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Title: Evaluation of Ultra-Low Background Materials for Uranium and Thorium Using ICP-MS

Abstract

An increasing number of physics experiments require low background materials for their construction. The presence of Uranium and Thorium and their progeny in these materials present a variety of unwanted background sources for these experiments. The sensitivity of the experiments continues to drive the necessary levels of detection ever lower as well. This requirement for greater sensitivity has rendered direct radioassay impractical in many cases requiring large quantities of material, frequently many kilograms, and prolonged counting times, often months. Other assay techniques have been employed such as Neutron Activation Analysis but this requires access to expensive facilities and instrumentation and can be further complicated and delayed by the formation of unwanted radionuclides. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is a useful tool and recent advancements have increased the sensitivity particularly in the elemental high mass range of U and Th. Unlike direct radioassay, ICP-MS is a destructive technique since it requires the sample to be in liquid form which is aspirated into a high temperature plasma. But it benefits in that it usually requires a very small sample, typically about a gram. Here we will discuss how a variety of low background materials such as copper, polymers, and fused silicamore » are made amenable to ICP-MS assay and how the arduous task of maintaining low backgrounds of U and Th is achieved.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1149242
Report Number(s):
PNNL-SA-96462
830403000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: Proceedings of the IV International Workshop in Low Radioactivity Techniques (LRT2013), April 10-12, 2013, Assergi, Italy. AIP Conference Proceedings, 1549:58-65
Country of Publication:
United States
Language:
English
Subject:
ICP-MS, Uranium, Thorium, Ultra-Trace, Radionuclides

Citation Formats

Hoppe, Eric W., Overman, Nicole R., and LaFerriere, Brian D. Evaluation of Ultra-Low Background Materials for Uranium and Thorium Using ICP-MS. United States: N. p., 2013. Web. doi:10.1063/1.4818076.
Hoppe, Eric W., Overman, Nicole R., & LaFerriere, Brian D. Evaluation of Ultra-Low Background Materials for Uranium and Thorium Using ICP-MS. United States. doi:10.1063/1.4818076.
Hoppe, Eric W., Overman, Nicole R., and LaFerriere, Brian D. 2013. "Evaluation of Ultra-Low Background Materials for Uranium and Thorium Using ICP-MS". United States. doi:10.1063/1.4818076.
@article{osti_1149242,
title = {Evaluation of Ultra-Low Background Materials for Uranium and Thorium Using ICP-MS},
author = {Hoppe, Eric W. and Overman, Nicole R. and LaFerriere, Brian D.},
abstractNote = {An increasing number of physics experiments require low background materials for their construction. The presence of Uranium and Thorium and their progeny in these materials present a variety of unwanted background sources for these experiments. The sensitivity of the experiments continues to drive the necessary levels of detection ever lower as well. This requirement for greater sensitivity has rendered direct radioassay impractical in many cases requiring large quantities of material, frequently many kilograms, and prolonged counting times, often months. Other assay techniques have been employed such as Neutron Activation Analysis but this requires access to expensive facilities and instrumentation and can be further complicated and delayed by the formation of unwanted radionuclides. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is a useful tool and recent advancements have increased the sensitivity particularly in the elemental high mass range of U and Th. Unlike direct radioassay, ICP-MS is a destructive technique since it requires the sample to be in liquid form which is aspirated into a high temperature plasma. But it benefits in that it usually requires a very small sample, typically about a gram. Here we will discuss how a variety of low background materials such as copper, polymers, and fused silica are made amenable to ICP-MS assay and how the arduous task of maintaining low backgrounds of U and Th is achieved.},
doi = {10.1063/1.4818076},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2013,
month = 8
}

