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Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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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!
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The U.S. Million Person Study of Low-Dose-Rate Health Effects
There is a critical knowledge gap regarding the health consequences of exposure to radiation received gradually over time. While there is a plethora of studies on the risks of adverse outcomes from both acute and high-dose exposures, including the landmark study of atomic bomb survivors, these are not characteristic of the chronic exposure to low-dose radiation encountered in occupational and public settings. In addition, smaller cohorts have limited numbers leading to reduced statistical power.
Blair P. Bromley
Nuclear Technology | Volume 194 | Number 2 | May 2016 | Pages 192-203
Technical Paper | doi.org/10.13182/NT14-101
Articles are hosted by Taylor and Francis Online.
Pressure-tube heavy water reactors (PT-HWRs) are highly advantageous for implementing plutonium-thorium (Pu-Th) fuels because of their high neutron economy and online refueling capability. The use of annular heterogeneous seed-blanket core concepts in a PT-HWR where higher-fissile-content seed fuel bundles are physically separate from lower-fissile-content blanket bundles allows more flexibility and control in fuel management. The lattice concept modeled was a 35-element bundle made with a homogeneous mixture of reactor-grade PuO2 (67 wt% fissile) and ThO2, with a central zirconia rod to reduce coolant void reactivity. Eight annular heterogeneous seed-blanket core concepts with plutonium-thorium–based fuels in a 700-MW(electric)–class PT HWR were analyzed, using a once-through-thorium cycle. Blanket region(s) represented 50% to 75% of the total fuel volume. There were 1, 2, and 3 different blanket regions and 1, 2, and 3 different seed regions. The seed fuel tested was 3 wt% or 4 wt% PuO2, while the blanket fuel tested was 1 wt% PuO2, mixed with ThO2. The impact of different fuel combinations on the core-average burnup, fissile utilization (FU), power distributions, and other performance parameters were evaluated. WIMS-AECL 3.1 was used to perform lattice physics calculations using two-dimensional, 89-group integral neutron transport theory, while RFSP 3.5.1 was used to perform the core physics and fuel management calculations using three-dimensional two-group diffusion theory. Among the different core concepts investigated, there were cores where the FU was up to 25% higher than is achieved in a PT-HWR using natural uranium fuel bundles. There were cores where up to 60% of the Pu was consumed, cores where up to 41% of the energy was produced from 233U, and cores where up to 236 kg/yr of fissile uranium (mainly 233U) was produced in the discharged fuel. This study is an extension of previous work that involved the analysis of homogeneous cores, two-region (one seed, one blanket) and eight-region (four seeds, four blankets) annular, and checkerboard-type heterogeneous seed-blanket cores.
