Terry Hamilton | Lawrence Livermore National Lab (original) (raw)

Papers by Terry Hamilton

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, May 1, 2008

spectrometry. Despite a pervasive interference from 90 Zr, our initial development has yielded an... more spectrometry. Despite a pervasive interference from 90 Zr, our initial development has yielded an instrumental background of ~10 8 atoms (75 mBq) per sample. Further refinement of our system (e.g., redesign of our detector, use of alternative target materials) is expected to push the background below 10 6 atoms, close to the theoretical limit for AMS. Once we have refined our system and developed suitable sample preparation protocols, we will utilize our capability in applications to homeland security, environmental monitoring, and human health.

Marine Radioactivity, 2005

Publisher Summary This chapter focuses on the linking legacies of the cold war to arrival of anth... more Publisher Summary This chapter focuses on the linking legacies of the cold war to arrival of anthropogenic radionuclides in the oceans through the 20th century. This chapter is intended to summarize the sources and occurrences of man-made radioactivity in the oceans, as well as provide a technical basis for addressing public misunderstandings about the risks posed by environmental radioactivity. The main contribution of dispersed radioactivity entering the environment has come from testing of atmospheric nuclear weapons from 1945 to 1980. The measured total global deposit of long-lived fission products, such as 90 Sr and 137 Cs is in agreement with the estimated fission yields and partitioning of radioactive debris in the atmosphere. Other unrestrained sources of radioactive contamination of the marine environment include, direct discharges of radioactive effluents into rivers and coastal seas from reprocessing and fuel cycle operations, and runoff or leakage from other land-based sources of contamination. Human activities involving nuclear materials will always be subject to accidents and accidental releases of radioactivity.

Re-entry vehicles on missiles launched from Vandenberg Air Force base in California re-enter at t... more Re-entry vehicles on missiles launched from Vandenberg Air Force base in California re-enter at the Western Test Range, the Regan Test Site (RTS) at Kwajalein Atoll. An Environmental Assessment (EA) was written at the beginning of the program to assess potential impact of DU and Be, the major RV materials of interest from a health and environmental perspective, for both ocean and land impacts. The chemical and structural form of Be and DU in RVs is such that they are insoluble in soil water and seawater. Thus, they are not toxic to plant life on the isalnd (no soil to plant uptake.) Similarly, due to their insolubility in sea water there is no uptake of either element by fish, mollusks, shellfish, sea mammals, etc. No increase in either element has been observed in sea life around Illeginnin Island where deposition of DU and Be has occured. The critical terrestrial exposure pathway for U and Be is inhalation. Concentration of both elements in air over the test period (1989 to 2006) is lower by a factor of nearly 10,000 than the most restrictive U.S. guideline for the general public. Uranium concentrations in air are also lower by factors of 10 to 100 than concentrations of U in air in the U.S. measured by the EPA (Keith et al., 1999). U and Be concentrations in air downwind of deposition areas on Illeginni Island are essentially indistinguishable from natural background concentrations of U in air at the atolls. Thus, there are no health related issues associated with people using the island.

Re-entry vehicles on missiles launched from Vandenberg Air Force base in California re-enter at t... more Re-entry vehicles on missiles launched from Vandenberg Air Force base in California re-enter at the Western Test Range, the Regan Test Site (RTS) at Kwajalein Atoll. An Environmental Assessment (EA) was written at the beginning of the program to assess potential impact of DU and Be, the major RV materials of interest from a health and environmental perspective, for both ocean and land impacts. The chemical and structural form of Be and DU in RVs is such that they are insoluble in soil water and seawater. Thus, they are not toxic to plant life on the isalnd (no soil to plant uptake.) Similarly, due to their insolubility in sea water there is no uptake of either element by fish, mollusks, shellfish, sea mammals, etc. No increase in either element has been observed in sea life around Illeginnin Island where deposition of DU and Be has occured. The critical terrestrial exposure pathway for U and Be is inhalation. Concentration of both elements in air over the test period (1989 to 2006) is lower by a factor of nearly 10,000 than the most restrictive U.S. guideline for the general public. Uranium concentrations in air are also lower by factors of 10 to 100 than concentrations of U in air in the U.S. measured by the EPA (Keith et al., 1999). U and Be concentrations in air downwind of deposition areas on Illeginni Island are essentially indistinguishable from natural background concentrations of U in air at the atolls. Thus, there are no health related issues associated with people using the island.

