Search Results

Advanced search parameters have been applied.


Description: A new rapid fusion method for the determination of plutonium in large rice samples has been developed at the Savannah River National Laboratory (Aiken, SC, USA) that can be used to determine very low levels of plutonium isotopes in rice. The recent accident at Fukushima Nuclear Power Plant in March, 2011 reinforces the need to have rapid, reliable radiochemical analyses for radionuclides in environmental and food samples. Public concern regarding foods, particularly foods such as rice in Japan, highlights the need for analytical techniques that will allow very large sample aliquots of rice to be used for analysis so that very low levels of plutonium isotopes may be detected. The new method to determine plutonium isotopes in large rice samples utilizes a furnace ashing step, a rapid sodium hydroxide fusion method, a lanthanum fluoride matrix removal step, and a column separation process with TEVA Resin� cartridges. The method can be applied to rice sample aliquots as large as 5 kg. Plutonium isotopes can be determined using alpha spectrometry or inductively-coupled plasma mass spectrometry (ICP-MS). The method showed high chemical recoveries and effective removal of interferences. The rapid fusion technique is a rugged sample digestion method that ensures that any refractory plutonium particles are effectively digested. The MDA for a 5 kg rice sample using alpha spectrometry is 7E-5 mBq g{sup -1}. The method can easily be adapted for use by ICP-MS to allow detection of plutonium isotopic ratios.
Date: March 1, 2013
Creator: Maxwell, S.
Partner: UNT Libraries Government Documents Department

Status of Current Plutonium Evaluations And an Update Plan for ENDL99

Description: We review the current state of ENDL99, ENDF/B-VI.r8, JENDL-3.3, JEFF-3.0 and ENDF/B-VII.{beta}0 plutonium evaluations and lay out a tentative plan for updating all of the ENDL99 plutonium evaluations. In some specific cases, an evaluation for a particular isotope is of sufficient quality for us to adopt in ENDL99. More often, the quality of all evaluations for an isotope are low enough that we will need to perform a new evaluation.
Date: April 29, 2005
Creator: Brown, D A
Partner: UNT Libraries Government Documents Department

The Separation of Uranium and Plutonium Isotopes in Chemical Exchange Systems

Description: The theory and results of chemical exchange experiments for separation of Pu and U isotopes are presented. Solvent extraction systems were studied in both aqueous and organic media. Chemical exchange systems are proposed which could yield high separation factors. (W.L.H.)
Date: May 16, 1955
Creator: Hahn, H.T.
Partner: UNT Libraries Government Documents Department

Selection of Actinide Chemical Analogues for WIPP Tests: Potential Nonradioactive Sorbing and Nonsorbing Tracers for Study of Ion Transport in the Environment

Description: Chemical characteristics of the actinides (Th, U, Np, Pu, Am) have been studied relative to nonradioactive chemical elements that have similar characteristics in an attempt to identify a group of actinide chemical analogues that are nonradioactive. In general, the chemistries of the actinides, especially U, Np, Pu, and Am, are very complex and attempts to identify a single chemical analogue for each oxidation state were not successful. However, the rationale for selecting a group of chemical analogues that would mimic the actinides as a group is provided. The categorization of possible chemical analogues (tracers) with similar chemical properties was based on the following criteria. Categorization was studied according.
Date: August 1, 1998
Creator: Spall, Dale & Villarreal, Robert
Partner: UNT Libraries Government Documents Department

Radionuclide Concentrations in Soils and Vegetation at Low-Level Radioactive Waste Disposal Area G during the 1997 Growing Season

Description: Soil and overstory and understory vegetation (washed and unwashed) collected at eight locations within and around Area G-a low-level radioactive solid-waste disposal facility at Los Alamos National Laboratory-were analyzed for 3H, 238Pu, 239Pu, 137CS, 234U, 235U, 228AC, Be, 214Bi, 60Co, 40& 54Mn, 22Na, 214Pb and 208Tl. In general, most radionuclide concentrations, with the exception of 3Ef and ~9Pu, in soils and overstory and understory vegetation collected from within and around Area G were within upper (95'%) level background concentrations. Although 3H concentrations in vegetation from most sites were significantly higher than background (>2 pCi mL-l), concentrations decreased markedly in comparison to last year's results. The highest `H concentration in vegetation was detected from a juniper tree that was growing over tritium shaft /+150; it contained 530,000 pCi 3H mL-l. Also, as in the pas~ the transuranic waste pad area contained the highest levels of 239Pu in soils and in understory vegetation as compared to other areas at Area G.
Date: August 1, 1998
Creator: L. Naranjo, Jr.; Fresquez, P. R. & Wechsler, R. J.
Partner: UNT Libraries Government Documents Department

