The report is available at: https://www.gao.gov/products/gao-23-105813

The report states that "several challenges must be overcome to achieve commercial fusion, and stakeholders' projections of this timeline range from 10 years to several decades. One key scientific challenge is in the physics of plasmas, the state of matter needed for fusion. Researchers do not fully understand the behavior of burning plasmas, those whose main source of heat is from the fusion reaction itself rather than an external source. Researchers have made advancements in this area but lack sufficient experimental data to validate their simulations. One key engineering challenge is the development of materials that can withstand fusion conditions for decades, such as extreme heat and neutron damage, and no facility exists where materials can be fully tested. More generally, the task of extracting energy from fusion to provide an economical source of electric power presents several complex systems engineering problems that have yet to be solved.

Public and private sector misalignments, regulatory uncertainty, and other factors also present challenges to fusion energy development. One area of misalignment is research priorities. Public sector efforts prioritize basic science, but fusion energy development requires an additional emphasis on technology and engineering research. Another factor is regulatory uncertainty, which could slow development of fusion energy, although developing appropriate regulations to ensure safety without constraining development is difficult. Doing so may require significant public engagement, but little is known about public perception of fusion energy in the U.S."

The report states:

"Various factors make the economic viability of commercial fusion power plants uncertain.

The costs of commercial fusion energy power are unknown, making cost estimates likely unreliable. Fusion energy could have some cost advantages, such as potentially inexpensive fuel. However, other costs, such as capital costs and maintenance and operations, will be determined by many of the factors previously discussed in this report. For example, fusion energy will likely not be economically viable without significant advancements in materials for components susceptible to damage from plasma, as materials affect the amount of time a plant can produce energy and generate revenue. Maintenance costs and run time may also be impacted by complex engineering challenges, such as how the system is designed for ease of maintenance or reliability. National lab representatives told us that they do not trust the accuracy of estimated costs for fusion energy until there is more information on the materials and maintenance routines proposed for a fusion power plant. Regulations could also impact costs, such as by increasing timelines and costs of capital, but regulatory decisions may depend on how fusion energy develops and whether new risks emerge or existing risks, such as tritium handling, are mitigated. Fusion energy, if it becomes viable, will face competition with other developing energy technologies."