ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Division Spotlight
Fusion Energy
This division promotes the development and timely introduction of fusion energy as a sustainable energy source with favorable economic, environmental, and safety attributes. The division cooperates with other organizations on common issues of multidisciplinary fusion science and technology, conducts professional meetings, and disseminates technical information in support of these goals. Members focus on the assessment and resolution of critical developmental issues for practical fusion energy applications.
Meeting Spotlight
2024 ANS Annual Conference
June 16–19, 2024
Las Vegas, NV|Mandalay Bay Resort and Casino
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!
Latest Magazine Issues
May 2024
Jan 2024
Latest Journal Issues
Nuclear Science and Engineering
June 2024
Nuclear Technology
Fusion Science and Technology
Latest News
Proving DRACO will deliver
The United States is now closer than it has been in over five decades to launching the first nuclear thermal rocket into space, thanks to DRACO—the Demonstration Rocket for Agile Cislunar Orbit.
M. Segev, G. Raitses, J. M. Paratte
Nuclear Science and Engineering | Volume 131 | Number 1 | January 1999 | Pages 123-131
Technical Paper | doi.org/10.13182/NSE99-A2023
Articles are hosted by Taylor and Francis Online.
The radial distribution of capture rate and effective cross section in fuel rods of radii R, forming a light water reactor (LWR) lattice, is derived with routine cell calculations. Any internal radial subrange (r1,r2) is treated through the assessment of absorption in the two corresponding annular absorbers (r1,R) and (r2,R). The lattice of the latter absorbers, whose pitch is exactly the original LWR lattice pitch, is equivalenced to a lattice of solid cylindrical rods. Thus, for example, to obtain a tenfold radial distribution, ten routine cell calculations are required.In determining the radius s of a cylinder equivalent to the annulus (r,R), the neutron escape from the annulus is first preserved by making the s rod have a circumference of 2R[1 - (0.5 - (1/)cos-1(r/R))G], where G is the "sticking" probability in the annulus for neutrons entering it from within. The radius s is then the result of making the solid rod and the annulus have the same average chord. In addition, a lattice is assigned to the s rods such that the original Dancoff factor is preserved. Finally, a Bell factor is determined for the s rod such that the actual grayness of the annulus (r,R) is preserved.A special program for transport-related probabilities is invoked in obtaining the sticking and Dancoff probabilities just described, as well as the Bell factor.Application of the theory was conducted with the ELCOS system BOXER cell code. Three benchmarks were considered. The first was the one suggested by Tellier et al. for a fuel pin of a typical pressurized water reactor cell. The second was almost identical to the first, except that the fuel was saturated with hydrogen to generate a flatter radial distribution than in the first benchmark. The third benchmark was based on detailed space-energy calculations for a boiling water reactor rod, performed in 1978.All three benchmark testings resulted in satisfactory comparisons. Hence, the present theory may provide a practical, routine way of obtaining the in-rod distribution of absorption and cross section, calling just for a repeated use of straightforward cell calculations.