In response to sponsor interest in October 2005 we proposed two methods for enhancing the precisi... more In response to sponsor interest in October 2005 we proposed two methods for enhancing the precision of 233 U accelerator mass spectrometry (AMS) capabilities at the Lawrence Livermore National Laboratory (LLNL). In a previous report we evaluated the first method and demonstrated that by increasing sample loading by a factor of four coupled with performing four replicates of each sample, we could achieve measurement precision of~1%. Recent modifications to our system have enabled us to test the second proposed method. By changing our setup to normalize 233 U ions counted in a gas ionization chamber to 238 U measured as a current in an off-axis Faraday cup we were able to attain 1% precision without the need for replicate analysis. This method could be further refined to achieve 0.5% precision in samples of interest.

Between 1965 and 1981, five objects - six naval reactor pressure vessels (RPVs) from four former ... more Between 1965 and 1981, five objects - six naval reactor pressure vessels (RPVs) from four former Soviet Union submarines and a special containers from the icebreaker Lenin, each of which contained damaged spent nuclear fuel (SNF) - were dumped in a variety of containments, using a number of sealing methods, at four sites in the Kara Sea. All objects were dumped at sites that varied in depth from 12 to 300 m. This paper examines the use of the long-lived radionuclides ⁵⁹Ni, ⁹⁹Tc, and ²³⁶U encased within these objects to monitor the breakdown of the containments due to corrosion. Included are discussions of the radionuclide inventory and their release rate model, the estimated radionuclide mass in a typical seawater sample, and the potential for radionuclide measurement via Accelerator Mass Spectrometry (AMS).

International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes, 1986

A method is described for deposition of polonium isotopes on rotating silver discs. Rapid rotatio... more A method is described for deposition of polonium isotopes on rotating silver discs. Rapid rotation during deposition gives a uniform deposit of high yield within an hour, and good GL energy resolution simplifies the quantitative evaluation of the spectra.

Science of The Total Environment, 1992

Trace metal fluxes have been determined for two lakes in southeastern Australia. Lakes in the Mel... more Trace metal fluxes have been determined for two lakes in southeastern Australia. Lakes in the Melbourne metropolitan area and in a remote region of the Australian Alps were examined. Historic fluxes were calculated from the combination of trace metal concentrations and sedimentation rates. The trace metal concentrations of Pb, Cu and Zn were determined by conventional atomic absorption spectrophotometric methods, and the rates of sedimentation by 21°pb dating. In the last 80 years the flux of Zn has increased 42-fold and Cu 30-fold in the Melbourne area. The flux of stable lead has increased 90-fold in the urban environment and 35-fold in the remote location. At the Melbourne site the average Pb flux over recent years has been 230 mg m-2 year-l.

