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'''Nuclear forensics''' is the investigation of [[nuclear materials]] to find evidence for example the source, the trafficking, and the enrichment of the material. The material can be recovered from various sources including dust from the vicinity of a nuclear facility, or from the radioactive debris following a [[nuclear explosion]].<ref>{{cite web| url= http://cstsp.aaas.org/files/Complete.pdf| title = Nuclear Forensics: Role, State of the Art, and Program Needs| editor = May, Michael| isbn=978-0-87168-720-3}}</ref><ref name="Erdmann Haystack">{{cite web|last=Erdmann|first=Nicole|title=Particle Analysis - Finding the Needle in the Haystack|url=http://ec.europa.eu/dgs/jrc/downloads/jrc_presentation_erdmann_particle_analysis.pdf|accessdate=24 November 2013|coauthors=Magnus Hedberg}}</ref> | |||
Results of nuclear forensic testing are used by different organisations to make decisions. The information is typically combined with other sources of information such as law enforcement and [[Intelligence assessment|intelligence information]].<ref name="Erdmann Haystack" /><ref>{{cite web | url=http://www.dhs.gov/national-technical-nuclear-forensics-center | title=National Technical Nuclear Forensics Center - Definition and Role of Nuclear Forensics | publisher=US Department of Homeland Security | accessdate=2013-05-14}}</ref> | |||
==History== | |||
The first seizures of nuclear or otherwise radioactive material were reported in Switzerland and Italy in 1991. Later, reports of incidents of nuclear material occurred in Germany, the Czech Republic, Hungary and other central European countries. Nuclear Forensics became a new branch of scientific research with the intent of not only determining the nature of the material, but also the intended use of the seized material as well as its origin and about the potential trafficking routes. Nuclear forensics relies on making these determinations through measurable parameters including, but not limited to chemical impurities, isotopic composition, microscopic appearance, and microstructure. By measuring these parameters, conclusions can be drawn as to the origin of the material. Identification of these parameters is an ongoing area of research, however, data interpretation also relies on the availability of reference information and on knowledge of the fuel cell operations. | |||
The first investigative radiochemical measurements began in the early days of nuclear fission. In 1944, the US Airforce made the first attempts to detect [[Nuclear fission|fissiogenic]] <sup>133</sup>Xe in the atmosphere in order to indicate the production of plutonium through the irradiation of uranium and chemical reprocessing in an effort to gather intelligence on the status of the [[German nuclear energy project|German nuclear program]]. However, no <sup>133</sup>Xe was detected. In the subsequent years it became increasingly valuable to gather information on the [[Soviet atomic bomb project|Soviet nuclear weapons program]], which resulted in the development of technologies that could gather [[particulates|airborne particles]] in a [[Boeing B-29 Superfortress variants#WB-29|WB-29]] weather reconnaissance plane. On September 3<sup>rd</sup> 1949, these particles were used to determine that the detonation time of the first Soviet atomic test, "[[RDS-1|Joe 1]]".<ref name="Glaser Bielefeld">{{cite web|last=Glaser|first=Alexander|title=Nuclear Forensics - Revision 5 Capabilities, Limits, and the "CSI Effect"|url=http://www.princeton.edu/~aglaser/talk2008_forensics.pdf|accessdate=25 November 2013|coauthors=Tom Bielefeld}}</ref><ref name=Wellerstein>{{cite web|last=Wellerstein|first=Alex|title=Semipalatinsk Then and Now|url=http://blog.nuclearsecrecy.com/2012/06/15/friday-images-semipalantisk-then-now/|accessdate=25 November 2013}}</ref> Further analysis revealed that this bomb was a replicate of the "[[Fat Man]]", which was the bomb dropped on [[Nagasaki]] in 1915. This investigative methodology combined radiochemistry and other techniques to gather intelligence on nuclear activities. | |||
" | |||
The first seizures of nuclear materials from trafficking in the early 1990s allowed the nuclear forensic methodology to be adopted by a wider scientific community. When scientific laboratories outside the weapons and intelligence community took an interest in this methodology was when the term "Nuclear Forensics" was coined. Unlike standard forensics, nuclear forensics focuses mainly on the nuclear or radioactive material and aims to provide knowledge of the intended use of the materials.<ref>{{cite journal|author=Klaus Mayer|coauthor=Maria Wallenius|title=Atomic Detectives-An Introduction to Nuclear Forensics.|journal=Strahlenschutzpraxis|volume=1|pages=27–36|year= 2009}}</ref> | |||
