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 Nuclear Energy Conference & Expo (NECX)
August 24–27, 2026
Dallas, TX|Hilton Anatole
Latest Magazine Issues
Jul 2026
Jan 2026
2026
Latest Journal Issues
Nuclear Science and Engineering
September 2026
Nuclear Technology
August 2026
Fusion Science and Technology
Latest News
The human factor in licensing and operating the next generation of nuclear plants
As human factors specialists working at the intersection of human performance and nuclear operations, we are witnessing one of the nuclear sector’s most significant transitions in decades. The emergence of small modular reactors, microreactors, and other advanced designs is reshaping the industry’s landscape. Digital instrumentation and controls, passive safety systems, and increased automation are creating opportunities for greater safety margins and more flexible operation. These same features also fundamentally redefine what it means to “operate” a nuclear plant. Interactions among human roles, automation, and passive systems shape how people maintain awareness, exercise judgment, and intervene when necessary. These developments affect both operational realities and the regulatory foundations on which nuclear safety is built.
Sümer Şahin, Elliot B. Kennel
Nuclear Technology | Volume 107 | Number 2 | August 1994 | Pages 155-181
Technical Paper | Fission Reactor | doi.org/10.13182/NT94-A34985
Articles are hosted by Taylor and Francis Online.
A thermo-hydrodynamic-neutronic analysis is performed for a fast, uranium carbide (UC) fueled spacecraft nuclear in-core thermionic reactor. The thermo-hydrodynamic analysis shows that a hybrid thermionic spacecraft nuclear reactor can be designed for both electricity generation and nuclear thermal propulsion purposes. This reactor would deliver a thermal thrust ∼5000 N by a specific impulse of 670 s at a hydrogen exit temperature ∼1900K. During the nuclear thermal thrust phase, the electricity generation will drop, depending on the entry temperature of the hydrogen propellant. Fresh hydrogen can be preheated through nozzle cooling up to 1000 K or more before entering the reactor. The hydrogen pressure and velocity at reactor entry are selected p = 30 atm and ν = 200 m/s, respectively. The pressure drop along the reactor core height (= 35 cm) is calculated Δp = 8.59 atm. The neutronic analysis has been conducted in S8-P3 approximation with the help of one- and two-dimensional neutron transport codes ANISN and DORT, respectively. The calculations have shown that a UC fueled electricity generating single mode thermionic nuclear reactor can be designed to be extremely compact because of the high atomic density of the nuclear fuel (by 95 % sintering density), namely, with a core radius of 8.7 cm and core height of 25 cm, leading to power levels as low as 5 kW(electric) by an electrical output on an emitter surface of 1.243 W/cm2. A reactor control with boronated reflector drums at the outer periphery of the radial reflector of 16-cm thickness would make possible reactivity changes of Δkeff > 10%—amply sufficient for a fast reactor—without a significant distortion of the fission power profile during all phases of the space mission. The hybrid thermionic spacecraft nuclear reactor mode contains cooling channels in the nuclear fuel for the hydrogen propellant. This increases the critical reactor size because of the lower uranium atomic density in this design concept. Calculations have lead to a reactor with a core radius of 22 cm and core height of 35 cm leading to power levels ∼50 kW(electric) under the aforementioned thermionic conversion conditions.