Neutron Fission of 235,237,239U and 241,243Pu: Cross Sections, Integral Cross Sections and Cross Sections on Excited States

Description: In a recent paper submitted to Phys. Rev. C they have presented estimates for (n,f) cross sections on a series of Thorium, Uranium and Plutonium isotopes over the range E{sub n} = 0.1-2.5 MeV. The (n,f) cross sections for many of these isotopes are difficult or impossible to measure in the laboratory. The cross sections were obtained from previous (t,pf) reaction data invoking a model which takes into account the differences between (t,pf) and (n,f) reaction processes, and which includes improved estimates for the neutron compound formation process. The purpose of this note is: (1) to compare the estimated cross sections to current data files in both ENDF and ENDL databases; (2) to estimate ratios of cross sections relatively to {sup 235}U integrated over the ''tamped flattop'' critical assembly spectrum that was used in the earlier {sup 237}U report; and (3) to show the effect on the integral cross sections when the neutron capturing state is an excited rotational state or an isomer. The isomer and excited state results are shown for {sup 235}U and {sup 237}U.
Date: July 10, 2003
Creator: Younes, W & Britt, H C
Partner: UNT Libraries Government Documents Department

Time and frequency domain measurements for plutonium metal rings

Description: The {sup 252}Cf-source-driven noise analysis method was used to measure the neutron multiplication factor for subcritical systems and to identify fissionable materials and configurations. These measurements with the moderator-ring configuration have shown that the {sup 252}Cf-source-driven noise methods, both in the time and frequency domain, can be used to identify and distinguish the {sup 242}Pu from the {sup 239}Pu ring. Signatures for each ring can be used to track and confirm the presence of these two types of Pu rings. Because of the sensitivity of these signatures to mass, these measurements can also confirm the Pu mass. These preliminary measurements have not yet explored the full range of capability of this method for this application.
Date: September 1996
Creator: Mihalczo, J. T.; Pare, V. K.; Blakeman, E. D.; Valentine, T. E.; Vessard, S. & Pruvost, N. L.
Partner: UNT Libraries Government Documents Department

Methods to Collect, Compile, and Analyze Observed Short-lived Fission Product Gamma Data

Description: A unique set of fission product gamma spectra was collected at short times (4 minutes to 1 week) on various fissionable materials. Gamma spectra were collected from the neutron-induced fission of uranium, neptunium, and plutonium isotopes at thermal, epithermal, fission spectrum, and 14-MeV neutron energies. This report describes the experimental methods used to produce and collect the gamma data, defines the experimental parameters for each method, and demonstrates the consistency of the measurements.
Date: September 29, 2011
Creator: Finn, Erin C.; Metz, Lori A.; Payne, Rosara F.; Friese, Judah I.; Greenwood, Lawrence R.; Kephart, Jeremy D. et al.
Partner: UNT Libraries Government Documents Department

Low energy gamma-transitions in Pu{sup 238} and Pu{sup 240}

Description: We investigated electron and gamma spectra of mixtures of isotopes of curium. This was done on a beta spectrometer with double focusing at an angle of {pi}{radical}2 and on a scintillation gamma spectrometer with a 40 {times} 40 mm NAI(Tl) single crystal detector. The observed electron spectrum are interpolated and presented. Also, experimental results of the ratio of conversion at L and M subshells are presented and compared to theoretical values.
Date: March 27, 1967
Creator: Akalaev, G. G.; Vartanov, N. A. & Samoilov, P. S.
Partner: UNT Libraries Government Documents Department

Preparation of actinide targets by molecular plating for Coulomb excitation studies at ATLAS.

Description: Molecular plating is now routinely used to prepare sources and targets of actinide elements. Although the technique is simple and fairly reproducible, because of the radioactive nature of the target it is very useful to record various parameters in the preparation of such targets. At Argonne, {approximately}200 {micro}g/cm{sup 2} thick targets of Pu and Cm were required for Coulomb Excitation (COULEX) Studies with the Argonne-Notre Dame BGO gamma ray facility and later with the GAMMASPHERE. These targets were plated on 50 mg/cm{sup 2} Au backing and were covered with 150 {micro}g/cm{sup 2} Au foil. Targets of {sup 239}Pu, {sup 240}Pu, {sup 242}Pu, {sup 244}Pu and {sup 248}Cm were prepared by dissolving the material in isopropyl alcohol and electroplating the actinide ions by applying 600 volts. The amount of these materials on the target was determined by alpha particle counting and gamma ray counting. Details of the molecular plating and counting will be discussed.
Date: November 18, 1998
Creator: Greene, J. P.
Partner: UNT Libraries Government Documents Department

