Separation and purification and beta liquid scintillation analysis of 151Sm in Savannah River Site and Hanford Site DOE high level waste

This paper describes development work to obtain a product phase of ¹⁵¹Sm pure of any other radioactive species so that it can be determined in US Department of Energy high level liquid waste and low level solid waste by liquid scintillation b-spectroscopy. The technique provides separation from mCi/ml levels of ¹³⁷Cs, Pu a- and ²⁴¹Pu b-decay activity, and ⁹⁰Sr/⁹⁰Y activity. The separation technique is also demonstrated to be useful for the determination of ¹⁴⁷Pm.     

Low-Flux NAA Applications at the Savannah River Site

Neutron activation analysis using low-flux isotopic neutron sources is put to use in addressing areas of applied interest in managing the Savannah River Site. Some of the applications are unique due the site's operating history and its chemical processing facilities. Because sensitivity needs for many of the applications are not severe, they can be accomplished using a 6 mg ²⁵²Cf neutron activation analysis facility. Overviews of the facility and several example applications are presented.     

Law enforcement tools available at the Savannah River Site

A number of nuclear technologies developed and applied at the Savannah River Site in support of nuclear weapons material production and environmental remediation can be applied to problems in law enforcement. Techniques and equipment for high-sensitivity analyses of samples are available to identify and quantify trace elements and establish origins and histories of forensic evidence removed from crime scenes. While some of these capabilities are available at local crime laboratories, state-of-the-art equipment and breakthroughs in analytical techniques are continually being developed at DOE laboratories. Extensive experience with the handling of radioactive samples at the DOE labs minimizes the chances of cross-contamination of evidence received from law enforcement. In addition to high-sensitivity analyses, many of the field techniques developed for use in a nuclear facility can assist law enforcement personnel in detecting illicit materials and operations, in retrieving of pertinent evidence and in surveying crime scenes. Some of these tools include chemical sniffers, hand-held detectors, thermal imaging, etc. In addition, mobile laboratories can be deployed to a crime scene to provide field screening of potential evidence. A variety of portable sensors can be deployed on vehicle, aerial, surface or submersible platforms to assist in the location of pertinent evidence or illicit operations. Several specific nuclear technologies available to law enforcement and their potential uses are discussed.     

Analysis of 36Cl in Savannah River Site radioactive waste

The present work shows the activity levels of ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ¹³⁷Cs in bottom sediments collected from eight locations of Mumbai Harbour Bay. The study has shown that ⁴⁰K and ²²⁸Ra concentration is nearly uniform throughout the studied area while ²²⁶Ra and ¹³⁷Cs are more concentrated in the southern regions of the bay. The significant variation in the activity levels of radionuclides within the study site might be due to their sorption/desorption processes onto the surface of sediment materials. The low mean value of ²²⁶Ra/²²⁸Ra ratio (0.72) in the sediments indicates that ²³⁸U has relatively greater solubility and mobility than ²³²Th. Similarly, low activity ratio (0.18) for ¹³⁷Cs/⁴⁰K reflects the presence of very high content of ⁴⁰K in sediment due to presence of primary minerals in sediment. Silt and clay were reported to dominate the composition of the sediment. A significant positive correlation between ²²⁶Ra and ²²⁸Ra and ¹³⁷Cs and ⁴⁰K suggest a similar origin of their geochemical sources and identical behavior during transport in the sediment system.     

Analysis of radioiodine in ground litter samples downwind of the Savannah River Site

Ground litter samples were collected and analyzed for radioiodine (¹²⁹I) content from distances of 1.4–128 km away from the Savannah River Site nuclear fuel reprocessing facility. Analysis methods consisted of thermo-chromatographic separation of the iodine from the sample matrix followed by isotope dilution thermal ionization mass spectrometry (ID-TIMS). The results indicate that measurable quantities of radioiodine are released and that the accumulation decreases as a function of distance from the source in agreement with a simple approximation described in the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) report.     

