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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The geochemical coherence of Pu and Nd and the Pu-244/U-238 ratio of the early solar system

Two very different sets of Pu-244/U-238 ratios have been reported for early solar system materials, one high and the other low, and this paper examines how one of these groups may yield an incorrect ratio. Recently measured partition coefficients for Pu and Sm (Jones, 1981) are used to evaluate Pu-Nd fractionation during achondrite genesis, and Pu-244/U-238 ratios of chondrites, achondrites, and Ca-Al-rich inclusions are compared and discussed. A low Pu-244/U-238 ratio is favored, and some implications of this low ratio for galactic nucleosynthesis and meteorite age dating are briefly discussed.

Jones, J. H.↗
NASA NTRS2016

Economical Production of Pu-238: NIAC Phase I Final Report

All space exploration missions traveling beyond Jupiter must use radioisotopic power sources for electrical power. The best isotope to power these sources is plutonium-238 (Pu-238). The US supply of Pu-238 is almost exhausted and will be gone within the next decade. The Department of Energy has initiated a production program with a $10M allocation from NASA but the cost is estimated at over $100M to get to production levels. The Center for Space Nuclear Research (CSNR) has conceived of a potentially better process to produce Pu-238 earlier and for significantly less cost. Potentially, the front end capital costs could be provided by private industry such that the government only had to pay for the product produced. In the Phase I NIAC (NASA Innovative Advanced Concepts) grant, the CSNR has evaluated the feasibility of using a low power, commercially available nuclear reactor to produce 1.5 kg of Pu-238 per year. The impact on the neutronics of the reactor have been assessed, the amount of Neptunium target material estimated, and the production rates calculated. In addition, the size of the post-irradiation processing facility has been established. Finally, as the study progressed, a new method for fabricating the Pu-238 product into the form used for power sources has been identified to reduce the cost of the final product. In short, the concept appears to be viable, can produce the amount of Pu-238 needed to support the NASA missions, can be available within a few years, and will cost significantly less than the current DOE program.

Plutonium↗
NASA NTRS1972

Fission xenon from extinct Pu-244 in 14,301.

Xenon extracted in step-wise heating of lunar breccia 14,301 contains a fission-like component in excess of that attributable to uranium decay during the age of the solar system. There seems to be no adequate source for this component other than Pu-244. Verification that this component is in fact due to the spontaneous fission of extinct Pu-244 comes from the derived spectrum which is similar to that observed from artificially produced Pu-244. It thus appears that Pu-244 was extant at the time lunar crustal material cooled sufficiently to arrest the thermal diffusion of xenon. Subsequent history has apparently maintained the isotopic integrity of plutonium fission xenon. Of major importance are details of the storage itself. Either the fission component is the result of in situ fission of Pu-244 and subsequent storage in 14,301 material, or the fission xenon was stored in an intermediate reservoir before incorporation into 14,301.

Drozd, R.↗
NASA NTRS1987

Experimental geochemistry of Pu and Sm and the thermodynamics of trace element partitioning

An experimental study of the partitioning of Pu and Sm between diopside/liquid and whitlockite/liquid supports the hypothesis that Pu behaves as a light rare earth element during igneous processes in reducing environments. D-Pu/D-Sm is found to be about 2 for both diopsidic pyroxene and whitlockite, and the amount of fractionation would be decreased further if Pu were compared to Ce or Nd. Data indicate that temperature, rather than melt composition, is the most important control on elemental partitioning, and that P2O5 in aluminosilicate melts serves as a complexing agent for the actinides and lanthanides.

Jones, John H.↗
NASA NTRS1986

I-Pu-Xe dating and the relative ages of the earth and moon

The ages of the earth and moon as determined by various chronometric systems are discussed with primary emphasis placed on the development of an I-Pu-Xe chronometer. Data on excess fission xenon are reviewed with attention given to the strengths and weaknesses of the assumptions required for lunar I-Pu-Xe chronometry. Using I-Pu-Xe dating, it is estimated that the retention of excess fission xenon in lunar samples began no more than 63 + or - 42 m.y. after the time of primitive meteorite formation.

Swindle, T. D.↗
NASA NTRS1973

On Pu-244 in lunar rocks from Fra Mauro and implications regarding their origin.

