Radiative Capture Of Thermal Neutrons Research Articles

A measurement of the thermal neutron radiative capture cross section of 238U

The 228U ( n, γ) 238U cross section has been measured using the standard thermal neutron flux facility available at the National Physical Laboratory. The 239U activity induced in the reaction was determined after irradiation by absolute counting techniques. Values of 2.69 ± 0·03 b for the 2200 m/sec capture cross section and 23.40 ± 0.05 m for the half life of the 231U ground state were obtained.

Konfigurationsmischungen in 169Yb

The level structure of 169Yb has been studied by radiative capture of thermal neutrons in 168Yb. High resolution measurements of the gamma-ray spectrum have been performed using a Ge(Li) anti-Compton spectrometer in the low-energy region and a Ge(Li) pair spectrometer for the high-energy transitions. The target was Yb 2O 3 enriched to 19.5% in 168Yb thus corresponding to a cross section contribution of (97.5 −2.3 +0.8)% for 168Yb. More than 300 gamma lines have been detected in the spectrum. The high accuracy of the data allows the application of Ritz' combination principle to excitation energies up to 1.5 MeV. The results clearly demonstrate the presence of remarkable band-mixing effects. The analysis suggests the following spectroscopic interpretation (bandhead energies and dominant structure): 0 keV, 7 2 +(633) ; 24.25 keV, 1 2 −(521) ; 191.18 keV; 5 2 −(512) ; 569.78 keV, 5 2 −(523) ; 659.61 keV, 3 2 −(521)+ 1 2 −(521)+Q 2−2 ; 720.02 keV, 7 2 +(633)+Q 2−2+ 3 2 +(651) ; 813.46 keV, 5 2 −(512)+Q 2−2+ 1 2 −(510) ; 960.28 keV, case7 2 −(514) ; 1033.82 keV, 1 2 +(660)+ 1 2 +(660)+Q 20(?) ; 1110.68 keV, 1 2 −(521)+Q 22 ; 1204.28 keV, 3 2 +(651)+ 7 2 (633)+Q 2−2 ; 1231.45 keV, 1 2 −(521)+Q 2−2+ 3 2 −(521) ; 1319.72 keV, 1 2 −(510)+… . The neutron binding energy was found to be 6867.21±0.46 keV. Theoretical calculations have been performed which take into account pair correlation, quasiparticle-phonon interaction, rotation-vibration interaction and Coriolis coupling. The energy and structure of individual levels, the ratios of intensities for gamma-ray transitions and multipolarity admixtures are predicted. In general, good agreement is achieved between the theoretical calculations and the experimental results.

The Chemical Effects of Radiative Thermal Neutron Capture

The Chemical Effects of Radiative Thermal Neutron Capture

Nuclear resonant scattering of gamma rays in Cu, Sn and Bi

Nuclear resonant scattering experiments have been carried out employing γ-lines from thermal neutron radiative capture. The cross sections for nuclear resonant scattering and absorption have been measured at different temperatures. Angular distributions of the resonance scattered γ-rays have been analysed. The level width for the ground-state transition and the total width have been derived for each resonance.

Strahlungseinfang langsamer Neutronen im thermischen und Resonanz-Bereich

Within the framework of the many-levelR-matrix formalism the theory ofLane andLynn allows one to calculate the partial cross sections for radiative capture of thermal and resonance energy neutrons. If the cross section for capture to a given final state of the product nucleus has been measured for a number of neutron energies in the thermal and resonance regions, then the variation of the above cross section with incident neutron energy can be completely determined. This calculation has been carried out for the reaction Mn55(n, γ) Mn56 for two distinct final states of Mn56, where enough data are available to fix the parameters for resonance internal capture.

Gamma-Ray Spectra from Radiative Capture of Thermal and Resonance Neutrons in Mercury and Tungsten

A 20-cc lithium-drifted germanium detector has been used in conjunction with the R.P.I. Electron Linac Neutron Velocity Selector to examine the high-energy gamma-ray spectra arising from thermal and resonance neutron capture in mercury, and from resonance capture in tungsten. The effective gamma-ray energy resolution of 12-18 keV allowed 29 transitions to be examined in the energy range 4.67 to 8.02 MeV following capture of thermal neutrons and resonance neutrons of energy 34, 130, and 175 eV in $^{199}\mathrm{Hg}$ (116 transitions in all). The spectra are interpreted in terms of levels in the compound nucleus $^{200}\mathrm{Hg}$. An analysis of the strengths of 88 $E1$ transitions indicates a Porter-Thomas distribution, the best fit being achieved with a ${\ensuremath{\chi}}^{2}$ function with $0.96_{\ensuremath{-}0.17}^{}{}_{}{}^{+0.24}$ degrees of freedom. The mean reduced partial radiation width for transitions to states in $^{200}\mathrm{Hg}$ above the pairing energy gap is shown to be significantly higher than the corresponding mean width for transitions to collective states below the pairing energy. No such effect is obvious in the case of resonance capture in $^{183}\mathrm{W}$. A comparison between resonance capture in $^{198}\mathrm{Hg}$ and $^{182}\mathrm{W}$, where no pairing energy gap exists, shows that the mean partial radiation width is a factor 4 larger for $^{198}\mathrm{Hg}$ than for the highly distorted $^{182}\mathrm{W}$.

