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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 1,459 records · Page 81
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Search for one-phonon mixed-symmetry states in the radioactive nucleus {sup 140}Nd

Low-spin excited states of {sup 140}Nd have been studied via the {sup 140}Ce({sup 3}He,3n){sup 140}Nd reaction. The data show that one of the candidates for the one-phonon mixed-symmetry state (MSS) of {sup 140}Nd, namely, the 2{sub 3}{sup +} state at 2140 keV with an effective lifetime of 220(90) fs, exhibits a fast M1 decay to the 2{sub 1}{sup +} state. Thus, this state can be considered, at least, as a fragment of the one-phonon MSS of {sup 140}Nd. This is the first example where mixed symmetry character is tentatively assigned to a state of an unstable nucleus from the mass A{approx_equal}140 region based on the data on absolute M1 transition rates. However, the data are not conclusive on whether this decay exhausts the total M1 strength or whether the one-phonon MSS of {sup 140}Nd is fragmented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Noncharacteristic half-lives in radioactive decay

Half-lives of radionuclides span more than 50 orders of magnitude. We characterize the probability distribution of this broad-range data set at the same time that we explore a method for fitting power laws and testing goodness-of-fit. It is found that the procedure proposed recently by Clauset et al.[SIAM Rev. 51, 661 (2009)] does not perform well as it rejects the power-law hypothesis even for power-law synthetic data. In contrast, we establish the existence of a power-law exponent with a value around 1.1 for the half-life density, which can be explained by the sharp relationship between decay rate and released energy, for different disintegration types. For the case of alpha emission, this relationship constitutes an original mechanism of power-law generation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

β -Delayed Neutron Spectroscopy Using Trapped Radioactive Ions

Here, a novel technique for β-delayed neutron spectroscopy has been demonstrated using trapped ions. The neutron-energy spectrum is reconstructed by measuring the time of flight of the nuclear recoil following neutron emission, thereby avoiding all the challenges associated with neutron detection, such as backgrounds from scattered neutrons and γ rays and complicated detector-response functions. 137 I + ions delivered from a 252 Cf source were confined in a linear Paul trap surrounded by radiation detectors, and the β-delayed neutron-energy spectrum and branching ratio were determined by detecting the β - and recoil ions in coincidence. Systematic effects were explored by determining the branching ratio three ways. Improvements to achieve higher detection efficiency, better energy resolution, and a lower neutron-energy threshold are proposed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

New Fe 59 Stellar Decay Rate with Implications for the Fe 60 Radioactivity in Massive Stars

The discrepancy between observations from γ-ray astronomy of the 60 Fe/ 26 Al γ-ray flux ratio and recent calculations is an unresolved puzzle in nuclear astrophysics. The stellar β-decay rate of 59 Fe is one of the major nuclear uncertainties impeding us from a precise prediction. The important Gamow-Teller strengths from the low-lying states in 59 Fe to the 59 Co ground state are measured for the first time using the exclusive measurement of the 59 Co(t,3He+γ) 59 Fe charge-exchange reaction. The new stellar decay rate of 59 Fe is a factor of 3.5±1.1 larger than the currently adopted rate at T=1.2 GK. Stellar evolution calculations show that the 60 Fe production yield of an 18 solar mass star is decreased significantly by 40% when using the new rate. Our result eliminates one of the major nuclear uncertainties in the predicted yield of 60 Fe and alleviates the existing discrepancy of the 60 Fe/ 26 Al ratio.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

The advancement of a technique using principal component analysis for the non-intrusive depth profiling of radioactive contamination

A non-intrusive technique using principal component analysis, to infer the depth of the fission fragment caesium-137, when it is buried under silica sand has been described. Using energy variances within different {gamma}-ray spectra, a complete depth model was produced for a single caesium-137 source buried under 1 mm depths ranging between 5-50 mm. This was achieved using a cadmium telluride detector and a bespoke phantom. In this paper we describe the advancement of the technique by further validating it using blind tests for applications outside of the laboratory, where not only the depth (z) but also the surface (x, y) location of {gamma}-ray emitting contamination is often poorly characterised. At present the technique has been tested at the point of maximum activity above the entrained {gamma}-ray emitting source (where the optimal x, y location is known). This is not usually practical in poorly characterized environments where the detector cannot be conveniently placed at such an optimal location to begin with and scanning at multiple points around the region of interest is often required. Using a uniform scanning time, the point of maximum intensity can be located by sampling in terms of total count rate, and converging on this optimal point of maximum intensity. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Radioactive source localization in urban environments with sensor networks and the Internet of Things

The use of radiation detectors as an element in the so-called “Internet of Things” has recently become viable with the available of low-cost, mobile radiation sensors capable of streaming geo-referenced data. New methods for fusing the data from multiple sensors on such a network is presented. The traditional simple and ordinary Kriging methods present a challenge for such a network since the assumption of a constant mean is not valid in this application. In conclusion, a variety of Kalman filters are introduced in an attempt to solve the problem associated with this variable and unknown mean. Results are presented on a deployed sensor network.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Approach for Configuring a Standardized Vessel for Processing Radioactive Waste Slurries

