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Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
Standards Program
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.
C. D. Bowman, D. C. Bowman, T. Hill, J. Long, A. P. Tonchev, W. Tornow, F. Trouw, Sven Vogel, R. L. Walter, S. Wender, V. Yuan
Nuclear Science and Engineering | Volume 159 | Number 2 | June 2008 | Pages 182-198
Technical Paper | doi.org/10.13182/NSE159-182
Articles are hosted by Taylor and Francis Online.
High-resolution Bragg-edge transmission measurements were conducted on granular as well as solid samples of graphite to understand the basis for a bulk measurement of the diffusion length 24% larger than predicted by MCNP5 for bulk reactor-grade graphite. High resolution enabled a measurement of the total diffraction cross section from 1 to 200 meV. This was subtracted from the total cross section to find the inelastic cross section in the same energy range. Small-angle scattering, which has been thought to contribute to the total cross section in the region of the lowest Bragg edge, is shown not to be present in our measurement or in those of others claiming to find it. Instead, neutron total reflection from the surface of graphite microcrystals is shown to contribute to the cross section at low energies. Reactor-grade graphite is shown to have an inelastic scattering cross section over most of the energy range larger by at least 10 than the nearly perfect crystal structure of pyrolytic graphite. The ratio of inelastic scattering to diffraction at 25 meV for our graphite is inferred to be twice as large as that of graphite manufactured 50 yr ago, and we believe that our larger diffusion coefficient is rooted in this difference. The distortions in the microcrystalline structure introduced in the manufacturing of the graphite studied here at 24°C are found to be equivalent to the uncertainty in atom positions seen in heating perfect crystal graphite to a temperature of ~1800°C.
