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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Quantitative Voltammetry Measurements of High-Concentration Actinides in Molten Chloride Fuel Salts

Molten chloride mixtures containing high concentrations of UCl 3 (i.e., >70 wt%) are candidates for next-generation molten salt reactor (MSR) fuel salts that enable new plant optimization and fuel cycle strategies. MSR licensing, however, is contingent on the development of effective material control and accounting (MC&A) practices for these salts. To close this gap, we have developed an electroanalytical approach that enables accurate in situ measurements of uranium concentrations in these highly loaded fuel salts. This methodology uses a multielectrode array voltammetry sensor combined with digital simulations that account for non-idealities such as uncompensated resistance effects. The theory-based numerical simulations of voltammetry responses yielded correction factors that are agnostic of electrochemical cell geometry and produced consistent voltammetry peak current results when correcting for varying amounts of ohmic resistance. In doing so, we have demonstrated accurate concentration measurements for UCl 3 in LiCl-KCl-UCl 3 across a range of mass fractions between 55 and 72.3 wt% at 550 °C.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

TRU BISON Simulation Overview [Slides]

The BISON fuel performance code has been used to model minor actinide (MA) bearing metallic ternary fuel. This presentation gives an overview on the progress made so far on this effort, focusing on the modeling of EBR-II experiment X501-G591. Comparisons with PIE have also been made.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Dynamic Control of Sodium Cold Trap Purification Temperature Using LSTM System Identification

This study investigates the dynamic regulation of the sodium cold trap purification temperature at Argonne National Laboratory’s liquid sodium test facility, employing long short-term memory (LSTM) system identification techniques. The investigation introduces an innovative hybrid approach by integrating model predictive control (MPC) based on first principles dynamic models with a multi-step time–frequency LSTM model in predicting the temperature profiles of a sodium cold trap purification system. The long short-term memory–model predictive controller (LSTM-MPC) model employs a sliding window scheme to gather training samples for multi-step prediction, leveraging historical data to construct predictive models that capture the non-linearities of the complex system dynamics without explicitly modeling the underlying physical processes. The performance of the LSTM-MPC and MPC were evaluated through simulation experiments, where both models were assessed on their capacity to maintain the cold trap temperature within predefined set-points while minimizing deviations and overshoots. Results obtained show how the data-driven LSTM-MPC model demonstrates stability and adaptability. In contrast, the traditional MPC model exhibits irregularities, particularly evident as overshoots around set-point limits, which can potentially compromise its effectiveness over long prediction time intervals. The findings obtained offer valuable insights into integrating data-driven techniques for enhancing real-time monitoring systems.

LSTM-MPC↗
NASA NTRS1972

An out-of-core version of a six cell heat-pipe heated thermionic converter array

A thermionic system concept is described which incorporates a heat-pipe cooled fast spectrum reactor and six-cell thermionic converter modules located in the space radiator. Much of the technology being developed for the in-core thermionic reactor concept is directly applicable to this out-of-core concept, particularly the fuel and converter development activity. The major technology extension required is in the area of heat-pipes for cooling the reactor and carrying thermal energy from the reactor station to the converters. The performance characteristics of an out-of-core thermionic system at power levels between 40 and 70 kWe are summarized, the adaptation of in-core technology to the out-of-core concept is described and applicable heat-pipe technology programs now underway are discussed.

Kroeger, E. W.↗
NASA NTRS1973

International Symposium on Combustion, 14th, Pennsylvania State University, University Park, Pa., August 20-25, 1972, Proceedings.

Some elementary steps for the formation and destruction of nitric oxide in the H-N-O system, high-temperature oxidation of hydrogen by nitrous oxide in shock waves, and high-temperature fast-flow reactor studies of metal-atom oxidation kinetics are among the topics covered in papers concerned with elementary reactions in combustion. Other areas covered include oscillatory, turbulent, and supersonic combustion; flames in furnaces and combustors; and pollutant formation and destruction in flames. Individual items are announced in this issue.

Source record↗
NASA NTRS1976

System Design for a Nuclear Electric Spacecraft Utilizing Out-of-core Thermionic Conversion

Basic guidelines are presented for a nuclear space power system which utilizes heat pipes to transport thermal power from a fast nuclear reactor to an out of core thermionic converter array. Design parameters are discussed for the nuclear reactor, heat pipes, thermionic converters, shields (neutron and gamma), waste heat rejection systems, and the electrical bus bar-cable system required to transport the high current/low voltage power to the processing equipment. Dimensions are compatible with shuttle payload bay constraints.

Estabrook, W. C.↗
NASA NTRS1976

Thermodynamic properties of a high pressure subcritical UF6/He gas volume (irradiated by an external source)

A computer simulation study concerning a compressed fissioning UF6 gas is presented. The compression is to be achieved by a ballistic piston compressor. Data on UF6 obtained with this compressor were incorporated in the simulation study. As a neutron source to create the fission events in the compressed gas, a fast burst reactor was considered. The conclusion is that it takes a neutron flux in excess of 10 to the 15th power n/sec sq cm to produce measurable increases in pressure and temperature, while a flux in excess of 10 to 19th power n/sq cm sec would probably damage the compressor.