In 1994 560 grams of plutonium and uranium oxide were intercepted at [[Munich airport]] in an airplane coming from Moscow.<ref name="Glaser Bielefeld" /> The precise composition was 363 grams plutonium (87% of which was [[Plutonium-239]]) and 122 grams of uranium.<ref name="Glaser Bielefeld" /> | |||
==Chronometry== | |||
Determining a nuclear material's age is critical to nuclear forensic investigations. Dating techniques can be utilized to identify a material's source as well as procedures performed on the material. This can aid in determining the information about the potential participant in the "age" of the material of interest. [[Nuclide]]s, related through radioactive decay processes will have relative sample concentrations that can be predicted using parent-daughter in-growth equations and relevant half-lives. Because radioactive isotopes decay at a rate determined by the amount of the isotope in a sample and the half-life of the parent isotope, the relative amount of the decay products compared to the parent isotopes can be used to determine "age". Heavy element nuclides have a 4n+2 relationship, where the mas number divided by 4 leaves a remainder of two. The decay network begins with <sup>238</sup>Pu and proceeds through the in-growth of long-lived <sup>234</sup>U, <sup>230</sup>Th, and <sup>226</sup>Ra. If any member of the 4n+2 decay chain is purified it will immediately begin to produce descendant species. The time since a sample was last purified can be calculated from the ratio of any two concentrations among the decaying nuclides. | |||
Essentially, if a nuclear material has been put through a refinement process to remove the daughter species, the time elapsed since purification can be "back-calculated" using radiochemical separation techniques in conjunction with analytical measurement of the existing parent-daughter ratios. For example, the α decay of <sup>239</sup>Pu to <sup>235</sup>U can be used as an example of this procedure. with the assumption of a perfect purification time ''T''<sub>0</sub> then there will be a linear relationship between the in-growth of <sup>235</sup>U and time elapsed since purification. There are, however, various instances where the correlation is not as clear. This strategy may not apply when the parent-daughter pair achieve secular equilibrium very rapidly or when the half-life of the daughter nuclide is significantly shorter than the time that has elapsed since purification of the nuclear material, e.g. <sup>237</sup>Np/<sup>233</sup>Pa. Another possible complication is if in environmental samples, non-equivalent metal/ion transport for parents and daughter species may complicate or invalidate the use of chronometric measurements. Special age-dating relationships exist, including the commonly employed <sup>234</sup>U/<sup>230</sup>Th and <sup>241</sup>Pu/<sup>241</sup>Am chronometers. In special circumstances, parent-granddaughter relationships can be used to elucidate the age of nuclear materials when the material is intentionally made to look older through the addition of daughter nuclides. | |||
Chronometry is based on the concept that the composition of the nuclear material changes as samples are prepared and analyzed. This barrier can be substantial for species that decay quickly or whose daughter products put forth spectral interferences. The decay of <sup>233</sup>U, for example, has a t<sub>1/2</sub>~1.6x10<sup>5</sup>years which is rapid in comparison to many species and yield <sup>229</sup>Th, which emits an α particle that is isoenergetic, having the same energy, as the parent. To avoid this, freshly prepared samples as well as complementary analysis methods are used for confident nuclear materials characterization. The decay of nuclear samples makes rapid analysis methods highly desirable.<ref>{{cite journal|last=Stanley|first=Floyd E.|coauthors=Stalcup A.M., Spitz, H.B|title=A Brief Introduction to Analytical Methods in Nuclear Forensics|journal=J Radioanal Nucl Chem|year=2013|volume=295|pages=1385–1393|doi=10.1007/s10967-012-1927-3}}</ref> | |||
==Separations== | |||
Chemical separation techniques are frequently utilized in nuclear forensics as a method of reducing the interferences and to facilitate the measurement of low level radionuclides. Purification that occurs rapidly as progeny in-growth begins immediately following purification is ideal. | |||
