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
2025 ANS Winter Conference & Expo
November 9–12, 2025
Washington, DC|Washington Hilton
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
Sep 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
September 2025
Nuclear Technology
Fusion Science and Technology
October 2025
Latest News
Shifting the paradigm of supply chain
Chad Wolf
When I began my nuclear career, I was coached up in the nuclear energy culture of the day to “run silent, run deep,” a mindset rooted in the U.S. Navy’s submarine philosophy. That was the norm—until Fukushima.
The nuclear renaissance that many had envisioned hit a wall. The focus shifted from expansion to survival. Many utility communications efforts pivoted from silence to broadcast, showcasing nuclear energy’s elegance and reliability. Nevertheless, despite being clean baseload 24/7 power that delivered a 90 percent capacity factor or higher, nuclear energy was painted as risky and expensive (alongside energy policies and incentives that favored renewables).
Economics became a driving force threatening to shutter nuclear power. The Delivering the Nuclear Promise initiative launched in 2015 challenged the industry to sustain high performance yet cut costs by up to 30 percent.
Taro Ueki
Nuclear Science and Engineering | Volume 160 | Number 2 | October 2008 | Pages 242-252
Technical Paper | doi.org/10.13182/NSE160-242
Articles are hosted by Taylor and Francis Online.
The stationarity diagnostics of source distribution in the iterated-source Monte Carlo computation for nuclear criticality and static nuclear reactor analysis have been studied using relative entropy and the Wilcoxon signed rank sum. Novel aspects of the diagnostics are (a) the relative entropy of permuted and nonpermuted source distributions and (b) a series of differenced relative entropies. Item (a) combined with averaging over random permutations has some smoothing effect on the fluctuation through iteration cycles. The benefit of item (b) is twofold: The differencing works as decorrelation, and the mean in stationarity of a differenced series is exactly zero. Therefore, the Wilcoxon signed rank sum has been applied to check the stationarity of the differenced relative entropy series. Another novel aspect of the diagnostics is the use of a problem-independent number of iteration cycles preceding the current iteration cycle upon the computation of the Wilcoxon signed rank sum. In addition, it has been shown that the progressive relative entropy in previous work can be used and the moving average of the Wilcoxon signed rank sums of its differenced series is a stringent measure of stationarity. Numerical results are presented for two- and three-dimensional modeling of an initial core of pressurized water reactors.
