José Raúl Ortiz
Mexican Nuclear Society (SNM)
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Safety Regulations to Mitigate Nuclear Energy Risks

Wed, 02/19/2014 - 15:45

Q: How can Mexico ensure that its nuclear activities meet the highest safety standards?

A: The two GE reactors at Laguna Verde are boiling water reactors; there are more than 30 reactors of this type operating in the US, so we apply the same security norms here as are applied in the US. The agreements we have with the International Atomic Energy Agency (IAEA) force us to follow their norms when there is no national regulation on the matter. Usually these norms are more lax than the more detailed and specific norms in place in the US. When the IAEA asked for the local norms and we told them that although Mexico does not have its own, we have adopted and applied the well-known US norms, they gave us permission to operate the reactor. The US norms satisfy the standards of IAEA. SNM ensures compliance with IAEA agreements and applies the US regulations. Of course, we have the freedom to analyze the regulation and add to it or remove elements from it, if needed. Nowadays Mexico belongs to a regulatory forum that tries to homogenize norms. There is an Ibero-American forum of regulators that meets periodically, including members from Spain, Brazil, Argentina, Mexico, Chile and other countries that do not necessarily have nuclear reactors. Mexico attends the meetings of this organism and promotes the forums for international regulators which allow for an interchange of knowledge.

Q: What are the main risks that nuclear plants pose?

A: The main risk is the fusion of the core. As a reactor is operating, it accumulates a great amount of radioactive material in its core. That radioactive material is confined in the fuel matrix and in the fuel rod, but if for some reason the reactor needs to be turned off, the control rods stop absorbing the neutrons, the neutrons disappear and there is no fission reaction. What is left is waste heat generated by the amount of accumulated reagent. That waste heat lowers rapidly and in an hour or two the reactor is shut down to 5-6% of its initial potential, falling further to 1-2% in 24 hours. A large amount of heat is produced in the process, and the reactor requires constant cooling. It takes many days to reach a cold shutdown but after that presents no risk with the reactor.

To prevent problems that occur during a nuclear plant shutdown, the plant uses energy from the exterior to keep cooling systems functioning. If there is no external energy, then a battery of diesel motors that generates electricity is essential to keep the cooling system working. If there is a failure in these mechanisms, there is a battery bank that lasts for eight hours to substitute the necessary energy while we repair the problem.

Q: How can new technology make nuclear power safer?

A: The third generation reactors that are in the market right now are advanced boiling water reactors, simplified boiling water reactors and advanced high-pressure water reactors. They incorporate passive security systems that do not need electricity to function. By using gravity, convection, and evaporation, the probability of a fusion of the core is 10 times lower. These reactors also have a lower probability of failure because they have more efficient systems that make better use of the fuel, reducing the radioactive waste content.