Molten Salt Reactor Experiment (MSRE) Description
Contact: Mauricio Tano, mauricio.tanoretamales.at.inl.gov
Model summarized and documented by Andres Fierro, Dr. Samuel Walker, and Dr. Mauricio Tano
The MSRE was a graphite moderated flowing salt type reactor with a design maximum operating power of 10 MW(th) developed by Oak Ridge National Laboratory (Robertson, 1965). The reactor ran for more than 13,000 hours at full power before its final shutdown in 1969. The general layout of the experiment is shown in Figure 1.
Figure 1: Schematic design of MSRE loops (Fratoni et al., 2020).
The fuel salt was a fluoride-based ionic liquid containing lithium, beryllium, zirconium and uranium fuel. The coolant salt was a mixture of lithium fluoride and beryllium fluoride. The reactor consisted of two flow loops: a primary loop and a secondary loop. The primary loop connected the reactor vessel to a fuel salt centrifugal pump and the shell side of the shell-and-tube salt-salt heat exchanger. The secondary loop connected the tube-side of the shell-and-tube heat exchanger to a coolant salt centrifugal pump and the tube side of an air-cooled radiator. Two axial blowers supplied cooling air to the radiator. Piping, drain tanks, and “freeze valves” made up the remaining components of the heat transport circuits. The heat generated in the core was transferred to the secondary loop through the heat exchanger and ultimately rejected to the atmosphere through the radiator.
The three main features of this experiment are:
The core circulation system, where the molten salt fuel flows through rounded-rectangular channels in the vertical graphite moderator stringers
The centrifugal pump that provided continuous circulation, facilitated heat transfer and the removal of fission products
The two-loop heat exchanger system with an approximately 25-second fuel loop circulation time in the reactor.
We note that the MSRE was a thermal reactor with a highly negative reactivity temperature coefficient. The vertical graphite stringers are shown in Figure 2.
Table 1: MSRE Reactor Specifications
| Parameter | Value |
|---|---|
| Core Power | 10 MW (MegaWatt Thermal) |
| Core height | 1.63 m |
| Core diameter | 1.39 m |
| Fuel Salt | LiF-BeF-ZrF-UF |
| Fuel salt molar mass | 65.0%-29.1%-5.0%-0.9% |
| Fuel salt enrichment | 33.0% |
| Channels in graphite moderator | 3.05 cm ✕ 1.016 cm |
| Channels' rounded corners radii | 0.508 cm |
| Vertical graphite stringers | 5.08 cm ✕ 5.08 cm |
Figure 2: Picture of MSRE core graphite stringers in core assembly (Briggs, 1964).
Material Properties and MSRE Setup
The fuel salt in the MSRE primary loop was LiF-BeF4-ZrF4-UF4 according to the design specifications of the MSRE (Beall et al., 1964; Cantor, 1968), of which the thermophysical properties are listed in Table 2.
Table 2: Thermophysical properties of the fuel salt
| Unit | LiF-BeF-ZrF-UF | ||
|---|---|---|---|
| Melting temperature | |||
| Density | |||
| Dynamic viscosity | |||
| Thermal conductivity | |||
| Specific heat capacity |
A conventional, cross-baffled, shell-and-tube type heat exchanger was used in MSRE. The fuel salt flows on the shell side while the coolant salt flows through the tube side. The coolant salt in the heat changer is LiF-BeF (0.66-0.34) (Guymon, 1973), of which the major thermophysical properties are summarized in Table 3. Due to the space limitation in the reactor cell, a U-tube configuration is adopted, which results in a heat exchanger of roughly 2.5 m in length. The shell diameter is 0.41 m while the tube has a diameter of 1.27 cm and a thickness of 1.07 mm. Given a triangular arrangement of the tubes, the hydraulic diameters are 2.09 cm (shell-side) and 1.06 cm (tube-side). The construction material of heat exchanger is Hastelloy® N alloy with the properties listed in Table 4. All the connecting pipes have a default diameter of 0.127 m. A centrifugal pump is utilized, and its head is adjusted to sustain the flow circulation.
Table 3: Thermophysical properties of the coolant salt in heat exchanger.
| Unit | LiF-BeF (0.66-0.34) | ||
|---|---|---|---|
| Melting temperature | |||
| Density | |||
| Dynamic viscosity | |||
| Thermal conductivity | |||
| Specific heat capacity |
Table 4: Thermophysical properties of Hastelloy® N alloy used in the heat exchanger.
| Unit | Hastelloy® N alloy | ||
|---|---|---|---|
| Density | |||
| Thermal conductivity | |||
| Specific heat capacity |
References
- S E Beall, P N Haubenreich, R B Lindauer, and J R Tallackson.
MSRE Design and Operations Report. Part V. Reactor Safety Analysis Report.
Technical Report ORNL-TM-732, Oak Ridge National Laboratory, Oak Ridge, TN, 1964.[BibTeX]
- R. Briggs.
Molten-salt reactor program semiannual progress report.
Technical Report ORNL-3626, Oak Ridge National Laboratory, 1964.[BibTeX]
- S Cantor.
Physical Properties of Molten-Salt Reactor Fuel, Coolant, and Flush Salts.
Technical Report ORNL-TM-2316, Oak Ridge National Laboratory, Oak Ridge, TN, 1968.
URL: https://www.osti.gov/biblio/4492893 https://www.osti.gov/servlets/purl/4492893, doi:10.2172/4492893.[BibTeX]
- Massimiliano Fratoni, Dan Shen, Germina Ilas, and Jeff Powers.
Molten salt reactor experiment benchmark evaluation.
Technical Report Project 16-10240, University of California Berkeley, 2020.[BibTeX]
- R H Guymon.
MSRE systems and components performance.
Technical Report ORNL-TM-3039, Oak Ridge National Laboratory, Oak Ridge, TN, 1973.[BibTeX]
- R C Robertson.
MSRE design and operations report. Part I. Description of reactor design.
Technical Report ORNL-TM-728, Oak Ridge National Laboratory, Oak Ridge, TN, 1965.[BibTeX]