Safety

 The safe operation of the nuclear power plants and the safety of the population living in their vicinity has always been a major concern of the nuclear industry. The design, construction and operation of the nuclear power plants obey the safety standards.

The Angra nuclear plants are of the PWR (pressurized water reactor) type and their design is based on the defense-in-depth concept, where multiple barriers are set up between the radioactive material contained in the reactor and the environment:

1. The first barrier is the fuel pellet made of ceramic material - uranium dioxide - that stands high temperatures - up to 2800°C; - without melting.
2. The second one is the fuel rod metallic cladding - a zirconium alloy - that in contact with water stands temperatures up to 1400°C;
3. The third one is the reactor pressure vessel made of steel plates, 20 cm thick in Angra 1, and 25 cm thick in Angra 2;
4. The forth one is a radiobiological shielding;
5. The fifth one is the 3 cm thick steel containment shell, which retains any radioactive material that could eventually release in case of accident, preventing environmental accidents.
6. Involving all those barriers, the concrete containment building functions as a sixth barrier and also protects the reactor from external agents.

Each of these barriers is combined with a set of passive and active safety systems intended to ensure their integrity. This design approach makes it extremely low the probability of an accident with the release of radioactive materials to the outside of the containment. In addition, rigorous procedures of follow-up, verification and control covering the basic design, components manufacture, systems assembling, plant construction and commissioning were adopted and continue throughout the plants operation, supported by a comprehensive Quality Assurance Program.

In case of abnormal operational occurrences, the engineered safety features and other devices act to shutdown the reactor in a safe way, remove the residual heat from the core, avoid the escape of radioactive materials and ensure emergency electric power supply to all the safety and protection systems in case of loss of external power.

The operational safety and the excellence in the Angra plants performance relies on periodical tests of systems and equipment, high level of operators qualification, constant improvement of safety systems and adoption of recommended international practices. The National Nuclear Energy Commission – CNEN is the governmental agency responsible for the licensing of nuclear installations in Brazil and acts along the whole process, evaluating the Safety Analysis Reports and other documents, verifying compliance with standards and regulations and carrying out inspections and audits in order to issue the construction and operation licenses.
In addition, the Brazilian Institute for Environment and Renewable Resources - IBAMA is the federal Agency responsible for the plants’ environmental licensing and international organizations such as the International Atomic Energy Agency – IAEA, the World Association of Nuclear Operators – WANO and the Institute of Nuclear Power Operations – INPO periodically evaluate the operational safety of the Angra nuclear plants.

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