Cesium-137 content in blood of Taiwan residents

Samples of blood from adults in good health in Taiwan have been analyzed for their¹³⁷Cs content by gross beta counting using a low background gas-flow counter. The level of¹³⁷Cs content in blood was 8.3+6.3x10^–3 pCi.ml^–1 for ages 24+7 y. The deposition of fission product¹³⁷Cs in Taiwan, which was monitored by water tray for fallout, was also studied since January 1979.     

Cesium-137 in air late after the Chernobyl reactor accident

Summary Cesium-137 in air as high as 88.1 μBq ^. m^-3 was recorded in Thessaloniki, Northern Greece (40°38’N, 22°58’E) on June 3, 1998 very late after the Chernobyl reactor accident following a radiological incident occurred in a steel factory at Acerinox, Spain.     

Recovery and determination of adsorbed technetium on Savannah River Site charcoal stack samples

Experimental results are provided for the sample analyses for technetium in charcoal samples placed in-line with a Savannah River Site (SRS) processing stack effluent stream as a part of an environmental surveillance program. The method for Tc removal from charcoal was based on that originally developed with high purity charcoal. Presented is the process that allowed for the quantitative analysis of ⁹⁹Tc in SRS charcoal stack samples with and without ⁹⁷Tc as a tracer. The results obtained with the method using the ⁹⁷Tc tracer quantitatively confirm the results obtained with no tracer added. All samples contain ⁹⁹Tc at the pg·g⁻¹ level.     

Radium-226 analysis methodology in Savannah River Site high activity waste matrices

Waste cleanup efforts currently underway at the Savannah River Site have created a need to characterize Radium-226 levels in the various high activity waste matrices currently in Site inventories. The traditional method our laboratory used for analyzing Ra-226 in higher activity matrices was based on classic cation exchange methodology. Radiochemical separations were often initiated in remotely operated shielded analytical cells followed by additional hands-on separations in radiological hoods. Methodology based on IBC advanced technologies SuperLig 640 extractant, mounted in 3M Empore filter media has been developed to streamLine the radium analyses.     

Radiochemical analyses for the defense waste processing facility startup at the Savannah River Site

Highly radioactive waste from defense-related activities at the Savannah River Site in South Carolina are to be incorporated into a borosilicate glass in the Defense Waste Processing Facility (DWPF) for long-tem geological isolation. Processing and repository safety considerations require the determination of 24 radioisotopes that meet the reporting criteria. These isotopes include fission products, activation products, and daughter nuclei that grow into the waste. Four isotopes,¹³⁷Cs,⁹⁰Sr,²³⁸Pu and²³⁸U will be routinely measured in the DWPF operation for process control. This work shows that the concentrations of the other 20 reportable radioisotopes in the final glass product can be predicted from a thorough characterization of the high level waste (HLW) tanks and a knowledge of the concentrations of the major non-radioactive components in the vitrification process.     

Neutron activation analysis applications at the Savannah River Site using an isotopic neutron source

NAA using ²⁵²Cf is used to address important areas of applied interest of the Savanah River Site (SRS). Sensitivity needs for many of the applications are not severe; analyses are accomplished using a 21 mg ²⁵²Cf NAA facility. Because NAA allows analysis of bulk samples, it offers strong advantages for samples in difficult-to-digest matrices when its sensitivity is sufficient. Following radiochemical separation with stable carrier addition, chemical yields for a number of methods are determined by neutron activation of the stable carrier. In some of the cases where no suitable stable carriers exist, the source has been used to generate radioactive tracers to yield separations.     

