53 Matching Results

Search Results

Advanced search parameters have been applied.

Preparation and Properties of Nitrate-Deficient Gadolinium Nitrate Solutions

Description: Because of the high neutron absorption cross sections of some gadolinium isotopes, gadolinium salts in solution are used to control nuclear reactivity in aqueous systems. The present studies concern the preparation and analysis of nitrate-deficient solutions, the effect of time and gamma radiation on their stability, and the determination of the solubility of gadolinium hydroxide in H2O and D2O.
Date: March 15, 2001
Creator: Baumann, E.W.
Partner: UNT Libraries Government Documents Department

FAST NEUTRON COVARIANCES FOR EVALUATED DATA FILES.

Description: We describe implementation of the KALMAN code in the EMPIRE system and present first covariance data generated for Gd and Ir isotopes. A complete set of covariances, in the full energy range, was produced for the chain of 8 Gadolinium isotopes for total, elastic, capture, total inelastic (MT=4), (n,2n), (n,p) and (n,alpha) reactions. Our correlation matrices, based on combination of model calculations and experimental data, are characterized by positive mid-range and negative long-range correlations. They differ from the model-generated covariances that tend to show strong positive long-range correlations and those determined solely from experimental data that result in nearly diagonal matrices. We have studied shapes of correlation matrices obtained in the calculations and interpreted them in terms of the underlying reaction models. An important result of this study is the prediction of narrow energy ranges with extremely small uncertainties for certain reactions (e.g., total and elastic).
Date: June 5, 2006
Creator: HERMAN, M.; OBLOZINSKY, P.; ROCHMAN, D.; KAWANO, T. & LEAL, L.
Partner: UNT Libraries Government Documents Department

Use of high-pressure ion exchange for the production of gadolinium-153. Status report

Description: A large high-pressure ion-exchange column, which had been designed for the separation of gadolinium from europium, was tested in the laboratory. Good separations were obtained. Subsequently, columns of the same design were installed in a hot cell and have been used successfully for the separation of gadolinium-153 from irradiated natural europium. The gadolinium-153 production achieved using these columns is substantially greater than that achieved using the previous process. Rapid damage of the resin is a problem and frequent resin changes are required.
Date: April 1, 1986
Creator: Posey, J.C.
Partner: UNT Libraries Government Documents Department

Phenomena at very high spins. [Approx. 70 h-bar; review]

Description: The present talk has three parts: first, a discussion of current ideas about the physics of very high spin states; second, some comments about noncollective behavior up to the highest spins where it is known, approx. 40 h; and finally, a presentation of the newest method for studying collective behavior up to spins of 60 to 70 h. The intention is that the overview presented in the first part will be sufficiently broad to indicate the relationship of the noncollective and collective behavior discussed in the other parts, and to provide some understanding of the compromise in behavior that seems to occur at the very highest spins. 13 figures.
Date: March 1, 1980
Creator: Stephens, F.S.
Partner: UNT Libraries Government Documents Department

Superdeformed nuclei

Description: This paper reviews the most recent advances in the understanding of the physics of superdeformed nuclei from the point of view of the experimentalists. It covers among other subjects the following topics: (1) the discovery of a new region of superdeformed nuclei near A=190, (2) the surprising result of the occurrence of bands with identical transition energies in neighboring superdeformed nuclei near A=150 and A=190, (3) the importance of octupole degrees of freedom at large deformation and (4) the properties associated with the feeding and the decay of superdeformed bands. The text presented hereafter will appear as a contribution to the Annual Review of Nuclear and Particle Science, Volume 41. 88 refs., 11 figs.
Date: January 1, 1991
Creator: Janssens, R.V.F. & Khoo, Teng Lek.
Partner: UNT Libraries Government Documents Department

