years. The only identified impact on supply chain and interdependencies are when demand shifts and the water used for cooling. For demand shifts, nuclear power is not as quickly able to adjust power production as other technologies including natural gas. Generally, this is accounted for with forecasting and planning.

The largest vulnerability of nuclear power facilities is the intake water used for cooling. High temperatures can make it difficult for water to reach temperatures cool enough to be discharged and, due to permitting restrictions, may require generation curtailment (Galbraith 2011). A case study on the 2011 Texas heat wave was performed and augmented with facility-specific data for curtailments at several facilities, including a study finding 25 water-related curtailments in the United States between 2000-2015 (McCall et al. 2016). The impacts on power generation were similar across all data reviewed: water availability and temperature affected generation systems that rely on cooling water. The majority of curtailments occur due to water intake and/or discharge issues related to water temperature (>90%) with many of these (79%) occurring during heatwave/drought conditions. One example occurred for winter weather, where snow and ice restricted the amount of intake water available. Specific design and operation parameters associated with environmental regulations and permitting were the major cause of curtailment (water temperatures exceeding permitted levels and/or water availability). This was also seen in France in August 2018. Here four nuclear reactors were shut down because river temperatures were too high to allow for water discharge (Shugerman 2018).

_Costs, Impacts and Resilient Design Considerations for Nuclear-Fired Generation._ The key vulnerability of existing nuclear power plants is the reliance on intake water for cooling. The design guidelines for constructing a facility include seismic considerations (where applicable) and resilience to withstand high windspeeds, flooding, and other hazards, Table 11.

**<u>Table 11 – Nuclear Power Plants, Costs and Resilient Design Considerations</u>**

|Hurricane|Drought/Heat Wave|Earthquake|
|---|---|---|
|* Design plants to withstand<br>winds up to 580 kph (Reuters<br>2011)<br>* Steel reinforced concrete<br>containmentwith at least 1-<br>meter thick walls(Conca 2017)<br>* Build plants at higher<br>elevations (Steven Mufson<br>2012) <br>* Keep backup generators in<br>case of power failure (Steven<br>Mufson 2012)|* Install power mix that doesn't<br>all depend on water for<br>generation (Alvaro 2018)|* Build plants to withstand<br>earthquakes above maximum<br>magnitude recorded (N. Watson<br>2013)|

One modification that has been made is found in Arizona (USA): The Palo Verde plant. This facility does not sit on a body of water but instead uses recycled municipal water (APS 2018) and therefore operates under different rules for intake and discharge temperatures. This reliability on grey municipal water changes the regulations for cooling water and may provide an operational case study for future designs.

_3.2.5 – Solar Generation._ Solar generation facilities are unique in that they can operate at almost any size, from a single panel to large, utility-scale plants. In the case studies reviewed, the main vulnerability of solar was found to be high winds that damaged the panels, although this was directly related to the design standard they were built to. For detailed information, see Section 4.

18