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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

INFN LASA in-kind contribution to PIP-II

This paper reports the status and recent progress of INFN LASA’s in-kind contribution to the PIP-II project at Fermilab, with updates on key activities and major procurements. Production efforts for the 38 INFN LASA-designed, 5-cell cavities (β=0.61) for the LB650 section of the linac are underway and two pre-series prototypes are being realized as a first step to validate the manufacturing and treatment sequence. Concurrently, preliminary testing on existing prototypes is progressing to gain a deeper understanding of the surface preparation and qualification procedures, including cross-validation at different infrastructures. Series LB650 cavities will be industrially produced and surface-treated to achieve the stringent performance targets, qualified via vertical cold tests at DESY AMTF, and delivered installation-ready for string assembly.

Paparella, Rocco [INFN, Pisa; LASA, Segrate]↗
DOE OSTI2023

PIP-II Project Overview and Status

The Proton Improvement Plan II (PIP-II) project is an essential upgrade to Fermilab’s particle accelerator complex to enable the world’s most intense neutrino beam for LBNF/DUNE and a broad particle physics program for many decades to come. PIP-II will deliver 1.2 MW of proton beam power from the Main Injector, upgradeable to multi-MW capability. The central element of PIP-II is an 800 MeV superconducting radio frequency (SRF) linac, which comprises a room temperature front end followed by an SRF section. The SRF section consists of five different flavors of cavities/cryomodules, including Half Wave Resonators (HWR), Single Spoke and elliptical resonators operating at, or above, state-of-the-art parameters. The first two PIP-II cryomodules, Half Wave Resonator (HWR) and Single Spoke Resonator 1 (SSR1) were installed in the PIP-II Injector Test facility (PIP2IT) and have accelerated beam to above 17 MeV. PIP-II is the first U.S. accelerator project that will be constructed with significant contributions from international partners, including India, Italy, France, United Kingdom and Poland. The project was baselined in April 2022, and the construction phase is underway.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

The ASD Scorpius Accelerator at the NNSS. Recruitment Slides for the University of Nevada, Reno [Slides]

The Scorpius Accelerator: Supports the maintenance of the US nuclear stockpile, helps the US not return to nuclear testing, is one of four diagnostics being installed 963 feet below ground, probes subcritical implosions of nuclear material, and supports the validation of LANL and LLNL computer codes. We are searching engineers and scientists with experienced in: Mechanical Engineering, Electrical Engineering, Pulsed Power, Plasma Physics, Controls, Diagnostics, and Fluids and pressure systems.

42 ENGINEERING↗
DOE OSTI2021

VTR Casting Furnace Conceptual Design

This TEV describes the development of a conceptual design for a fuel casting system to be used in the development and demonstration of fuel designs for the new Versatile Test Reactor (VTR). This system will be installed in the Fuel Manufacturing Facility (FMF). The system will be in a shielded glovebox and will be used to melt fuel materials and injection cast these materials into fuel slugs, which will further be used to fabricate fuel elements for the VTR. This TEV covers only the injection casting system itself. Operations such as removing the castings from the injection molds, trimming of the castings, and installation of the castings into fuel element cladding are beyond the scope of the TEV. The conceptual design herein is principally concerned with the mechanical portion of the casting system and does not include details of the control or power supply systems.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

LAMP Project Facility and Space Requirements

The project will require significant space over the lifetime of the project to successfully execute design, technology maturation, component testing and verification, and final removal and installation. The types of space required falls into three general categories: office, storage, and laboratory. Figure 1 below summarizes the project space requirements by project lifecycle. The specific color coding indicates the availability (and potential risk to the project) of the particular type of space: green indicates space that is already allocated and in use by the LAMP project; yellow indicates space that is expected to be easily transitioned from its current use to the project; red indicates a space that is use by multiple users or other projects, and will most likely require high-level negotiations and planning to become available to the project. Figure 2 summarizes the LAMP Space Requirements by calendar year and type throughout the duration of the project. As can be seen in Fig. 2, the maximum space needed by the project exceeds 40,000 square feet, with an average space requirement over the lifetime of the project equal to approximately 25,000 square feet.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Nuclear Material Control and Accountancy Approach for Pebble Fueled Reactors using a Novel Pebble-Type Identification and Classification Technology