Assessment of Fission Product Cross-Section Data for Burnup Credit Applications

Description: Past efforts by the Department of Energy (DOE), the Electric Power Research Institute (EPRI), the Nuclear Regulatory Commission (NRC), and others have provided sufficient technical information to enable the NRC to issue regulatory guidance for implementation of pressurized-water reactor (PWR) burnup credit; however, consideration of only the reactivity change due to the major actinides is recommended in the guidance. Moreover, DOE, NRC, and EPRI have noted the need for additional scientific and technical data to justify expanding PWR burnup credit to include fission product (FP) nuclides and enable burnup credit implementation for boiling-water reactor (BWR) spent nuclear fuel (SNF). The criticality safety assessment needed for burnup credit applications will utilize computational analyses of packages containing SNF with FP nuclides. Over the years, significant efforts have been devoted to the nuclear data evaluation of major isotopes pertinent to reactor applications (i.e., uranium, plutonium, etc.); however, efforts to evaluate FP cross-section data in the resonance region have been less thorough relative to actinide data. In particular, resonance region cross-section measurements with corresponding R-matrix resonance analyses have not been performed for FP nuclides. Therefore, the objective of this work is to assess the status and performance of existing FP cross-section and cross-section uncertainty data in the resonance region for use in burnup credit analyses. Recommendations for new cross-section measurements and/or evaluations are made based on the data assessment. The assessment focuses on seven primary FP isotopes (103Rh, 133Cs, 143Nd, 149Sm, 151Sm, 152Sm, and 155Gd) that impact reactivity analyses of transportation packages and two FP isotopes (153Eu and 155Eu) that impact prediction of 155Gd concentrations. Much of the assessment work was completed in 2005, and the assessment focused on the latest FP cross-section evaluations available in the international nuclear data community as of March 2005. The accuracy of the cross-section data was investigated by ...
Date: December 1, 2007
Creator: Leal, Luiz C; Derrien, Herve; Dunn, Michael E & Mueller, Don
Partner: UNT Libraries Government Documents Department

Nuclear data for Gd-153 production

Description: A compilation of neutron activation cross section data is provided. Data on this gadolinuim is needed because of its use as the working ingredient in an advanced medical scanning machine that can detect loss of bone minerals such as calcium, a possible cause of the disease osteoporosis. 4 refs.
Date: January 1, 1986
Creator: Holden, N.E.
Partner: UNT Libraries Government Documents Department

Recent experiments at Brookhaven: level structure of N = 86 isotones /sup 156/Yb and /sup 150/Gd

Description: States of the N = 86 isotones /sup 156/Yb and /sup 150/Gd have been studied by means of the /sup 144/Sm(/sup 16/O,4n)/sup 156/Yb, /sup 113/In(/sup 46/Ti,p2n)/sup 156/Yb, and /sup 124/Sn(/sup 30/Si,4n)/sup 150/Gd reactions. Levels have been established to spin 36 h-bar and over 12.5 MeV in excitation in /sup 150/Gd and to beyond spin 25 h-bar in /sup 156/Yb. The systematics of levels in the N = 86 isotones from /sup 150/Gd to /sup 156/Yb are described, and the near-spherical shell model description for states in this region to near spin 30 h-bar is discussed. A T/sub 1/2/ = 6 ns, 72-keV isomeric transition in /sup 156/Yb has been discovered, and an E1 multipolarity is assigned to this transition. The spin-parity of the isomeric state is established as 11/sup -/. 6 figures.
Date: January 1, 1980
Creator: Sunyar, A W
Partner: UNT Libraries Government Documents Department

Sandwich targets for heavy-ion experiments

Description: Techniques for producing sandwich targets such as Gd + Pb are described. Better contact between the materials is sometimes assured by evaporating one material onto the other rather than by rolling the two together. Experimental data using both types of targets will be shown.
Date: January 1, 1982
Creator: Thomas, G.E.
Partner: UNT Libraries Government Documents Department

Octupole instability in the heavy barium region

Description: Quasi-molecular rotational bands characterized by spin states of alternating parity connected by enhanced E1 transitions have recently been observed in several transitional nuclei around /sup 224/Th. The appearance of such bands can easily be understood by assuming the absence of intrinsic parity symmetry in these nuclei. Another likely region on the chart of nuclides to find octupole-unstable nuclei is the region of nuclei around /sup 146/Ba. In fact, in several Xe, Ba and Ce isotopes with n approximately equal to 88, calculations yield octupole-unstable ground states. The main goal of the present study was to calculate equilibrium deformations of doubly-even Xe, Ba, Ce, Nd, Sm and Gd nuclei with neutron numbers between 84 and 94. The method used was the Woods-Saxon-Bogolyubov cranking model method combined with the shell correction approach. The results of these calculations confirm previous expectations of octupole deformed mean fields at low and medium spins in Xe-Sm nuclei with neutron numbers around N = 86. Recent experimental data support theoretical results. 8 refs., 1 fig. (DWL)
Date: January 1, 1987
Creator: Nazarewicz, W.; Leander, G.A. & Tabor, S.
Partner: UNT Libraries Government Documents Department

