March 26, 2026

NRC Unveils Final Part 53

At long last, the Nuclear Regulatory Commission has finalized its new regulatory framework for advanced reactors that are designed to  accelerate regulatory reviews by simplifying and tailoring the review and safety burdens to the specific types of reactor being reviewed, which is why the regulation is titled “Risk-Informed, Technology-Inclusive Regulatory Framework for Advanced Reactors.”

The Nuclear Energy Innovation and Modernization Act (NEIMA), signed in 2019 formally directed the NRC to develop the new, technology-inclusive regulatory approach, since prior to this time, only light water reactors have been licensed by the NRC. The resulting rule—10 CFR Part 53—brings an updated, modernized approach to regulatory and, hence, safety reviews for next generation reactors and industry participants.

Newly appointed NRC Chairman, Ho Nieh, said “This is really a historic milestone. With the addition of Part 53 to Part 50 and 52—and I believe some of you know that we’re working on a microreactor licensing framework—America now has many options available to applicants and licensees that want to pursue the development and deployment of new nuclear technologies.” This final rule from the NRC action is intended to provide a clear risk-informed, technology-inclusive licensing framework that enables advanced nuclear designs to move from concept to construction more rapidly and safely.

Part 53’s shift from a technology-specific to a technology-neutral approach to reactor licensing is intended to address a long-standing issue in regulatory frameworks that were developed specifically for light water reactor technology. Licensing reactors that do not use LWR technology has required applicants to seeking regulatory exemptions to many burdensome prescriptive requirements, leading to a cumbersome licensing process.

“Part 53 offers a comprehensive new approach to license advanced reactors, including non-light-water reactors, across their life cycles,” according to the NRC release. “It provides designers and operators with more flexibility in how they build and run their plants while continuing to ensure safety.”

This week’s announcement comes more than a year after the NRC first published their Part 53 proposed rule, which was widely viewed as not being the solution the industry was looking for. Some 158 public comments were accepted including from Westinghouse, The Breakthrough Institute, the Nuclear Energy Institute, the Idaho National Laboratory and many others. Apparently, the newly revised rule incorporated many of the changes requested by commenters and eliminated sections of the rule that some parties deemed unusable.  Nieh said the final version of Part 53 addresses many of the complaints and comments he and the NRC heard regarding earlier versions of the rule. “I do believe this framework does provide the appropriate flexibility and risk-informed approaches that will make it a usable tool among the other options that are already available,” said Nieh.

According to Acting Deputy Office Director for New Reactors Jeremy Bowen,  Part 53 could enable reactor designs to receive approval in 18 months or less. The cost of the application could be reduced by half or more, given the shorter review and the added flexibility of Part 53. A 2023 analyses of the earlier draft regulation estimated the net averted costs to the industry and the agency for just one applicant could range from $53.6 million to $68.2 million, which may be bigger under the updated final rule.

History: Part 53 is the first new reactor licensing framework issued by the NRC since 1989, when the agency introduced Part 52. NRC officials added that it is the first major update to reactor licensing standards since 1956, when the Atomic Energy Commission (the NRC’s predecessor) issued Part 50. The final rule’s has been long awaited by the industry but, even with the five year time frame that it took, was issued ahead of the 2027 deadline ordered by NEIMA. Today's rules will hopefully update rules that were put in place many, many decades ago that were being used to license the first wave of nuclear reactors built in the United States in the ’60s and ’70s. Said Ho, "We did not know as much about the technology [then] that we know today, where we [did] not have the sophistication and analytical tools to evaluate safety cases that we have today. . . . To me, I see this as removing the friction in legacy frameworks that are no longer needed today.”

According to the NRC website, the Part 53 final rule will be published on April 3, and the rule will go into effect 30 days after it appears in the Federal Register. As part of the posting, the NRC will publish nine additional guidance documents, with additional guidance to follow.

