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Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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Deep Space: The new frontier of radiation controls
In commercial nuclear power, there has always been a deliberate tension between the regulator and the utility owner. The regulator fundamentally exists to protect the worker, and the utility, to make a profit. It is a win-win balance.
From the U.S. nuclear industry has emerged a brilliantly successful occupational nuclear safety record—largely the result of an ALARA (as low as reasonably achievable) process that has driven exposure rates down to what only a decade ago would have been considered unthinkable. In the U.S. nuclear industry, the system has accomplished an excellent, nearly seamless process that succeeds to the benefit of both employee and utility owner.
J. Appel and B. Roos
Nuclear Science and Engineering | Volume 34 | Number 3 | December 1968 | Pages 201-213
Technical Paper | doi.org/10.13182/NSE68-A21086
Articles are hosted by Taylor and Francis Online.
An exact formulation is presented for the release of metallic fission products. Such radioactive atoms are created through fission processes inside the kernel of fuel particles. They can diffuse through the coating of a fuel particle and the surrounding charcoal matrix into the structural graphite of the reactor core. Some atoms traverse this graphite along internal surfaces and finally enter the coolant gas. To find the number of radioactive atoms released into the coolant gas, the diffusion equation in one space dimension is solved numerically taking into account as driving forces both the gradient of the chemical potential and that of the temperature field. The chemical potential is determined respectively by the Langmuir and Freundlich adsorption isotherms for small and large concentrations of metal atoms adsorbed at the highly active internal surfaces of charcoal and graphite. As an example, a parameter study of the release is presented for the most danagerous radioactive metallic isotope, 90Sr. The calculation of the release rate from a single fuel particle shows that the coating does not act as an effective diffusion barrier in this case. It is found that the structural graphite governs the release by virtue of its good adsorptive properties and its low diffusion constant. The results for the concentration profile, the mass current (or flux), and the release of 90Sr are highly sensitive to experimental information on diffusion and adsorption coefficients, in part because of the temperature-activated nature of adsorption and diffusion processes. Since the experimental variables are known with limited accuracy only, a parameter study of the 90Sr release is carried out, that is centered around the best available empirical values for diffusion and adsorption coefficients.
