The Southern Nuclear operating fleet is in the midst of an industry-wide initiative for identifying and evaluating potential tornado missile protection issues in response to an NRC regulatory issue summary issued in June 2015.
Along with other industry partners, Southern Nuclear has worked with the NEI to develop a risk-informed methodology called the Tornado Missile Risk Evaluator (TMRE) with the goal of providing a simplified yet technically rigorous risk-informed approach to resolving tornado missile protection issues.
“Contrasted with current industry tornado missile analysis programs or physical modifications, using the TMRE methodology could result in cost savings of millions of dollars, multiple years of analysis, and unnecessary disruptions to plant operations and outage schedules for SNC,” explained Ken Shelley, Fleet Design engineering analyst.
Systems, structures and components important to the safety of nuclear power plants are designed to withstand natural phenomena such as earthquakes, tornadoes, hurricanes and floods without the loss of capability to safely maintain the plant. However, strong winds from tornadoes are capable of generating missiles from objects (e.g. construction material, utility poles, fencing, automobiles) lying within the path of the tornado and from the debris of nearby damaged structures such as buildings used for offices or warehouses.
To ensure the safety of nuclear power plants in the event of a tornado strike, NRC regulations require that nuclear power plant designs consider the impact of tornado-generated missiles (i.e., objects moving under the action of aerodynamic forces induced by the tornado wind) in addition to the direct action of the tornado wind and pressure.
As an industry leader and partner with NEI, SNC Risk-Informed Engineering, Regulatory Affairs and Vogtle Site Design are all contributing to the development of TMRE, a cost-effective resolution through a risk-informed license amendment request (LAR).
SNC employees Alex Gilbreath, Risk Informed engineer, and Ken Lowery, Regulatory Affairs licensing engineer, are members of the industry steering committee that contributed to the development of the TMRE, while Franchelli Febo and Justin Huber, Vogtle Site Design engineers, are supporting development of the TMRE methodology by providing site-specific tornado missile information to the Risk-Informed Engineering department to modify the plant’s internal events probabilistic risk assessment model.
“Plant Vogtle is a TMRE pilot and one of only three plants in the industry engaged in piloting the TMRE methodology,” said Ken Shelley, “Development of the TMRE methodology has received extensive engagement and support from the NRC.”