In FY21, Argonne National Laboratory (ANL) with researchers at Texas A&M University (TAMU) designed and engineered a prototypical device for accounting types of irradiated pebbles (for example with different 235U enrichments or pure graphite) in Pebble-Fueled Reactors (PFRs). Through engagements with reactor designers, a need arose to assist in identifying and categorizing types of pebbles as a complementary nuclear material control method that would synergize with designers’ use of fuel burnup measurements for material accountancy needs. As part of an overall nuclear material control approach, a concept of pebble batch accounting was investigated using extrinsic non-radiological features to identify intrinsic characteristics. This concept of batch accounting led to the ability of identifying types of pebbles based on characteristics such as initial 235U enrichment of pebble batches or dates of introduction into the reactor core. Identification was achieved by embedding the 5-mm thick graphite periphery of pebbles with 2-mm diameter inert Yttria-Stabilized Zirconia (YSZ) microspheres to achieve an averaged volumetric density (i.e., common spacing between microspheres) unique to that type of pebble. With an ultrasound imaging system in proximity with each pebble, the YSZ microspheres in the pebble proved visible and their spacing became the unique feature upon which pebble type categorization could occur. At the culmination of FY21, ANL intended on delivering and installing the prototype at TAMU for initial testing but, due to the on-going pandemic, this was postponed until FY22.

Gariazzo, Claudio↗
DOE OSTI2020

Interdigital Capacitance Sensor for Cable Insulation Test and Monitoring

A substantial body of work suggests feasibility to measure cable jacket and insulation conditions using various forms of interdigital capacitance (IDC) sensors. The sensors can either be used to manually test local cable conditions or as permanently installed sensors. Eligible cables subject to these measurements do not include shielded cables but the set of candidate cables is expanded from only unjacketed cables by the ability to assess insulation condition through the jacket. Dual gap IDC sensors are confirmed to be able to sense the insulation condition beneath a polymer jacket and, moreover, the IDC is the only known way to assess the insulation condition through the jacket. PNNL has filed a patent for this approach and is exploring commercial partnerships to exploit IDC technology for actionable field measurements.

NDE, cable, IDC, capacitance, permittivity, insula↗
DOE OSTI2022

CISCC Countermeasures for Spent Fuel Canisters in Concrete Casks

Aging management of spent fuel is an important issue worldwide. Chloride-induced stress corrosion cracking (CISCC) of welded canisters is particularly important for concrete casks, where it occurs in response to a combination of environmental, material, and residual stress factors. In this paper, we introduce a countermeasure to prevent the occurrence of CISCC by adjusting the flow rate of the cooling air into the concrete cask so that the canister surface temperature does not decrease below 100°C, which is a conservative deliquesce temperature threshold for CISCC occurrence. The flow adjustment device was installed in a cask model, and two tests were conducted under the heat rate conditions corresponding to those of an actual canister. In the first test, the device was operated under a condition where the canister surface temperature was below 100°C to verify whether it could increase the canister surface temperature to above 100°C. In the second test, the heat rate was decreased from a state where the canister surface temperature was above 100°C, to verify whether the device could maintain the canister surface temperature above 100°C. Good results were obtained in both cases. However, in the case of a low decay heat rate of spent fuel after extended dry storage, the temperature of the canister surface may decrease below 100°C even if no air supply is provided. Therefore, in this case, it may be necessary to take measures such as blocking air outlets.

Takeda, Hirofumi↗
DOE OSTI2024

SPC-71145 Rev 0 MARVEL Process Heat Extraction System Conceptual Design

The Microreactor Applications Research Validation and Evaluation (MARVEL) reactor will offer experimental capabilities that are not currently available at DOE’s national laboratories. The MARVEL reactor is a microreactor which uses eutectic sodium-potassium alloy (NaK) as a primary coolant. The primary coolant is circulated through four primary loops by natural convection of the coolant. In each loop is a closed well which will accommodate an intermediate heat exchanger (IHX) for extracting heat from the loop. These wells will be referred to in this specification as the “IHX wells”. It is intended for the IHX containment to also be filled with NaK. The MARVEL design team is currently looking for alternative means of extracting heat from these wells to be utilized in downstream applications. This Heat Utilization System (HUS) will enable MARVEL operations including the ability to test, demonstrate, and address issues related to installation, startup, and operations. In addition, it will allow down-stream utilization of process heat for various uses. Depending on the methodology used, the interface between the secondary coolant and the HUS is the Process Heat Extraction System (PHES) and is the subject of this specification.

