Search NASA⌕ Search

SEARCH · Search NASA

Results for “NEUTRON ACTIVATION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Chemical fractionations in meteorites. V - Volatile and siderophile elements in achondrites and ocean ridge basalts.

Eighteen achondrites and 4 terrestrial basalts (3 ocean ridge, 1 continental) were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Co, Cs, Cu, Ga, In, Ir, Rb, Se, Tl and Zn. Samples included 7 eucrites, 5 howardites, 2 nakhlites, 2 shergottites, an angrite, and an aubrite. Light and dark portions of the gas-rich meteorites Kapoeta and Pesyanoe were analyzed separately. Nakhlites and shergottites have volatile element abundances similar to those in ocean ridge basalts; eucrites, howardites, and angrites show greater depletions by an order of magnitude and less similar abundance patterns. In terms of a two-component model of planetary accretion, the parent planets contained the following percentages of low-temperature material: eucrites 0.8, nakhlites 38, shergottites 28. Shergottites may be genetically related to L-chondrites. The siderophile element pattern of achondrites resembles that of the moon, but with less extreme depletions.

Laul, J. C.↗
NASA NTRS1972

Elemental abundances in stone meteorites.

Measurement of abundances of Na, Al, Sc, Cr, Mn, Fe, Co, and Cu by instrumental neutron activation analyses of 103 chondrites and 17 achondrites. Various sources of error in the method, including sampling errors, are discussed in detail. Examination of the patterns of coherence of the elements determined suggests the presence of effects of fractionation during condensation from the solar nebula of matter parental to chondrites. Such effects seem to be exhibited both in the abundances of lithophilic elements, perhaps being related to varied temperatures of accretion and in the abundances of those elements which would be affected by metal-silicate fractionation in the solar nebula. Atomic abundances relative to Si vary little in carbonaceous chondrites, suggesting that efficient mixing processes operated on these meteorites prior to or during their formation. It is suggested that, at present, no single class of carbonaceous chondrites is clearly more primitive than another. Carbonaceous and unequilibrated ordinary chondrites may represent aggregates of material accreted from the solar nebula at relatively low temperatures. The present data support a model of equilibration and minor mobilization of nonvolatile elements within small domains of chondrites after accretion. Such a model would be consistent with the petrologic types of Van Schmus and Wood (1967).

Schmitt, R. A.↗
NASA NTRS1972

Advanced techniques for determining long term compatibility of materials with propellants

The search for advanced measurement techniques for determining long term compatibility of materials with propellants was conducted in several parts. A comprehensive survey of the existing measurement and testing technology for determining material-propellant interactions was performed. Selections were made from those existing techniques which were determined could meet or be made to meet the requirements. Areas of refinement or changes were recommended for improvement of others. Investigations were also performed to determine the feasibility and advantages of developing and using new techniques to achieve significant improvements over existing ones. The most interesting demonstration was that of the new technique, the volatile metal chelate analysis. Rivaling the neutron activation analysis in terms of sensitivity and specificity, the volatile metal chelate technique was fully demonstrated.

Green, R. L.↗
NASA NTRS1973

Lunar crater Copernicus - Search for debris of impacting body at Apollo 12 site.

In an attempt to characterize meteoritic material at the Apollo 12 site, 4 KREEP concentrates from soil 12033 have been analyzed by neutron activation analysis. These contain a meteoritic component in which siderophile Ir, Re, and Sb are depleted by about a factor of 2, while volatile Se, Zn, Ag, and Bi are depleted by a factor of more than 5 relative to Au. This pattern does not closely resemble any major chondrite or iron meteorite group, but is very similar to that observed in high-alkali samples from Apollo 14. The meteoritic component in KREEP at both sites is therefore predominantly derived from Imbrian ejecta. However, a second, small component of primitive composition seems to be present in Apollo 12 KREEP, judging from the slight, uniform enrichments in Ir, Re, Sb, and Zn relative to Au. This component does not seem to be due to micrometeorites. If it is attributed to the Copernican projectile, the crater Copernicus may have been formed by a cometary nucleus, 4 km in diameter, with an impact velocity of 30 to 40 km/sec. These conclusions depend critically on the assumption that the meteoritic component in Apollo 12 KREEP is representative of the entire impact.

Morgan, J. W.↗
NASA NTRS1972

Bulk, rare earth, and other trace elements in Apollo 14 and 15 and Luna 16 samples.

Measurement of 24 and 34 bulk, minor, and trace elements in lunar specimens by instrumental and radiochemical neutron activation analysis shows greater Al2O3, Na2O, and K2O abundances and higher TiO2, FeO, MnO and Cr2O3 depletions in Apollo 14 soil samples as compared to Apollo 11 samples and to most of Apollo 12 samples. The uniform abundances in 14230 core tube soils and three other Apollo 14 soils indicate that the regolith is uniform to at least 22 cm depth and within about 200 m from the lunar module.