A standardized vessel design is being considered at the Waste Treatment and Immobilization Plant (WTP) that is under construction at Hanford, Washington. The standardized vessel design will be used for storing, blending, and chemical processing of slurries that exhibit a variable process feed including Newtonian to non-Newtonian rheologies over a range of solids loadings. Developing a standardized vessel is advantageous and reduces the testing required to evaluate the performance of the design. The objectives of this paper are to: 1) present a design strategy for developing a standard vessel mixing system design for the pretreatment portion of the waste treatment plant that must process rheologically and physically challenging process streams, 2) identify performance criteria that the design for the standard vessel must satisfy, 3) present parameters that are to be used for assessing the performance criteria, and 4) describe operation of the selected technology. Vessel design performance will be assessed for both Newtonian and non-Newtonian simulants which represent a range of waste types expected during operation. Desired conditions for the vessel operations are the ability to shear the slurry so that flammable gas does not accumulate within the vessel, that settled solids will be mobilized, that contents can be blended, and that contents can be transferred from the vessel. A strategy is presented for adjusting the vessel configuration to ensure that all these conditions are met.

pulse jet mixing↗
DOE OSTI2013

Bayesian analysis of energy and count rate data for detection of low count rate radioactive sources

We propose a radiation detection system which generates its own discrete sampling distribution based on past measurements of background. The advantage to this approach is that it can take into account variations in background with respect to time, location, energy spectra, detector-specific characteristics (i.e. different efficiencies at different count rates and energies), etc. This would therefore be a 'machine learning' approach, in which the algorithm updates and improves its characterization of background over time. The system would have a 'learning mode,' in which it measures and analyzes background count rates, and a 'detection mode,' in which it compares measurements from an unknown source against its unique background distribution. By characterizing and accounting for variations in the background, general purpose radiation detectors can be improved with little or no increase in cost. The statistical and computational techniques to perform this kind of analysis have already been developed. The necessary signal analysis can be accomplished using existing Bayesian algorithms which account for multiple channels, multiple detectors, and multiple time intervals. Furthermore, Bayesian machine-learning techniques have already been developed which, with trivial modifications, can generate appropriate decision thresholds based on the comparison of new measurements against a nonparametric sampling distribution. (authors)

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2015

TU-F-CAMPUS-T-01: Dose and Energy Spectra From Neutron Induced Radioactivity in Medical Linear Accelerators Following High Energy Total Body Irradiation

Purpose: To assess the risk posed by neutron induced activation of components in medical linear accelerators (linacs) following the delivery of high monitor unit 18 MV photon beams such as used in TBI. Methods: Gamma spectroscopy was used to identify radioisotopes produced in components of a Varian 21EX and an Elekta Synergy following delivery of photon beams. Dose and risk estimates for TBI were assessed using dose deliveries from an actual patient treatment. A 1 litre spherical ion chamber (PTW, Germany) has been used to measure the dose at the beam exit window and at the total body irradiation (TBI) treatment couch following large and small field beams with long beam-on times. Measurements were also made outside of the closed jaws to quantify the benefit of the attenuation provided by the jaws. Results: The radioisotopes produced in the linac head have been identified as {sup 187}W, {sup 56}Mn, {sup 24}Na and {sup 28}Al, which have half-lives from between 2.3 min to 24 hours. The dose at the beam exit window following an 18 MV 2197 MU TBI beam delivery was 12.6 µSv in ten minutes. The dose rate at the TBI treatment couch 4.8 m away is a factor of ten lower. For a typical TBI delivered in six fractions each consisting of four beams and an annual patient load of 24, the annual dose estimate for a staff member at the treatment couch for ten minutes is 750 µSv. This can be further reduced by a factor of about twelve if the jaws are closed before entering the room, resulting in a dose estimate of 65 µSv. Conclusion: The dose resulting from the activation products for a representative TBI workload at our clinic of 24 patients per year is 750 µSv, which can be further reduced to 65 µSv by closing the jaws.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2017

Unstable nuclei in dissociation of light stable and radioactive nuclei in nuclear track emulsion

A role of the unstable nuclei {sup 6}Be, {sup 8}Be and {sup 9}B in the dissociation of relativistic nuclei {sup 7,9}Be, {sup 10}B and {sup 10,11}C is under study on the basis of nuclear track emulsion exposed to secondary beams of the JINR Nuclotron. Contribution of the configuration {sup 6}Be + n to the {sup 7}Be nucleus structure is 8 ± 1% which is near the value for the configuration {sup 6}Li + p. Distributions over the opening angle of α-particle pairs indicate to a simultaneous presence of virtual {sup 8}Be{sub g.s}. and {sup 8}Be{sub 2+} states in the ground states of the {sup 9}Be and {sup 10}C nuclei. The core {sup 9}B is manifested in the {sup 10}C nucleus with a probability of 30 ± 4%. Selection of the {sup 10}C “white” stars accompanied by {sup 8}Be{sub g.s}. ({sup 9}B) leads to appearance in the excitation energy distribution of 2α2p “quartets” of the distinct peak with a maximum at 4.1 ± 0.3 MeV. {sup 8}Be{sub g.s}. decays are presented in 24 ± 7% of 2He + 2H events of the {sup 11}C coherent dissociation and 27 ± 11% of the 3He ones. The channel {sup 9}B + H amounts 14 ± 3%. The {sup 8}B{sub g.s}. nucleus is manifested in the coherent dissociation {sup 10}B → 2He + H with a probability of 25 ± 5% including 13 ± 3% of {sup 9}B decays. A probability ratio of the mirror channels {sup 9}B + n and {sup 9}Be + p is estimated to be 10 ± 1.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Variation in the State of 19m Sn Impurity Atoms in PbTe during the Establishment of the Radioactive Equilibrium of 119m Te/ 119 Sb Isotopes

The parameters of the emission Mössbauer spectra of PbTe using the 119m Sn daughter isotope with different parent nuclei 119mm Sn, 119 Sb, and 119m Te are compared. This comparison makes it possible to identify impurity tin atoms in both lead-telluride sublattices. It is found that the ratio of tin concentrations in different sublattices depends on the time after source preparation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