PNNL

Abstract

This study is part of the U.S. Nuclear Regulatory Commission’s (NRC) Probabilistic Flood Hazard Assessment (PFHA) research plan that aims to develop regulatory tools and guidance to support and enhance the NRC’s capacity to perform thorough and efficient reviews of license applications and license amendment requests. In Year 1, Pacific Northwest National Laboratory staff prepared an annual report that summarized recent scientific findings on climate change, with a particular focus on climatic elements that are relevant to NRC concerns on a regional level (i.e., increasing air and water temperatures, decreasing water availability, increasing frequency and intensity of storms and flooding, and sea-level rise). This report summarizes Year 2 activities, which focused on reviewing scientific findings regarding region-specific climatic extremes for the southeastern United States. According to the U.S. Global Change Research Program Third National Climate Assessment, the U.S. Southeast Region consists of 11 southeastern states, Puerto Rico, and the Virgin Islands. Except for Kentucky, Puerto Rico, and the Virgin Islands, all included states have operating nuclear power plants. Further, new nuclear power reactor permit and license applications have been submitted to the NRC in the recent past for sites located in several southeastern states. Therefore, having an improved understanding of potential climate changes and their hydrologic impacts in the Southeast Region is important to inform the PFHA research plan. Climatic features relevant to the NRC for the Southeast Region include high temperature extremes, precipitation extremes, flooding, high winds associated with tropical cyclones and tornadoes, sea-level rise, and storm surge and associated inland inundation. Drawing primarily from the climate assessment reports and peer-reviewed literature, this Year 2 annual report summarizes the observed climate, its past changes, and its projected changes, as well as 21st century hydrologic impacts in the Southeast Region. Despite the relatively mild changes observed in the past and projected in the future for the mean climate of the Southeast Region, many aspects of climatic extremes such as extreme precipitation have exhibited changes in the last century. In addition, climate and hydrologic models project further changes in the future. Pacific Northwest National Laboratory staff presented updates summarizing these findings at the Second Annual PFHA Research Workshop, which took place from January 23 to 25, 2017, at NRC Headquarters in Rockville, Maryland.