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.
Dmitry V. Paramonov, Mohamed S. El-Genk
Nuclear Technology | Volume 117 | Number 1 | January 1997 | Pages 1-14
Technical Paper | Fission Reactor | doi.org/10.13182/NT97-A35332
Articles are hosted by Taylor and Francis Online.
The Soviet-made TOPAZ-II space nuclear power system unit designated Ya-21u underwent a total of 15 tests both in the Union of Soviet Socialist Republic (USSR) (1989–1990) and in the United States (August 1993 to March 1995) for a cumulative test/operation time of 7681 h at conditions far exceeding design limits. These tests included steady-state operation at different power levels, fast start-ups and power optimizations, and shock and vibration tests. Test results are presented and analyzed. Results indicate a gradual change in the performance parameters such as the optimum cesium pressure and optimum load voltage. The electric power and conversion efficiency of the unit at an input thermal power of 105 kW decreased from 3.7 kW(electric) and 4% in the test in the USSR to 2.13 kW(electric) and 2.3 % in the last test in the United States. A discussion and qualitative assessment of potential causes of the performance changes of the Ya-21u unit are given.
