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.
Explore membership for yourself or for your organization.
Conference Spotlight
2026 Annual Conference
May 31–June 3, 2026
Denver, CO|Sheraton Denver
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
Dec 2025
Jul 2025
Latest Journal Issues
Nuclear Science and Engineering
January 2026
Nuclear Technology
December 2025
Fusion Science and Technology
November 2025
Latest News
Natura executes an OTA with the DOE
Progress in the Department of Energy’s Reactor Pilot Program continues as Natura Resources has executed an Other Transaction Agreement (OTA) with the DOE for the company’s Molten Salt Research Reactor being pursued in close collaboration with Abilene Christian University (ACU) in Texas. Reactor projects participating in the program would progress through DOE authorization and oversight rather than Nuclear Regulatory Commission licensing.
Nader M. A. Mohamed
Nuclear Science and Engineering | Volume 173 | Number 2 | February 2013 | Pages 172-181
Technical Paper | doi.org/10.13182/NSE11-77
Articles are hosted by Taylor and Francis Online.
Zirconium is studied in this paper as a reflector for light water reactors. An exploratory analysis of using zirconium as a reflector for two simple reactor core models was carried out. The study showed that use of zirconium as a reflector has a valuable impact on the core reactivity. The study also showed that zirconium-water reflector is more effective than water reflector or stainless steel-water reflector. A typical Westinghouse 1150-MW(electric) pressurized water reactor was simulated using the Monte Carlo code MCNP5 as a case study. The simulation was carried out at the beginning of the core cycle of three batch cores with 235U enrichments of 2.25, 2.8, and 3.3 wt%. The simulation showed that use of Zircaloy-4 reflector between the fuel assemblies and the core barrel adds a positive reactivity Δkeff of 0.00686, while use of stainless steel reflector adds a positive reactivity Δkeff of 0.0037.Use of Zircaloy-4 reflector increases the relative power density in the peripheral assemblies by ˜38%. The power peaking factor is shifted from the center toward the periphery, and the assembly power peaking factor is reduced by ˜13%. The use of Zircaloy-4 reflector with this increase of the reactivity of the peripheral assemblies increases the fast neutron current (E > 0.5 MeV) that reaches the reactor pressure vessel (RPV) by 70%, while the use of stainless steel reflector reduces it by 44%.Adjusting the 235U enrichment in the peripheral assemblies batch to compensate for the excess reactivity caused by using Zircaloy-4 reflector reduces the 235U enrichment by 8.5% in this batch. This means a reduction of 3.35% of the core 235U average enrichment can be achieved by the use of Zircaloy-4 reflector. This reduction in the 235U enrichment reduces the increase of the fast neutron current that reaches the RPV to 23%. In this case, increasing the water gap between the core barrel and the RPV by 3 cm reduces the fast neutron current that reaches the RPV to 95% of that of the basic case. The use of Zircaloy-4 reflector has a good effect on flattening the fission density distribution in the peripheral assemblies batch both before and after reducing 235U enrichment.