Plutonium measurements by accelerator mass spectrometry at LLNL

Description: Mass spectrometric methods provide sensitive, routine, and cost-effective analyses of long-lived radionuclides. Here the authors report on the status of work at Lawrence Livermore National Laboratory (LLNL) to develop a capability for actinide measurements by accelerator mass spectrometry (AMS) to take advantage of the high potential of AMS for rejection of interferences. This work demonstrates that the LLNL AMS spectrometer is well-suited for providing high sensitivity, robust, high throughput measurements of plutonium concentrations and isotope ratios. Present backgrounds are {approximately}2 x 10{sup 7}atoms per sample for environmental samples prepared using standard alpha spectrometry protocols. Recent measurements of {sup 239+240}Pu and {sup 241}Pu activities and {sup 240}Pu/{sup 239}Pu isotope ratios in IAEA reference materials agree well with IAEA reference values and with alpha spectrometry and recently published ICP-MS results. Ongoing upgrades of the AMS spectrometer are expected to reduce backgrounds below 1 x 10{sup 6} atoms per sample while allowing simplifications of the sample preparation chemistry. These simplifications will lead to lower per-sample costs, higher throughput, faster turn around and, ultimately, to larger and more robust data sets.
Date: October 26, 1999
Creator: McAninch, J E; Hamilton, T F; Broan, T A; Jokela, T A; Knezovich, T J; Ognibene, T J et al.
Partner: UNT Libraries Government Documents Department


Description: Minimizing plutonium measurement uncertainty is essential to nuclear material control and international safeguards. In 2005, the International Organization for Standardization (ISO) published ISO 12183 'Controlled-potential coulometric assay of plutonium', 2nd edition. ISO 12183:2005 recommends a target of {+-}0.01% for the mass of original sample in the aliquot because it is a critical assay variable. Mass measurements in radiological containment were evaluated and uncertainties estimated. The uncertainty estimate for the mass measurement also includes uncertainty in correcting for buoyancy effects from air acting as a fluid and from decreased pressure of heated air from the specific heat of the plutonium isotopes.
Date: March 18, 2009
Creator: Holland, M. & Cordaro, J.
Partner: UNT Libraries Government Documents Department

Project AN0115A Annual Report, 1976: Migration of Plutonium and Americium in the Lithosphere

Description: Annual report of Argonne National Laboratory project ANO115A. Abstract: Studies have been carried out on the migration of plutonium and americium in solutions flowing through porous and crushed rock and through fissures. The migration process can be described in terms of the surface absorption of these elements. In addition, chemical effects on the absorption have been observed. One of these effects is possibly due to the presence of a plutonium polymer that migrates at a more rapid rate than normal plutonium.
Date: 1976
Creator: Hines, J. J.; Friedman, M. A.; Fried, S.; Atcher, Robert Whitehill; Quarterman, L. A. & Volesky, A.
Partner: UNT Libraries Government Documents Department

Monte Carlo calculations of gamma-ray spectra for calibration

Description: We have developed a methodology to simulate gamma-ray energy spectra to aid those who assay special nuclear materials (SNM) such as Pu or U. Isotopic standards of SNM are difficult to make and certify and therefore costly; computer simulation can create gamma-ray spectra representative of isotopic standards. These simulations, while not substituting completely for physical standards, can help.
Date: December 1, 1996
Creator: Wang, Tzu-Fang
Partner: UNT Libraries Government Documents Department

The radiological hazard of plutonium isotopes and specific plutonium mixtures

Description: The US Department of Energy defines the hazard categories of its nuclear facilities based upon the potential for accidents to have significant effects on specific populations and the environment. In this report, the authors consider the time dependence of hazard category 2 (significant on-site effects) for facilities with inventories of plutonium isotopes and specific weapons-grade and heat-source mixtures of plutonium isotopes. The authors also define relative hazard as the reciprocal of the hazard category 2 threshold value and determine its time dependence. The time dependence of both hazard category 2 thresholds and relative hazards are determined and plotted for 10,000 years to provide useful information for planning long-term storage or disposal facilities.
Date: November 1, 1995
Creator: Heindel, G.; Clow, J.; Inkret, W. & Miller, G.
Partner: UNT Libraries Government Documents Department
Back to Top of Screen