21 - SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLAN↗
DOE OSTI2024

Offshore Wind Turbine Blade (85 to120meters ultra-long blade) static and fatigue test

Offshore blades are not just longer, they are wider, heavier and more flexible. These longer blades are a key component of larger wind turbines and for turbines to be more efficient in low wind speeds. These longer blades help reduce the LCOE further and make offshore wind even more competitive. As described earlier, it is essential for the blades to be fully tested to verify and validate the blade designs and manufacturing processes to ensure a reliable product is installed in the field. Through this project WTTC developed and procured new testing equipment required to test longer blades with larger deflections and higher loads. R&D’s BCDA system commissioned was the largest fatigue test exciter system in the world and set the bar for other blade testing facilities worldwide.

17 WIND ENERGY↗
DOE OSTI2023

Multipacting Processing in Cryomodules For LCLS-II And LCLS-II-HE

Multipacting (MP) is a phenomenon which can affect stability in particle accelerators and limit performance in superconducting radio frequency cavities. In the TESLA shaped, 1.3 GHz, 9-cell cavities used in the LCLS-II (L2) and LCLS-II-HE (HE) projects, the MP-band (~17-24 MV/m) lies within the required accelerating gradients. For HE, the operating gradient of 20.8 MV/m lies well within the MP-band and cryomodule testing has confirmed that this is an issue. As such, MP processing for the HE cryomodule test program will be discussed. Early results on MP processing in cryomodules installed in the L2 linac will also be presented, demonstrating that the methods used in cryomodule acceptance testing are also successful at conditioning MP in the accelerator and that this processing is preserved in the mid-term.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Report of METL Mutual Inductance Level Sensor Development for Use in Liquid Metals – FY2023

A robust mutual inductance level sensor (MILS) for use in high temperature liquid metals has been developed at Argonne National Laboratory (ANL). The current design utilizes mineral insulated cables with a 300-series stainless steel sheath, magnesium oxide insulation, and a single copper conductor. Two coils are wrapped on a common core made of a 300-series stainless steel tube. One coil is energized with an alternating current (AC) source, and this electromagnetically couples with the second coil to generate an induced voltage. The voltage is measured to determine the mutual induction between the coils, and the mutual inductance measurement can be used to determine the level of a nearby liquid metal volume. The MILS can be located in an isolating thimble that is fully sealed to a vessel containing liquid metal for ease of maintenance and replacement. When the primary coil is energized with the AC source, the coil not only electromagnetic (EM) couples with the second coil, but also the surrounding liquid metal. The EM coupling with the surrounding liquid metal reduces the EM coupling with the second coil, producing an inverse-linear relationship between liquid metal level and secondary coil voltage. This has all been demonstrated at the Mechanisms Engineering Test Loop (METL) liquid sodium facility at ANL. The most current iteration of the MILS system is the MILS-MK-II. This sensor system has been commissioned in a non-sodium test stand where calibrations were performed using a sodium analog. The calibrations proved to be highly linear and repeatable. The MILS-MK-II has been installed in the METL expansion tank where high temperature sodium tests have been performed. The MILS-MK-II has been calibrated against a known standard at temperature of 300°C, and the calibrations have proved to be highly linear and repeatable. The calibrated MILS-MK-II has been in operation in the METL facility for several thousands of hours at temperatures around 300°C. The experimental data has been used to develop and validate electromagnetic finite element models in COMSOL Multiphysics, and now these models can be used to advance the development of the sensor system. Next steps will include temperature compensation to allow for operation at various temperatures. Additionally, efforts to incorporate a self-calibration methodology are underway.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Technology Demonstration of a High-Pressure Swirl Oxy-Coal Combustor

