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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!
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Latest News
Seconds Matter: Rethinking Nuclear Facility Security for the Modern Threat Landscape
In today’s rapidly evolving threat environment, nuclear facilities must prioritize speed and precision in their security responses—because in critical moments, every second counts. An early warning system serves as a vital layer of defense, enabling real-time detection of potential intrusions or anomalies before they escalate into full-blown incidents. By providing immediate alerts and actionable intelligence, these systems empower security personnel to respond decisively, minimizing risk to infrastructure, personnel, and the public. The ability to anticipate and intercept threats at the earliest possible stage not only enhances operational resilience but also reinforces public trust in the safety of nuclear operations. Investing in such proactive technologies is no longer optional—it’s essential for modern nuclear security.
Edwin M. Pennington
Nuclear Science and Engineering | Volume 19 | Number 2 | June 1964 | Pages 215-220
Technical Paper | doi.org/10.13182/NSE19-02-215
Articles are hosted by Taylor and Francis Online.
First-collision probabilities for a regular lattice of cylindrical fuel rods and moderator are calculated using the assumption that neutrons reaching the outer boundary of the unit cell are returned isotropically. Comparisons are made with results using Fukai's exact method and other approximate methods. The collision probabilities are used in calculating thermal-disadvantage factors which are compared with those from discrete-ordinate calculations using various boundary conditions. The treatment is extended to lattices with cladding on the fuel, and average thermal fluxes are compared with those computed by the THERMOS code. Collision probabilities calculated by the method presented here are in rather good agreement with exact values.