Marine Pollution Bulletin, 2008

The activity concentration of Cesium-137 (137Cs) and naturally-occurring Polonium-210 (210Po) wer... more The activity concentration of Cesium-137 (137Cs) and naturally-occurring Polonium-210 (210Po) were measured in the muscle tissue, kidney and liver of Pacific walrus (Odobenus rosmarus divergens) and bearded seal (Erignathus barbatus) collected by native hunters from the Bering Sea. The mean 137Cs concentrations in muscle, liver and kidney of Pacific walrus were 0.07, 0.09 and 0.07 Bq kg-1 (N= 5, wet weight), respectively, and 0.17, 0.10, and 0.17 Bq kg-1 (N=2, wet weight), respectively, in bearded seal. In general, 137Cs tissue concentrations are significantly lower than those previously reported for mammals from other regions. By comparison, 210Po activity concentrations appear to be higher than those reported elsewhere but a larger variation. The mean 210Po concentration in the muscle tissue, liver and kidney of Pacific walrus (N=5, wet weight) were 28.7, 189, and 174 Bq kg−1, respectively. This compares with 210Po concentration values (N=2, wet weight) of 27, 207, and 68 Bq kg−1 measured in the muscle tissue, liver and kidney, of bearded seal, respectively. Estimated bioaccumulation factors-as defined by the radionuclide concentration ratio between the target tissue to that in sea water-were two to three orders of magnitude higher for 210Po that those of 137Cs. We conclude from radiological dose estimates that ingestion of 137Cs in foods derived from walrus and seal will pose no threat to human health. This work has important implications for assessing health risks to Alaskan coastal communities concerned about the dumping of nuclear waste in the Russia Arctic.

Journal of Radioanalytical and Nuclear Chemistry, 2005

Accelerator mass spectrometry (AMS) is a sensitive and robust technique typically applied to the ... more Accelerator mass spectrometry (AMS) is a sensitive and robust technique typically applied to the quantification of long-lived radioisotopes in samples too small to be decay-counted. AMS is characterized by a high rejection of interferences and a low susceptibility to matrix components, which reduce the demands on sample preparation chemistry. At Lawrence Livermore National Laboratory (LLNL) Center for Accelerator Mass Spectrometry (CAMS), we have developed an AMS capability for the measurement of actinide concentrations and isotopic ratios. To date, this capability has been primarily devoted to the measurement of 239 Pu and 240 Pu in bioassay and environmental samples including soils, sediments, waters, and human urine. For these analyses, a known amount of 242 Pu is added to the samples as a reference isotope for normalization. Measurements of standard and intercomparison samples have shown that quantification is accurate and precise from at least 10 6 to 10 11 atoms/sample. Recently, the ratios of 240 Pu, 241 Pu, 242 Pu, and 244 Pu to intrinsic 239 Pu have been successfully measured in soil samples from nuclear test sites. In addition, initial measurements of U and Np isotopes have yielded results consistent with the Pu measurements with respect to sensitivity, accuracy, precision, and linear range.

Journal of Radioanalytical and Nuclear Chemistry, 2000

The Lawrence Livermore National Laboratory has developed an extensive quality assurance program t... more The Lawrence Livermore National Laboratory has developed an extensive quality assurance program to provide high quality data and assessments in support of the Marshall Islands Dose Assessment and Radioecology Program. Our quality assurance objectives begin with the premise of providing integrated and cost-effective program support (to meet wide-ranging programmatic needs, scientific peer review, and build public confidence) and continue through

The following document has been prepared as a hardcopy supplement to the U.S. Department of Energ... more The following document has been prepared as a hardcopy supplement to the U.S. Department of Energy web site,

The U.S. Department of Energy (DOE) has recently implemented a series of strategic initiatives to... more The U.S. Department of Energy (DOE) has recently implemented a series of strategic initiatives to address long-term radiological surveillance needs at former US test sites in the Marshall Islands. The plan is to engage local atoll communities in developing shared responsibilities for implementing radiation protection programs for resettled and resettling populations. As part of this new initiative, DOE agreed to design and construct a radiological laboratory on Enewetak Island, and help develop the necessary local resources to maintain and operate the facility. This cooperative effort was formalized in August 2000 between the DOE, the Republic of the Marshall Islands (RMI), and the Enewetak/Ujelang Local Atoll Government (EULGOV). The laboratory facility was completed in May 2001. The laboratory incorporates both a permanent whole body counting (WBC) system to assess internal exposures to 137 Cs, and clean living space for people providing 24-h void urine samples. DOE continues to provide ongoing technical assistance, training, and data quality review while EULGOV provides manpower and infrastructure development to sustain facility operations on a full-time basis. This paper will detail the special construction, transportation and installation issues in establishing a whole body counting facility in an isolated, harsh environmental setting.