Reduced E1, E2, and E3 transition probabilities for transitions in /sup 156 -160/Gd and /sup 160 -164/Dy

Description: Direct E2 and E3 Coulomb excitation of 2/sup +/ and 3/sup -/ states with 13.5-MeV /sup 4/He ions on isotopically enriched targets of /sup 156 -160/Gd and /sup 160 -164/Dy was measured by means of ..gamma..-ray spectroscopy. Several 2/sup +/ states and /sup 3 -/ octupole vibrational states were identified in each nucleus. The B(Elambda, 0 ..-->.. J = lambda) is obtained for excitation of each state, and information is given on the reduced transition probabilities for the different decay modes of these states. The experimental results are compared with theoretical predictions of nuclear models describing these states. 2 tables.
Date: January 1, 1980
Creator: McGowan, F.K.; Milner, W.T. & Stelson, P.H.
Partner: UNT Libraries Government Documents Department

High-spin configurations in /sup 147/Gd from alignment of seven, nine, and eleven particles

Description: Detailed spectroscopic studies of the discrete ..gamma..-rays feeding the 550-ns isomer at 8.590 MeV in /sup 147/Gd are reported. The resulting decay scheme indicates single-particle nature of the states up to the highest observed spin 79/2 h at 16.938 MeV of excitation energy. Comparison with Deformed Independent Particle Model calculations makes it possible to suggest configuration assignments to many of the levels. Five neutrons and six protons with their angular momenta aligned form the highest yrast states.
Date: January 1, 1983
Creator: Sletten, G.; Bjornholm, S. & Borggreen, J.
Partner: UNT Libraries Government Documents Department

Low energy E0 transitions in odd-mass nuclei of the neutron deficient 180 < A < 200 region

Description: The region of neutron-deficient nuclei near Z = 82 and N = 104 provides the most extensive example of low-energy shape coexistence anywhere on the mass surface. It is shown that E0 and E0 admixed transitions may be used as a fingerprint to identify shape coexistence in odd-mass nuclei. It is also shown that all the known cases of low energy E0 and E0 admixed transitions in odd-mass nuclei occur where equally low-lying O/sup +/ states occur in neighboring even-even nuclei. A discussion of these and other relevant data as well as suggestions for new studies which may help to clarify and, more importantly, quantify the connection between E0 transitions and shape coexistence are presented. 60 refs., 7 figs., 4 tabs.
Date: January 1, 1987
Creator: Zganjar, E.F.; Kortelahti, M.O.; Wood, J.L. & Papanicolopulos, C.D.
Partner: UNT Libraries Government Documents Department

Structure studies of low-lying O/sup plus/ states in the deformed rare-earth region

Description: To better understand the structure of the low lying O/sup +/ states of even-even nuclides in the deformed rare-earth region, we have carried out calculations to generate the wavefunctions, energies and pair transfer rates from/to these states within a framework of exact diagonalization of the residual pairing and n-p forces. First we carried out exact diagonalization for the neutron and proton systems separately, using as a basis space the 126 vector space of four/five pairs within nine appropriate deformed Nilsson orbitals. For the pairing force we included both monopole and quadrupole terms. Next, we used the lowest eight eigenfunctions from both the neutron and the proton systems to generate a new basis space composed of the 64 possible neutron-proton product vectors. The n-p force was approximated by a quadrupole-quadrupole force term which was then diagonalized within the new basis space. The resulting wave functions were used to calculate the neutron pair transfer strength from and to the various low O/sup +/ states below 3 MeV in the even-even Gd, Dy and Er isotopes. Furthermore, for the case where the deformation parameters do not change appreciably between the pair of nuclides involved in the pair transfer reaction, reasonable global agreement was obtained for the measured (t,p) and (p,t) pair transfer reaction strengths both to the ground and excited states O/sup +/ states accessible in these isotopes. The observed enhancement of (t,p) pair transfer strength to excited states in some of these isotopes was reproduced by the calculation. The enhancement is due to subshell gap and large relative pair transfer amplitude for an orbital near the Fermi surface. 24 refs., 7 figs.
Date: November 1, 1988
Creator: Shihab-Eldin, A.A.; Rasmussen, J.O. & Stoyer, M.
Partner: UNT Libraries Government Documents Department

