A Structural Design Approach Tailored for the Rapid Preliminary Design of Microreactor Components

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Abstract

High-temperature microreactors can play a role in developing reliable, portable energy sources for off-grid remote locations, microgrid concepts, and industrial process heat. Portability and passive safety criteria tend to skew microreactor structural component designs toward complex geometries, high thermal stresses, and design bases with large numbers of startup/shutdown cycles. Current design rules, as typified by Section III of the American Society of Mechanical Engineers (ASME) Boiler & Pressure Vessel Code, are less than optimal for these conditions, particularly for preliminary component designs where developers need to rapidly consider a large number of potential component configurations. This paper presents a design method targeted toward rapid, efficient evaluation of preliminary component designs using modern finite element analysis. The new method retains key connections with the ASME Code rules and design data while streamlining the design approach. This paper presents the design method, several verification examples illustrating the similarities and differences between the new method and the current ASME rules, and the application of the new approach to the evaluation of a test article mimicking key features of a heat pipe–cooled microreactor.

Keywords:

• Microreactor
• structural design
• high-temperature design
• design method

Acronyms

ANL:	=	Argonne National Laboratory
ASME:	=	American Society of Mechanical Engineers
CRBRP:	=	Clinch River Breeder Reactor Program
DOE:	=	U.S. Department of Energy
EPP:	=	elastic perfectly plastic
FEA:	=	finite element analysis

Nomenclature

$S_{mt}$	=	= time-dependent allowable stress guarding against creep rupture, tertiary creep, and excessive creep deformation, as well as plastic collapse and yielding.
$S_r$	=	= minimum stress to rupture guarding only against creep rupture.
$t_r$	=	= time corresponding to a rupture stress of S and a local temperature T using the ASME Code minimum stress to rupture data.

Acknowledgments

The authors gratefully acknowledge discussions on the test article design with Holly Trellue, Robert Reid, Lindsey Gaspar, and Katrina Sweetland, all of the Los Alamos National Laboratory.

This paper has been co-authored by UChicago Argonne LLC under contract no. DE-AC02-06CH11357 and by Battelle Energy Alliance under contract no. DE-AC07-05ID14517 with the U.S. Department of Energy (DOE). Programmatic direction was provided by the Office of Nuclear Reactor Deployment of the Office of Nuclear Energy, DOE. The U.S. government retains and the publisher, by accepting the paper for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this paper, or allow others to do so, for U.S. government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan: (http://energy.gov/downloads/doe-public-accessplan).

Disclosure Statement

No potential conflict of interest was reported by the authors.

Notes

^a The difference between a secondary and a peak stress is largely historical. A peak stress is caused by a stress concentration, i.e., a feature that would not be included in a traditional shell model of a vessel.