The evidence for in situ produced fission xenon from Pu-244 in rock 14321 is presented. The inferred abundance ratio Pu-244/U-238 is found to be consistent with values observed in a meteorite. Data from a stepwise release of the xenon permits a characterization of the trapped component, which can be shown to be distinct from solar xenon. We discuss the evidence for the presence of fission gases and of uncorrelated radiogenic argon in this and in other Apollo 14 rocks and some implications regarding their origin.

Marti, K.↗
NASA NTRS1976

The case for an unfractionated Pu-244/U-238 ratio in high-temperature condensates

The coarse-grained, Ca-rich inclusions in the Allende meteorite are the highest-temperature condensates from the cooling solar nebula and, as such, the oldest solid objects in the solar system. All refractory elements with condensation points above the accretion temperature of the inclusions whose concentrations in them have been measured are seen to be present in the inclusions in unfractionated proportion to one another relative to Cl chondrites when data are averaged for a large number of inclusions. Observational data for U and theoretical data for both U and Pu suggest that these elements exhibited refractory behavior in the solar nebula. An experiment is proposed in which fissiogenic Xe and U contents are measured in a suite of these inclusions to obtain the Pu-244/U-238 ratio of the solar system at the time of initial condensation with an uncertainty of plus or minus 15%.

Ganapathy, R.↗
NASA NTRS1977

Sm-Nd-Pu timepieces in the Angra dos Reis meteorite

Isotope ratios and age estimations are presented for the ultramafic pyroxenite Angra dos Reis meteorite. A pyroxene-phosphate internal isochron age of 4.55 plus or minus 0.04 eons was obtained, in agreement with reported Pb-Pb ages. It is suggested that Sm-146 decay led to an increase in the ratio of Nd-142 to Nd-144 in pyroxene, which is greater than the ratio of the Nd isotopes in phosphates. The effect of Pu-244 on the fission xenon components in pyroxene and phosphate is examined. The ratios of Pu-244 to Nd, U-238, and Th-232 are compared for pyroxene and phosphate separates. The exposure age of the meteorite, as obtained by the Kr-81 to Kr-83 method, was found to be 55.5 plus or minus 1.2 million years.

Lugmair, G. W.↗
NASA NTRS1978

Fractionation in the solar nebula. II - Condensation of Th, U, Pu and Cm

Reasonable assumptions concerning activity coefficients allow the calculation of the relative volatility of the actinide elements under conditions expected during the early history of the solar system. Several of the light rare earths have volatilities similar to Pu and Cm and can be used as indicators of the degree of fractionation of these extinct elements. Uranium is considerably more volatile than either Pu or Cm, leading to fractionations of about a factor of 50 and 90 in the Pu/U and Cm/U ratio in the earliest condensates from the solar nebula. Ca,Al-rich inclusions from the Allende meteorite, including the coarse-grained inclusions, have a depletion of U relative to La of about a factor of three, suggesting that these inclusions may have been isolated from the nebular gas before condensation of U was complete. The inclusions, however, can be used to determine solar Pu/U and Cm/U ratios if the rare earth patterns are determined in addition to the other normal measurements.

Boynton, W. V.↗
NASA NTRS1984

The I-Pu-Xe age of the Moon

The Rb-Sr analyses of some lunar samples which indicate that the Moon is close to the age of primitive meteorites are only reliable to within about 100 m.y. A potentially more precise chronometer is the I-Pu-Xe system. I129 has a 17 m.y. halflife and decays to Xe129; Pu244, with an 82 m.y. halflife, produces Xe131 to Xe136 in fission. The I129/Pu244 ratio has a halflife of 21 m.y. Xenon retention for the Earth could have begun as late as the event that gave birth to the Moon. For the Moon, it is hard to imagine that xenon retention could have begun before re-accretion of the fissioned (and initially dispersed?) material, particularly if that material got hot enough to account for the depletion of the volatile elements. Thus, if fission model are correct, xenon retention in the Earth certainly began no later than in the Moon, and possibly began earlier. Therefore, the I-Pu-Xe system is only marginally consistent with a fission origin. If further study confirms that the I/U ratio of the Moon is .01 or less, or if gas-rich lunar highland breccias with higher ratios of I129 to Pu244 are found, it would be difficult to explain the results in an earth-fission model of lunar origin.