In July 1993 and June 1995 drit%ng sediment traps were deployed near the Po outflow,in the coasta... more In July 1993 and June 1995 drit%ng sediment traps were deployed near the Po outflow,in the coastal zone and in the Jabuka Pit in order to obtain quantitative information on the vertical flux of particulate material and export of organic carbon in the Northern and Middle Adriatic Sea. During these periods and in July 1994, the standing stock of carbon and nitrogen in the water column were also " @mated_ Carbon and nitrogen concentrations were higher in the north with a mean of 266 pg C 1-' in surbce waters as compared to 92 pg C 1-1in Middle AdriatiG maximum concentrations were associated to the less-saline surtkx-subsurtke waters in the north and to the chlorophyll a maximum in the Middle Adriatic. Organic carbon flux was roughly five times higher near the Po than in the more oligotrophic waters of the catral regior4 with ovemll values (0.8 to 11.5 mg m-2d-') being low compared to the open Northwestern Mediterranean. Comparison with primary production measurements yielded estimates of carbon export (f-ratio) of 4.7 and 3.4% in the Po and Pit stations, respedvely, in 1993 and of 1.6 and 3.6% in the central part of the Adriatic in 1995. These amsistently low values suggest enhanced carbon recycling in the upper water colmq even in regions characterized by different production and organic flux regimes. Zoopkmkton f~pellets were important conveyom of organic carbon in this regioq particularly those produced by tishes in the North and coastal sites.

Rare earth element (REE) composition of sinking particles was examined in time-series sediment tr... more Rare earth element (REE) composition of sinking particles was examined in time-series sediment trap samples collected from four depths (200, 500, 1000, 2000 m) in the Gulf of Lions. Vertical flux profiles showed the occurrence of a sedimentation pulse which resulted in the rapid sinking of phytoplankton aggregates to 2000 m depth. These particles were characterized by REE patterns similar to those in the upper 200 m indicating that little, if any, additional REE scavenging occurred during the sedimentation event. In contrast, after the sedimentation pulse, particles from deep waters showed an enrichment of light-REE (LREE) relative to heavy-REE (HREE) and a positive Ce anomaly. Comparing REE patterns in particles from the upper water column (200 m) with those from depth (1000, 2000 m) during and following the sedimentation pulse indicates that time is a key factor in determining REE scavenging by sinking particles. This is particularly evident for the preferential scavenging of Ce (IV) which is most pronounced in the finer, slowly sinking, and presumably older particles. These findings are consistent with REE patterns in sea water from the northwestern Mediterranean which show a strong negative Ce anomaly and gradual enrichment of REE with increasing atomic number. The enrichment of LREE relative to HREE in particles from deep waters results either preferential scavenging of LREE on particles, analogous to the enrichment of Ce, or selective dissolution of HREE in association with particle remineralization processes, or both; this aspect of REE behaviour merits further study.

Dissolved and particlulate Thorium-234 (234 Th) were measured in near surface waters from the Cen... more Dissolved and particlulate Thorium-234 (234 Th) were measured in near surface waters from the Central and Northern Adriatic Sea in order to gain an insight into the intensity and variability of active scavenging and particle removal processes. Dissolved 234 Th to Uranium-238 (238 U) activity ratios vary from 0.21 to 0.75 and clearly imply that 234 Th is being actively scavenged from sea water on a timescale of <3 months. The scavenging rate of dissolved 234 Th with respect to scavenging onto particles appears to correlate with primary productivity measurements. Scavenging and rapid removal of particulate 234 Th from the water column is best explained by a mechanism of zooplankton grazing and fecal pellet production. At one sight in the Jabuka Pit, particulate 234 Th residence times below the pycnocline are long (30-40 days) suggesting that particles are being more readily recycled at these depths. By comparison, in a seawater profile collected near the Po outflow region, 234 Th is depleted with respect to 238 U through the entire water column. We conclude from this assessment that particles in waters near the Po River outflow will be more efficiently transported to bottom sediments compared with those in deeper waters over the Jabuka Pit.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, May 1, 2008

