Improved nuclear accident code helps policymakers assess risks from small reactors

Sandia expands software to support regulators’ evaluation of next-generation reactors

Sandia National Laboratories recently updated the Maccs code to better aid the Nuclear Regulatory Commission and the global nuclear industry in assessing the consequences of nuclear accidents. The Maccs code can also evaluate the potential health and environmental risks posed by advanced nuclear reactors and small modular nuclear reactors.

Small modular reactors range from scaled-down conventional nuclear reactors with modern safety features to completely innovative designs that use different cooling methods and fuel designs. Some could even be constructed at a central facility and transported to wherever reliable carbon-neutral electricity is needed.

One of the chief improvements to the Maccs code is that it can now model nuclear accident consequences much closer to the reactor building. Previously, Maccs was not recommended for modeling consequences closer than five football fields from the reactor. The improved Maccs can now model consequences starting much closer to the reactor building as well as options to improve the model’s results out to 1,000 miles.

“Advanced reactors and small modular reactors are expected to be smaller, therefore leading to an expectation of lower radioactive releases in the case of an accident,” said Jenn Leute, a Sandia nuclear engineer who is working on the Maccs updates. “With this expectation that releases will be lower, we want to ensure we can model much closer to the point of release, as understanding consequences closer in will become more important. This will allow for decision-makers to make the most informed decisions about new plants and mitigate these very unlikely consequences.”

Smaller reactors require refined code

Maccs is used by the Nuclear Regulatory Commission and the nuclear industry world-wide to assess the environmental impact for new and existing nuclear power plants, Leute said. The system is also used for assessing the risks of licensing new reactors, especially next-generation nuclear reactors, and informing the industry and regulators about decisions on upgrading existing power plants.

“We, essentially, look at what happens outside the building in the case of an accident at a nuclear power plant, and we model how any radioactive material released moves through the atmosphere and environment,” Leute said. “We look at where the radioactive material goes and any type of radiological health effects and economic effects.”

Small modular reactors are expected to take up to one-tenth or less of the area of a current nuclear power plant, while producing about one-quarter to one-eighth of the carbon-neutral electricity of a current nuclear power plant, said Dan Clayton, another Sandia nuclear engineer involved in updating Maccs. Additionally, advanced reactors will be even safer than previous generations of nuclear reactors, taking 60 years’ worth of experience and technological improvement into account.

Read the complete news release.

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