Sterritt, D. E.↗
NASA NTRS1980

Nuclear-induced excimer fluorescence

A theoretical calculation of a proposed atomic iodine laser system excited by a nuclear-powered photon source is considered. Overall system efficiency of 1.6% is calculated for the KrF fluorescent system and 2.3% for the Ar2F system. Laser power output of about 30 kW is estimated for a laser tube 1.8 cm in diameter and 60 cm long when used with a fast burst reactor. Such systems should easily scale to very high power.

Wilson, J. W.↗
NASA NTRS1980

Absolute concentrations of O/3P/ in the lower thermosphere at night

A rocketborne instrument module for detecting atomic oxygen concentrations by the resonance fluorescence technique is reported. The module contained a source lamp emitting O I 1304 A photons and a detector for the scattered photons. The module was constructed so that it could be coupled to a fast flow reactor for calibration purposes. During the flight the module was radially deployed from the payload on an oscillating boom with a maximum extension of 90 cm from the skin. Analysis of the initial flight data indicates that the shock formed by the motion of the rocket had a substantial effect on the data and the maximum concentration of the layer at 93 km was about 1.1 x 10 to the 11th/cu cm.

Sharp, W. E.↗
NASA NTRS1983

Constitutive Equations for Use in Design Analyses of Long-life Elevated Temperature Components

Design analysis needs and procedures relative to elevated temperature components in liquid metal fast breeder reactor (LMFBR) system were examined. The effects of the thermal transients on the pressure boundary components are enhanced by the excellent heat transfer properties of the liquid sodium coolant. Design criteria for high temperature nuclear reactor components recognize the potential occurrence of inelastic structural response. Specifically, criteria and limits were developed which reflect a recognition of this potential and employ design by analysis concepts that requires that inelastic (elastic-plastic and creep) analyses be performed. Constitutive equations to represent multiaxial time-dependent responses of LMFBR alloys are established. The development of equations applicable under cyclic loading conditions are outlined.

Pugh, C. E.↗
NASA NTRS1985

Analytical simulation of weld effects in creep range

The inelastic analysis procedure used to investigate the effect of welding on the creep rupture strength of a typical Liquid Metal Fast Breeder Reactor (LMFBR) nozzle is discussed. The current study is part of an overall experimental and analytical investigation to verify the inelastic analysis procedure now being used to design LMFBR structural components operating at elevated temperatures. Two important weld effects included in the numerical analysis are: (1) the residual stress introduced in the fabrication process; and (2) the time-independent and the time-dependent material property variations. Finite element inelastic analysis was performed on a CRAY-1S computer using the ABAQUS program with the constitutive equations developed for the design of LMFBR structural components. The predicted peak weld residual stresses relax by as much as 40% during elevated temperature operation, and their effect on creep-rupture cracking of the nozzle is considered of secondary importance.

Dhalla, A. K.↗
NASA NTRS1988

Laboratory studies of sticking coefficients and heterogeneous reactions important in the Antarctic stratosphere

Laboratory studies of sticking coefficients of H2O, HCl, Cl2, and HNO3 on ice and heterogeneous reactions of ClONO2 with ice or HCl/ice have been performed in a fast flow reactor. A quadrupole mass spectrometer with electron impact ionization was used as a detector. Measured sticking coefficients are: 0.3 (+0.7, -0.1) for H2O, 0.4 (+0.6, -0.2) for HCL, less than 0.0001 for Cl2, and 0.3 (+0.7, -0.1) for HNO3 at 200 K. The reaction probability of ClONO2 on ice was found to be 0.06 (+ or - 0.03) while HOCl was observed as a sole product in the gas phase. With HCl present in ice, the reaction probability of ClONO2 is greatly enhanced, approaching 0.27 (+0.73, -0.13) while molecular chlorine was found to be the major product in the gas phase. Another reaction product was nitric acid which remained in the solid phase. Since the polar stratospheric clouds contain ice particles or possibly HCl/ice particles on the surface, the present results should be a major factor in producing the observed springtime ozone depletion in the Antarctic stratosphere.

Leu, Ming-Taun↗
NASA NTRS1988

Heterogeneous reactions of N2O5 with H2O and HCl on ice surfaces - Implications for Antarctic ozone depletion

This paper reports on the measurements of reaction probabilities for heterogeneous reaction of N2O5 with H2O and HCl on ice surfaces at 195 K, using a fast-flow reactor coupled with a quadrupole mass spectrometer. The reaction probability for N2O5 on pure-water ice was found to be 0.028 + or - 0.011, with nitric acid in the solid phase as the sole product. In the presence of HCl in ice, the probability of N2O5 reaction was enhanced (to 0.037); the reaction produced, besides solid-phase nitric acid, ClNO2 and ClONO which were released into the gas phase within a few milliseconds. The latter two compounds can be readily photolyzed in the austral spring to form active chlorine which would remove stratospheric ozone. It is suggested that, since the polar stratospheric clouds are believed to contain HCl-ice mixture on the surface, the reactions of N2O5 on H2O/HCl particles is a major factor in the Antarctic springtime ozone depletion.