Spectrum of γ-rays from the Fe 56(n, γ)Fe 57 reaction

Measurements are given of a spectrum of γ-rays emitted in radiative capture of thermal neutrons by Fe nuclei. Energies and intensities are determined for 61 lines. A Fe 57 γ-transition scheme is constructed on the basis of the data obtained. Radiative properties of the levels of this nucleus are discussed. From a comparison of yields in the (n, γ) and (d, p) reactions on Fe 56 as well as from the data on Fe 57 level decay it is concluded that the direct capture does not play the main role in the absorption of a thermal neutron by Fe 56.

Influence of Crystal Defects on the Annealing of Chemical Radiation Damage

RECENT investigations have shown that crystal defects determine the fate of the fragments generated in solids by radiative thermal neutron capture as well as the kinetics of subsequent annealing reactions1,2. So far, there has been no experimental evidence for the influence of defects on the annealing of chemical damage produced in solids by irradiation. We have now obtained such evidence in the case of annealing in lead nitrate.

Radiative Thermal Neutron Capture in some Phosphorus Compounds

Radiative Thermal Neutron Capture in some Phosphorus Compounds

Chemical effects of radiative thermal neutron capture. Part 11.—Thermal and radiation annealing in neutron irradiated phosphates

A study of the neutron irradiation of a number of phosphates was carried out using paper electrophoresis for the separation of the products. The processes of thermal and radiation annealing were examined and by using lowtemperature neutron irradiations a more complete picture of these processes was established. Chemical and paper electrophoretic separations were found to give comparable results. A limiting wavelength for photo-annealing is reported. Mechanisms for the annealing reactions are proposed and the identities of the metastable fragments are discussed. (auth)

Chemical effects of radiative thermal neutron capture. Part 13.—Influence of crystal defects

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Chemical effects of radiative thermal neutron capture. Part 10.—Influence of crystal defects on the retention

Download options Please wait... Article information DOI https://doi.org/10.1039/TF9635900924 Article type Paper Download Citation Trans. Faraday Soc., 1963,59, 924-934 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Chemical effects of radiative thermal neutron capture. Part 10.—Influence of crystal defects on the retention A. G. Maddock, F. E. Treloar and J. I. Vargas, Trans. Faraday Soc., 1963, 59, 924 DOI: 10.1039/TF9635900924 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author A. G. Maddock F. E. Treloar J. I. Vargas

Chemical effects of radiative thermal neutron capture. Part 12.—Annealing by compression

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INFLUENCE OF THE DEFECT CENTERS ON THE SZILARD–CHALMERS ANNEALING

Reactor-irradiated copper and cobalt oxinates were studied for the behavior of Cu64 and Co60 atoms produced by radiative thermal neutron capture. The annealing processes associated with the Szilard–Chalmers effect were followed by means of retention. Both substances exhibit annealing at room temperature, formally following first-order kinetics. The retention was found to increase with reactor exposure time, following kinetics similar to that for post-irradiation thermal annealing. The interpretation of experimental data relies on the assumption that fractions annealed at room temperature decrease with increasing density of defect centers containing an annealable Szilard–Chalmers atom.

U238Radiative Capture in PWR-2 Blanket Geometry

Measurements of rho/sup 28/, the ratio of epithermal to thermal neutron radiative capture in U/sup 238/, was carried out in the plate fuel geometry planned for the second Shippingport Pressurized Water Reactor (PWR-2). The experimental results are compared with two-dimensional diffusion theory analyses, and the agreement is considered satisfactory. (auth)

Transitions between low-lying excited states of Mn 54 and Ho 166

The measurement of coincidence of cascade-quanta is used as a technique for investigating the low-lying levels nucleus of Mn 54 and Ho 144 arising in the radiative capture of thermal neutrons. Reduced probabilities of M1 and E2 mixed radiative transitions with energies of 25 and 85 keV are found for Mn 54. The rotational band O −, 2 −, 154.2 KeV and 4 − (174 keV) is detected in the strongly deformed nucleus Ho 166.

Chemical effects of radiative thermal neutron capture. Part 9.—Photochemical annealing in neutron-irradiated phosphates

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Chemical effects of radiative thermal neutron capture. Part 8.—Retention in solid solutions of chromates

The initial retention, the limiting retention after thermal annealing, and the susceptibility to radiation annealing, of thermal neutron-irradiated solid solutions of potassium chromate in potassium fluoberyllate were shown to be linear functions of the composition of the mixed crystals. Such a relation is found to be incompatible with the activated exchange model for the radiation annealing process. The susceptibilities of a number of chromates and dichromates to thermal and radiation annealing were determined and the behavior of ammonium dichromate and anhydrous lithium chromate studied in more detail. No evidence of the epithermal reaction of the fragments with ammonium ions was obtained. Some futher data on mixed crystals of chromates and sulfates are reported. (auth)

Atlas of γ‐Ray Spectra from Radiative Capture of Thermal Neutrons

<i>Atlas of γ‐Ray Spectra from Radiative Capture of Thermal Neutrons</i>

The chemical effects of radiative thermal neutron capture. Part 6.—Potassium chlororhenite, isotope effects and the annealing process

The thermal annealing of the recoil damage, following neutron capture in potassium chlororhenite, was investigated for both the Re/sup 186/ and Re/sup 188/ isotopes. Although the initial retentions are different the two isotopic fragments seem to recombine at the same speed. The slow annealing process is shown to be zero order with a very small energy of activation. The radiation annealing and a combination radiation and thermal annealing were also examined. (auth)