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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Pressure Drop-Flow Rate Curves for Single Phase Steam in Steam Generator U-tubes During Severe Accidents

Thermally induced steam generator tube rupture (TI-SGTR) can occur in pressurized water reactors (PWRs) with U-tube steam generators (SGs) during high pressure severe accident sequences resulting in containment bypass. Robust natural circulation patterns including in-vessel natural circulation and countercurrent flow to and from the SGs of superheated steam and other hot gases heats cooler structures in the reactor coolant system (RCS). The buoyancy driven flows return cooler and denser gases back to the core slowing the progression of some core degradation phenomena and failure of the lower head. As much as 50 percent of the decay energy and energy produced from core degradation oxidation reactions can be transported from the core to SGs resulting in the heat up and thermal creep of RCS pressure boundary components including hot leg nozzles, pressurizer surge line, and the SG tubes, many of which contain flaws. The creep failure of an individual tube is dependent on the transitory heating of the tube, a function of the mass flow rate through the tube and local temperature history of steam entering the tube. Buoyancy driven natural circulation flow rates are determined by changes in gravitational head, a combination of changes in fluid density due to heat transfer and change in elevation, and irreversible pressure drops resulting primarily from friction loss in the flow paths and other form losses. The nonuniform flow distribution in U-tubes of varying lengths and heights during single-phase liquid and two-phase natural circulation has been extensively studied in scaled test facilities and verified numerically in previous works. We hypothesize the countercurrent natural circulation of single-phase superheated steam in U-tube SGs is governed by the same characteristic pressure drop-flow rates curves of single-phase liquid and two-phase natural circulations in U-tubes connected to common plena derived in. Secondly, we propose flow distribution is a function of U-tube geometry - height, length, hydraulic diameter, etc., and the larger SGs of Combustion Engineering (CE) style 2 x 4 PWRs, which are the focus of this study, will show greater nonuniformity in tube by tube flow rates and ratio of forward flowing tubes to reverse flowing tubes. This work derives characteristic pressure drop-flow rate curves for single-phase superheated steam in CE-type SGs during a high pressure station blackout (SBO) sequence with failed auxiliary feedwater (AFW) and dry secondary side which is closely related to the TI-SGTR event. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Steam reforming of simulated bio-oil on K-Ni-Cu-Mg-Ce-O/Al 2 O 3 : The effect of K

Steam reforming of simulated bio-oil (ethanol, acetone, phenol, and acetic acid) and phenol has been studied on K-Ni-Cu-Mg-Ce-O/Al 2 O 3 composite catalysts. Complementary characterization techniques, such as nitrogen sorption, XRD, H2-TPR, H2-TPD, CO-TPD, CO-DRIFTS, and in situ XPS, were used to correlate surface structure and functionality to catalytic performance of potassium (K) doped catalysts. K doping of the Ni-Cu-Mg-Ce-O/Al 2 O 3 catalyst created a Ni°/Ni 2+ mixed active phase, which not only enhanced steam reforming activity, but also suppressed the methanation reaction. In addition, K doping changed the surface acid-basic properties of the catalyst, which instead favor the water-gas shift reaction. With the combination of these effects, K doping of Ni-Cu-Mg-Ce-O/Al 2 O 3 catalysts led to higher C1 yield and much lower methane formation, favoring hydrogen production in steam reforming of both phenol and simulated bio-oil.

Yu, Ning↗
DOE OSTI2019

High-Fidelity Simulation of Flow-Induced Vibrations in Helical Steam Generators for Small Modular Reactors

Flow-induced vibration (FIV) is a widespread problem in energy systems as they rely on fluid movement for energy conversion. Vibrating structures may be damaged as fatigue or wear occur. Given the importance of reliable components in the nuclear industry, FIV has long been a major concern in the safety and operation of nuclear reactors. In particular, nuclear fuel rods and steam generators have been known to suffer from FIV and related failures. In this paper we discuss the use of the computational fluid dynamics code Nek5000 coupled to the structural code Diablo to simulate the flow in helical coil heat exchangers and associated FIV. In particular, one-way coupled calculations are performed, where pressure and tractions data are loaded into the structural model. The main focus of this paper is on validation of this capability. Fluid-only Nek5000 large eddy simulations are first compared against dedicated high-resolution experiments. Then, one-way coupled calculations are performed with Nek5000 and Diablo for two data sets that provide FIV data for validation. These calculations were aimed at simulating available legacy FIV experiments in helical steam generators in the turbulent buffeting regime. In this regime one-way coupling is judged sufficient since the pressure loads do not cause substantial displacements. It is also the most common source of vibration in helical steam generators at the low flows expected in integral pressurized water reactors. We discuss validation of two-way coupled experiments and benchmarks toward the simulation of fluid elastic instability. We briefly discuss the application of these methods to grid-to-rod fretting.

