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
September 2025
Nuclear Technology
August 2025
Fusion Science and Technology
Latest News
INL makes a case for eliminating ALARA and setting higher dose limits
A report just released by Idaho National Laboratory reviews decades of radiation protection standards and research on the health effects of low-dose radiation and recommends that the current U.S. annual occupational dose limit of 5,000 mrem be maintained without applying ALARA—the “as low as reasonably achievable” regulatory concept first introduced in 1971—below that threshold.
Noting that epidemiological studies “have consistently failed to demonstrate statistically significant health effects at doses below 10,000 mrem delivered at low dose rates,” the report also recommends “future consideration of increasing this limit to 10,000 mrem/year with appropriate cumulative-dose constraints.”
Matthew J Memmott, Annalisa Manera
Nuclear Technology | Volume 191 | Number 3 | September 2015 | Pages 199-212
Technical Paper | Fission Reactors | doi.org/10.13182/NT14-103
Articles are hosted by Taylor and Francis Online.
Integral pressurized water reactors are innovative reactors in which all of the components typically associated with the nuclear steam supply system of a nuclear power station are located within the reactor pressure vessel. In order to facilitate this modification in large [∼1000-MW(electric)] light water reactors (LWRs), compact heat exchangers such as microchannel heat exchangers must be used. Previous attempts at using microchannel heat exchangers were unsuccessful since they are prone to vapor locking and crud blockage when the primary coolant boils. Therefore, the authors propose the use of a flashing drum to facilitate boiling in conjunction with a primary microchannel heat exchanger for a large integral LWR. The integral inherently safe light water reactor (I2S-LWR) is used as a basis for the implementation of this novel concept. The high-temperature, high-pressure secondary water generated in the secondary loop through heating in the microchannel primary heat exchanger of the I2S-LWR is sent to a flashing drum where 99.9% pure vapor is extracted and sent to the turbines. This prevents boiling in the primary heat exchanger that in turn reduces crud deposition, flow instabilities, and the potential for channel blockage or vapor locking in the small channel sizes of microchannel heat exchangers. The benefits and disadvantages of this approach are presented in this paper. Unfortunately, this innovative approach to nuclear steam generation for integral LWRs is challenged by a potential decrease in thermodynamic efficiency. Therefore, a sensitivity study is presented that explores the impact of several design variables on the thermodynamic efficiency of the plant. As part of this study, a simple and a complex Rankine cycle were modeled in order to determine the impact that system design modifications can play in recovering thermodynamic efficiency lost by the steam drum. Both cycles utilize turbines, condensers, and condensate/recirculation pumps, while the complex Rankine cycle utilizes a four-stage turbine with subsequent separation and open feedwater heaters. The optimized efficiencies for the simple and complex Rankine cycles are 31% and 33%, respectively, indicating that additional system enhancements to the power conversion system could compensate for the inclusion of a flashing drum.