Swindle, T. D.↗
NASA NTRS1985

Noble gas component organization in Apollo 14 breccia 14318 I-129 and Pu-244 regolith chronology

Drozd et al. (1972) have first detected the presence of Xe-129 in lunar material. Bernatowicz et al. (1979, 1980) established that this xenon component resides exclusively on grain surfaces and confirmed previous observations that it is less tightly bound than other surface components. The present investigation extends many of the observations made on the basis of a study of the 14301 to 14318, which is the only other lunar regolith breccia for which the isotopic structure of 'parentless xenon' has been accurately resolved. Actually this isotope has two parents, including Pu-244 and I-129, which are both now extinct. Attention is given to the analyzed samples, the employed analytical methods, the petrology and chemistry of the grain size separates, and stepwise heating experiments. On the basis of the obtained results, it is concluded that the I-Pu-Xe system can be used as a chronometer.

Swindle, T. D.↗
NASA NTRS1987

Al-26, Pu-244, Ti-50, REE, and trace element abundances in hibonite grains from CM and CV meteorites

Hibonites from the CM meteorites Murchison, Murray, and Cold Bokkeveld, and hibonites and Ti-rich pyroxene from the CV chondrite Allende are studied. Electron microprobe measurements of major element concentrations and track and ion probe measurements of Mg and Ti isotopic ratios, rare earth elements (REEs), and trace element abundances are analyzed. Correlations between isotopic anomalies in Ti, Al-26, Pu-244, and Mg-26(asterisk) are examined. Ti isotopic anomalies are compared with REE and trace element abundance patterns. Reasons for the lack of Al-26 in the hibonites are investigated and discussed. It is observed that there is no correlation between the Ti isotopic compositions, and the presence of Mg-26(asterisk), Pu-244, and REE and trace element patterns in individual hibonite samples. The data reveal that hibonites are not interstellar dust grains but formed on a short time scale and in localized regions of the early solar system.

Fahey, A. J.↗
NASA NTRS1987

Lava fountain heights at Pu'u 'O'o, Kilauea, Hawaii - Indicators of amount and variations of exsolved magma volatiles

Factors most important in determining fountain height in Hawaiian-type basaltic eruptions were assessed on the basis of theoretical calculations and observations at Pu'u 'O'o vent, east rift zone of Kilauea, Hawaii. It is shown that fountain height is very sensitive to changes in exsolved gas content (and, thus, can be used to estimate variability in exsolved gas content) and relatively insensitive to large variations in volume flux. Volume flux was found to be the most important parameter determining the equilibrium vent diameter. The results of calculations also indicate that there was a general increase in magma gas content over the first 20 episodes of the Pu'u 'O'o eruption and that gas depletion took place in the conduit beneath the vent during repose periods.

Head, James W., III↗
NASA NTRS1988

Nature of local magma storage zones and geometry of conduit systems below balsatic eruption sites - Pu'u 'O'o, Kilauea East Rift, Hawaii, example

The fluid dynamics of the well-documented eruptive episodes at Pu'u 'O'o, Kilauea are used to investigate quantitatively the size and shape of the shallow conduit system beneath the vent. The possible geometry of this region is considered. The dynamics of the eruptive episodes is used to place restrictions on the size and shape of the region and thermal calculations are used to show that the geometry is consistent with the region being the fluid residue of the partially cooled, major preepisode 1 dike. The Pu'u 'O'o example is used to illustrate some general properties of shallow magma storage zones.

Wilson, Lionel↗
NASA NTRS1989

The early solar system abundance of Pu-244 as inferred from the St. Severin chondrite

The isotopic composition of Xe released in stepwise heating of neutron-irradiated samples of the St. Severin chondrite was measured. This analysis shows that at the time of formation of most chondritic meteorites, approximately 4.56 x 10 to the 9th yr ago, the atomic ratio of Pu-244/U-238 was 0.0068 + or - 0.0010 in chondritic meteorites. This value is believed to be more reliable that inferred from earlier analyses of St. Severin and is the best estimate for the early solar system abundance of Pu-244. The comparison of Xe compositions between irradiated and unirradiated samples shows that the composition of trapped (ambient) Xe in St. Severin has a significantly lower value of Xe-136/Xe-130 than average carbonaceous chondrites.