Flow-Induced Vibration↗
DOE OSTI2020

Field-assisted suppression of coke in the methane steam reforming reaction

Electric fields were applied to an unsupported nickel catalyst during methane steam reforming with a low steam-to-methane ratio of 2:1. As expected, catalysts operated in standard mode (without an applied field) experienced high levels of coking. Coke formation was almost completely suppressed by the application of a positive electric field. This is explained using density functional theory computations which indicate that positive electric fields (1) increase the affinity for water adsorption on the surface, thereby increasing the amount of oxygen available to remove carbon, (2) stabilize individual carbon fragments, thus reducing their tendency to polymerize, and (3) increase the oxygen storage capabilities of the catalyst by inducing sub-surface oxygen formation and bulk oxidation.

Gray, Jake T.↗
DOE OSTI2017

Flow-induced vibration analysis of a helical coil steam generator experiment using large eddy simulation

This paper describes a numerical study of flow-induced vibration in a helical coil steam generator experiment conducted at Argonne National Laboratory in the 1980s. In the experiment, a half-scale sector model of a steam generator helical coil tube bank was subjected to still and flowing air and water, and the vibrational characteristics were recorded. The research detailed in this document utilizes the multi-physics simulation toolkit SHARP developed at Argonne National Laboratory, in cooperation with Lawrence Livermore National Laboratory, to simulate the experiment. SHARP uses the spectral element code Nek5000 for fluid dynamics analysis and the finite element code DIABLO for structural analysis. The flow around the coil tubes is modeled in Nek5000 by using a large eddy simulation turbulence model. Transient pressure data on the tube surfaces is sampled and transferred to DIABLO for the structural simulation. The structural response is simulated in DIABLO via an implicit time-marching algorithm and a combination of continuum elements and structural shells. Tube vibration data (acceleration and frequency) are sampled and compared with the experimental data. Currently, only one-way coupling is used, which means that pressure loads from the fluid simulation are transferred to the structural simulation but the resulting structural displacements are not fed back to the fluid simulation

CFD↗
DOE OSTI2013

Steam Oxidation of Fossil Power Plant Materials. Collaborative Research to Enable Advanced Steam Power Cycles

Research into improved materials systems and associated manufacturing and reliability issues is a major part of initiatives to produce cleaner and cheaper energy systems in the UK and the USA. Under the auspices of a Memorandum of Understanding on Energy R&D, a work programme concerned with steam oxidation has been conducted. The focus was on the generation of definitive information regarding the oxidation behaviour in steam of current and developmental ferritic steels, austenitic steels, and nickel-based alloys required to enable advanced steam power cycles. The results were intended to provide a basis for quantifying the rate of metal loss expected under advanced steam cycle conditions, as well as understanding of the evolution of oxide scale morphologies with time and temperature to identify features that could influence scale exfoliation characteristics. This understanding and acquired data were used to develop and validate models of oxide growth and loss by exfoliation. This paper provides an overview of the activity and highlights a selection of the results coming from the programme.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2015

Effect of Cobalt Particle Size on Acetone Steam Reforming

Abstract Carbon‐supported cobalt nanoparticles with different particle sizes were synthesized and characterized by complementary characterization techniques such as X‐ray diffraction, N 2 sorption, acetone temperature‐programmed desorption, transmission electron microscopy, and CO chemisorption. Using acetone steam reforming reaction as a probe reaction, we revealed a volcano‐shape curve of the intrinsic activity (turnover frequency of acetone) and the CO 2 selectivity as a function of the cobalt particle size with the highest activity and selectivity observed at a particle size of approximately 12.8 nm. Our results indicate that the overall performance of acetone steam reforming is related to a combination of particle‐size‐dependent acetone decomposition, water dissociation, and the oxidation state of the cobalt nanoparticles.

Sun, Junming↗
DOE OSTI2017

Operational Efficiency Evaluation of a Setup for Removing Stresses in the Steam Header of PGV-1000 Steam Generator

The effectiveness of a setup for removing stresses in the steam header of a PGV-1000 steam generator is evaluated. The evaluation is based on an investigation of the stress state by means of magnetic anisotropy measurements performed in the zone of the No. 111 weld seam of the hot header of steam generators operating in one of the power-generating units with a V-320 series reactor arrangement. Inspections made it possible to obtain cartograms of the distribution of the difference of the principal mechanical stresses along the perimeter of the weld connection of a PGV-1000 header equipped with a cooling mantle and headers without such a mantle. By means of statistical analysis of the data, a diagram of the distribution of the principal mechanical stresses was obtained. In addition, the distribution of the standard deviation of the principal mechanical stresses as a measure of the dispersion of a random quantity relative to its mathematical expectation was determined.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2012

