ML25147A211
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| ML25147A211 | |
| Person / Time | |
|---|---|
| Site: | Abilene Christian University |
| Issue date: | 05/28/2025 |
| From: | Abilene Christian University, Natura Resources, Nuclear Energy eXperimental Testing Lab |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| Download: ML25147A211 (1) | |
Text
Presentation Title Fuel Qualification Methodology Overview May 28, 2025
Presentation Title Outline
- Introduction
- Background
- Fuel Design Description
- Fuel Content Adjustment
- Fuel Qualification Methodology
- Fuel Laboratory Testing
- Conclusions Fuel Qualification Methodology Overview
Presentation Title Introduction
- White paper describes ACUs methods for qualifying liquid salt fuel for the ACU Molten Salt Research Reactor (MSRR).
- Primary objective to provide validated inputs for models used in the MSRR safety analysis.
- MSRR is a 1MWt loop-type, liquid fueled molten salt reactor that will be constructed and operated as a class 104(c) utilization facility.
- Desired fuel source is the EBR II HALEU stock. Fuel design, specification, and subsequent qualification uses this assumption.
- MSRR Fuel Qualification to serve as foundation for future commercial MSRs fuel qualification. 10 CFR 50.43(e)
- Fuel salt interactions with materials are investigated by separate programs Fuel Qualification Methodology Overview
Presentation Title
Background
Fuel Qualification Methodology Overview
Presentation Title
Background
- Fuel Salt supports the MSRR fundamental safety features due to its intrinsic thermophysical and chemical properties.
- Fuel salts provide good heat transfer characteristics, minimal stress on pressure vessels, core homogeneity, fuel structure stability at high burnup, online refueling, and FP retention.
- MSRR utilizes functional containment to reduce release of radioactive materials from the facility to below safe levels in accident cases.
- Fuel Salt is a barrier for non-gaseous radionuclides as they remain bound within the salt and salt wetted surfaces.
- Reactor loop provides the primary boundary to fission product release.
- Reactor thermal management system catches salt in case of salt leak and provides a barrier to release of non-volatile FPs.
- Leak tight reactor enclosure provides a final boundary to FP release.
Fuel Qualification Methodology Overview
Presentation Title
Background:
Regulatory Review
- MSRR Fuel Qualification informed by:
- NUREG/CR-7299 Fuel Qualification for Molten Salt Reactors (2022) and NUREG - 2246 Fuel Qualification for Advanced Reactors (2022).
- Regulations Identified:
- 10 CFR 50.34(b), 50.34(b)(2), 50.34(b)(3), and 50.34(b)(4)
- Relevant MSRR Principal Design Criteria
- PDC 10: Reactor Design
- PDC 11: Reactor Inherent Protection
- PDC 16: Containment Design
- PDC 71: Fuel Salt Compositional Control Fuel Qualification Methodology Overview
Presentation Title Fuel Design Description
- Nominal Composition: LiF-BeF2-UF4 [molar ratio: 63:32:5]
- Lithium enrichment: at least 99.99 mol % Li-7
- Liquidus point of fuel salt: around 460 °C
- Typical operating range: 550°C - 650°C
- Fuel Salt is maintained above 550°C during operations with Reactor Thermal Management System.
- Fuel salt reaches up to 750°C briefly during postulated accidents and does not violate steel container temperature safety limits.
- Fuel Salt composition changes during operation due to:
- Fission product buildup, depletion of U-235, UF4 Addition/Refueling, generation of corrosion products, and contaminants in cover gases
- Specific limits will be defined for impurities after corrosion testing and fuel qualification laboratory testing is complete.
Fuel Qualification Methodology Overview
Presentation Title Online Fuel Content Adjustment
- Fuel Salt Composition changes are managed to stay within the qualified range.
- MSRR Fuel Salt samples collected and analyzed during operation
- ICP-MS measures composition
- Combustion analysis measures oxygen levels
- Redox potential which indicates corrosivity is measured via electrochemistry techniques
- Fuel salt processed as needed based on data from sample
- Oxygen/oxidative impurities can be removed via Fuel Salt Purification Vessel H2-HF treatment
- Salt can be mechanically filtered
- Beryllium can be added to adjust redox potential
- UF4 can be added to compensate for burnup Fuel Qualification Methodology Overview
Presentation Title Fuel Qualification
- Thermophysical properties are a function of the salts chemical composition and temperature.
- Relevant properties: heat capacity, thermal conductivity, liquidus temperature, density, and viscosity.
- Fuel Qualification will address how these properties respond to changes in chemical composition - corresponding to the MSRR fuel operating envelope.
- MSRR Fuel performance requirements:
- Fuel salt is maintained in its qualified chemical composition
- Fuel salt remains a liquid during operation
- Fuel salt retains non-volatile fission products
- Fuel salt maintains adequate heat transfer properties.
Fuel Qualification Methodology Overview
Presentation Title Fuel Qualification Methodology
- Laboratory tests measure the thermophysical properties of the fuel salt for both normal operation and transient conditions for the entire range of salt compositions relevant to the MSRR.
- Laboratory tests utilize salts that are loaded with fission product surrogates to mimic fuel burnup. Surrogate elements are chosen to represent elements with similar chemical behavior to fission products.
- Ultimate goal of validating salt properties used in analysis which demonstrate the MSRR is safe in normal and transient conditions.
- Uncertainty and accuracy requirements are determined using safety analysis tools.
Fuel Qualification Methodology Overview
Presentation Title Fuel Qualification Methodology
- Fuel performance envelope is the bounding set of conditions the fuel salt is qualified for. The laboratory test envelope covers the ranges of temperatures, chemical compositions, and surrogate fission products that are expected in the MSRR.
Fuel Qualification Methodology Overview
Presentation Title Laboratory Testing
- For the range of compositions and temperatures, the test program will measure:
- density
- viscosity
- thermal conductivity
- heat capacity
- heat of fusion
- liquidus point Fuel Qualification Methodology Overview
Presentation Title Laboratory Testing Fuel Qualification Methodology Overview
Presentation Title Conclusions
- ACU will assess the thermophysical properties of the MSRR fuel salt for a range of compositions and temperatures.
- Testing the thermophysical properties will confirm the design basis for MSRRs safety systems and verify that they achieve the fundamental safety functions.
- The results of the Program described in this white paper will be used to establish a fuel salt performance envelope that will be applied through operating limits specified in the MSRR Technical Specifications.
Fuel Qualification Methodology Overview