spectrometry. Despite a pervasive interference from 90 Zr, our initial development has yielded an... more spectrometry. Despite a pervasive interference from 90 Zr, our initial development has yielded an instrumental background of ~10 8 atoms (75 mBq) per sample. Further refinement of our system (e.g., redesign of our detector, use of alternative target materials) is expected to push the background below 10 6 atoms, close to the theoretical limit for AMS. Once we have refined our system and developed suitable sample preparation protocols, we will utilize our capability in applications to homeland security, environmental monitoring, and human health.

Marine Radioactivity, 2005

Publisher Summary This chapter focuses on the linking legacies of the cold war to arrival of anth... more Publisher Summary This chapter focuses on the linking legacies of the cold war to arrival of anthropogenic radionuclides in the oceans through the 20th century. This chapter is intended to summarize the sources and occurrences of man-made radioactivity in the oceans, as well as provide a technical basis for addressing public misunderstandings about the risks posed by environmental radioactivity. The main contribution of dispersed radioactivity entering the environment has come from testing of atmospheric nuclear weapons from 1945 to 1980. The measured total global deposit of long-lived fission products, such as 90 Sr and 137 Cs is in agreement with the estimated fission yields and partitioning of radioactive debris in the atmosphere. Other unrestrained sources of radioactive contamination of the marine environment include, direct discharges of radioactive effluents into rivers and coastal seas from reprocessing and fuel cycle operations, and runoff or leakage from other land-based sources of contamination. Human activities involving nuclear materials will always be subject to accidents and accidental releases of radioactivity.

Re-entry vehicles on missiles launched from Vandenberg Air Force base in California re-enter at t... more Re-entry vehicles on missiles launched from Vandenberg Air Force base in California re-enter at the Western Test Range, the Regan Test Site (RTS) at Kwajalein Atoll. An Environmental Assessment (EA) was written at the beginning of the program to assess potential impact of DU and Be, the major RV materials of interest from a health and environmental perspective, for both ocean and land impacts. The chemical and structural form of Be and DU in RVs is such that they are insoluble in soil water and seawater. Thus, they are not toxic to plant life on the isalnd (no soil to plant uptake.) Similarly, due to their insolubility in sea water there is no uptake of either element by fish, mollusks, shellfish, sea mammals, etc. No increase in either element has been observed in sea life around Illeginnin Island where deposition of DU and Be has occured. The critical terrestrial exposure pathway for U and Be is inhalation. Concentration of both elements in air over the test period (1989 to 2006) is lower by a factor of nearly 10,000 than the most restrictive U.S. guideline for the general public. Uranium concentrations in air are also lower by factors of 10 to 100 than concentrations of U in air in the U.S. measured by the EPA (Keith et al., 1999). U and Be concentrations in air downwind of deposition areas on Illeginni Island are essentially indistinguishable from natural background concentrations of U in air at the atolls. Thus, there are no health related issues associated with people using the island.

Re-entry vehicles on missiles launched from Vandenberg Air Force base in California re-enter at t... more Re-entry vehicles on missiles launched from Vandenberg Air Force base in California re-enter at the Western Test Range, the Regan Test Site (RTS) at Kwajalein Atoll. An Environmental Assessment (EA) was written at the beginning of the program to assess potential impact of DU and Be, the major RV materials of interest from a health and environmental perspective, for both ocean and land impacts. The chemical and structural form of Be and DU in RVs is such that they are insoluble in soil water and seawater. Thus, they are not toxic to plant life on the isalnd (no soil to plant uptake.) Similarly, due to their insolubility in sea water there is no uptake of either element by fish, mollusks, shellfish, sea mammals, etc. No increase in either element has been observed in sea life around Illeginnin Island where deposition of DU and Be has occured. The critical terrestrial exposure pathway for U and Be is inhalation. Concentration of both elements in air over the test period (1989 to 2006) is lower by a factor of nearly 10,000 than the most restrictive U.S. guideline for the general public. Uranium concentrations in air are also lower by factors of 10 to 100 than concentrations of U in air in the U.S. measured by the EPA (Keith et al., 1999). U and Be concentrations in air downwind of deposition areas on Illeginni Island are essentially indistinguishable from natural background concentrations of U in air at the atolls. Thus, there are no health related issues associated with people using the island.

