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46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
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Calderoni, Pattrick
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Research plan for the development of optical fiber pressure sensors for nuclear applications
Fiber optic pressure sensors are desirable for nuclear applications because they are low mass/small size, immune to electromagnetic interference, high sensitivity, and have multiplexing and multimodal measurement capabilities. Much research and development has been conducted on developing fiber optic based sensors and they are now considered a class of standard instrumentation in many industries. Specifically, for pressure sensing, a wide range of fiber based sensors have been developed for various pressure ranges and environments. This vast body of research will be leveraged for the development of pressure sensors for nuclear applications. Four pressure measurement scenarios were considered which would benefit from a fiber optic based pressure sensor. These scenarios include pressure measurement in the fuel rod plenum, coolant pressure during LOCA testing, advanced coolant (helium, sodium, molten salt) pressure for flow loop operation, and high pressures resulting for direct fuel-coolant interaction. Each scenario has unique pressure, temperature, and material requirements for the sensor. From a survey of commercially available sensors and a literature review; it has been determined that an extrinsic Fabry-Perot interferometer approach is the most appropriate for the various measurement requirements. The experience and knowledge base for Fabry-Perot interferometers can be leveraged since they are the most common fiber optic based pressure sensors available commercially and found in literature. These pressure sensors rely on the interference of light in a gas filled cavity, which minimizes the impact of radiation induced attenuation and compaction on the measurement, compared to intrinsic sensing techniques. The measurement range of these sensors is based on the stiffness of the diaphragm that deflects under pressure. This allows for a suite of fiber based sensors to be developed by interchanging this diaphragm for the requirements of each application. Key material and design considerations have been identified for the development of a Fabry-Perot interferometry pressure measurement for nuclear applications. These include high temperature bonding between the glass fiber optic and metal housing, identifying diaphragm materials & geometry, and minimizing cross sensitivity to temperature or implementing compensation techniques found in literature. Overcoming these challenges will develop a pathway for a fiber optic based pressure sensor for nuclear applications, and additionally can be leveraged for other sensing application based on Fabry-Perot interferometers, such as temperature, strain (creep & deformation), vibration, and index of refraction.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Optimization of heat treatment and calibration procedures for high temperature irradiation resistant thermocouples [The development of calibration procedures for high temperature irradiation resistant thermocouples]
Here, a detailed description is provided for the optimization of heat treatment and calibrating procedure for Idaho National Laboratory’s high temperature irradiation resistant thermocouples (HTIR-TC). Also discussed is the implication of the procedures on the overall performance of the HTIR-TC finished product; in particular, for the case of long lead sections that are typical of sensors deployed in nuclear reactors. The effect on the measurement accuracy of fluctuations of the reference temperature and localized heating along the sensor lead is also investigated. A calibration graphical user interface (GUI) and accompanying script is presented for unifying the calibration process. A fifth-order polynomial function was found to be best for fitting HTIR-TC calibration data. The performance of the HTIR-TCs subject to the optimized heat treatment and calibration procedures is shown to be robust and consistent with other TC industry standards. Electromotive force curves versus length of the TC are presented to clarify positioning of TCs in general and how its effect on the calibrated temperatures.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Tritium Management Loop Design Status
This report summarizes physical, chemical, and engineering analyses that have been performed to support development of a test loop to study tritium migration in FLiBe (2LiF-BeF 2 ) salts. The loop will operate under turbulent flow, and a schematic of the apparatus has been used to develop a model in Mathcad to suggest flow parameters that should be targeted in loop operation. The introduction of tritium into the loop has been discussed, as well as various means to capture or divert the tritium from egress through a test assembly. Permeation was calculated, starting with the development of a Modelica model for a transport through a nickel window into a vacuum, followed by modification of the model for a FLiBe system with an argon sweep gas on the downstream side of the permeation interface. Results suggest that tritium removal with a simple tubular permeation device will occur readily. Although this system is idealized, it suggests that rapid measurement capability in the loop may be necessary to study and understand tritium removal from the system.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
In-Pile Instrumentation Initiative: A Multidisciplinary Scientific Approach for Characterization of Fuels and Materials
The In-Pile Instrumentation Initiative (I3) will conduct research needed to develop and deploy unique instruments to characterize the behavior of fuels and materials during irradiation tests conducted by Nuclear Energy (NE) programs within the Department of Energy. (Vision) I3 will provide real-time, accurate, spatially resolved information regarding performance of fuels and materials that can be directly tied to microstructure. This vision is reflected in the research direction of several NE programs that have identified a need to correlate material performance with evolving microstructure. Currently, these relationships can only be inferred through examination of materials in a post-irradiation environment. Realization of this vision will involve a sharp departure from the current approach that prioritizes instrument reliability over delivering optimal measurement capabilities. To realize this vision will require technical breakthroughs in several key areas, including materials science, modeling and simulation, advanced manufacturing, and instrument development. Insights gained from this initiative will be critical for advancing a number of NE objectives. Examples include expediting the development of accident-tolerant fuels, providing a deep understanding of materials suitable for the extreme environments associated with new reactor technologies, and providing unparalleled validation metrics for new science-based fuel performance codes.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
In-Pile Fuel Rod Deformation Measurements Using Miniaturized LVDT Technology
Different types of materials are being considered for fuel, cladding, and structures in existing and advanced nuclear reactors. These materials can undergo significant dimensional changes during irradiation. Currently in the US, such changes are measured with the ‘cook and look’ method (i.e. repeatedly irradiating a specimen for a specified period of time, and then removing it from the reactor for evaluation) – which leads to costly and time consuming experiments. In addition, such techniques provide limited data, and handling may disturb the phenomena of interest. Therefore, in-pile detection of geometric changes is needed to understand real-time behavior during irradiation testing of fuels and materials in high flux US Material and Test Reactors (MTRs). The developmental results of an advanced Linear Variable Differential Transformer (LVDT)-based test rig capable of detecting real-time changes in diameter or length of fuel rods or other material samples during irradiation in US MTRs are presented. The LVDT is being developed at the Idaho National Laboratory (INL), and will provide experimenters with the capability to measure dimensional changes associated with fuel and clad swelling, pellet-clad interaction, and crud buildup. The LVDT design utilizes the MTR’s loop pressure to drive the test specimen at a constant rate. This leads to a simplified construction which only requires three pressure boundary penetrations. Further, the LVDT pressure boundary is a leak tight hydraulic ram capable of actuating under low differential pressure (e.g. 1 psid), and is able to survive the high irradiation tests at Pressurized Water Reactor (PWR) conditions.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
FY17 Report for Instrumentation Development for the Transient Testing Program
This report details the technical activities and accomplishment carried out under the in-pile instrumentation work package supporting the transient testing program. These activities were performed in direct support of cross-cutting transient testing experiment objectives. The purpose of this report is to provide a complete summary of all work, which is of particular interest to nuclear irradiation test experimenters and in-pile instrumentation engineers with emphasis on transient testing applications. Development activities are focused on devices to perform online measurement of neutron flux, temperature, and mechanical behaviors in nuclear fuels experiments. A brief summary of activities and accomplishments is first provided for each major activity. Detailed reports are presented in appendices.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