=== Anion Exchange === | |||
Anion exchange separation methods are widely used in the purification of [[actinide]]s and actinide bearing materials through the use of resin columns. The anionic actinide complexes are retained by anion exchange sites that are on the resin and neutral species pass through the column unretained. Then the retained species can be eluted from the column by conversion to a neutral complex, typically by changing the mobile phase passed through the resin bed. | |||
Anion exchange-based separations of actinides, while valued for there simplicity and widely used, tend to be time consuming and are infrequently automated. Most are still dependent on gravity. Speeding up the flow of the mobile phase tends to introduce problems such as impurities and jeopardize future investigations. Hence, there is still a need for development of this technique to satisfy the nuclear forensic research priorities. | |||
===Co-Precipitation=== | |||
Actinide isolation by co-precipitation is frequently used for samples of relatively large volumes to concentrate analytes and remove interferences. Actinide carriers include [[iron hydroxide]]s, [[lanthanide fluoride]]s/[[lanthanide hydroxide|hydroxides]], [[manganese dioxide]], and a few other species. | |||
==Analysis== | |||
A wide range of instrumental techniques are employed in nuclear forensics. Radiometric counting techniques are useful when determining decay products of species with short half-lives. However, for longer half-lives, inorganic mass spec is a powerful means of carrying out elemental analysis and determining isotopic relationships. Microscopy approaches can also be useful in characterization of a nuclear material. | |||
===Counting Techniques=== | |||
Counting techniques of α,β,γ or neutron can be used as approaches for the analysis of nuclear forensic materials that emit decay species. The most common of these are alpha and gamma spectroscopy. β counting is used infrequently because most short lived β-emitters also give off characteristic γ-rays and produce very broad counting peaks. Neutron counting are found more rarely in analytical labs due in part to shielding concerns should such neutron emitters be introduced into a counting facility. | |||
====Alpha-particle spectroscopy==== | |||
Alpha-particle spectroscopy is a method of measuring the radionuclides based on emission of [[α particle]]s. They can be measured by a variety of detectors, including liquid scintillation counters, gas ionization detectors, and ion-implanted silicon semiconductor detectors. Typical alpha-particle spectrometers have low backgrounds and measure particles ranging from 3 to 10 MeV. [[Radionuclide]]s that decay through [[alpha decay|α emission]] tend to eject α particles with discrete, characteristic energies between 4 to 6 MeV. These energies become attenuated as they pass through the layers of sample. Increasing the distance between the source and the detector can lead to improved resolution, but decreased particle detection. | |||
The advantages of alpha-particle spectroscopy include relatively inexpensive equipment costs, low backgrounds, high selectivity, and good throughput capabilities with the use of multi-chamber systems. There are also disadvantages of alpha-particle spectroscopy. One disadvantage is that there must be significant sample preparation to obtain useful spectroscopy sources. Also, spectral interferences or artifacts from extensive preparation prior to counting, to minimize this high purity acids are needed. Another disadvantage is that measurements require a large quantity of material which can also lead to poor resolution. Also, undesired spectral overlap and long analysis times are disadvantages. | |||
====Gamma Spectroscopy==== | |||
[[Gamma spectroscopy]] yields results that are conceptually equivalent to [[alpha-particle spectroscopy]], however, can result in sharper peaks due to reduced attenuation of energy. Some radionuclides produce discrete [[gamma rays|γ-rays]] that produce energy between a few KeV to 10 MeV which can be measured with a [[gamma-ray spectrometer]]. This can be accomplished without destroying the sample. The most common gamma-ray detector is a semiconductor germanium detector which allow for a greater energy resolution than [[alpha-particle spectroscopy]], however gamma spectroscopy only has an efficiency of a few percent. Gamma spectroscopy is a less sensitive method due to low detector efficiency and high background. However, gamma spectroscopy has the advantage of having less time consuming sample procedures and portable detectors for field use. | |||