The ground state mass of /sup 147/Gd from single-neutron transfer reactions

Description: Thin targets of radioactive /sup 148/Gd were used to determine a precise value for the mass of /sup 147/Gd. The (p,d), (d,t), and /sup 3/He,..cap alpha..) reactions were used with high-resolution charged-particle spectrometry to determine Q-values for the /sup 148/Gd target relative to several calibration targets having known Q-values. By combining the measured Q-value with the /sup 148/Gd mass, the mass defect, ..delta..M(/sup 147/Gd) = 75356 +- 6 keV, 149 keV less than the value in the 1977 mass tabulation was obtained. 7 refs., 1 fig., 1 tab.
Date: October 12, 1984
Creator: Mann, L.G.; Decman, D.J.; Massey, T.N.; Struble, G.L.; Sisson, D.H.; Henderson, C.M. et al.
Partner: UNT Libraries Government Documents Department

Simple empirical method for determining the energy gap in nonspherical even--even nuclei

Description: It is shown that the energy gap in nonspherical even--even nuclei is rather sharply delineated in ..gamma..-ray spectra following average resonance neutron capture. The relation to other methods of determining the energy gap is also presented.
Date: January 1, 1978
Creator: Cizewski, J A; Casten, R F & Stelts, M L
Partner: UNT Libraries Government Documents Department

Radiochemical investigations of nuclear properties. Progress report, October 1, 1977--December 31, 1978. [Summaries of research activities at Purdue Univ]

Description: Results of (..cap alpha..,xn..gamma..) and (Heavy Ion, xn..gamma..) investigations of high spin excitations in spherical and transitional heavy nuclei are summarised. Considerable progress was made in studies of the level structures of /sup 187/,/sup 188/,/sup 189/Pt and of /sup 200/,/sup 201/,/sup 202/Pb. Investigations of the structure of the Z = 64, N = 82 nucleus /sup 146/Gd and of other nuclei consisting of the /sup 146/Gd core plus one, two or three valence nucleons are also briefly described. A list of publications is included.
Date: January 1, 1979
Creator: Daly, P.J.
Partner: UNT Libraries Government Documents Department

Gadolinium-153 production at the Oak Ridge National Laboratory

Description: Gadolinium-153 production at the Oak Ridge National Laboratory (ORNL) involves the neutron irradiation of natural europium oxide (47.8% /sup 151/Eu, 52.2% /sup 153/Eu). This target material undergoes a series of neutron captures and radioactive decays to produce the desired /sup 153/Gd product. Several undesirable europium isotopes (/sup 152/Eu, /sup 154/Eu, and /sup 156/Eu) are also produced during this irradiation process. Recent technical advances and other improvements in the radiochemical processing of this isotope have allowed ORNL to increase production by more than sevenfold. A newly developed electrochemical process has allowed the separation of the bulk of undesirable europium isotopes and has also effected a more efficient use of high-pressure ion exchange to achieve a final product radiochemical purity >99.999%. Specific activities >60 Ci/g of gadolinium oxide and product specific yields >2.9 Ci/g of irradiated europium oxide have been produced. Use of unique glove box manipulators and special equipment designed at ORNL have allowed final source fabrication to keep pace with the increased production rate while minimizing the radiation exposure to operating personnel. 5 refs., 4 figs., 4 tabs.
Date: January 1, 1987
Creator: Ramey, D.W.
Partner: UNT Libraries Government Documents Department

Neutron cross sections for /sup 152/Gd and /sup 153/Gd

Description: Cross section data is tabulated for /sup 152/Gd and /sup 153/Gd. Resonance data is given for /sup 152/Gd. Both reported and revised measurements are presented for cross sections and resonance parameters. Recommendations for further cross section and resonance research for these two isotopes are made. (DWL). 15 ref., 3 tabs.
Date: January 1, 1986
Creator: Holden, N.E.
Partner: UNT Libraries Government Documents Department