Leu, Ming-Taun↗
NASA NTRS1991

Heterogeneous reactions of chlorine nitrate and hydrogen chloride on type I polar stratospheric clouds

A fast-flow reactor coupled with a quadrupole mass spectrometer was used to study the heterogeneous reactions ClONO2 + HCl yields Cl2 + HNO3 (1) and ClONO2 + H2O yields HOCl + HNO3 (2) on vapor-deposited HNO3-H2O ice substrates. It was found that the sticking coefficient of HCl on these substrates was a strong function of the substrate composition, ranging from about 2 x 10 exp -5 at nitric acid trihydrate composition to 6 x 10 exp -3 at 45 wt pct HNO3. The HNO3-H2O ice substrates were found to have large internal surface areas, and corrections for gas-phase diffusion within the porous ices were applied to observed loss rates.

Leu, Ming-Taun↗
NASA NTRS1994

Heterogeneous Reactions of ClONO2, HCl, and HOCl on Liquid Sulfuric Acid Surfaces

The heterogeneous reactions of ClONO2 + H2O yields HNO3 + HOCl (1), ClONO2 + HCl yields C12 + HNO3 (2), and HOCl + HCl yields Cl2 + H2O (3) on liquid sulfuric acid surfaces have been studied using a fast flow reactor coupled to a quadrupole mass spectrometer. The main objectives of the study are to investigate: (a) the temperature dependence of these reactions at a fixed H2O partial pressure typical of the lower stratosphere (that is, by changing temperature at a constant water partial pressure, the H2SO4 content of the surfaces is also changed), (b) the relative importance or competition between reactions 1 and 2, and (c) the effect of HNO3 on the reaction probabilities due to the formation of a H2SO4/HNO3/H2O ternary system. The measurements show that all the reactions depend markedly on temperature at a fixed H2O partial pressure: they proceed efficiently at temperatures near 200 K and much slower at temperatures near 220 K. The reaction probability (gamma(sub 1)) for ClONO2 hydrolysis approaches 0.01 at temperatures below 200 K, whereas the values for gamma(sub 2) and gamma(sub 3) are on the order of a few tenths at 200 K. Although detailed mechanisms for these reactions are still unknown, the present data indicate that the competition between ClONO2 hydrolysis and ClONO2 reaction with HCl may depend on temperature (or H2SO4 Wt %): in the presence of gaseous HCl at stratospheric concentrations, reaction 2 is dominant at lower temperatures (less than 200 K), but reaction 1 becomes important at temperatures above 210 K. Furthermore, reaction probability measurements performed on the H2SO4/HNO3/ H2O ternary solutions do not exhibit noticeable deviation from those performed on the H2SO4/H2O binary system, suggesting little effect of HNO3 in sulfate aerosols on the ClONO2 and HOCl reactions with HCl. The results reveal that significant reductions in the chlorine-containing reservoir species (such as ClONO2 and HCl) can take place on stratospheric sulfate aerosols at high latitudes in winter and early spring, even at temperatures too warm for Polar Stratospheric Clouds (PSCs) to form or in regions where nucleation of PSCs is sparse. This is particularly true under elevated sulfuric acid loading, such as that after the eruption of Mt. Pinatubo. Comparisons between our results and those presently available have also been made.

Zhang, Renyi↗
NASA NTRS1994

Heterogeneous Interactions of ClONO2 and HCl with Sulfuric Acid Tetrahydrate: Implications for the Stratosphere

The reaction probabilities for ClONO2+H2O- HOCl + HNO3 and ClONO2+ HCl Cl2 +HNO3 have been investigated on sulfuric acid tetrahydrate (SAT, H2SO4-4H2O)surfaces at temperatures between 190 and 230 K and at reactant concentrations that are typical in the lower stratosphere, using a fast-flow reactor coupled to a quadrupole mass spectrometer. The results indicate that the reaction probabilities as well as HCl uptake depend strongly on the thermodynamic state of SAT surface: they decrease significantly with decreasing H2O partial pressure at a given temperature, and decrease with increasing temperature at a given H2O partial pressure, as the SAT changes from the H2O-rich form to the H2SO4-rich form. For H2O-rich SAT at 195 K gamma(sub 1) approx. = -0.01 and gamma(sub 2) greater or equal to 0.1, whereas the values for H2SO4-rich SAT decrease by more than 2 orders of magnitude. At low concentrations of HCl, close to those found in the stratosphere, the amount of HCl taken up by H2O-rich SAT films corresponds to a coverage of the order of a tenth of a monolayer (approx. = 10(exp 14) molecules/sq cm); H2SO4-rich SAT films take up 2 orders of magnitude less HCl (les than 10(exp 12) molecules/sq cm). Substantial HCl uptake at high HCl concentrations is also observed, as a result of surface melting. The data reveal that frozen stratospheric sulfate aerosols may play an important role in chlorine activation in the winter polar stratosphere via processes similar to those occurring on the surfaces of polar stratospheric cloud particles.

Zhang, Renyi↗