Laul, J. C.↗
NASA NTRS1972

Compositional characteristics of some Apollo 14 clastic materials.

Eighty-two subsamples of Apollo 14 materials have been analyzed by instrumental neutron activation analysis techniques for as many as 25 elements. In many cases, it was necessary to develop new procedures to allow analyses of small specimens. Compositional relationships among Apollo 14 materials indicate that there are small but systematic differences between regolith from the valley terrain and that from Cone Crater ejecta. Fragments from 1-2 mm size fractions of regolith samples may be divided into compositional classes, and the 'soil breccias' among them are very similar to valley soils. Multicomponent linear mixing models have been used as interpretive tools in dealing with data on regolith fractions and subsamples from breccia 14321. These mixing models show systematic compositional variations with inferred age for Apollo 14 clastic materials.

Lindstrom, M. M.↗
NASA NTRS1972

Major impacts on the moon - Characterization from trace elements in Apollo 12 and 14 samples.

Seventeen trace elements have been determined by neutron activation analysis in 33 lunar samples from Apollo 14, 5 from Apollo 12, and 2 from Luna 16. Apollo 14 soils and breccias contain at least two, and possibly three, ancient meteoritic components of unusual composition, probably derived from the Imbrian and Serenitatis impacts, and mixed planetesimal debris from the pre-Imbrian regolith. These components have a lower ratio of volatiles to siderophiles than any known class of chondrites. They also have Ir/Au, Ge/Au ratios outside the range for most iron meteorites, except groups IVA and possibly IIIA. One of these components, of very low Ir/Au, Re/Au ratio, occurs in light norites, 14321 microbreccias, and KREEP separates from 12033 soil. Another is found in dark norites, glasses, and several other Apollo 14 samples, as well as rock 12013 and Apollo 11 anorthosite. From these compositional clues it appears that the Imbrian body and the pre-Imbrian planetesimals, like the earth, were relatively rich in iron, but depleted in volatiles. Such a composition is consistent with the Imbrian body originating as an earth-crossing planetesimal.

Morgan, J. W.↗
NASA NTRS1973

Trace elements in fines from the Apollo 15 deep drill.

Samples of fines from the bottom of the Apollo 15 deep drill core and from each junction between the six 42.5-cm long segments of the drill stem were analyzed for Ag, Co, Cr, Cs, Cu, Ga, Hf, Rb, Sc, and Zn by neutron activation. The most striking feature of the results is the absence of significant variations in concentration for any element throughout the depth of the drill sample and despite the considerable stratigraphy of the cored material. The presence of a significant amount of KREEP material is indicated.

Helmke, P. A.↗
NASA NTRS1973

Rare earths, other trace elements and iron in Luna 20 samples.

The results of the analysis by neutron activation of six samples from the Luna 20 mission and one sample of less than 1 mm fines from Apollo 16 are reported. The concentrations of the rare-earth elements (REE) in the samples of fines from Luna 20 and Apollo 16 are less than those found for corresponding materials from the mare areas but a negative Eu anomaly is still present. The concentrations of the REE in fines from Luna 20 are only about two-thirds as great as in the sample of Apollo 16 fines, but the concentration of Co, Sc and Cr are greater by factors ranging from 1.5 to 2.3.

Helmke, P. A.↗
NASA NTRS1973

Oxygen and bulk element abundances in Luna 20 fines.

Abundances of O, Si, Al, and Mn determined in a Luna 20 fines sample by instrumental neutron activation analysis are presented and compared with those found in Apollo lunar soil samples. The results obtained include the finding that O/Si ratios exhibit very little variability among fines samples from various lunar landing sites, whereas the Al/Si ratio is highly variable.

Janghorbani, M.↗
NASA NTRS1973

Chemical composition of Luna 20 rocks and soil and Apollo 16 soils.

Review of the abundances of 24 major, minor, and trace elements measured by instrumental neutron activation analysis in Luna 20 metaigneous rocks, breccia, and soil, and in Apollo 16 soils. The similarities and differences observed are discussed. The bulk compositions of Luna 20 and Apollo 16 rocks and soils show close similarity between the two highland sites. Interelement correlations observed previously for maria are also found in highland samples. Luna 20 and Apollo 16 soils are low in alkalis. Both soils show an apparent Cd-Zn rich component similar to that observed at the mare sites and high Tl abundances relative to mare sites.

Laul, J. C.↗
NASA NTRS1973

Luna 20 soil - Abundance of 17 trace elements.