References

ANS, NRC unveils Part 53 Final Rule, March 26, 2026

December 11, 2025

INL Produces First-Ever Fuel Salt for Fast Molten Salt Reactor, Advancing CORE POWER’s Maritime Pathway ()

INL has produced the world’s first enriched chloride fuel salt for a fast molten salt reactor experiment — a major step for the MCRE project, involving CORE POWER, Southern Company, TerraPower, and the DOE...

November 8, 2025

Nucleation Portfolio Leaders Named to ANS 40 Under 40


Nucleation Capital extends a hearty congratulations to four founders from Nucleation portfolio companies—Matt Loszak and Yasir Arafat from Aalo Atomics, Jake Jurewicz from Blue Energy, and Jerrold Vincent from Nuclearn—who have been recognized by the America Nuclear Society for inclusion in their NuclearNews' 2025 “40 Under 40” list, which celebrates innovators shaping the future of nuclear energy. All four are doing amazing things with their companies and are extremely deserving of this recognition.

The complete list of 2025 NuclearNews 40 under 40 includes:

September 14, 2025

Anastassia Makarieva


Dr. anastassia makarieva

Dr. Anastassia Makarieva

In co-authorship with V.G. Gorshkov, Anastassia formulated the concept of the biotic pump of atmospheric moisture, highlighting key ecological feedbacks on atmospheric moisture transport (2007) and, in cooperation with an international team of colleagues, demonstrated the existence of life’s metabolic optimum (broadly universal rate of energy consumption across life’s kingdoms) (2008). Combining theoretical work with field observations, Anastassia spent over sixty months doing forest research in the Russian wilderness. Her current research interests focus on deepening the physical understanding of ecosystem feedbacks on the water cycle and moisture transport.

She is a recipient of the 2008 L’Oréal-UNESCO prize “For Women in Science” and is currently (since 2021) an Anna Boyksen fellow at the Institute for Advanced Study at the Technical University of Munich, Germany, where her research interests focus on deepening the physical understanding of ecosystem feedbacks on the water cycle and moisture transport.

Dr. Makarieva wrote: "The concept of biotic regulation is inherently interdisciplinary and builds, among other things, on research into the energetics of life. Much of that work preceded the biotic pump, which has since become our main focus. Yet understanding how natural ecosystems keep Earth habitable, and how we can avoid interfering, cannot be achieved within the limits of any single discipline."

As a scientific researcher at the Technical University of Munich, Institute for Advanced Study, Dr. Makarieva looked at drought mitigation through ecosystem restoration. She posted this about her work there:

Plant transpiration influences atmospheric processes locally, regionally and globally. Natural forest ecosystems have evolved a number of mechanisms to stabilize the terrestrial water cycle. While our understanding of them remains incomplete, the direct anthropogenic destruction and climate change are disrupting these stabilizing feedbacks. Conversely, preservation and restoration of natural ecosystems bear the promise of enhancing the water cycle resilience, including protection from extremes like droughts, floods and violent winds, as well as avoidance of tipping points towards aridity. The focus group will explore theoretical problems of how forest-mediated processes affect atmospheric dynamics, including scaling up individual plant processes to synoptically relevant scales. The research will combine TUM’s technical and scientific excellence with the knowledge of climate-regulating functions of least disturbed forest landscapes, most of which in Eurasia are located within Russian borders. The goal is to present quantitative evidence about the importance of natural forests for water-related aspects of regional and global climate stability. This information is required for informed stewardship towards global environmental resilience. 

Publications & Interviews

Dr. Makarieva has posited theories that are not yet mainstream but which do help to explain much about why global temperatures are rising well beyond the expectation of climate scientists relative to the amount of CO2 being added to the atmosphere.  In order to understand her theories, you will need to read her writing and hear her interviews, some of which we have listed below:


Sources

September 4, 2025

TVA and Entra1 Launch Largest SMR Deployment in U.S. History ()

The 6 GW program, the largest of its kind, will use NuScale’s advanced small modular reactor technology to expand U.S. clean energy capacity.

August 22, 2025

Google, Kairos Power, and TVA Announce First U.S. Utility Order for Gen IV Nuclear ()

TVA becomes the first U.S. utility to order Gen IV nuclear power under a new agreement with Google and Kairos Power.