Gamma-pulse-height evaluation of a USA Savannah River Site Burial Ground special configuration waste item

The Savannah River Site (SRS) Burial Ground had a container labeled as Box 33 for which they had no reliable solid waste stream designation. The container consisted of an outer box of dimensions 48″ × 46″×66″ and an inner box that contained high density and high radiation dose material. From the outer box Radiation Control measured an extremity dose rate of 22 mrem/h. With the lid removed from the outer box, the maximum dose rate measured from the inner box was 100 mrem/h extremity and 80 mrem/h whole body. From the outer box the material was sufficiently high in density that the Solid Waste Management operators were unable to obtain a Co-60 radiograph of the contents. Solid Waste Management requested that the Analytical Development Section of Savannah River National Laboratory perform a γ-ray assay of the item to evaluate the radioactive content and possibly to designate a solid waste stream. This paper contains the results of three models used to analyze the measured γ-ray data acquired in an unusual configuration.     

Observation and Measurement of 79Se in Savannah River Site High Level Waste Tank Fission Product Waste

We report the first observation of confirmed ⁷⁹Se activity in Savannah River Site high level fission product waste. ⁷⁹Se was measured after a seven step chemical treatment to remove interfering activity from ¹³⁷Cs, ⁹⁰Sr, and plutonium at levels 10⁵ times higher than the observed ⁷⁹Se content and to remove ⁹⁹Tc at levels 300 times higher than observed ⁷⁹Se. ⁷⁹Se was measured by liquid scintillation -decay counting after specific tests to eliminate uncertainties from possible contributions from ⁹⁹Tc, ¹⁴⁷Pm, ¹⁵¹Sm, ⁹³Zr, or ²⁴¹Pu, whose -decay spectra could appear similar to that of ⁷⁹Se, and whose content would be expected at levels near or greater than ⁷⁹Se.     

Sorbents for Analytical Determination of Cesium-137 and Strontium-90 in Natural Objects

The problem of determination of small activities of cesium and strontium in natural waters can be successfully solved by as design of highly sensitive lowbackground devices as development of new efficient techniques of concentrating radionuclides from large volumes of natural waters. While the problem of cesium concentrating may be solved quite successfully by a number of sorbents,the strontium concentrating is rather complicated.     

Determination of long-lived fission products and actinides in Savannah River Site HLW sludge and glass for waste acceptance

Savannah River Site (SRS) is immobilizing the radioactive, high-level waste sludge in Tank 51 into a borosilicate glass for disposal in a geologic repository. A requirement for repository aceeptance is that SRS report the concentrations of certain fission product and actinide radionuclides in the glass. This paper presents measurements of many of these concentrations in both Tank 51 sludge and the final glass. The radionuclides were measured by inductively coupled plasma mass spectrometry and α, β, and γ counting methods. Examples of the radionuclides are⁹⁰Sr,¹³⁷Cs,²³⁸U and,²³⁹Pu. Concentrations in the glass are 3.1 times lower due to dilution of the sludge with a nonradio-active glass forming frit in the vitrification process. Results also indicated that in both the sludge and glass the relative concentrations of the long lived fission products insoluble in caustic are in proportion to their yields from the fission of²³⁵U waste in the SRS reactors. This allowed the calculation of a fission yield scaling factor. This factor in addition to the sludge dilution factor can be used to estimate concentrations of waste acceptance radionuclides that cannot be measured in the glass. Examples of these radionuclides are⁷⁹Se,⁹³Zr, and¹⁰⁷Pd.     

Measurement of <Superscript>99</Superscript>Tc in Savannah River Site high activity waste

Summary Waste cleanup efforts currently underway at the Savannah River Site have created a need to characterize ⁹⁹Tc in the various high activity waste matrices currently in Site inventories. The traditional method our laboratory used for analyzing ⁹⁹Tc in higher activity matrices was a solvent-solvent extraction method using Aliquat-336 in xylene. In an effort to eliminate the resulting generation of mixed wastes, a variety of different separation methodologies have been studied. Eichrom TEVA solid phase extractions using column technology have been employed in a case by case basis over the last several years. More recently, applications using Eichrom TEVA extraction discs and 3M Empore Tc extraction discs have also been explored.     