Conference:
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  • An increasing number of physics experiments require low background materials for their construction. The presence of Uranium and Thorium and their progeny in these materials present a variety of unwanted background sources for these experiments. The sensitivity of the experiments continues to drive the necessary levels of detection ever lower as well. This requirement for greater sensitivity has rendered direct radioassay impractical in many cases requiring large quantities of material, frequently many kilograms, and prolonged counting times, often months. Other assay techniques have been employed such as Neutron Activation Analysis but this requires access to expensive facilities and instrumentation andmore » can be further complicated and delayed by the formation of unwanted radionuclides. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is a useful tool and recent advancements have increased the sensitivity particularly in the elemental high mass range of U and Th. Unlike direct radioassay, ICP-MS is a destructive technique since it requires the sample to be in liquid form which is aspirated into a high temperature plasma. But it benefits in that it usually requires a very small sample, typically about a gram. This paper discusses how a variety of low background materials such as copper, polymers, and fused silica are made amenable to ICP-MS assay and how the arduous task of maintaining low backgrounds of U and Th is achieved.« less
  • A rapid new method for determining the U and Th mass concentrations in high radiopurity plastics is described, consisting of 1) dry ashing the plastic sample and tracers in low mass crucibles made of ultra low background electroformed copper (ULB EF-Cu) foil cut and folded into boats, 2) dissolving both the ash and the boat in acid, 3) performing a column separation to remove copper, and 4) determining the elements of interest by isotope dilution mass spectrometry. This method was demonstrated on both unfluorinated and fluorinated plastics, demonstrating high tracer recoveries and detection limits to pg/g (i.e., parts per trillion)more » levels or below, corresponding to μBq/kg of material. Samples of biomedical polyester (Max-Prene® 955) and a fluoropolymer (polyvinylidene fluoride, PVDF) were analyzed in powder raw material forms as well as solids in the form of pellets or injection molded parts. The polyester powder contained 6 pg/g and 2 pg/g for Th and U respectively. These levels correspond to 25 and 25 μBq/kg radioactivity, respectively. Determinations on samples of PVDF powder were typically below 1 pg/g for Th and 2 pg/g for U, corresponding to 4 and 25 μBq/kg radioactivity, respectively. The use of low mass ULB EF-Cu boats for dry ashing successfully overcame the problem of crucible-generated contaminants in the analysis; absolute detection limits, calculated as 3 × standard deviation of the process blanks, were typically 20-100 fg within a sample set. Complete dissolution of the ash and low mass boat provided high tracer recoveries, and provides a convincing method to recover both the tracer and sample isotopes when full equilibration of tracer isotopes with sample isotopes is not possible prior to beginning chemical sample processing on solids.« less
  • Inductively coupled plasma mass spectrometry with a quadrupole mass analyzer (ICP-MS) is now regarded as a powerful technique to determine almost every element in the periodic table with ppt (pg/ml) level. So far, this technique has been used to measure long half-life radionuclides in the {open_quotes}polluted{close_quotes} environment. For example, {sup 239}Pu and {sup 240}Pu in the top-soil were measured precisely and relatively easily in the range of 0.2 to 2.6 mBq/g by using ICP-MS. Conventional radiometric methods which have very high sensitivity for short half-life radionuclides need, however, complex chemical pretreatment for isolation and concentration of focused isotopes, and aremore » time consuming. Higher sensitivity and lower detection limits are still needed for monitoring low concentration of long half-life radionuclides in the environmental samples. Recently, high-resolution (M/{Delta}M {approximately}10000) and high sensitivity (ppq = fg/ml level). In this study, HR-ICP-MS was applied to the determination of ultra-trace amounts of Ra, Th, and U in waste water sampled including high concentration of alkaline, alkaline earth and transition metal elements.« less
  • Cobalt foils and stainless steel samples were analyzed for induced {sup 6O}Co activity with both an ultra-low background germanium gamma-ray spectrometer and with a large NaI(Tl) multidimensional spectrometer, both of which use electronic anticoincidence shielding to reduce background counts resulting from cosmic rays. Aluminum samples were analyzed for {sup 22}Na. The results, in addition to the relative sensitivities and precisions afforded by the two methods, are presented.
  • The U.S. Department of Energy (DOE) Office of Legacy Management (LM) manages 27 sites that have groundwater containing uranium concentrations above background levels. The distal portions of the plumes merge into background groundwater that can have 50 μg/L or more uranium. Distinguishing background from site-related uranium is often problematic, but it is critical to determining if remediation is warranted, establishing appropriate remediation goals, and evaluating disposal cell performance. In particular, groundwater at disposal cells located on the upper Cretaceous Mancos Shale may have relatively high background concentrations of uranium. Elevated concentrations of nitrate, selenium, and sulfate accompany the uranium. LMmore » used geologic analogs and uranium isotopic signatures to distinguish background groundwater from groundwater contaminated by a former uranium processing site. The same suite of contaminants is present in groundwater near former uranium processing sites and in groundwater seeps emanating from the Mancos Shale over a broad area. The concentrations of these contaminants in Many Devils Wash, located near LM's Shiprock disposal cell, are similar to those in samples collected from many Mancos seeps, including two analog sites that are 8 to 11 km from the disposal cell. Samples collected from Many Devils Wash and the analog sites have high AR values (about 2.0)-in contrast, groundwater samples collected near the tailings disposal cell have AR values near 1.0. These chemical signatures raise questions about the origin of the contamination seeping into Many Devils Wash. (authors)« less