===Mass Spectrometry=== | |||
Mass spec techniques are essential in nuclear forensics analysis. Mass spec can provide elemental and isotopic information. Mass spec also requires less sample mass relative to counting techniques. For nuclear forensic purposes it is essential that the mass spectrometry offers excellent resolution in order to distinguish between similar analytes, e.g. <sup>235</sup>U and <sup>236</sup>U. Ideally, mess spec should offer excellent resolution/mass abundance, low backgrounds, and proper instrumental function. | |||
====Thermal Ionization MS==== | |||
In [[thermal ionization mass spectrometry]], small quantities of highly purified analyte are deposited onto a clean metal filament, rhenium or tungsten are typically used. The sample is heated in a vacuum of the ion source by applying a current to the filaments. A portion of the analyte will be ionized by the filament and then are directed down the flight tube and separated based on mass to charge rations. Major disadvantages include time consuming sample preparation and inefficient analyte ionization. | |||
====Multi-Collector Inductively Coupled Plasma-Mass Spectrometry==== | |||
This is a frequently used technique in nuclear forensics. In this technique a purified sample is nebulized in a spray chamber and then aspirated into a plasma. The high temperature of the plasma leads to sample dissociation and high efficiency of ionization of the analyte. The ions then enter the mass spectrometer where they are discriminated based on mass based on a double focusing system. Ions of various masses are detected simultaneously by a bank of detectors similar to those used in the thermal ionization mass spec. MC-ICP-MS has a more rapid analysis because i does not require lengthy filament preparation. For high quality, however, there is a requirement for extensive sample clean up. Argon plasma is also less stable and requires relatively expensive equipment as well as skilled operators. | |||
====Secondary-Ion MS==== | |||
[[Secondary ion mass spectrometry|SIMS]] is a micro-analytical technique valuable for three-dimensional analysis of a materials elemental composition and isotopic ratios. This method can be utilized in characterization of bulk materials with a [[detection limit]] in the low [[parts per billion]] (10<sup>−9</sup> or ng/g) range. Particles as small as a few 100 nanometer can be detected.<ref name="Hedberg 2011">{{cite journal|last=Hedberg|first=P. M. L.|coauthors=Peres, P.; Cliff, J. B.; Rabemananjara, F.; Littmann, S.; Thiele, H.; Vincent, C.; Albert, N.|title=Improved particle location and isotopic screening measurements of sub-micron sized particles by Secondary Ion Mass Spectrometry|journal=Journal of Analytical Atomic Spectrometry|date=1 January 2011|volume=26|issue=2|pages=406|doi=10.1039/c0ja00181c}}</ref> Ion production in this technique is dependent on the bombardment of solid samples with a focused beam of primary ions. The sputtered, secondary ions are directed onto the [[mass spectrometry]] system to be measured. The secondary ions are a result of kinetic energy transfer from the primary ions. These primary ions penetrate into the solid sample to some depth. This method can be used to detect any element, however the sputtering process is highly matrix dependent and ion yields vary. | |||
This method is especially useful, because it can be fully automated to find uranium particles in a sample of many million particles in a matter of hours. Particles of interest can then be imaged and further analyzed with very high [[Resolution (mass spectrometry)|isotopic precision]].<ref name="Hedberg 2011" /> | |||
===Additional Nuclear Forensic Methods=== | |||
Numerous additional approaches may be employed in the interrogation of seized nuclear material. In contrast to previously mentioned analysis techniques, these approaches have received relatively low attention in recent years in terms of novel advancement, and, typically, require greater quantities of sample. | |||
====Scanning electron microscope==== | |||
The [[scanning electron microscope]] can provide images of an object's surface at high magnification with a resolution on the order of nanometers. A focused beam of energetic electrons is scanned over the sample and electrons that a backscattered or emitted from the sample surface are detected. Images are constructed via measuring the fluctuations of electrons from the sample beam scanning position. This data is useful in determining what process may have been employed in the materials production and to distinguish between materials of differing origins. Measurement of backscattered electrons elucidate the average atomic number of the area being scanned. The emitted, or secondary electrons provide topological information. This is a relatively straight forward technique, however samples must be amenable to being under a vacuum and may require pre-treatment. | |||
