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
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!
Latest Magazine Issues
Jul 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
August 2025
Nuclear Technology
Fusion Science and Technology
July 2025
Latest News
Hash Hashemian: Visionary leadership
As Dr. Hashem M. “Hash” Hashemian prepares to step into his term as President of the American Nuclear Society, he is clear that he wants to make the most of this unique moment.
A groundswell in public approval of nuclear is finding a home in growing governmental support that is backed by a tailwind of technological innovation. “Now is a good time to be in nuclear,” Hashemian said, as he explained the criticality of this moment and what he hoped to accomplish as president.
Syed Hameed Qaiser, Masood Iqbal, Aamer Iqbal Bhatti, Raza Samar, Javed Qadir
Nuclear Science and Engineering | Volume 172 | Number 3 | November 2012 | Pages 327-336
Technical Paper | doi.org/10.13182/NSE11-46
Articles are hosted by Taylor and Francis Online.
This paper discusses a higher-order sliding-mode-observer design for estimating reactivity in a nuclear research reactor. The nonlinear model of the Pakistan Research Reactor-1 (PARR-1) has been tuned and validated with experimental data. This model is then used for higher-order sliding-mode-observer-based reactivity estimation. In thermal reactors, reactivity is a very important reactor variable, as it determines the change of output power variation and is the main variable being manipulated for reactor power control. Linear observers have been used in the past to estimate reactivity, but the bandwidth is limited, and performance gets degraded as the operating point is changed. A nonlinear observer can efficiently address this problem. In this paper a robust higher-order sliding-mode observer is employed to estimate this variable. The higher-order sliding-mode observer is efficient and has the main advantage of reduced chattering. The estimators predict this variable with the measurement of neutron flux only. The estimated value is in close agreement with the theoretically calculated value.