NSUF 23-1878: The effect of irradiation on the densities of chloride-bearing molten salts
The project will investigate the effect of neutron irradiation in chloride-bearing molten salts by comparing densities measured before and after irradiation. Densities can be measured in molten salts at high temperature by neutron radiography. Both Los Alamos National Laboratory and Oak Ridge National Laboratory (ORNL) have established programs for conducting these measurements. Recently, ORNL has submitted results of measurements on uranium chloride-potassium chloride systems that have been modeled using a Redlich-Kister fit incorporating two- and three-body interactions. The salts were contained in sealed quartz NMR tubes and were prepared under vacuum. The salts were heated several times between 400 and 800C and showed characteristic interfacial behavior as they were heated. The radiographs showed stable voids in the salt well above the melting point before percolating to the top of the melt. Another effect observed was the complex interaction between the salt and the surface of the quartz, which is supposedly inert to chloride salts. The change in meniscus and the establishment of concave or convex behavior after several heating and cooling cycles suggested that the wetting angle was affected by prior cycling. One explanation could be an ion exchange between the quartz and the salt.
These findings suggest that the complex physical and chemical behavior of molten chloride salts deserves more attention and suggest that the further complexity may arise from irradiation. Although recombination of the products of radiolysis is expected to occur rapidly in the heated salt, radiation damage of surfaces and radiation induced effects at interfaces are expected to occur. These may cause irreversible changes to the salt system and affect macroscopic property measurements such as density. Thus, we propose to submit three salts that have been used in density measurements, UCl3-KCl (two binary compositions) and UCl3-KCl-NaCl (one ternary mixture), for intense irradiation at MITR in the 2PH1 user facility for 10 min. These irradiations will be done when the salts are solid to minimize recombination and all three salts can be combined in one polyethylene rabbit. Once the salts have been subjected to the intense fields, they will counted for activation analysis and be allowed to cool radiolytically before neutron imaging. Then they will be returned to ORNL. There they will once again be introduced into the vacuum oven at the CG1D beamline at the ORNL High Flux Isotope Reactor (HFIR). The same protocol will be used for density measurements as was used in the past. The radiographs will be examined for macroscopic changes in salt volume (dilatometry), wetting angles, and will also be reviewed for changes in salt composition as a function of distance from the surface of the quartz container.
The use of the irradiation facility at MITR will be led by Dr. Boris Khaykovich of the physics department at MIT. The use of CG1D at HFIR will be requested with a user proposal led by Dr. Joanna McFarlane in a spring 2023 submission. The CG1D instrument scientist collaborator is Dr. Yuxuan Zhang at ORNL. The irradiation and cooling at MITR will take place in 2023 and the beamline proposal at HFIR will request time later in 2023 or early 2024 to allow the samples to cool and be returned to ORNL.
The investigation will allow direct comparison of the densities of the same salt samples before and after irradiation. This study will test the hypothesis that irradiation affects salt thermophysical properties and interfacial behavior. The radiography data will be interpreted by imaging analysis and by modeling salt mixtures. If additional species are made during irradiation, such as through activation or changes in the redox chemistry of the metals in the salt, these will need to be included in the model. Thus, if successful, this study may indicate new areas of scientific investigation of molten salts and the need to understand how salt properties change when irradiated.
Additional Info
| Field | Value |
|---|---|
| Abstract | The project will investigate the effect of neutron irradiation in chloride-bearing molten salts by comparing densities measured before and after irradiation. Densities can be measured in molten salts at high temperature by neutron radiography. Both Los Alamos National Laboratory and Oak Ridge National Laboratory (ORNL) have established programs for conducting these measurements. Recently, ORNL has submitted results of measurements on uranium chloride-potassium chloride systems that have been modeled using a Redlich-Kister fit incorporating two- and three-body interactions. The salts were contained in sealed quartz NMR tubes and were prepared under vacuum. The salts were heated several times between 400 and 800C and showed characteristic interfacial behavior as they were heated. The radiographs showed stable voids in the salt well above the melting point before percolating to the top of the melt. Another effect observed was the complex interaction between the salt and the surface of the quartz, which is supposedly inert to chloride salts. The change in meniscus and the establishment of concave or convex behavior after several heating and cooling cycles suggested that the wetting angle was affected by prior cycling. One explanation could be an ion exchange between the quartz and the salt. These findings suggest that the complex physical and chemical behavior of molten chloride salts deserves more attention and suggest that the further complexity may arise from irradiation. Although recombination of the products of radiolysis is expected to occur rapidly in the heated salt, radiation damage of surfaces and radiation induced effects at interfaces are expected to occur. These may cause irreversible changes to the salt system and affect macroscopic property measurements such as density. Thus, we propose to submit three salts that have been used in density measurements, UCl3-KCl (two binary compositions) and UCl3-KCl-NaCl (one ternary mixture), for intense irradiation at MITR in the 2PH1 user facility for 10 min. These irradiations will be done when the salts are solid to minimize recombination and all three salts can be combined in one polyethylene rabbit. Once the salts have been subjected to the intense fields, they will counted for activation analysis and be allowed to cool radiolytically before neutron imaging. Then they will be returned to ORNL. There they will once again be introduced into the vacuum oven at the CG1D beamline at the ORNL High Flux Isotope Reactor (HFIR). The same protocol will be used for density measurements as was used in the past. The radiographs will be examined for macroscopic changes in salt volume (dilatometry), wetting angles, and will also be reviewed for changes in salt composition as a function of distance from the surface of the quartz container. The use of the irradiation facility at MITR will be led by Dr. Boris Khaykovich of the physics department at MIT. The use of CG1D at HFIR will be requested with a user proposal led by Dr. Joanna McFarlane in a spring 2023 submission. The CG1D instrument scientist collaborator is Dr. Yuxuan Zhang at ORNL. The irradiation and cooling at MITR will take place in 2023 and the beamline proposal at HFIR will request time later in 2023 or early 2024 to allow the samples to cool and be returned to ORNL. The investigation will allow direct comparison of the densities of the same salt samples before and after irradiation. This study will test the hypothesis that irradiation affects salt thermophysical properties and interfacial behavior. The radiography data will be interpreted by imaging analysis and by modeling salt mixtures. If additional species are made during irradiation, such as through activation or changes in the redox chemistry of the metals in the salt, these will need to be included in the model. Thus, if successful, this study may indicate new areas of scientific investigation of molten salts and the need to understand how salt properties change when irradiated. |
| Award Announced Date | 2023-02-08T10:49:08.123 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Gordon Kohse, Kory Linton |
| Irradiation Facility | None |
| PI | Joanna McFarlane |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 4566 |