====X-Ray Fluorescence==== | |||
[[X-ray fluorescence]] offers rapid and non-destructive determination of the elemental composition of a nuclear material based on the detection of characteristic [[X-ray]]s. Direct sample irradiation allows for minimal sample preparation and portable instrumentation for field deployment. The [[detection limit]] is 10 ppm. This is well above mass spectrometry.{{citation needed|date=November 2013}} This technique tends to be hindered by matrix affects, which must be corrected for. | |||
====Neutron Activation Analysis==== | |||
The | [[Neutron activation analysis]] is a powerful non-destructive method of analyzing elements of mid to high atomic number. This method combines excitation by nuclear reaction and the radiation counting techniques to detect various materials. The measurement of characteristic radiation, following the bombardment completion, is indicative of the elements of interest. The equation for the production product is given by: <math>A + n \to B^{*} + \gamma</math> where <math>A</math> is the starting analyte, <math>n</math> is the incoming neutron, <math>B^{*}</math> is the excited product and <math>\gamma</math> is the detected radiation that results from the de-excitation of the product species. | ||
The advantages of this technique include multi-element analysis, excellent sensitivity, and high selectivity, and no time-consuming separation procedures. One disadvantage is the requirement of a nuclear reactor for sample preparation. | |||
== References == | |||
<references /> | |||
[[Category:Forensic techniques]] | |||
[[Category:Nuclear interdisciplinary topics]] | |||
Revision as of 12:27, 13 November 2013
Nuclear forensics is the investigation of nuclear materials to find evidence for example the source, the trafficking, and the enrichment of the material. The material can be recovered from various sources including dust from the vicinity of a nuclear facility, or from the radioactive debris following a nuclear explosion.[1][2]
Results of nuclear forensic testing are used by different organisations to make decisions. The information is typically combined with other sources of information such as law enforcement and intelligence information.[2][3]
History
The first seizures of nuclear or otherwise radioactive material were reported in Switzerland and Italy in 1991. Later, reports of incidents of nuclear material occurred in Germany, the Czech Republic, Hungary and other central European countries. Nuclear Forensics became a new branch of scientific research with the intent of not only determining the nature of the material, but also the intended use of the seized material as well as its origin and about the potential trafficking routes. Nuclear forensics relies on making these determinations through measurable parameters including, but not limited to chemical impurities, isotopic composition, microscopic appearance, and microstructure. By measuring these parameters, conclusions can be drawn as to the origin of the material. Identification of these parameters is an ongoing area of research, however, data interpretation also relies on the availability of reference information and on knowledge of the fuel cell operations.
The first investigative radiochemical measurements began in the early days of nuclear fission. In 1944, the US Airforce made the first attempts to detect fissiogenic 133Xe in the atmosphere in order to indicate the production of plutonium through the irradiation of uranium and chemical reprocessing in an effort to gather intelligence on the status of the German nuclear program. However, no 133Xe was detected. In the subsequent years it became increasingly valuable to gather information on the Soviet nuclear weapons program, which resulted in the development of technologies that could gather airborne particles in a WB-29 weather reconnaissance plane. On September 3rd 1949, these particles were used to determine that the detonation time of the first Soviet atomic test, "Joe 1".[4][5] Further analysis revealed that this bomb was a replicate of the "Fat Man", which was the bomb dropped on Nagasaki in 1915. This investigative methodology combined radiochemistry and other techniques to gather intelligence on nuclear activities.
