On-site pools for spent nuclear fuel at power plants and other facilities are reaching their design capacity across the country. With long-term storage plans for this spent fuel tied up in a political stalemate, the nation’s nuclear power reactors are turning to dry cask storage as an interim storage solution.
“Current practices in nuclear safeguards of spent nuclear fuel assemblies stored in dry casks only exist up to the point where the cask is sealed,” explains Athena Sagadevan, a student with the Center for Nuclear Security Science and Policy Initiatives (NSSPI). “Once sealed, there is no way of verifying its contents without opening the cask – a cumbersome, expensive and time-consuming endeavor.”
Sagadevan is working with NSSPI director Dr. Sunil Chirayath to develop a reliable remote monitoring system design for these dry casks. Remote monitoring systems allow inspectors to continually verify the contents of the dry casks after they are sealed.
According to Sagadevan, “This work is impactful because with continuous monitoring, governing bodies can verify the contents of dry casks without ever opening them – this ensures that the potential misuse of special nuclear material within dry casks will be detected immediately. Additionally, using remote monitoring technology is cost-saving, since on-site inspections can be reduced due to the presence of 24/7 monitoring.”
Starting first with a computational model developed using the Monte Carlo N-Particle (MCNP) transport code, Sagadevan devised two different remote monitoring system designs and tested their efficacy by simulating the systems’ response to fuel assembly diversions for various loading patterns and burnup values. She studied multiple assembly diversion scenarios including the removal of assemblies from different parts of the storage cannister and substitution with dummy assemblies. Determining that her designs performed well in the computational model, she then conducted a proof-of-concept experiment using Californium-252 sources with a scaled-down cask and detector system.
Sagadevan’s simulations and experiments showed that the designs were effective at monitoring the diversion of spent fuel from dry casks. Furthermore, she remarks, “The remote monitoring system designs are compact and cost effective as well as integrable with existing dry cask designs. The choice of detectors and shielding material ensure robustness of the system and simple operation procedure.”
With respect to her four years spent with NSSPI, Sagadevan reflects:
“They provided me with many opportunities to take classes in nuclear security, safeguards and policy that broadened my horizons and shaped my views. The classes were taught by professors who truly cared about imparting knowledge to students and went above and beyond to ensure it. In addition to regular classes, I was given the opportunity to manage panel discussions, organize international engagements with students and professors from all around the world as well as host and attend workshops and conferences. This exposure allowed me to network with professionals in the field and constantly be on the brink of new developments and research.”
In addition to her traditional classes, Sagadevan traveled to the UK as part of the International Nuclear Facilities Experience and visited numerous nuclear fuel cycle facilities, an experience she describes as having “an immeasurable lifelong impact.” She also had the opportunity to intern at Oak Ridge and Los Alamos National Laboratories, where she gained an “exceptional understanding of the nuclear industry and the role of nuclear safeguards.”
Sagadevan received her B.S and M.S degrees in Nuclear Engineering and Radiological Sciences from the University of Michigan in 2014 and 2016, respectively. Having successfully defended her dissertation on this work, Sagadevan will be graduating this summer with a Ph.D. in nuclear engineering. She has accepted a postdoctoral position at Los Alamos National Laboratory in the Safeguards Science & Technology group.