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NRC approves TerraPower construction permit
Today, the Nuclear Regulatory Commission announced that it has approved TerraPower’s construction permit application for Kemmerer Unit 1, the company’s first deployment of Natrium, its flagship sodium fast reactor.
This approval is a significant milestone on three fronts. For TerraPower, it represents another step forward in demonstrating its technology. For the Department of Energy, it reflects progress (despite delays) for the Advanced Reactor Demonstration Program (ARDP). For the NRC, it is the first approval granted to a commercial reactor in nearly a decade—and the first approval of a commercial non–light water reactor in more than 40 years.
Erhard A. Fischer, Werner Maschek
Nuclear Technology | Volume 71 | Number 1 | October 1985 | Pages 173-186
Technical Paper | Nuclear Safety | doi.org/10.13182/NT85-A33718
Articles are hosted by Taylor and Francis Online.
The role of vapor bubble dynamics during an energetic superprompt critical power excursion in a liquid-metal-cooled fast breeder reactor (LMFBR) unprotected loss-of-flow accident is examined by extending a known bubble dynamics model to the case of a rapid temperature rise. Generally, bubble dynamics is expected to influence such an excursion in at least two ways: 1. The fuel vapor pressure buildup—an important shutdown mechanism for the nuclear excursion—could be delayed by limiting the fuel evaporation rate; this would mean large superheat of the liquid fuel. 2. Shrinkage of initially present bubbles during the excursion could cause a strong reduction of neutron streaming, and therefore increase the reactivity of the system (potential of an autocatalytic effect). Both problems have been studied in this paper, and the following results have been obtained: For the rather high heating rate of 400 K/ms, fuel vapor bubbles grow for typically 1.5 ms, and then shrink again due to the rapidly rising pressure. Growth rates are found to be fast enough so that the expected delay in vapor pressure buildup is small and can be neglected in core disassembly analysis. The case that the initial configuration is a boiling fuel/steel pool was further examined. The pool has a high void fraction due to the presence of steel vapor bubbles. Collapse of these bubbles during a temperature transient was studied with the bubble dynamics model. The associated reduction in the neutron streaming effect leads to an increase in reactivity. Its influence on the nuclear excursion was examined with the core disassembly code KADIS, using a modified Behrens formula for the streaming reactivity. The data of a homogeneous 300-MW(electric) class LMFBR were used, with a 33 dollar/s reactivity ramp resulting from a recriticality driven by fuel compaction. Although the total streaming reactivity is as large as 2.32 dollars, it was found that its influence on the course of the power transient is only weak, because the bulk of it is released, at a high rate, only after the power peak, when nuclear shutdown by gross material motion is already in progress.