The first seizures of nuclear materials from trafficking in the early 1990s allowed the nuclear forensic methodology to be adopted by a wider scientific community. When scientific laboratories outside the weapons and intelligence community took an interest in this methodology was when the term "Nuclear Forensics" was coined. Unlike standard forensics, nuclear forensics focuses mainly on the nuclear or radioactive material and aims to provide knowledge of the intended use of the materials.[6]
In 1994 560 grams of plutonium and uranium oxide were intercepted at Munich airport in an airplane coming from Moscow.[4] The precise composition was 363 grams plutonium (87% of which was Plutonium-239) and 122 grams of uranium.[4]
Chronometry
Determining a nuclear material's age is critical to nuclear forensic investigations. Dating techniques can be utilized to identify a material's source as well as procedures performed on the material. This can aid in determining the information about the potential participant in the "age" of the material of interest. Nuclides, related through radioactive decay processes will have relative sample concentrations that can be predicted using parent-daughter in-growth equations and relevant half-lives. Because radioactive isotopes decay at a rate determined by the amount of the isotope in a sample and the half-life of the parent isotope, the relative amount of the decay products compared to the parent isotopes can be used to determine "age". Heavy element nuclides have a 4n+2 relationship, where the mas number divided by 4 leaves a remainder of two. The decay network begins with 238Pu and proceeds through the in-growth of long-lived 234U, 230Th, and 226Ra. If any member of the 4n+2 decay chain is purified it will immediately begin to produce descendant species. The time since a sample was last purified can be calculated from the ratio of any two concentrations among the decaying nuclides.
Essentially, if a nuclear material has been put through a refinement process to remove the daughter species, the time elapsed since purification can be "back-calculated" using radiochemical separation techniques in conjunction with analytical measurement of the existing parent-daughter ratios. For example, the α decay of 239Pu to 235U can be used as an example of this procedure. with the assumption of a perfect purification time T0 then there will be a linear relationship between the in-growth of 235U and time elapsed since purification. There are, however, various instances where the correlation is not as clear. This strategy may not apply when the parent-daughter pair achieve secular equilibrium very rapidly or when the half-life of the daughter nuclide is significantly shorter than the time that has elapsed since purification of the nuclear material, e.g. 237Np/233Pa. Another possible complication is if in environmental samples, non-equivalent metal/ion transport for parents and daughter species may complicate or invalidate the use of chronometric measurements. Special age-dating relationships exist, including the commonly employed 234U/230Th and 241Pu/241Am chronometers. In special circumstances, parent-granddaughter relationships can be used to elucidate the age of nuclear materials when the material is intentionally made to look older through the addition of daughter nuclides.
Chronometry is based on the concept that the composition of the nuclear material changes as samples are prepared and analyzed. This barrier can be substantial for species that decay quickly or whose daughter products put forth spectral interferences. The decay of 233U, for example, has a t1/2~1.6x105years which is rapid in comparison to many species and yield 229Th, which emits an α particle that is isoenergetic, having the same energy, as the parent. To avoid this, freshly prepared samples as well as complementary analysis methods are used for confident nuclear materials characterization. The decay of nuclear samples makes rapid analysis methods highly desirable.[7]
Separations
Chemical separation techniques are frequently utilized in nuclear forensics as a method of reducing the interferences and to facilitate the measurement of low level radionuclides. Purification that occurs rapidly as progeny in-growth begins immediately following purification is ideal.
Anion Exchange
Anion exchange separation methods are widely used in the purification of actinides and actinide bearing materials through the use of resin columns. The anionic actinide complexes are retained by anion exchange sites that are on the resin and neutral species pass through the column unretained. Then the retained species can be eluted from the column by conversion to a neutral complex, typically by changing the mobile phase passed through the resin bed. Anion exchange-based separations of actinides, while valued for there simplicity and widely used, tend to be time consuming and are infrequently automated. Most are still dependent on gravity. Speeding up the flow of the mobile phase tends to introduce problems such as impurities and jeopardize future investigations. Hence, there is still a need for development of this technique to satisfy the nuclear forensic research priorities.