Cesium-137 spatial activity in surface soils near and surrounding the Gurí Reservoir (Venezuela)

Summary The ¹³⁷Cs activities (Bq ^. kg^-1) were determined in more than ninety soil samples between 2 and 5 cm depths surrounding and near the Guri Reservoir (state of Bolivar, Venezuela). The measurements were performed by high-resolution gamma-ray spectroscopy, employing Soil-6 as a comparator. In general, the values of the ¹³⁷Cs activities were about double on the west side of the reservoir than on the east side, the environmental parameters were similar on both sides, but the soils were very different, they were untisols on the western side and entisols on the eastern one. The soils were highly mineralized and on the western side they were above rich iron deposits. Many of the sampling sites on the eastern side were annually covered with water, when the reservoir was at high levels. The anomalously high ¹³⁷Cs values, southeast of the reservoir were found in a small area that had very different environmental characteristics and can be explained by the direct deposition of the fallout by the clouds on the vegetation and surface, since this area is in a dense cloud forest.     

Mapping of the distribution of 137Cs in Irish Sea sediments

The Sellafield nuclear fuel reprocessing plant released a total of 41 PBq of ¹³⁷Cs into the Irish Sea in the period 1952–1998. The present work integrates a series of surveys of the ¹³⁷Cs distribution in sediment offshore Sellafield which was aimed at obtaining a detailed picture of the patterns of sediment contamination and their time evolution, and an estimate of the ¹³⁷Cs inventory in sediment. The authors applied NaI(Tl)-based underwater -ray spectrometry to record a series of 1800 one-minute spectra along 14 transects totaling 160 Nm. The dominant feature of the contamination pattern obtained from this survey remains a stripe extending northwestwards along the coast from the discharge point, as reported for previous surveys. Steep gradients are observed perpendicular to the coast, with ¹³⁷Cs countrates decreasing to half the recorded maximum over a distance of less than 2000 m.     

HEU measurements of holdup and recovered residue in the deactivation and decommission activities of the 321-M Reactor Fuel Fabrication Facility at the Savannah River Site

Summary This paper contains a summary of the holdup and material control and accountability (MC&A) assays conducted for the determination of highly enriched uranium (HEU) in the deactivation and decommissioning (D&D) of the Reactor Fuel Fabrication Facility at the Savannah River Site (SRS). The facility was used to fabricate HEU fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the SRS production reactors. The facility operated for more than 35 years. During this time thousands of uranium-aluminum alloy (U-Al) production reactor fuel tubes were produced. After the facility ceased operations in 1995, all of the easily accessible U-Al was removed from the building, and only residual amounts remained. The bulk of this residue was located in the equipment that generated and handled small U-Al particles and in the exhaust systems for this equipment (e.g., chip compactor, casting furnaces, log saw, lathes A & B, cyclone separator, Freon?cart, riser crusher, …, etc). The D&D project is likely to represent an important example for D&D activities across SRS and across the Department of Energy weapons complex. The Savannah River National Laboratory was tasked to conduct holdup assays to quantify the amount of HEU on all components removed from the facility prior to placing in solid waste containers. The ²³⁵U holdup in any single component of process equipment must not exceed 50 g in order to meet the container limit. This limit was imposed to meet criticality requirements of the low level solid waste storage vaults. Thus, the holdup measurements were used as guidance to determine if further decontamination of equipment was needed to ensure that the quantity of ²³⁵U did not exceed the 50 g limit and to ensure that the waste met the Waste Acceptance Criteria (WAC) of the solid waste storage vaults. Since HEU is an accountable nuclear material, the holdupassays and assays of recovered residue were also important for material control and accountability purposes. In summary, the results of the holdup assays were essential for determining compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to ensure that administrative criticality safety controls were not exceeded. This paper discusses theg-ray assay measurements conducted and the modeling of the acquired data to obtain measured holdup in process equipment, exhaust components, and fixed geometry scrap cans. It also presents development work required to model new acquisition configurations and to adapt available instrumentation to perform the assays.