This investigation explores thermal-fluid flow phenomena in a proportional flow control valve (FCV) within a 2 in. ID high-temperature piping transport system. The FCVs are critical components to ensure flexible nominal operation of a 2 MWth concentrating solar power (CSP) pilot-scale system in present development at Sandia National Laboratories (SNL). A computational fluid dynamics (CFD) / finite element analysis (FEA) model was developed in ANSYS that investigates multifluid phase-change transport within various sections of an FCV to explore plating and subsequent thermal-mechanical stress challenges that can exist with operations as high as 730°C. Results from the thermal-fluid model in development suggest salt vapor phase change in the N2 gas purge lines as low as approximately 476°C, which can have a negative impact on valve reliability.
In this investigation, heat transfer analysis of cold and hot pump-tank interfaces for a 2 MWth pilot-scale system is assessed using a developed computational fluid dynamics (CFD) model using ANSYS Fluent. A DOE Generation 3 concentrating solar power (CSP) ternary chloride molten salt mixture is used as the working fluid of each system and evaluated at different temperatures and pressures. In this CFD model work an analysis was performed for a pump assembly at the interface between the test loop and a storage tank. The model was developed for three scenarios with molten salt inlet temperatures set at 500 °C, 720 °C, and 730 °C. The real-world complex geometry was simplified and evaluated as a two- dimensional model with the purpose of estimating overall heat transfer and velocity profiles for the respective system configurations. Preliminary results indicate that pump field insulation absorbs most of the heat from radiating from the molten salt region at a max temperature of 39.48 °C and that heat transfer within the N2 ullage gas region is primarily due to natural convection and radiation.
Several Department of Energy (DOE) facilities have materials stored in robust, welded, stainless - steel containers with presumed fire - induced pressure response behaviors. Lack of test data related to fire exposure requires conservative safety analysis assumptions for container response at these facilities. This conservatism can in turn result in the implementation of challenging operational restrictions with costly nuclear safety controls. To help address this issue for sites that store DOE 3013 stainless - steel containers, a series of ten tests were undertaken at Sandia National Laboratories. The goal of this test series was to obtain the response behavior for various configurations of DOE 3013 containers with various payload compositions when exposed to one of two ASTM fire conditions. Key parameters measured in the test series included identification of failure - specific characteristics such as pressure, temperature, and whether or not a vessel was breached during a test . Numerous failure - specific characteristics were identified from the ten tests. This report describes the implementation and execution of the test series performed to identify these failure - specific characteristics. Discussions on the test configurations, payload compositions, thermal insults, and experimental setups are presented. Test results in terms of pressurization and vessel breach (or no - breach) are presented along with corresponding discussions for each test.
The formation of a stress corrosion crack (SCC) in the canister wall of a dry cask storage system (DCSS) has been identified as a potential issue for the long-term storage of spent nuclear fuel. The presence of an SCC in a storage system could represent a through-wall flow path from the canister interior to the environment. Modern, vertical DCSSs are of particular interest due to the commercial practice of using relatively high backfill pressures (up to approximately 800 kPa) in the canister to enhance internal natural convection. This pressure differential offers a comparatively high driving potential for blowdown of any particulates that might be present in the canister. In this study, the rates of gas flow and aerosol transmission of a spent fuel surrogate through an engineered microchannel with dimensions representative of an SCC were evaluated experimentally using coupled mass flow and aerosol analyzers. The microchannel was formed by mating two gage blocks with a linearly tapering slot orifice nominally 13 μm (0.005 in.) tall on the upstream side and 25 μm (0.0010 in.) tall on the downstream side. The orifice is 12.7 mm (0.500 in.) wide by 8.89 mm (0.350 in.) long (flow length). Surrogate aerosols of cerium oxide, CeO2, were seeded and mixed with either helium or air inside a pressurized tank. The aerosol characteristics were measured immediately upstream and downstream of the simulated SCC at elevated and ambient pressures, respectively. These data sets are intended to demonstrate a new capability to characterize SCCs under well-controlled boundary conditions. Modeling efforts were also initiated that evaluate the depletion of aerosols in a commercial dry storage canister. These preliminary modeling and ongoing testing efforts are focused on understanding the evolution in both size and quantity of a hypothetical release of aerosolized spent fuel particles from failed fuel to the canister interior and ultimately through an SCC.
Several Department of Energy (DOE) facilities have nuclear or hazardous materials stored in robust, welded, stainless-steel containers with undetermined fire-induced pressure response behaviors. Lack of test data related to fire exposure requires conservative safety analysis assumptions for container response at these facilities. This conservatism can in turn result in the implementation of challenging operational restrictions with costly nuclear safety controls. To help address this issue for sites that store DOE 3013 stainless-steel containers, a series of five tests were undertaken at Sandia National Laboratories. The goal of this test series was to obtain the response behavior for various configurations of the DOE 3013 containers when exposed to various fire conditions. Key parameters measured in the test series included identification of failure-specific characteristics such as pressure, temperature, and leak/burst failure type. This paper describes the development and execution of the test series performed to identify these failure-specific characteristics. Work completed to define the test configurations, payload compositions, thermal insults, and experimental setups are discussed. Test results are presented along with corresponding discussions for each test.
Certification of radioactive material (RAM) packages for storage and transportation requires multiple tiers of testing that simulate accident conditions in order to assure safety. One of these key testing aspects focuses on container response to thermal insults when a package includes materials that decompose, combust, or change phase between-40 °C and 800 °C. Thermal insult for RAM packages during testing can be imposed from a direct pool fire, but it can also be imposed using a furnace or a radiant heat system. Depending on variables such as scale, heating rates, desired environment, intended diagnostics, cost, etc., each of the different methods possess their advantages and disadvantages. While a direct fire can be the closest method to represent a plausible insult, incorporating comprehensive diagnostics in a controlled fire test can pose various challenges due to the nature of a fire. Radiant heat setups can instead be used to impose a comparable heat flux on a test specimen in a controlled manner that allows more comprehensive diagnostics. With radiant heat setups, however, challenges can arise when attempting to impose desired nonuniform heat fluxes that would account for specimen orientation and position in a simulated accident scenario. This work describes the development, implementation, and validation of a series of techniques used by Sandia National Laboratories to create prescribed non-uniform thermal environments using radiant heat sources for RAM packages as large as a 55-gallon drum.
Often in fire resistance testing of packaging vessels and other components, both the heat source temperature and the incident heat flux on a test specimen need to be measured and correlated. Standards such as ASTM E1529 require a specified temperature range from the heat source and a specified heat flux on the surface of the test specimen. There are other standards that have similar requirements. The geometry of the test environment and specimen may make heat flux measurements using traditional instruments (directional flame thermometers (DFTs) and water-cooled radiometers) difficult to implement. Orientation of the test specimen with respect to the thermal environment is also important to ensure that the heat flux on the surface of the test specimen is properly measured. Other important factors in the flux measurement include the thermal mass and surface emissivity of the test specimen. This paper describes the development of a cylindrical calorimeter using water-cooled wide-angle Schmidt-Bolter gauges to measure the incident heat flux for a vessel exposed to a radiant heat source. The calorimeter is designed to be modular to be modular with multiple configurations while meeting emissivity and thermal mass requirements via a variable thermal mass. The results of the incident heat flux and source temperature along with effective/apparent emissivity calculations are discussed.