Palo Alto, Calif. – Sept. 25, 2012 – EPRI has released a report examining various options – including additional cooling water spraying systems, flooding, and filtered venting – for how operators could minimize the release of radioactive contaminants in the event of a severe nuclear plant accident. The analysis found that combining strategies is more effective in minimizing releases than using individual measures.
The Fukushima Daiichi event in Japan in 2011 has prompted significant interest in the effectiveness of existing technologies and measures for reducing the amount of radioactive material released following a nuclear plant accident that damages the reactor fuel. Such practices potentially can minimize the contamination of surrounding areas. The EPRI analysis assumed that evacuation procedures had been enacted to safeguard public health and that fuel damage had occurred.
To enable a consistent comparison among the various strategies, EPRI used its MAAP accident analysis software code to model the progression of a hypothetical beyond-design-basis accident and the resulting radionuclide release. Each of the options was compared in terms of the amount of cesium released, which can be correlated to the magnitude of land contamination.
The analysis found that significant benefits can be achieved by implementing specific operator actions in the event of an accident. For example, the analysis confirmed that cooling of the debris from the reactor after an accident is required to maintain containment integrity and that spraying the containment atmosphere with water can further reduce aerosol radioactivity. Many of these actions are similar to those in existing severe accident management guidelines.
“The analysis provided some additional insights that may not be widely understood and appreciated,” said Neil Wilmshurst, EPRI vice president. “For example, the early venting of certain gases can reduce the overall amount of radioactive contaminants released, and the controlled opening and closing of a vent can provide significant reductions as well. Based on our modeling results, controlled cycling of the vent would result in greater than a 10-fold reduction in the amount of cesium released compared to opening the vent and leaving it open.”
The results are applicable to boiling water reactors with Mark I and Mark II containment designs. EPRI will be conducting follow-on analyses to examine the available strategies for other boiling water reactor designs and for pressurized water reactor designs.
About the Electric Power Research Institute
The Electric Power Research Institute, Inc. (EPRI, www.epri.com) conducts research and development relating to the generation, delivery and use of electricity for the benefit of the public. An independent, nonprofit organization, EPRI brings together its scientists and engineers as well as experts from academia and industry to help address challenges in electricity, including reliability, efficiency, health, safety and the environment. EPRI's members represent approximately 90 percent of the electricity generated and delivered in the United States, and international participation extends to more than 30 countries. EPRI's principal offices and laboratories are located in Palo Alto, Calif.; Charlotte, N.C.; Knoxville, Tenn.; and Lenox, Mass.