In response to sponsor interest in October 2005 we proposed two methods for enhancing the precisi... more In response to sponsor interest in October 2005 we proposed two methods for enhancing the precision of 233 U accelerator mass spectrometry (AMS) capabilities at the Lawrence Livermore National Laboratory (LLNL). In a previous report we evaluated the first method and demonstrated that by increasing sample loading by a factor of four coupled with performing four replicates of each sample, we could achieve measurement precision of~1%. Recent modifications to our system have enabled us to test the second proposed method. By changing our setup to normalize 233 U ions counted in a gas ionization chamber to 238 U measured as a current in an off-axis Faraday cup we were able to attain 1% precision without the need for replicate analysis. This method could be further refined to achieve 0.5% precision in samples of interest.

Between 1965 and 1981, five objects - six naval reactor pressure vessels (RPVs) from four former ... more Between 1965 and 1981, five objects - six naval reactor pressure vessels (RPVs) from four former Soviet Union submarines and a special containers from the icebreaker Lenin, each of which contained damaged spent nuclear fuel (SNF) - were dumped in a variety of containments, using a number of sealing methods, at four sites in the Kara Sea. All objects were dumped at sites that varied in depth from 12 to 300 m. This paper examines the use of the long-lived radionuclides ⁵⁹Ni, ⁹⁹Tc, and ²³⁶U encased within these objects to monitor the breakdown of the containments due to corrosion. Included are discussions of the radionuclide inventory and their release rate model, the estimated radionuclide mass in a typical seawater sample, and the potential for radionuclide measurement via Accelerator Mass Spectrometry (AMS).

International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes, 1986

A method is described for deposition of polonium isotopes on rotating silver discs. Rapid rotatio... more A method is described for deposition of polonium isotopes on rotating silver discs. Rapid rotation during deposition gives a uniform deposit of high yield within an hour, and good GL energy resolution simplifies the quantitative evaluation of the spectra.

Science of The Total Environment, 1992

Trace metal fluxes have been determined for two lakes in southeastern Australia. Lakes in the Mel... more Trace metal fluxes have been determined for two lakes in southeastern Australia. Lakes in the Melbourne metropolitan area and in a remote region of the Australian Alps were examined. Historic fluxes were calculated from the combination of trace metal concentrations and sedimentation rates. The trace metal concentrations of Pb, Cu and Zn were determined by conventional atomic absorption spectrophotometric methods, and the rates of sedimentation by 21°pb dating. In the last 80 years the flux of Zn has increased 42-fold and Cu 30-fold in the Melbourne area. The flux of stable lead has increased 90-fold in the urban environment and 35-fold in the remote location. At the Melbourne site the average Pb flux over recent years has been 230 mg m-2 year-l.

Marine Pollution Bulletin, 2008

The activity concentration of Cesium-137 (137Cs) and naturally-occurring Polonium-210 (210Po) wer... more The activity concentration of Cesium-137 (137Cs) and naturally-occurring Polonium-210 (210Po) were measured in the muscle tissue, kidney and liver of Pacific walrus (Odobenus rosmarus divergens) and bearded seal (Erignathus barbatus) collected by native hunters from the Bering Sea. The mean 137Cs concentrations in muscle, liver and kidney of Pacific walrus were 0.07, 0.09 and 0.07 Bq kg-1 (N= 5, wet weight), respectively, and 0.17, 0.10, and 0.17 Bq kg-1 (N=2, wet weight), respectively, in bearded seal. In general, 137Cs tissue concentrations are significantly lower than those previously reported for mammals from other regions. By comparison, 210Po activity concentrations appear to be higher than those reported elsewhere but a larger variation. The mean 210Po concentration in the muscle tissue, liver and kidney of Pacific walrus (N=5, wet weight) were 28.7, 189, and 174 Bq kg−1, respectively. This compares with 210Po concentration values (N=2, wet weight) of 27, 207, and 68 Bq kg−1 measured in the muscle tissue, liver and kidney, of bearded seal, respectively. Estimated bioaccumulation factors-as defined by the radionuclide concentration ratio between the target tissue to that in sea water-were two to three orders of magnitude higher for 210Po that those of 137Cs. We conclude from radiological dose estimates that ingestion of 137Cs in foods derived from walrus and seal will pose no threat to human health. This work has important implications for assessing health risks to Alaskan coastal communities concerned about the dumping of nuclear waste in the Russia Arctic.