This technical report presents the exploration of the design and prototyping of a High-Pressure Swirl Oxy-coal Combustor. Pressurized oxy-coal combustion systems have the potential to improve efficiency along with an increased carbon capture rate. Reduction of flue gas at higher pressure, smaller system size, and capital cost reductions render high-pressure oxy-coal systems particularly attractive as next-generation energy-producing systems. High-pressure oxy-coal combustion systems are a recent concept, and thus operability issues of combustor designs for such systems are not fully understood. Significant challenges exist to maintain oxy-coal combustion stability at elevated pressure and a high CO 2 diluent environment. Although a body of knowledge exists for high-pressure oxygen combustion in rocket engines (or similar applications), it is yet to be strategized how these fundamental concepts can be translated to low-temperature CO 2 diluent combustion regimes. The realization of the pressurized oxy-coal based systems requires combustor components to be designed and demonstrated for an operating pressure over 10 bar. However, pressurized oxy-coal combustor design information at this pressure range and scale relevant to validate those proposed systems is currently limited. Experimental data from MWth scale oxy-coal combustors are needed to identify the optimal trade-off between net efficiency and systems size. The proposed effort is aimed at demonstrating a 1 MWth down-fired swirl Oxy-Coal combustor and investigate the interrelation between combustor operating conditions (pressure; flame stability; flue gas recirculation ratio) and conversion efficiencies to minimize oxygen requirements. One of the key challenges is to configure burner design (i.e., swirl number and injector) and operating conditions for high-pressure oxy-coal combustion systems. These experiments differ from current systems partly due to the high theoretical flame temperature and related burner operability issues associated with oxy-combustion. An ASPEN PLUS® model study for 550 MWe TIPS and ENEL pressurized oxy-coal systems with CO 2 recirculation was performed to evaluate system design, subsystems sizing, and operating condition determination. The system analysis effort included TRL and technology gap determination of subsystems and critical components. This information was scaled to develop design requirements (design pressure and flue gas recirculation: RR Flue Gas = $\frac{m_{flue}}{m_{total}}$) for the 1 MWth combustor. The effects of a wide range of carbon dioxide recirculation ratios on the thermal efficiency of ENEL and TIPS cycles are studied. The pressure of 10 bar and 80 bar are used for ENEL and TIPS cycles, respectively. The thermal efficiency of ENEL is significantly higher than the efficiency of TIPS at a pressure of less than 10 bar. The insights from system analysis were then used to design a 1 MWth swirl oxy-coal combustor. Flame temperature analysis and material strength analysis was performed to determine the combustor thickness. The structural integrity of the combustor was validated by finite element analysis using Abacus® and Hypermesh®. Feasibility of igniters and secondary burners are investigated in successful high-pressure oxy-methane combustion. The secondary burners are designed in such a way that it can operate between 100 to 500 kW firing input. Three generations of the pintle injector were designed based on swirl numbers (S=0, 0.9, and 1.2). Key pintle injector parameters such as pintle size, pintle orifice size, spray pattern were investigated by cold flow tests. Information from these tests was used to modify injector design for smooth and successful operation. A 5 mm pintle orifice size was decided upon as the optimum size for oxy-coal operation for the combustor. Shadow sizing experiments were performed to identify the atomization rate of each injector. Different coal water slurry mixtures (30 – 50% coal by wt% in the mixture) at various total momentum ratios (TMR) were investigated for this purpose. These experiments provided decisive information to choose the best design of the injector. The injector with 1.2 swirl provided higher atomization in all cases than other designs. The mean equivalent droplet size of the jet was similar at different TMR and mixture ratios using this injector, thus making it suitable for use in most cases. Therefore, the 1.2 swirl-pintle injector was chosen for the shakedown test. The combustor and other sub-systems, including feed systems and control and data acquisition, have been manufactured, assembled, and integrated. The total system integration and installation began on July 1, 2020. The shake-down tests and initial operational capability demonstration are expected to be completed by September 30, 2020.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2024