Simulation of a main steam line break with steam generator tube rupture using trace

A simulation of the OECD/NEA ROSA-2 Project Test 5 was made with the thermal-hydraulic code TRACE5. Test 5 performed in the Large Scale Test Facility (LSTF) reproduced a Main Steam Line Break (MSLB) with a Steam Generator Tube Rupture (SGTR) in a Pressurized Water Reactor (PWR). The result of these simultaneous breaks is a depressurization in the secondary and primary system in loop B because both systems are connected through the SGTR. Good approximation was obtained between TRACE5 results and experimental data. TRACE5 reproduces qualitatively the phenomena that occur in this transient: primary pressure falls after the break, stagnation of the pressure after the opening of the relief valve of the intact steam generator, the pressure falls after the two openings of the PORV and the recovery of the liquid level in the pressurizer after each closure of the PORV. Furthermore, a sensitivity analysis has been performed to know the effect of varying the High Pressure Injection (HPI) flow rate in both loops on the system pressures evolution. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Synergistic Coupling of Proton Conductors BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3–δ and La 2 Ce 2 O 7 to Create Chemical Stable, Interface Active Electrolyte for Steam Electrolysis Cells

For the first time, proton conductors BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3–δ (BZCYYb) and La 2 Ce 2 O 7 (LCO) are combined to create an interface active and steam-tolerant electrolyte for high-performance proton-conducting solid oxide electrolysis cells. LCO shows good chemical compatibility with BZCYYb. The readily fabricated LCO/BZCYYb bilayer electrolyte can be densified at a temperature of as low as 1300 °C versus ~1600 °C for the benchmark steam-stable BaZr 0.8 Y 0.2 O 3–δ electrolyte. With Pr 2 NiO 4+δ as the anode and Ni as the cathode catalyst, this bilayer electrolyte cell yields a current density of 975 and 300 mA/cm 2 under a 1.3 V applied potential at 700 and 600 °C, respectively. This performance is among the best of all H-SOECs equipped with a chemically stable electrolyte so far. A BZCYYb layer in the bilayer electrolyte promotes the hydrogen evolution reaction at the cathode side, resulting in a 108% improvement over the cell without this layer. The LCO layer, on the other hand, effectively protects this functional BZCYYb layer from the high concentration of steam in a practical SOEC operation condition. The cell without the LCO layer shows degradation in terms of an increased electrolyzing potential from 1.07 to 1.29 V during a constant 400 mA/cm 2 operation at 700 °C. In contrast, the bilayer electrolyte cell maintains the same electrolyzing potential of 1.13 V under the same conduction for a 102 h operation. These findings demonstrate that this synergic bilayer electrolyte design is a vital strategy to overcome the dilemma between performance and stability faced by the current benchmark Zr- or Ce-rich Ba(CeZr)O 3–δ electrolysis cells to achieve excellent performance and stability at the same time.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Inspect and Repair Steam Traps - Steam Tip Sheet #1

This revised AMO tip sheet on inspecting and repairing steam traps provides how-to advice for improving industrial steam systems using low-cost, proven practices and technologies.

industry, manufacturing, AMO, inspect, repair, mai↗
DOE OSTI2017

Reducing Reaction Temperature, Steam Requirements, and Coke Formation During Methane Steam Reforming Using Electric Fields: A Microkinetic Modeling and Experimental Study

In this study, we approach several common problems with the Ni-catalyzed methane steam reformation reaction (MSR) using a two-pronged approach combining density functional theory (DFT) calculations with experimental work. Specifically, we look at the deactivation of a Ni catalyst due to coke formation, its high operating temperature requirements, and the high steam-to-methane (H 2 O/CH 4 ) ratio needed for proper MSR operation. A DFT-based microkinetic model was developed in the presence and absence of electric fields and the results were compared with experimental results. The microkinetic model shows that under various electric fields, the most favorable MSR mechanism changed slightly. It also shows that the presence of a positive electric field decreases the surface coverage of carbon, increases the water coverage, accelerates the rate-limiting step of the C-H bond cleavage in methane, and increases the desorption rates of the syngas product (CO + H 2 ) during MSR. Consequently, for a given methane conversion, a positive electric field allows for significantly lower H 2 O/CH 4 ratio and operating temperatures as compared to systems without an electric field. These findings correspond well with experimental tests under a variety of operating conditions. In addition, improvement in the catalytic activity due to the presence of a positive electric field remained significant even at industrially relevant applied pressures improving the hydrogen yield greatly. Overall, we find that an applied electric field can play a significant role in improving the catalytic activity of heterogeneous reactions. Here, this information can guide the design of heterogeneous reactions in the presence of an electric field. By utilizing the electric field generated by various renewable energy sources, electric field assisted heterogeneous reactions can open up a paradigm in future energy research.

03 NATURAL GAS↗