • Operation • Transport (personnel, equipments and fuel) • Accident Condition The site selection must follow siting criteria stages: • Exclusion Criteria (site elimination) • Avoidance Criteria (site more flexible elimination) • Suitability Criteria (Scoring of utility functions) • Suitability Criteria Weighting (tradeoffs) Eletronuclear Northeast Nuclear Power Plants

  9. CANDIDATE AREAS AND SUITABILITY CRITERIA After the two first stages of site elimination (exclusion and avoidance), it were selected 15 to 20 sites among the remainders. They are called candidate areas, on which will be applied the suitability criteria. Suitability criteria are performed with the aim of identify and classify a few number of candidate areas to more detailed studies This stage demands more detailed studies with comparison of 50 criteria (require larger investments), which are classified in four groups based on characteristics and issues addressed: Health/Safety; Environmental; Land Use/Socioeconomics; Engineering/Cost-related Eletronuclear Northeast Nuclear Power Plants

  10. SITE SELECTION GUIDE Eletronuclear Northeast Nuclear Power Plants

  11. EXAMPLE OF WEIGHTING FACTORS APLIED TO OTHER SUITABILITY CRITERIA Eletronuclear Northeast Nuclear Power Plants

  12. EXEMPLE OF SITING PROCESS RESULTS Application of the siting criteria method at North Anna, Savannah River, Portsmouth, Surry and INEEL for a new unit in existent nuclear facilities. Eletronuclear Northeast Nuclear Power Plants

  13. INFORMATION INTEGRATION ON GIS PROVIDE BASE FOR SELECTION OF CANDIDATE SITES Candidate Sites (Bahia and Alagoas) Eletronuclear Northeast Nuclear Power Plants

  14. ESP and TECHNOLOGY SELECTION versus LICENSING • ETN requires the use of envelope of plant parameters to apply for early site permit (ESP), based on NRC new licensing process (subpart A of 10 CFR Part 52). • Nuclear Regulatory Authority in Brazil (CNEN) designed an expert committee to review the regulation for site approval to nuclear power plants. They are evaluating the implications of the two options (current two part licensing or new combined licensing) and will prepar a report to subside authorities decision • For the two northeastern plants, It was decided to acquire advanced light water reactors (the choice should be between EPR and AP1000) • The other two plants planned to southeast (São Paulo and Minas Gerais States) are under discussion in the government. There are some experts that defend the idea to work at least in one of these sites with a CANDU reactor in order to operate Thorium fuel cycles due to Brazilian reserves, even greater than Uranium reserves.

  15. LWR Water Circulation Reactor components Coolant Fuel Cladding Decommisioning 14C, 3H Leakage Reprocessing Plants Immobilization Absorption from off-gas 14C Discharge Disposal Environment Simplified diagram of 14C and 3H flows in an LWR reactor

  16. Aquatic Pathway – Hydrodinamics and Transport Modelling • The mathematical models to represent hydrodinamics and contaminant transport in water bodies are generaly based on conceptual laws or principles expressed by differential equations • Numerical or Numerical-Analytical models translate mathematical equations to computational language (e.g. finite differences,finite elements or probabilistic models) and has high predictive power and little loss of information • The uncertainty can be largely reduced with calibration process and model validation • For these reasons, the recommendation to move from box-model hydrological models (with high uncertainty level) to hydrodinamic process-oriented numerical modelling should be considered as an important issue for tritium assessment

  17. Database System for Environmental Hydrodinamics (SisBAHIA) • System of computational modelling applied to hydrodinamical circulation and advection-difusion contaminant transport in natural water bodies under different metereological, fluvial, lacustrine or oceanographic scenarios • Continued Developed by the Program on Coastal and Ocenographic Engineering of Federal University of Rio de Janeiro (Prof. Rosman) since 1987

  18. System Attributes for Hydrodinamics • The FIST (filtered in space and time) hydrodinamic turbulence model is based in Large Eddy Simulation (LES) to simulate vortices • The model computes flow velocities either on three-dimensional (3D) or on two-dimensional vertical averaged (2DH) • The spatial discretization is made through 4th order finite elements with two-quadratic squares or quadratic triangles or both • Sigma transformation is used to vertical discretization resulting in finite element mesh pile • Processing time is faster than 50 the real time, i.e. one day of circulation is simulated in less than half hour.

  19. System Attributes for Transport Modelling (Eulerian Modules) • Eulerian advective-difusive transport module with kinetic reactions is suitable for simulating the dispersion of dissolved substances • It is possible to apply this module for 2DH or to selected layers of 3D hydrodynamic output • Solve scale conflict with adaptative (changing) mesh only around the contaminant • Gain factor between modelling time and real time in processing are 5 to 8 times faster than FIST3D

  20. System Attributes for Transport Modelling (Lagrange Modules) • Lagrangean advective-difusive transport module with kinetic reactions is suitable for the scale of contaminant spots that are small in comparison with the domain. • It is useful for pratically any kind of kinetic reaction of contaminant decay or production • The contaminant is represented as a cloud with countless particles, computing the position in space of each one. As the particle space position is continuous the scale conflict disappears. • The gain is around 10 to 100 times faster than FIST3D, which means that 1 day of real time takes only one minute of simulation • Two models: • Deterministic - useful to simulate efluent discharge along the coast, water mixture, residence time mapping and • Probabilistic - computed from N events or during some time interval T, allows, for instance, the evaluation of the probability of contaminant discharge pass in some spots with activity concentrations above the derived limites or other value previously defined

  21. After Processing and Source Codes • The model results can be exported to any graphic software. SisBAHIA uses automatic visualization of data in form of maps (Surfer) and charts (Grapher) • The system also developed multimidia interface that produces GIF files that shows results in animated view. • The source code of these interfaces as well as the hydrodinamical and transport models in Fortran language are opened and can be made available through agreement of technical cooperation with the university.

  22. ILHA GRANDE BAY 2DH DOMAIN FOR H-3 DISPERSION MODELLING (ROUTINE RELEASE) Discretization with a mesh containing 1163 finite elements (quadratic squares) and 5403 knots. Mesh refinement in the discharge area

  23. Flow velocities output with around 330 hours of simulation (Rising tide in Sygyzy condition)

  24. Flow velocities output with around 330 hours of simulation low tide with Sygyzi condition

  25. Dispersion pattern of 3H and 137Cs after 51 simulated days (Steady-state condition reached during neap tide)

  26. WHAT ARE THE MAIN TROPICAL ISSUES • The main concern about Tritium in tropical environments is related with the possible role of DOC high concentra-tion in river or coastal waters for quick formation of DOT from potential accidental releases of high activity HTO or HT. • If organic colloids could assimilate tritium from water in its exchangeable positions, it would be readily uptake by organisms in the form of OBT (buried tritium) • As organic colloids have high stability with large residence times in water column this process could lead to tritium biomagnification • If biomagnification possibility were confirmed for tropical aquatic environments, in accident scenario, it would give place to tritium issues, perhaps worse than Cardiff Case. • Customization of aquatic pathway models (AQUATRIT, OURSON) with tropical parameters and species (we have no experimental data available for tritium)

  27. WHAT CAN BE DONE • Modelling of Tritium transport in some selected scenarios (real and hypothetical) of accidental releases from NPPs or Radiopharmaceutical factories • Modelling Tritium speciation in presence of organic colloids to simulate the production of DOT and OBT formation in the water • Discuss some possible simple experimental work with some colleagues from university to selected tropical aquatic organisms (bioindicator for tritium ?) • I hope that we can establish collaborative work with colleagues interested in aquatic pathway for beyond of that year and beyond the end of EMRAS II

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