We present an overview of the National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST), its instruments, and support facilities. The 4 m aperture DKIST provides the highest-resolution observations of the Sun ever achieved. The large aperture of DKIST combined with state-of-the-art instrumentation provide the sensitivity to measure the vector magnetic field in the chromosphere and in the faint corona, i.e. for the first time with DKIST we will be able to measure and study the most important free-energy source in the outer solar atmosphere – the coronal magnetic field. Over its operational lifetime DKIST will advance our knowledge of fundamental astronomical processes, including highly dynamic solar eruptions that are at the source of space-weather events that impact our technological society. Design and construction of DKIST took over two decades. DKIST implements a fast (f/2), off-axis Gregorian optical design. The maximum available field-of-view is 5 arcmin. A complex thermal-control system was implemented in order to remove at prime focus the majority of the 13 kW collected by the primary mirror and to keep optical surfaces and structures at ambient temperature, thus avoiding self-induced local seeing. A high-order adaptive-optics system with 1600 actuators corrects atmospheric seeing enabling diffraction limited imaging and spectroscopy. Five instruments, four of which are polarimeters, provide powerful diagnostic capability over a broad wavelength range covering the visible, near-infrared, and mid-infrared spectrum. New polarization-calibration strategies were developed to achieve the stringent polarization accuracy requirement of 5×10−4. Instruments can be combined and operated simultaneously in order to obtain a maximum of observational information. Observing time on DKIST is allocated through an open, merit-based proposal process. DKIST will be operated primarily in “service mode” and is expected to on average produce 3 PB of raw data per year. A newly developed data center located at the NSO Headquarters in Boulder will initially serve fully calibrated data to the international users community. Higher-level data products, such as physical parameters obtained from inversions of spectro-polarimetric data will be added as resources allow.

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Despite the recommendations of the 2012 Blue Ribbon Commission Report, the US government has made no substantial progress toward the permanent, or even temporary, consolidated storage of used 1 civilian nuclear fuel. To complicate matters, a November 2013 decision by the United States Court of Appeals (2013) in Washington, DC eliminated the very fee designed to finance used-fuel storageÑwhich had accumulated over $30 billion so farÑintroducing a further obstacle (Nuclear Energy Institute, 2014a). It was not supposed to be this way. The 1982 Nuclear Waste Policy Act bound the federal government by law to take custody of all civilian waste from power companies for final disposal, under the assumption that the waste would be permanently stored in a deep geological repository at NevadaÕs Yucca Mountain and overseen by the Energy Department. The Act obligated the US government to begin accepting waste by 1998, but the government was unable to fulfill this promise, forcing it to remunerate the utility companies for continuing to store the waste and assume liability. This situation cannot continue. As a solution, the commission argues that the US government should establish a widely distributed series of regional, government-run sites that would take in the used fuel from the cooling pools of several reactors, thereby consolidating the interim storage of used fuel and putting this nuclear waste into stronger, safer, more secure, more manageableÑand ultimately more affordableÑdry casks, as a first step toward ultimate disposal. Dry casks have withstood earthquakes and floods, and are designed to withstand the heat of fires and the impact of airplanes; the 100-ton structures are hard to steal or damage, and require no cooling systems or power supplies. These are some of the many reasons why making the transition to dry cask-based interim storage should be made as quickly as possible, regardless of oneÕs opinion of civilian nuclear power.

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Nuclear power continues to offer the potential to be a major, worldwide, scalable, carbon-free energy sourceÑif the challenges of safety, nonproliferation, waste management, and economic competitiveness are addressed. The international community has spent decades attempting to find a pragmatic approach to address waste-management concerns. Along the way, the advocates of open and closed nuclear fuel cycles have engaged in a running debate. For those who favor an open cycle, Sweden and Finland serve as excellent models today for successfully navigating both technical issues and public opinion to dispose of their spent nuclear fuel in a permanent repository that does not allow used fuel to be retrieved. But these successes have yet to be replicated elsewhere. For closed-cycle advocates, economically convincing technology solutions have yet to surface; as a result, leading reprocessing advocates claim that the future value of accumulated waste material can provide the economic justification for nuclear recycling. The authors discuss a middleground path that encourages research and development on advancements in fuel cycle technology while providing for safe waste storage on a century-long, or intermediate, timescale. Acknowledging the risks of pursuing such a venture, the authors also write on the importance of establishing performance metrics that would support nuclear energy as a sustainable, secure, and safe energy choice. The authors argue that the most important metric is the establishment of a surety index that could capture the nonproliferation and security risks of alternate fuel cycles.