Hudson, G. B.↗
NASA NTRS1993

On a thermonuclear origin for the 1980-81 deep light minimum of the symbiotic nova PU Vul

The puzzling 1980-81 deep light minimum of the symbiotic nova PU Vul is discussed in terms of a sequence of quasi-static evolutionary models of a hot, 0.5 solar mass white dwarf accreting H-rich matter at a rate 1 x 10 exp -8 solar mass/yr. On the basis of the morphological behavior of the models, it is suggested that the deep light minimum of PU Vul could have been the result of two successive, closely spaced, hydrogen shell flashes on an accreting white dwarf whose core thermal structure and accreted H-rich envelope was not in a long-term thermal 'cycle-averaged' steady state with the rate of accretion.

Sion, Edward M.↗
NASA NTRS1973

Extinct lunar radio activities - Xenon from Pu-244 and I-129 in Apollo 14 breccias.

Two Apollo 14 breccias have been found to contain xenon from the spontaneous fission of 82 my Pu-244. A third contains 60 times as much fission xenon as local uranium can account for and is probably of similar character. One of the breccias shows a Xe-129 excess most likely due to the decay of 17 my I-129. That these components can be separated and identified at all implies that complete isotopic homogenization has not occurred over a period which encompasses both extinction of these radionuclides and compaction of the breccias into their final form. In this sense isotope pre-history has been preserved in some lunar breccias providing information that pre-dates the formation of the rock itself (as determined by conventional techniques).

Behrmann, C. J.↗
NASA NTRS1993

The onset of Wolf-Rayet wind outflow and the nature of the hot component in the symbiotic nova PU Vulpecula

We have analyzed temporal variations in the far ultraviolet He II (1640), Si IV (1393, 1402), and C IV (1548, 1550) line profiles in eight high dispersion, International Ultraviolet Explorer Short Wavelength Prime spectra of the symbiotic nova PU Vul by comparatively examining these profiles on a common velocity scale. We see clear evidence of the onset of a Wolf-Rayet-like wind outflow from the bloated, contracting white dwarf hot component with terminal velocity of approximately equals -550 to -600 km/s. We have quantitatively analyzed the complicated He II (1640) emission region for the first time and show that the discrete absorption features seen in the He II region occur at precisely the same velocites in each spectrum, thus demonstrating that the absorbing source is steady and not affected by any orbital motion. We demonstrate that there is an underlying He II wind emission feature whose true shape is hidden by superposed absorption due to the foreground red giant wind flowing in front of the white dwarf and abscuring the white dwarf's wind outflow. We present synthetic spectra of He II emission behind an absorbing slab with u = 20 km/s, T = 5000 K, and column densities in the range N = 1 x 10(exp 22) and 1 x 10(exp 23)/sq cm which explain these absorptions. Our analysis of the Si IV and C IV resonance doublets, in velocity space, reveal temporal variations in the profile between 1987 and 1991 with the emergence of clear P Cygni profiles in Si IV by 1990. A nebular emission feature in C III 1909 also appears in the most recent spectra (e.g., SW42538H) while it was absent or extremely weak in the earliest spectra (e.g., SW36332H), thus strengthening evidence that the nebular emission, as seen in permitted and semiforbidden lines, intensities in step with the onset of the hot, fast, wind outflow. We also report the first detection of narrow interstellar (circumbinary shell?) absorption lines near -1 km/s, most strongly in Al III (1854, 1862) and Si IV (1392, 1402). We have carried out a rough quantitative analysis of the He II wind emission by using the theoretical He II Wolf-Rayet profiles of Hamann & Schmutz (1987). We obtain a lower limit to the He II net emission equivalent width of approximately 1 A, a hot component temperature in the range 25,000 to 35,000 K, a hot component radius in the range 5 solar radius to 30 solar radius, a maximum wind velocity of approximately equals -600 km/s and a rough upper limit to the mass-loss rate of less than 1 x 10(exp -5) solar mass/yr. To our knowledge, this is the first quantitative wind analysis, albeit crude, to be carried out for the hot component of a symbiotic nova or symbiotic variable.

Sion, Edward M.↗