Papers by Alfredo Marchetti
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2004
We report on the development of an accelerator mass spectrometry (AMS) system for the measurement... more We report on the development of an accelerator mass spectrometry (AMS) system for the measurement of actinides at Lawrence Livermore National Laboratory. This AMS system is centered on a recently completed heavy isotope beam line that was designed particularly for high sensitivity, robust, high-throughput measurements of actinide concentrations and isotopic ratios. A fast isotope switching capability has been incorporated in the system, allowing flexibility in isotope selection and for the quasi-continuous normalization to a reference isotope spike. Initially, our utilization of the heavy isotope system has concentrated on the measurement of Pu isotopes. Under current operating conditions, background levels equivalent to ~1 X 10 5 atoms are observed during routine 239 Pu and 240 Pu measurements. Measurements of samples containing ~10 13 238 U atoms demonstrate that the system provides a 238 U rejection factor during 239 Pu measurements of ~10 7 . Measurements of known materials, combined with results from an externally organized inter-comparison program, indicate that our 239 Pu measurements are accurate and precise down to the µBq level (~10 6 atoms). Recently, we have investigated the performance of our heavy isotope AMS system in measurements of 237 Np and 236 U. Results of these investigations are discussed. The sensitivity shown by our Pu measurements, combined with the high throughput and interference rejection capabilities of our AMS system, demonstrate that AMS can provide a rapid and cost-effective measurement technique for actinides in a wide variety of studies.
Neither the United States Government nor the University of California nor any of their employees,... more Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of
Projectile-like fragments weredetected andcharacterized interms ofA,Z,mad energy forthereactions ... more Projectile-like fragments weredetected andcharacterized interms ofA,Z,mad energy forthereactions 37CIon 40Caand209BiatE/A = 7.3MeV, and35CIon209Bi atE/A = 15MeV, atangles close tothegrazing angle. Mass andcharge distributions weregenerated intheN-Z plane asa function ofenergy loss, andhavebeen pararneterized interms oftheir centroids, variances, andcoefficients ofcorrelation. Therewas anattempt tomeasure light-charged particles incoincidence withprojcctilclike fragments forthereaction 35CIon 209Bi, buttheresults werenotconclusive. Due toexperimental problems, themassresolution corresponding tothe35CIon 209Bireaction was verypoor.Thisprompted thestudy andapplication ofa dcconvolution technique for peakenhancement. The drifts ofthecharge andmasscentroids forthesystem37CIon 40Caarc consistent witha process ofmass andcharge equilibration mediated bynucleon exchange betweenthetwo partners, followed by evaporation. The asymmetric systems show a strong &ifttowards larger asymmetry, withtheproduction of neutron-rich nuclei. Itwas concluded that this isindicative ofa nettransfer of protons fromthelight totheheavypartner, anda netflowofneutrons intheopposite direction. The variances forall systems increase withenergy loss, asit wouldbe expected fromanucleon exchange mechanism.However,thevariances forthe reaction 37CIon 4°Caarehigher thanthose expected fromthat mechanism.The coefficients of correlation indicate that the transfer of nucleons between projectile and target is correlated, as expected from Q-value constraints to the valley of 13-stability. The results were compared to the predictions of two current models based on a stochastic nucleon exchange mechanism. In general, the comparisons between experimental and predicted variances support this mechanism. However, the need for more realistic driving forces in the model calculations is indicated by the disagreement between predicted and experimental centroids.
Volume 4: Potential Ground and Surface Water Impacts
... 4 Volume 4: Potential Ground and Surface Water Impacts Chapter 4: Screening Model Evaluation ... more ... 4 Volume 4: Potential Ground and Surface Water Impacts Chapter 4: Screening Model Evaluation of the Effects of Ethanol on Benzene Plume Lengths Authors Walt McNab* Stephen E. Heermann1Brendan Dooher* Editor G. Cannon* Contributor R. Depue* December 1999 ...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
Major, minor, and trace uranium isotopes were measured at Lawrence Livermore National Laboratory ... more Major, minor, and trace uranium isotopes were measured at Lawrence Livermore National Laboratory in environmentally acquired samples using different instruments to span large variations in concentrations. Multi-collector inductively-coupled plasma mass spectrometry (MC-ICPMS) can be used to measure major and minor isotopes: 238 U, 235 U, 234 U and 236 U. Accelerator mass spectrometry (AMS) can be used to measure minor and trace isotopes: 234 U, 236 U, and 233 U. The main limit of quantification for minor or trace uranium isotopes is the abundance sensitivity of the measurement technique; i.e., the ability to measure a minor or trace isotope of mass M in the presence of a major isotope at M±1 mass units. The abundance sensitivity for 236 U/ 235 U isotope ratio measurements using MC-ICPMS is around ~2x10-6. This compares with a 236 U/ 235 U abundance sensitivity of ~1x10-7 for the current AMS system, with the expectation of 2-3 orders of magnitude improvement in sensitivity with the addition of another high energy filter. Comparing 236 U/ 234 U from MC-ICPMS and AMS produced agreement within ~10% for samples at 236 U levels high enough to be measurable by both techniques.