FY24 Report on Water NSTF Testing: Lower Tank Inlet Piping Configuration

The following report serves as a summary of the accomplishments and testing results by the Natural convection Shutdown heat removal Test Facility (NSTF) experimental program over the past 12-month period. A major activity included reconfiguration of the chimney piping geometry which altered the discharge position into the tank from the original 50% tank height to a new lower position at a 10.9% tank height. This modification increases the volume of available coolant thus extending long-term operating capacity, however also results in a decreased liquid driving head which has the potential to reduce the natural circulation efficiency and decrease overall performance. Examination of the tradeoffs for these two configurations is an area of interest for RCCS designers and drove planned test activities this year. Ten matrix tests were performed in FY24, totaling 195 hours of heated operations and 12.9 MWh of electrical heating throughout the year, with eight classified as Accepted per NQA-1 and two classified as Trending. Testing prior to the facility reconfiguration examined the facility response to throttling at the tank inlet, demonstrating increased sensitivity of flow instabilities to throttling within the two-phase region when compared to throttling at the lower sensitivity single-phase inlet region. Testing after the chimney reconfiguration began with a baseline test at conditions of 80% inventory fill and prototypic thermal power input of 2.1 MW t . In addition to establishing a reference for nominal system behavior and performance, repeat testing with multiple subsequent runs demonstrated strong repeatability between tests performed at the same conditions in this new configuration. These tests also examined if influences would occur to system behavior with installation of new higher-resolution instrumentation within the upper chimney. In this critical region where boiling and flashing phenomena dominate, the test results provided confidence that the new instrumentation does not uncharacteristically influence the observed behaviors. An inventory parametric series was then initiated to examine system behavior with the new chimney configuration at six varying initial inventory levels, ranging from high 80% to low 20% fill. Two-phase oscillations with similar peak and mean flow rates were observed when comparing to the previous mid tank configuration. Generally, similar system response trends with inventory were also observed, such as two phase oscillations suppressing as inventories were lowered. However, in one absolute inventory comparison at the highest fill of 80%, flow oscillations saw a gradual growth over the 4 hours of two-phase operation in the new lower tank inlet configuration, opposite of the gradual dampening observed in the mid tank inlet configuration. This can be attributed to, in part, a greater hydrostatic head pressure above the two-phase discharge region where the boiling front is developed. Furthermore, the change resulted in greater sensitivity to liquid degassing phenomena during single-phase heating, causing loop instabilities to form which trigged moderate flow degradation during the period approaching saturation and boiling conditions. This behavior had been observed previously under some conditions but was a common occurrence in recent testing with the newer lower tank inlet configuration. Initial observations from these first data sets suggest an overall larger window of stability for the mid tank inlet configuration compared to the lower tank inlet. Lastly, the lowest inventory fill test was repeated over an extended testing window to examine depletion behavior. Natural circulation flow and effective heat removal performance were observed during most of the testing period; only after the tank became fully drained (0% fill) did flow stagnate and violent geysering events occur. This early observation confirms one relative advantage over the mid tank inlet configuration, which stagnated under comparable conditions at ~20% inventory remaining in the tank.

42 ENGINEERING↗
DOE OSTI2025

MaPSA Quality Control and AI-Enhanced Grading For the CMS Phase-II Tracker Upgrade

The Compact Muon Solenoid (CMS) experiment will undergo changes as part of the Large Hadron Collider upgrade. The CMS tracker will be upgraded to cope with the new radiation environment and to provide tracking at the first level trigger. This upgrade features a new type of silicon module called PS Module, which combines a Pixel sensor and a Strip sensor in the same module. The pixel portion of the PS module has a sensor bump bonded to 16 Macro Pixel ASICs (MPA) to form a Macro Pixel Sub Assembly (MaPSA). At Fermilab, MaPSAs are tested for quality control before being assembled with the strip sensors, readout and service electronics to form a PS Module. All of this test data is stored in a centralized database, and is used to grade the final module to determine if it will be installed in the detector. The Phase II Outer Tracker Analyzer of Test Outputs (POTATO) is the software that processes this data and determines the module grades. Using recent technologies, an AI agent is being im plemented into POTATO in order to allow users to more efficiently sort through the large amounts of analysis data and ensure that only the user specified data is being considered. This poster will display the process of testing a MaPSA, how that test data is relevant to module assembly and grading, and how the POTATO grading tool is being improved with the use of an embedded AI agent.

Gzamouranis, Olivia [Purdue U.]↗
DOE OSTI2021

Summary of Thermocouple Performance in the Advanced Gas Reactor Experiment AGR-5/6/7 During Irradiation in the Advanced Test Reactor

