The Molten Salt Reactor Adventure
A Glimpse into Oak Ridge's MSR Experiment
Introduction:
In the mid-20th century, Oak Ridge National Laboratory (ORNL) embarked on a groundbreaking journey in nuclear energy research by exploring the potential of Molten Salt Reactors (MSRs). The linked web-page delves into the historical development of MSRs at Oak Ridge and their contributions to the field of nuclear energy. We will also discuss the role of thorium, the challenges faced by MSR technology, and the prospects for its future.
The Birth of Molten Salt Reactors:
The idea of MSRs originated during the post-World War II era, when Oak Ridge researchers Ed Bettis and Ray Briant proposed the concept as part of efforts to design a nuclear-powered aircraft for the Air Force. (before the advent of ICBMs)
The stability of molten fluoride salts at high temperatures and under radiation made them an attractive choice for this application. Thus, an active development program for aircraft reactors using molten salt fuel was carried out at Oak Ridge from 1950 to 1956.
Shift to Civilian Nuclear Power:
In 1956, as interest in nuclear-powered aircraft waned, Alvin Weinberg, then director of Oak Ridge National Laboratory, sought to explore the adaptability of molten fluoride fuel technology for civilian nuclear power reactors. The unique properties of molten salts, such as their solubility of uranium and thorium, thermodynamic stability, low vapor pressure, and compatibility with materials like graphite, laid the foundation for further research.
The Molten Salt Reactor Experiment (MSRE):
The culmination of Oak Ridge's MSR journey was the successful operation of the Molten Salt Reactor Experiment from 1965 to 1969. The MSRE employed a circulating fuel salt solution consisting of uranium tetrafluoride (UF4) and thorium tetrafluoride (ThF4), along with beryllium and lithium fluorides. The use of liquid fuel allowed for continuous removal of gaseous fission products and facilitated continuous fuel purification.
Challenges and Potential:
While the MSRE demonstrated promising results and highlighted the practicality of MSRs, the technology faced several challenges. Materials compatibility, radiation effects on structural materials, tritium production and capture, and fuel salt processing were among the issues that required further development. However, progress was made in addressing some of these challenges during the MSRE's operational phase. The scientists at Oak Ridge are still confident these could be addressed overcome with more research and development.
Implications and Future Prospects:
The MSR program at Oak Ridge faced funding constraints and competition from the fast breeder reactor (LMFBR) program, which received significant government support. Ultimately, “budgetary” considerations led to the termination of the MSR program in 1973, with subsequent reinstatements and subsequent closures. Despite the discontinuation of the program, the knowledge and expertise gained from Oak Ridge's MSR adventure remain valuable.
Looking ahead, the landscape of nuclear energy has evolved. The decreased rate of electricity demand growth, high capital costs of fast breeder reactors, concerns about plutonium proliferation, and public sensitivity to reactor safety have hampered this critical technology. Fortunately the public distribution of the technologies positive factors have sparked renewed interest in advanced reactor systems, including MSRs. The MSR's potential as a relatively simple, low-cost converter reactor (MSCR) and its ability to use various fuels make it an attractive option.
International interest in MSRs persists, with ongoing research and development efforts in countries like Japan, Italy, France, India, China, and the former USSR. The accumulated knowledge from Oak Ridge's MSR program, coupled with advancements in technology and evolving energy needs, positions MSRs as a contender for future nuclear energy generation.
http://moltensalt.org/references/static/downloads/pdf/WhyMSRsAbandonedORNLWeinbergsFiringV3.pdf
Conclusion:
The story of Oak Ridge's MSR experiment is a testament to the ingenuity and persistence of researchers who sought to push the boundaries of nuclear energy. Although the MSR program faced challenges and eventual discontinuation, its legacy lives on.