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

EMRAS II PROJECT – WORKING GROUP 7

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

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

Brazilian Nuclear Facilities

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

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

SITE SELECTION IN THE NORTHEAST REGION

Eletronuclear Northeast Nuclear Power Plants

FOCUSED AREA

• 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

BENCHMARK FOR SITE SELECTION IN THE NORTHEAST REGION

Eletronuclear Northeast Nuclear Power Plants

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

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.

Eletronuclear Northeast Nuclear Power Plants

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

SITE SELECTION GUIDE

Eletronuclear Northeast Nuclear Power Plants

EXAMPLE OF WEIGHTING FACTORS APLIED TO OTHER SUITABILITY CRITERIA

Eletronuclear Northeast Nuclear Power Plants

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

INFORMATION INTEGRATION ON GIS PROVIDE BASE FOR SELECTION OF CANDIDATE SITES

Eletronuclear Northeast Nuclear Power Plants

Candidate Sites

(Bahia and Alagoas)

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.

Simplified diagram of 14C and 3H flows in an LWR reactor

Water Circulation LWR

Fuel Reactor componentsCladding Coolant

Reprocessing Plants Decommisioning 14C, 3H Leakage

Absorption from off-gas Immobilization

14C Discharge Disposal

Environment

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

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

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.

• 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

System Attributes for Transport Modelling (Eulerian 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

System Attributes for Transport Modelling (Lagrange Modules)

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.

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

Flow velocities output with around 330 hours of simulation (Rising tide

in Sygyzy condition)

Flow velocities output with around 330 hours of simulation low tide

with Sygyzi condition

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

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)

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