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 ANS Annual Conference
May 31–June 3, 2026
Denver, CO|Sheraton Denver
Latest Magazine Issues
Mar 2026
Jan 2026
Latest Journal Issues
Nuclear Science and Engineering
April 2026
Nuclear Technology
February 2026
Fusion Science and Technology
Latest News
60 Years of U: Perspectives on resources, demand, and the evolving role of nuclear energy
Recent years have seen growing global interest in nuclear energy and rising confidence in the sector. For the first time since the early 2000s, there is renewed optimism about the industry’s future. This change is driven by several major factors: geopolitical developments that highlight the need for secure energy supplies, a stronger focus on resilient energy systems, national commitments to decarbonization, and rising demand for clean and reliable electricity.
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.