August 18, 2025

Maria Goeppert Mayer

Maria goeppert mayer

Dr. Maria Goeppert Mayer (1906–1972) was a theoretical physicist who revolutionized nuclear physics by developing the nuclear shell model, explaining why certain “magic numbers” of protons and neutrons lead to especially stable atomic nuclei. In 1963, she became only the second woman to win the Nobel Prize in Physics, following Marie Curie.

Born in Kattowitz, Germany (now Katowice, Poland), Mayer moved to the U.S. after completing her doctorate in physics at the University of Göttingen under Max Born in 1930. Despite her credentials, she spent much of her early career in unpaid research roles due to anti-nepotism policies that restricted her from being employed at the same institutions as her husband. She held unpaid appointments at Johns Hopkins, Columbia, and later the University of Chicago.

During World War II, Mayer contributed to the Manhattan Project, working on isotope separation and uranium enrichment. After the war, she joined Argonne National Laboratory, where she conducted her most important work on nuclear structure. Her shell model theory, developed in collaboration with German physicist J. Hans D. Jensen, proposed that protons and neutrons fill energy levels within the nucleus in a manner similar to electrons in atomic orbitals.

In 1960, Mayer was appointed professor of physics at the University of California, San Diego—her first salaried academic position. She remained there until her death in 1972, remembered not only for her scientific achievements but also for breaking institutional barriers facing women in physics.

Awards & Recognition

  • Nobel Prize in Physics, 1963 (shared with J. Hans D. Jensen)
  • Member of the National Academy of Sciences
  • Fellow of the American Physical Society
  • Namesake of the Maria Goeppert Mayer Award (American Physical Society)
  • Namesake of the Goeppert Mayer Distinguished Fellowship at Argonne National Laboratory
  • First woman appointed professor of physics at UC San Diego
  • Contributed significantly to the Manhattan Project nuclear research

Sources

July 15, 2025

Leona Woods Marshall Libby

Leona Woods

Dr. Leona Woods Libby (1919–1986) was a physicist who played a vital role in the Manhattan Project and the early development of nuclear science in the United States. At just 23 years old, she was the only woman present when the world’s first nuclear reactor, Chicago Pile-1, went critical in 1942. Her work — particularly her design of the boron trifluoride neutron counter — was essential in confirming that a self-sustaining nuclear chain reaction had occurred.

Born in La Grange, Illinois, Libby showed remarkable academic promise from a young age. She attended Lyons Township High School and graduated in 1934 at just 14 years old. She then entered the University of Chicago, where she earned a B.S. in Chemistry by 19 and completed her Ph.D. in physical chemistry just three years later. She was quickly recruited to join Enrico Fermi’s team at the university’s Metallurgical Laboratory, where she became a key figure in reactor physics and instrumentation.

After the initial CP-1 experiment, Libby relocated with Fermi’s team to help oversee reactor development at Hanford. There, she contributed to resolving the unexpected xenon poisoning that threatened the B Reactor’s operation. Despite being pregnant during her work at Hanford, she concealed it under loose clothing to remain on the job — highlighting the barriers women scientists faced even at the height of wartime urgency.

Following the war, Libby held fellowships at the University of Chicago’s Institute for Nuclear Studies, Princeton’s Institute for Advanced Study, and Brookhaven National Laboratory. She later held academic positions at New York University, the University of Colorado, and UCLA, where she expanded her research into climate science, environmental studies, food irradiation, and engineering. Over her lifetime, she published more than 200 scientific papers and several books.

Libby remained a staunch defender of her work on the Manhattan Project, arguing that the bomb had shortened the war and prevented even greater loss of life. She was also a public advocate for nuclear energy and scientific responsibility.

Awards & Recognition

  • Named one of Mademoiselle magazine’s “Women of the Year” in 1946 for her contributions to nuclear science

  • Honored posthumously for her contributions to the Manhattan Project and early reactor development

  • One of the few women prominently recognized in historical accounts of CP-1 and Hanford’s B Reactor


 

Sources

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