Chapter 9 ACTIVATION MEASUREMENTS FOR FAST NEUTRONS Part D. Evaluation of Cosmic-Ray-Induced 63Ni Background in
As a result of a joint collaboration between the University of Utah, LLNL, the Technical Universi... more As a result of a joint collaboration between the University of Utah, LLNL, the Technical University Munich and the Ludwig Maximilians University Munich, it became possible to determine A-bomb induced 63Ni in pure copper samples from Hiroshima beyond a ground range of 1,000 m (see Chapter 9, Part B). The low 63Ni activities induced in copper samples due to
Developments in the Measurement of Actinides AND129I at LLNL by Accelerator Mass Spectrometry
ABSTRACT
Tracer-isotope development in environmental and biological sciences
Measurement of Actinides in Environmental Samples at Micro-Becquerel Levels by Accelerator Mass Spectrometry
The need for ultra-sensitive actinide measurements continues to expand in the fields of environme... more The need for ultra-sensitive actinide measurements continues to expand in the fields of environmental stewardship, nuclear isotope forensics, radiobioassay and environmental research. We have developed a heavy isotope accelerator mass spectrometry (AMS) system at Lawrence Livermore National Laboratory's Center for Accelerator Mass Spectrometry (CAMS). The system was designed particularly for the measurement of actinide concentrations and isotopic ratios. A fast isotope switching capability has been incorporated in the system, allowing flexibility in isotope selection and for the quasi-continuous normalization to a reference isotope spike. Initially, our utilization of the system has concentrated on the measurement of Pu isotopes. Under current operating conditions, background levels equivalent to <10ⶠatoms are observed during routine ²³â¹Pu and ²â´Â°Pu measurements. Measurements of samples containing 10¹³ ²³â¸U atoms demonstrate that the system provides a ²³â...
Use of a correlated compound-binomial model to assess absence of non-counting noise in Pu-isotope ratios measured by AMS at LLNL
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2004
Methods for error analysis pertaining to isotopic ratio measures made by accelerator mass spectro... more Methods for error analysis pertaining to isotopic ratio measures made by accelerator mass spectrometry (AMS) typically focus on accuracy/precision of detected counts of a single rare isotope (e.g. 14C), relative to a current strength indicating the abundance of an isotope present in far greater amounts (e.g. 13C). Because AMS analysis of the relative abundance of actinide isotopes involves comparing detected
We report on the development of an accelerator mass spectrometry (AMS) system for the measurement... more We report on the development of an accelerator mass spectrometry (AMS) system for the measurement of actinides at Lawrence Livermore National Laboratory. This AMS system is centered on a recently completed heavy isotope beam line that was designed particularly for high sensitivity, robust, high-throughput measurements of actinide concentrations and isotopic ratios. A fast isotope switching capability has been incorporated in the system, allowing flexibility in isotope selection and for the quasi-continuous normalization to a reference isotope spike. Initially, our utilization of the heavy isotope system has concentrated on the measurement of Pu isotopes. Under current operating conditions, background levels equivalent to ~1 X 10 5 atoms are observed during routine 239 Pu and 240 Pu measurements. Measurements of samples containing
Chemosphere, 2003
The addition of oxygen-bearing compounds to diesel fuel considerably reduces particulate emission... more The addition of oxygen-bearing compounds to diesel fuel considerably reduces particulate emissions. TGME and DBM have been identified as possible diesel additives based on their physicochemical characteristics and performance in engine tests. Although these compounds will reduce particulate emissions, their potential environmental impacts are unknown. As a means of characterizing their persistence in environmental media such as soil and groundwater, we conducted a series of biodegradation tests of DBM and TGME. Benzene and methyl tertiary butyl ether (MTBE) were also tested as reference compounds. Primary degradation of DBM fully occurred within 3 days, while TGME presented a lag phase of approximately 8 days and was not completely degraded by day 28. Benzene primary degradation occurred completely by day 3 and MTBE did not degrade at all. The total mineralized fractions of DBM and TGME achieved constant values as a function of time of $65% and $40%, respectively. Transport predictions show that, released to the environment, DBM and TGME would concentrate mostly in soils and waters with minimal impact to air. From an environmental standpoint, these results combined with the transport predictions indicate that DBM is a better choice than TGME as a diesel additive. Published by Elsevier Science Ltd.