Co-Precipitation
Actinide isolation by co-precipitation is frequently used for samples of relatively large volumes to concentrate analytes and remove interferences. Actinide carriers include iron hydroxides, lanthanide fluorides/hydroxides, manganese dioxide, and a few other species.
Analysis
A wide range of instrumental techniques are employed in nuclear forensics. Radiometric counting techniques are useful when determining decay products of species with short half-lives. However, for longer half-lives, inorganic mass spec is a powerful means of carrying out elemental analysis and determining isotopic relationships. Microscopy approaches can also be useful in characterization of a nuclear material.
Counting Techniques
Counting techniques of α,β,γ or neutron can be used as approaches for the analysis of nuclear forensic materials that emit decay species. The most common of these are alpha and gamma spectroscopy. β counting is used infrequently because most short lived β-emitters also give off characteristic γ-rays and produce very broad counting peaks. Neutron counting are found more rarely in analytical labs due in part to shielding concerns should such neutron emitters be introduced into a counting facility.
Alpha-particle spectroscopy
Alpha-particle spectroscopy is a method of measuring the radionuclides based on emission of α particles. They can be measured by a variety of detectors, including liquid scintillation counters, gas ionization detectors, and ion-implanted silicon semiconductor detectors. Typical alpha-particle spectrometers have low backgrounds and measure particles ranging from 3 to 10 MeV. Radionuclides that decay through α emission tend to eject α particles with discrete, characteristic energies between 4 to 6 MeV. These energies become attenuated as they pass through the layers of sample. Increasing the distance between the source and the detector can lead to improved resolution, but decreased particle detection.
The advantages of alpha-particle spectroscopy include relatively inexpensive equipment costs, low backgrounds, high selectivity, and good throughput capabilities with the use of multi-chamber systems. There are also disadvantages of alpha-particle spectroscopy. One disadvantage is that there must be significant sample preparation to obtain useful spectroscopy sources. Also, spectral interferences or artifacts from extensive preparation prior to counting, to minimize this high purity acids are needed. Another disadvantage is that measurements require a large quantity of material which can also lead to poor resolution. Also, undesired spectral overlap and long analysis times are disadvantages.
Gamma Spectroscopy
Gamma spectroscopy yields results that are conceptually equivalent to alpha-particle spectroscopy, however, can result in sharper peaks due to reduced attenuation of energy. Some radionuclides produce discrete γ-rays that produce energy between a few KeV to 10 MeV which can be measured with a gamma-ray spectrometer. This can be accomplished without destroying the sample. The most common gamma-ray detector is a semiconductor germanium detector which allow for a greater energy resolution than alpha-particle spectroscopy, however gamma spectroscopy only has an efficiency of a few percent. Gamma spectroscopy is a less sensitive method due to low detector efficiency and high background. However, gamma spectroscopy has the advantage of having less time consuming sample procedures and portable detectors for field use.
Mass Spectrometry
Mass spec techniques are essential in nuclear forensics analysis. Mass spec can provide elemental and isotopic information. Mass spec also requires less sample mass relative to counting techniques. For nuclear forensic purposes it is essential that the mass spectrometry offers excellent resolution in order to distinguish between similar analytes, e.g. 235U and 236U. Ideally, mess spec should offer excellent resolution/mass abundance, low backgrounds, and proper instrumental function.
Thermal Ionization MS
In thermal ionization mass spectrometry, small quantities of highly purified analyte are deposited onto a clean metal filament, rhenium or tungsten are typically used. The sample is heated in a vacuum of the ion source by applying a current to the filaments. A portion of the analyte will be ionized by the filament and then are directed down the flight tube and separated based on mass to charge rations. Major disadvantages include time consuming sample preparation and inefficient analyte ionization.