Journal of Radioanalytical and Nuclear Chemistry, 2005

Accelerator mass spectrometry (AMS) is a sensitive and robust technique typically applied to the ... more Accelerator mass spectrometry (AMS) is a sensitive and robust technique typically applied to the quantification of long-lived radioisotopes in samples too small to be decay-counted. AMS is characterized by a high rejection of interferences and a low susceptibility to matrix components, which reduce the demands on sample preparation chemistry. At Lawrence Livermore National Laboratory (LLNL) Center for Accelerator Mass Spectrometry (CAMS), we have developed an AMS capability for the measurement of actinide concentrations and isotopic ratios. To date, this capability has been primarily devoted to the measurement of 239 Pu and 240 Pu in bioassay and environmental samples including soils, sediments, waters, and human urine. For these analyses, a known amount of 242 Pu is added to the samples as a reference isotope for normalization. Measurements of standard and intercomparison samples have shown that quantification is accurate and precise from at least 10 6 to 10 11 atoms/sample. Recently, the ratios of 240 Pu, 241 Pu, 242 Pu, and 244 Pu to intrinsic 239 Pu have been successfully measured in soil samples from nuclear test sites. In addition, initial measurements of U and Np isotopes have yielded results consistent with the Pu measurements with respect to sensitivity, accuracy, precision, and linear range.

Journal of Radioanalytical and Nuclear Chemistry, 2000

The Lawrence Livermore National Laboratory has developed an extensive quality assurance program t... more The Lawrence Livermore National Laboratory has developed an extensive quality assurance program to provide high quality data and assessments in support of the Marshall Islands Dose Assessment and Radioecology Program. Our quality assurance objectives begin with the premise of providing integrated and cost-effective program support (to meet wide-ranging programmatic needs, scientific peer review, and build public confidence) and continue through

The following document has been prepared as a hardcopy supplement to the U.S. Department of Energ... more The following document has been prepared as a hardcopy supplement to the U.S. Department of Energy web site,

The U.S. Department of Energy (DOE) has recently implemented a series of strategic initiatives to... more The U.S. Department of Energy (DOE) has recently implemented a series of strategic initiatives to address long-term radiological surveillance needs at former US test sites in the Marshall Islands. The plan is to engage local atoll communities in developing shared responsibilities for implementing radiation protection programs for resettled and resettling populations. As part of this new initiative, DOE agreed to design and construct a radiological laboratory on Enewetak Island, and help develop the necessary local resources to maintain and operate the facility. This cooperative effort was formalized in August 2000 between the DOE, the Republic of the Marshall Islands (RMI), and the Enewetak/Ujelang Local Atoll Government (EULGOV). The laboratory facility was completed in May 2001. The laboratory incorporates both a permanent whole body counting (WBC) system to assess internal exposures to 137 Cs, and clean living space for people providing 24-h void urine samples. DOE continues to provide ongoing technical assistance, training, and data quality review while EULGOV provides manpower and infrastructure development to sustain facility operations on a full-time basis. This paper will detail the special construction, transportation and installation issues in establishing a whole body counting facility in an isolated, harsh environmental setting.

