Argonne Liquid-Metal Advanced Burner Reactor : components and in-vessel system thermal-hydraulic research and testing experience - pathway forward.
During the 1970s and 1980s, the U.S. DOE sponsored a substantial effort in the development of sodium-cooled fast nuclear reactors. Initially, these fission reactors were to be breeders with the designation Liquid Metal Fast Breeder Reactor (LMFBR). Later the breeding stipulation was dropped, and the name was changed to Liquid Metal Reactor (LMR) or Advanced Burner Reactor (ABR). The most important feature of the earlier breeder reactor was to significantly extend the useful life of the world’s supply of fissionable uranium by implementing a system of breeder reactors with the goal of producing about 10% more fissionable material each year than consumed in producing electricity. At that time, LMFBRs had only been built in small size, and it was appropriate for DOE to sponsor the development of the commercial-scale technology because the project was too large for private industry and because it was of great national interest and potential benefit. To this end, DOE sponsored a variety of research and development programs to advance this technology.
In response to DOE during the 1970s, Argonne conducted thermal–hydraulic studies of individual LMR components supporting EBR-II, FFTF, and CRBR development. After cancellation of CRBR, DOE in order to begin transferring LMR technology developed under federally funded programs to the U.S. industry funded a design competition between General Electric (GE) and Rockwell International/Combustion Engineering (RI/CE) to design a commercially viable LMR for future deployment. The GE design was called PRISM (Prototype Reactor Inherently Safe Module) and the RI/CE design was called SAFR (Sodium Advanced Fast Reactor). In the mid-1980s and early 1990s, Argonne conducted forced- and natural- convection phenomena studies on complete in-vessel system experimental test models of the GE/PRISM and RI/CE/SAFR designs. These DOE-funded studies were carried out in collaboration with GE and RI/CE. Further development of LMR expertise/design knowledge is vital to the future deployment of safe, reliable, and high-performance LMR Advanced Burner Reactors (ABRs) currently being proposed by DOE under the GNEP initiative for deployment in 2025. This near-term deployment does not involve breeder reactors.
This white paper has been written to summarize the thermal-hydraulic understanding that has been developed over the last 30 plus years, highlight important phenomena that must be factored into future reactor designs, and describe additional developmental efforts still needed. In particular, it describes the need for further LM-ABR technology development support in the form of better testing infrastructure, improved engineering knowledge, and improved/validated computational modeling tools. The paper also addresses the impact of thermal hydraulics on reactor system operation and on the behavior/performance of individual components (thermal duty and structural impact) during normal operation and postulated off-normal low-flow accident events related to safety.
Argonne has been a pioneer in the study of thermal-buoyancy-force governed flows under various important reactor transient conditions, such as the transition from forced to natural convection, instabilities generated by parallel flow paths, and structural thermal stresses caused by thermal stratification and their influence on heat-sink effectiveness.
8Argonne from the early 1970s through the early 1990s was DOE’s lead laboratory for LMR thermal-hydraulic development. During the 1970s and into the mid-1980s, Argonne conducted thermal-hydraulic studies and experiments on individual reactor components supporting EBR- II, FFTF, and CRBR. In the 1980s and into the early 1990s, Argonne conducted studies on forced- and natural-convection (thermal-buoyancy-force) phenomena in complete in-vessel models of GE/PRISM and RI/SAFR. These two reactor initiatives involved Argonne working closely with U.S. industry and the DOE. This paper describes the very important impact of thermal hydraulics on reactor global operation and on individual component behavior/performance (thermal duty, structural impact, and safe operation) during normal operation and postulated off-normal low-flow accident events related to safety. Argonne’s LMR expertise and design knowledge are vital to the further development of a safe, reliable, and high-performance LM-ABR.
In the 1980s Argonne developed/built a large water test facility called the Mixing Components Test Facility (MCTF) for performing steady and thermal-transient experimental simulations of important reactor components under a wide range of operation scenarios. (The MCTF was decommissioned in 1993.) Modeling studies were also conducted by Argonne relative to ascertaining if the thermal-buoyancy phenomena being studied could be effectively addressed through the use of water for testing of both individual LMR components and complete in-vessel system geometries. This modeling is discussed in detail in Section 4.2.1 and in Appendix 1 of this report. These modeling studies also highlighted where water testing was not adequate for addressing certain phenomena.
All of the Argonne studies involved fundamental experimental thermal-hydraulic testing and a strongly integrated component of computational fluid dynamics (CFD) code development and simulation analysis. The CFD analyses were predominately performed with the Argonne COMMIX code, which was augmented by some initial effort at utilization of commercial CFD codes like STAR-CD. One of the first uses of three-dimensional CFD analysis for addressing LMR thermal-hydraulics, which used the COMMIX code, was to address buoyancy-governed reactor flows. This computational modeling was driven and guided by Argonne’s thermal- hydraulic experiments on reactor components such as piping, plenums, steam generators, and heat exchangers.
The contents of this white paper are as follows:
Section 2 briefly describes the new DOE GNEP initiative relative to the pre-conceptual design features of the Argonne proposed LM-ABR, which would be one of the GNEP building blocks. Knowing the general technical features associated with the ABR allowed us to focus on and exploit what has been learned over the last 30 plus years about LMR thermal hydraulics relative to the importance to GNEP. Finally, this section also describes, based on the 1993 GE/PRISM close-out report, what industry ideas were at that time as to what further development and testing were needed to deploy a U.S. LMR. This information helped to further focus the recommendations given in this report regarding a thermal-hydraulic pathway forward.
Section 3 describes Argonne studies and the status of our understanding of thermal buoyancy phenomena occurring in individual reactor components such as:
␣ Piping/plenum interfaces and thermal plumes
␣ Heat exchangers
␣ Steam generators
␣ Multiple coolant stream thermal mixers
Section 4 describes Argonne’s past studies on reactor in-vessel thermal hydraulics, which initially addressed generic core outlet and plenum flow interactions guided by CRBR needs. These studies in their later stages investigated forced- and natural-convection (thermal- buoyancy-force) phenomena using complete in-vessel models of the GE/PRISM and RI- CE/SAFR designs. Complete in-vessel model experiments were used because the flow and thermal behavior in a given sub-region of the reactor vessel is the result of complex interactions with the rest of the reactor in-vessel components. These interactions are especially important for pool designs under low-flow conditions and the transition to natural convection. They have the potential for strongly affecting reactor:
␣ Thermal-hydraulic performance
␣ Emergency cooling
␣ Structural integrity
␣ Heat-sink effectiveness
These complete in-vessel experimental studies provided GE and RI-CE designers with information vital to the design and assessment of the workability of the various features that were being incorporated into their innovative and inherently safe reactors.
Finally, Section 5 describes a pathway forward regarding further research and development needed to support the GNEP/LM-ABR initiative.