The Advanced Gas Reactor -5/6/7 (AGR-5/6/7) experiment was the fourth and final experiment in the AGR experiment series and completed irradiation in July 2020. It serves as the formal fuel qualification test for the TRISO fuels under development by the US Department of Energy. This experiment was designed to irradiate fuel particles at temperatures ranging from 800°C ? 1500°C. The high end of the range created unique challenges for thermocouple-based temperature measurements. Commercially available high-temperature platinum-rhodium thermocouples (Types S, R, and B) and tungsten-rhenium thermocouples (Type C) suffer rapid decalibration due to transmutation of the thermoelements from neutron absorption. A special low neutron cross-section thermocouple system based on molybdenum/niobium thermoelements called High Temperature Irradiation Resistant thermocouple (HTIR-TC) has been under development at INL since circa 2004. Several examples of this thermocouple type were incorporated into regions of the test operating above 1200°C. For regions in the test operating in the 1000°C ? 1200°C range, high-performance versions of Type N thermocouples recently developed at Cambridge University were installed. Standard Type N thermocouples were used in regions of the test operating below 1000°C. A total of 54 thermocouples were incorporated into the test. A report of the performance of this large heterogenous set of thermocouples over the first third of the irradiation was previously provided (ANIMMA 2019). This follow-on paper discusses results from the balance of the experiment (Feb 2019 - July 2020). Special attention is focused on potential drift of thermocouples operating in the higher temperature regions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Summary of Thermocouple Performance in the Advanced Gas Reactor Experiment AGR-5/6/7 During Irradiation in the Advanced Test Reactor

This is a conference presentation ppt file. The following abstract is for the entire conference paper - which will later be the subject of a PRS artifact The Advanced Gas Reactor -5/6/7 (AGR-5/6/7) experiment was the fourth and final experiment in the AGR experiment series and completed irradiation in July 2020. It serves as the formal fuel qualification test for the TRISO fuels under development by the US Department of Energy. This experiment was designed to irradiate fuel particles at temperatures ranging from 800°C ? 1500°C. The high end of the range created unique challenges for thermocouple-based temperature measurements. Commercially available high-temperature platinum-rhodium thermocouples (Types S, R, and B) and tungsten-rhenium thermocouples (Type C) suffer rapid decalibration due to transmutation of the thermoelements from neutron absorption. A special low neutron cross-section thermocouple system based on molybdenum/niobium thermoelements called High Temperature Irradiation Resistant thermocouple (HTIR-TC) has been under development at INL since circa 2004. Several examples of this thermocouple type were incorporated into regions of the test operating above 1200°C. For regions in the test operating in the 1000°C ? 1200°C range, high-performance versions of Type N thermocouples recently developed at Cambridge University were installed. Standard Type N thermocouples were used in regions of the test operating below 1000°C. A total of 54 thermocouples were incorporated into the test. A report of the performance of this large heterogenous set of thermocouples over the first third of the irradiation was previously provided (ANIMMA 2019). This follow-on paper discusses results from the balance of the experiment (Feb 2019 - July 2020). Special attention is focused on potential drift of thermocouples operating in the higher temperature regions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Advancing reliability assessments of photovoltaic modules and materials using combined-accelerated stress testing

Previously undiscovered failure modes in photovoltaic (PV) modules continue to emerge in field installations despite passing protocols for design qualification and quality assurance. Failure to detect these modes prior to widespread use could be attributed to the limitations of present-day standard accelerated stress tests (ASTs), which are primarily designed to identify known degradation or failure modes at the time of development by applying simultaneous or sequential stress factors (usually two at most). Here, we introduce an accelerated testing method known as the combined-accelerated stress test (C-AST), which simultaneously combines multiple stress factors of the natural environment. Simultaneous combination of multiple stress factors allows for improved identification of failure modes with better ability to detect modes not known a priori. A demonstration experiment was conducted that reproduced the field-observed cracking of polyamide- (PA-) and polyvinylidene fluoride (PVDF)–based backsheet films, a failure mode that was not detected by current design qualification and quality assurance testing requirements. In this work, a two-phase testing protocol was implemented. The first cycle (“Tropical”) is a predominantly high-humidity and high-temperature test designed to replicate harsh tropical climates. The second cycle (“Multi-season”) was designed to replicate drier and more temperate conditions found in continental or desert climates. Testing was conducted on 2 × 2-cell crystalline-silicon cell miniature modules constructed with both ultraviolet (UV)–transmitting and UV-blocking encapsulants. Cracking failures were observed within a cumulative 120 days of the Tropical condition for one of the PA-based backsheets and after 84 days of Tropical cycle followed by 42 days of the Multi-season cycle for the PVDF-based backsheet, which are both consistent with failures seen in fielded modules. In addition to backsheet cracking, degradation modes were observed including solder/interconnect fatigue, various light-induced degradation modes, backsheet delamination, discoloration, corrosion, and cell cracking. The ability to simultaneously apply multiple stress factors may allow many of the test sequences within the standardized design qualification procedure to be performed using a single test setup.

14 SOLAR ENERGY↗