Multi-Collector Inductively Coupled Plasma-Mass Spectrometry
This is a frequently used technique in nuclear forensics. In this technique a purified sample is nebulized in a spray chamber and then aspirated into a plasma. The high temperature of the plasma leads to sample dissociation and high efficiency of ionization of the analyte. The ions then enter the mass spectrometer where they are discriminated based on mass based on a double focusing system. Ions of various masses are detected simultaneously by a bank of detectors similar to those used in the thermal ionization mass spec. MC-ICP-MS has a more rapid analysis because i does not require lengthy filament preparation. For high quality, however, there is a requirement for extensive sample clean up. Argon plasma is also less stable and requires relatively expensive equipment as well as skilled operators.
Secondary-Ion MS
SIMS is a micro-analytical technique valuable for three-dimensional analysis of a materials elemental composition and isotopic ratios. This method can be utilized in characterization of bulk materials with a detection limit in the low parts per billion (10−9 or ng/g) range. Particles as small as a few 100 nanometer can be detected.[8] Ion production in this technique is dependent on the bombardment of solid samples with a focused beam of primary ions. The sputtered, secondary ions are directed onto the mass spectrometry system to be measured. The secondary ions are a result of kinetic energy transfer from the primary ions. These primary ions penetrate into the solid sample to some depth. This method can be used to detect any element, however the sputtering process is highly matrix dependent and ion yields vary.
This method is especially useful, because it can be fully automated to find uranium particles in a sample of many million particles in a matter of hours. Particles of interest can then be imaged and further analyzed with very high isotopic precision.[8]
Additional Nuclear Forensic Methods
Numerous additional approaches may be employed in the interrogation of seized nuclear material. In contrast to previously mentioned analysis techniques, these approaches have received relatively low attention in recent years in terms of novel advancement, and, typically, require greater quantities of sample.
Scanning electron microscope
The scanning electron microscope can provide images of an object's surface at high magnification with a resolution on the order of nanometers. A focused beam of energetic electrons is scanned over the sample and electrons that a backscattered or emitted from the sample surface are detected. Images are constructed via measuring the fluctuations of electrons from the sample beam scanning position. This data is useful in determining what process may have been employed in the materials production and to distinguish between materials of differing origins. Measurement of backscattered electrons elucidate the average atomic number of the area being scanned. The emitted, or secondary electrons provide topological information. This is a relatively straight forward technique, however samples must be amenable to being under a vacuum and may require pre-treatment.
X-Ray Fluorescence
X-ray fluorescence offers rapid and non-destructive determination of the elemental composition of a nuclear material based on the detection of characteristic X-rays. Direct sample irradiation allows for minimal sample preparation and portable instrumentation for field deployment. The detection limit is 10 ppm. This is well above mass spectrometry.Potter or Ceramic Artist Truman Bedell from Rexton, has interests which include ceramics, best property developers in singapore developers in singapore and scrabble. Was especially enthused after visiting Alejandro de Humboldt National Park. This technique tends to be hindered by matrix affects, which must be corrected for.
Neutron Activation Analysis
Neutron activation analysis is a powerful non-destructive method of analyzing elements of mid to high atomic number. This method combines excitation by nuclear reaction and the radiation counting techniques to detect various materials. The measurement of characteristic radiation, following the bombardment completion, is indicative of the elements of interest. The equation for the production product is given by: where is the starting analyte, is the incoming neutron, is the excited product and is the detected radiation that results from the de-excitation of the product species.
The advantages of this technique include multi-element analysis, excellent sensitivity, and high selectivity, and no time-consuming separation procedures. One disadvantage is the requirement of a nuclear reactor for sample preparation.
References
- ↑ Template:Cite web
- ↑ 2.0 2.1 Template:Cite web
- ↑ Template:Cite web
- ↑ 4.0 4.1 4.2 Template:Cite web
- ↑ Template:Cite web
- ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - ↑ 8.0 8.1 One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang