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Radiation-induced mesotheliomas in rats

Description: Mesotheliomas have been reported in rats that inhaled plutonium, but these tumors have not been extensively studied. To investigate a possible role for inhaled radionuclides in the induction of mesotheliomas, four life-span studies conducted at the Inhalation Toxicology Research Institute are reviewed. A total of 3076 F344 rats were exposed by inhalation to aerosols of {sup 239}PuO{sub 2}, mixed uranium-plutonium oxide, or {sup 144}CeO{sub 2}. Results showed that a low incidence of pleural mesotheliomas was induced by either alpha- or beta-emitting radionuclides deposited and retained in the lung. Chronic alpha irradiation was more effective per unit dose in producing mesotheliomas than chronic beta irradiation of the lung by a factor of 15. 7 refs., 1 tab., 7 figs. (MHB)
Date: January 1, 1990
Creator: Hahn, F.F.; Haley, P.J.; Hubbs, A.F.; Hoover, M.D. & Lundgren, D.L.
Partner: UNT Libraries Government Documents Department

Double beta decay of U-238

Description: During the last period, two samples of 33 yr old uranyl nitrate have been examined for the accumulation of Pu-238 formed as a result of double beta decay. The 2.5 kg sample has led only to an upper limit of 6 {times} 10{sup 20} yr. The 8.5 kg sample has produced positive results corresponding to a half-life of 2 {times} 10{sup 21 } yr. The possibility of contaminating nuclear reactions has been carefully examined and eliminated. The possibility that contamination may have been introduced by the large quantities of chemicals that were used is being investigated. 5 refs.
Date: November 1, 1990
Creator: Turkevich, A. & Economou, T.
Partner: UNT Libraries Government Documents Department

Characteristics of the samples in the FNG fission deposit collection

Description: Information concerning the samples in the Fast Neutron Generator (FNG) Group's fission deposit collection has been assembled. This includes the physical dimensions, isotopic analyses, half-lives, alpha emission rates specific activities and deposit weights. 10 refs., 9 figs., 5 tabs.
Date: December 1, 1990
Creator: Meadows, J.W.
Partner: UNT Libraries Government Documents Department

sup 176 Lu: An unreliable s-process chronometer

Description: A level scheme of {sup 176}Lu up to {approximately}1400 keV excitation energy is deduced from a gamma-gamma coincidence experiment and previously published particle transfer data. 170 gamma-ray transitions are placed between 85 levels, confirming many of the previously established levels and some of the decay scheme. A level at 835.5 keV (J{sup {pi}} = 5{sup {minus}}, t{sub 1/2} < 10 ns) decays with substantial strength to both the ground state (7{sup {minus}}, 4.08 {times} 10{sup 10} yr) and the 122.9 keV isomer (1{sup {minus}}, 3.7 hr). The presence of this level guarantees the thermal equilibration of {sup 176}Lu{sup g,m} for temperatures greater than 3 {times} 10{sup 8} K and therefore during s-process nucleosynthesis. The resulting extreme temperature sensitivity of its effective half-life rules out the use of {sup 176}Lu as an s-process chronometer. The use of {sup 176}Lu to determine s-process temperatures is discussed. 30 refs., 11 figs., 3 tabs.
Date: November 1, 1990
Creator: Lesko, K.T.; Norman, E.B.; Larimer, R.M. & Sur, B.
Partner: UNT Libraries Government Documents Department

An evaluation of the Nb-93(n,n prime )Nb-93m dosimeter reaction for ENDF/B-VI

Description: The Nb-93(n,n{prime})Nb-93m reaction plays an important role in nuclear energy applications. Because of its low threshold energy and relatively long half-life, it is a desirable reaction for long-term neutron fluence dosimetry in nuclear fission reactors. An evaluation of the differential cross section for this reaction was completed in 1985 by this laboratory as part of a comprehensive effort involving all neutron cross sections for niobium. The objective was to provide input for ENDF/B-VI. It was difficult to produce a reliable evaluation for this reaction in 1985 because the information available then was sparse and quite uncertain. In fact, that evaluation was based entirely on nuclear model calculations. The evaluated cross sections below 0.7 MeV were derived from calculations carried out in this laboratory, while the higher energy values were obtained from the work of Strohmaier and co-workers. In 1985 there was only one published experimental differential cross section value to consider for this reaction. Even the half-life of Nb-93m was in serious doubt. During the five years between the completion of the earlier evaluation and the finalization of ENDF/B-VI there have been some significant improvements and additions to the experimental database for this reaction. Also, new model calculations have been performed. Therefore, it was considered worthwhile to produce a new evaluation of Nb-93(n,n{prime})Nb-93m for ENDF/B-VI which would supplant the one that had been completed in 1985.
Date: November 1, 1990
Creator: Smith, D.L. & Geraldo, L.P.
Partner: UNT Libraries Government Documents Department

Safety and environmental aspects of HYLIFE-II

Description: The HYLIFE-II inertial confinement fusion reactor uses a Flibe spray for blast chamber protection and tritium breeding. HYLIFE-II is passively safe, having no large sources of energy available to disperse radioactive materials. The dominant activation product is {sup 18}F (half-life 110 minutes). Only a small fraction (< 10{sup {minus}5}) of the Flibe activation products would be mobilized. The offsite dose from a severe accident involving simultaneous failure of the blast chamber and containment building would be < 0.2 mSv (20 mrem), and N-stamp requirements could be avoided in the blast chamber and coolant systems. The required tritium removal efficiencies are quantified. 10 refs., 1 fig.
Date: January 1, 1990
Creator: Dolan, T.J. & Longhurst, G.R. (Idaho National Engineering Lab., Idaho Falls, ID (USA))
Partner: UNT Libraries Government Documents Department

An interesting finding in sup 229 Th

Description: Work at INEL has recently established that the first excited states of {sup 229}Th forms a closely spaced doublet with the ground state, the separation being 1 {plus minus} 4 electron volts. A discussion of the data and the reasoning supporting this unprecedented finding is given. Some potential applications are briefly mentioned. 27 refs., 3 figs., 2 tabs.
Date: January 1, 1990
Creator: Reich, C.W.
Partner: UNT Libraries Government Documents Department