Chemosphere, 2003
The addition of oxygen-bearing compounds to diesel fuel considerably reduces particulate emission... more The addition of oxygen-bearing compounds to diesel fuel considerably reduces particulate emissions. TGME and DBM have been identified as possible diesel additives based on their physicochemical characteristics and performance in engine tests. Although these compounds will reduce particulate emissions, their potential environmental impacts are unknown. As a means of characterizing their persistence in environmental media such as soil and groundwater, we conducted a series of biodegradation tests of DBM and TGME. Benzene and methyl tertiary butyl ether (MTBE) were also tested as reference compounds. Primary degradation of DBM fully occurred within 3 days, while TGME presented a lag phase of approximately 8 days and was not completely degraded by day 28. Benzene primary degradation occurred completely by day 3 and MTBE did not degrade at all. The total mineralized fractions of DBM and TGME achieved constant values as a function of time of $65% and $40%, respectively. Transport predictions show that, released to the environment, DBM and TGME would concentrate mostly in soils and waters with minimal impact to air. From an environmental standpoint, these results combined with the transport predictions indicate that DBM is a better choice than TGME as a diesel additive. Published by Elsevier Science Ltd.
Determination of plutonium activity concentrations and 240Pu/239Pu atom ratios in Brown Algae (Fucus distichus) collected from Amchitka Island, Alaska
Abstract Plutonium-239 (239 Pu) and plutonium-240 (240 Pu) activity concentrations and 240 Pu/239... more Abstract Plutonium-239 (239 Pu) and plutonium-240 (240 Pu) activity concentrations and 240 Pu/239 Pu atom ratios are reported for Brown Algae (Fucus distichus) collected from the littoral zone of Amchitka Island (Alaska), and at a control site at Unalaska, Alaska. The ...
A search for neutron reactions that may be useful for Hiroshima dose reconstruction
ABSTRACT Results are presented of a detailed search for neutron reactions that could potentially ... more ABSTRACT Results are presented of a detailed search for neutron reactions that could potentially be useful in reconstructing the neutron fluence in Hiroshima, with emphasis on fast neutrons in the 1-MeV range. Searches were made for suitable reactions in several neutron cross-section libraries from the U.S., Europe, Japan, China, and the former U.S.S.R. Because of the long time (∼ 50 yr) since the atomic bombing of Hiroshima, reaction products evaluated in this search were limited to those with half-lives between 5 and 109 yr. From the about 100 reactions within this category, only six appear to have some potential utility for fast neutron measurements of suitable materials from Hiroshima. The technology may currently be available to measure two of these reactions if suitable materials can be obtained.
Comparative Environmental Performance of Two Diesel-Fuel Oxygenates: Dibutyl Maleate (DBM) and Tripropylene Glycol Monomethyl Ether (TGME)
Many studies have shown that the addition of oxygen bearing compounds to diesel fuel can signific... more Many studies have shown that the addition of oxygen bearing compounds to diesel fuel can significantly reduce particulate emissions. To assist in the evaluation of the environmental performance of diesel-fuel oxygenates, we have implemented a suite of diagnostic models for simulating the transport of compounds released to air, water, and soils/groundwater as well as regional landscapes. As a means of studying the comparative performance of DBM and TGME, we conducted a series of simulations for selected environmental media. Benzene and methyl tertiary butyl ether (MTBE) were also addressed because they represent benchmark fuel-related compounds that have been the subject of extensive environmental measurements and modeling. The simulations showed that DBM and TGME are less mobile in soil because of reduced vapor-phase transport and increased retention on soil particles. The key distinction between these two oxygenates is that DBM is predicted to have a greater potential than TGME for aerobic biodegradation, based on chemical structure.
Determination of plutonium activity concentrations and 240 Pu/239 Pu atom ratios in Brown Algae (Fucus distichus) collected from Amchitka Island, Alaska
… of radioanalytical and …, 2009
Abstract Plutonium-239 (239 Pu) and plutonium-240 (240 Pu) activity concentrations and 240 Pu/239... more Abstract Plutonium-239 (239 Pu) and plutonium-240 (240 Pu) activity concentrations and 240 Pu/239 Pu atom ratios are reported for Brown Algae (Fucus distichus) collected from the littoral zone of Amchitka Island (Alaska), and at a control site at Unalaska, Alaska. The ...
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Papers by Alfredo Marchetti