In July 1993 and June 1995 drit%ng sediment traps were deployed near the Po outflow,in the coasta... more In July 1993 and June 1995 drit%ng sediment traps were deployed near the Po outflow,in the coastal zone and in the Jabuka Pit in order to obtain quantitative information on the vertical flux of particulate material and export of organic carbon in the Northern and Middle Adriatic Sea. During these periods and in July 1994, the standing stock of carbon and nitrogen in the water column were also " @mated_ Carbon and nitrogen concentrations were higher in the north with a mean of 266 pg C 1-' in surbce waters as compared to 92 pg C 1-1in Middle AdriatiG maximum concentrations were associated to the less-saline surtkx-subsurtke waters in the north and to the chlorophyll a maximum in the Middle Adriatic. Organic carbon flux was roughly five times higher near the Po than in the more oligotrophic waters of the catral regior4 with ovemll values (0.8 to 11.5 mg m-2d-') being low compared to the open Northwestern Mediterranean. Comparison with primary production measurements yielded estimates of carbon export (f-ratio) of 4.7 and 3.4% in the Po and Pit stations, respedvely, in 1993 and of 1.6 and 3.6% in the central part of the Adriatic in 1995. These amsistently low values suggest enhanced carbon recycling in the upper water colmq even in regions characterized by different production and organic flux regimes. Zoopkmkton f~pellets were important conveyom of organic carbon in this regioq particularly those produced by tishes in the North and coastal sites.

Rare earth element (REE) composition of sinking particles was examined in time-series sediment tr... more Rare earth element (REE) composition of sinking particles was examined in time-series sediment trap samples collected from four depths (200, 500, 1000, 2000 m) in the Gulf of Lions. Vertical flux profiles showed the occurrence of a sedimentation pulse which resulted in the rapid sinking of phytoplankton aggregates to 2000 m depth. These particles were characterized by REE patterns similar to those in the upper 200 m indicating that little, if any, additional REE scavenging occurred during the sedimentation event. In contrast, after the sedimentation pulse, particles from deep waters showed an enrichment of light-REE (LREE) relative to heavy-REE (HREE) and a positive Ce anomaly. Comparing REE patterns in particles from the upper water column (200 m) with those from depth (1000, 2000 m) during and following the sedimentation pulse indicates that time is a key factor in determining REE scavenging by sinking particles. This is particularly evident for the preferential scavenging of Ce (IV) which is most pronounced in the finer, slowly sinking, and presumably older particles. These findings are consistent with REE patterns in sea water from the northwestern Mediterranean which show a strong negative Ce anomaly and gradual enrichment of REE with increasing atomic number. The enrichment of LREE relative to HREE in particles from deep waters results either preferential scavenging of LREE on particles, analogous to the enrichment of Ce, or selective dissolution of HREE in association with particle remineralization processes, or both; this aspect of REE behaviour merits further study.

Dissolved and particlulate Thorium-234 (234 Th) were measured in near surface waters from the Cen... more Dissolved and particlulate Thorium-234 (234 Th) were measured in near surface waters from the Central and Northern Adriatic Sea in order to gain an insight into the intensity and variability of active scavenging and particle removal processes. Dissolved 234 Th to Uranium-238 (238 U) activity ratios vary from 0.21 to 0.75 and clearly imply that 234 Th is being actively scavenged from sea water on a timescale of <3 months. The scavenging rate of dissolved 234 Th with respect to scavenging onto particles appears to correlate with primary productivity measurements. Scavenging and rapid removal of particulate 234 Th from the water column is best explained by a mechanism of zooplankton grazing and fecal pellet production. At one sight in the Jabuka Pit, particulate 234 Th residence times below the pycnocline are long (30-40 days) suggesting that particles are being more readily recycled at these depths. By comparison, in a seawater profile collected near the Po outflow region, 234 Th is depleted with respect to 238 U through the entire water column. We conclude from this assessment that particles in waters near the Po River outflow will be more efficiently transported to bottom sediments compared with those in deeper waters over the Jabuka Pit.