Review of the results of radiochemical neutron activation analysis of two Luna 20 fine soil and breccia samples for the abundance of 17 mainly siderophile and volatile elements that are strongly depleted in lunar surface rocks and hence represent sensitive indicators of meteoritic materials. These results are compared with those previously obtained for Apollo 16 soils. Some of the source rocks of Luna 20 regolith are identified.

Morgan, J. W.↗
NASA NTRS1973

Abundance of 17 trace elements in carbonaceous chondrites.

Seventeen trace elements (Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Rb, Re, Sb, Se, Te, Tl, U, and Zn) were measured by neutron activation analysis in eight C1 samples (1 Alais, 3 Ivuna, 4 Orgueil and in three C2 samples (one each of Mighei, Murchison, Murray). The results show far less scatter than earlier literature data. The standard deviation of a single measurement from the mean of eight C1 samples lies between 2 and 14%, except for the following four elements: Au, Ag, Rb, and Br. The first two probably reflect contamination and sample heterogeneity, the last two, analytical error. Apparently C1 chondrites have a far more uniform composition than some authors have claimed.

Kraehenbuehl, U.↗
NASA NTRS1973

Minor and trace elements in some meteoritic minerals.

Despite the information available (Mason, 1971) on trace elements in different types of meteorites, relatively little is known about the distribution of these elements among the individual mineral phases. The mineral phases including olivine, orthopyroxene, clinipyroxene, troilite, nickel-iron, plagioclase, chromite, and the phosphates were separated from several meteorites. The purified minerals were analyzed for trace and minor elements by spark source mass spectrometry and instrumental neutron activation analysis. The elements are classified as siderophile, lithophile, and chalcophile.

Allen, R. O., Jr.↗
NASA NTRS1973

Uranium and thorium in achondrites.

The abundances of U and Th in 19 achondrites and two pallasite olivines have been measured by radiochemical neutron activation analysis. Brecciated eucrites are enriched relative to chondrites in both elements by factors between 10 and 20, perhaps as a result of a magmatic differentiation process. Two unbrecciated eucrites are far less enriched, possibly due to their origin as igneous cumulates. The diogenites Johnstown and Shalka contain approximately chondritic levels of U and Th, but Ellemeet is 10 times lower. The abundances in three howardites are in good agreement with those expected from major element data for a mixing model with eucrite and diogenite end members. The high O-18 basaltic achondrites Nakhla, Shergotty and Angra dos Reis have a range of U and Th abundances similar to the brecciated eucrites and howardites, but have systematically higher Th/U ratios.

Morgan, J. W.↗
NASA NTRS1973

Elemental composition of individual chondrules from ordinary chondrites.

Sequential nondestructive neutron activation analysis was used to determine the bulk abundance of Fe, Al, Na, Mn, Cr, Sc, Co, and Ir in approximately 300 individual chondrules from 16 chondrites representing the H(3-5), L4, and LL(3-6) compositional and petrologic classes. The histograms indicate that the most probable abundances for lithophilic elements, except Cr, are enriched in the chondrules, while the siderophilic elements are depleted in the chondrules compared to the whole chondrite. Some of the abundance populations, such as Al and Fe, appear to be multimodal. Systematic variations in the composition of the chondrules with increasing petrologic type were observed; most consistent are an increasing Na-Al and Cr-Al correlation, a decreasing Na-Mn correlation, increasing Na abundance, and decreasing Na and Mn dispersions among chondrules.

Osborn, T. W.↗
NASA NTRS1973

Extralunar materials in cone-crater soil 14141.

Radiochemical neutron activation analysis has been used to determine Ni, Zn, Ga, Ge, Cd, In, Ir, and Au in duplicate samples of lunar soil 14141 and in one additional replicate each of soils 14163 and 14259. The concentrations of extralunar trace elements Ni, Ge, Ir, and Au in 14141 and 14163 are, respectively, about 69 and 82% as high as those in 14259. Although most of the mass of 14141 appears to be ejecta from Cone Crater, a sizable contamination by mature Fra Mauro soil such as 14259 is also present. The siderophilic-element concentrations of the subregolith Fra Mauro materials are estimated to be 25 plus or minus 25% of those observed in 14259.

Wasson, J. T.↗
NASA NTRS1974

Trace geochemistry of lunar material

The lunar samples from the Apollo 16 and 17 flights which were analyzed include soil, igneous rock, anorthositic gabbro, orange soil, subfloor basalt, and norite breccia. Up to 57 elements including majors, minors, rare earths and other trace elements were determined in the lunar samples. The analytical techniques used were spark source mass spectrometry and neutron activation analysis. The latter was done either instrumentally or with group radiochemical separations. The differences in abundances of the elements in lunar soils at the various sites are discussed. With regard to the major elements only Si is about the same at all the sites. A detailed analysis which was performed on a sample of the Allende meteorite is summarized.

Morrison, G. H.↗