Fission Product Radionuclides Research Articles

Application of the method of vacuum withdrawal inert radioactive gases to control of fuel rods leaking of nuclear reactors WWER types while operation

Currently, a comprehensive approach is being developed for the integrity control of fuel rod claddings in pressurized water reactor (PWR) nuclear power plants. One of the key stages is the reliable detection of leaking fuel rods within the reactor's active zone during power operation. This study examines the general trends in the activity of fission product radionuclides in the primary coolant of various generations and designs of PWRs. The experience of Novovoronezh Nuclear Power Plant is considered regarding the method of sampling and separation of inert radioactive gases from the primary coolant. A comparison is made between different methods of measuring inert radioactive gases in the primary coolant: direct spectrometry, cryogenic method, and vacuum extraction method. The issue of reliable detection of fuel rod leakage during reactor operation is discussed, using the example of Unit 5 at Novovoronezh Nuclear Power Plant. Comparative results are presented for the analysis of the integrity of fuel rod claddings based on key reference radionuclides. The most reliable results indicating fuel rod leakage were obtained through the control of specific activities and analysis of changes in the ratio of inert radioactive gases using the vacuum extraction method. Control of the specific activity of inert radioactive gases in the primary coolant enables a highly reliable assessment of the condition of physical barriers. The proposed method of sampling and separation of inert radioactive gases demonstrates high reliability and convergence of results, serving as an additional tool for integrity control of fuel rod claddings during power operation. Having representative data on the specific activities of inert radioactive gases allows for a reliable assessment of the condition of fuel rod claddings within the reactor core.

A plastic scintillator and HPGe [formula omitted] coincidence detection system

A network of specialist laboratories support the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) with re-measurements of radionuclide samples, including xenon gas. The measurement of four xenon fission product radionuclides (133Xe, 135Xe, 131mXe and 133mXe) can be used to detect an underground nuclear explosion. Laboratories use a range of techniques to measure the radionuclides, including beta-gamma (β−γ) coincidence spectrometry. These highly-sensitive measurements are capable of detecting concentrations of down to 500 atoms of 133Xe in a few cm3 of xenon. In some detector systems, detection of the metastable isomers (131mXe and 133mXe) can be more challenging due to interferences between the signatures of different radionuclides. Recent work has shown that using high-purity Germanium (HPGe) high-resolution gamma detectors, these interferences can be reduced, lowering the dependence of the detection limits on radionuclide sample isotopic composition. One downside of these detectors is the reduction in detection efficiency, which impacts the overall detection sensitivity; so assessing different detector systems is a priority for radionuclide laboratories. This work presents a coincidence detector system comprising of a plastic scintillator gas cell and a large-crystal high-purity germanium detector. The energy resolution, coincidence detection efficiency, MDA and interference factors are determined from measurements of synthetic radioxenon gas samples.

Radionuclide Chemistry in Nuclear Facilities Based on Heavy Liquid Metal Coolants: Past, Present and Future.

Heavy liquid metals such as lead and lead bismuth eutectic (LBE) are considered as spallation target material for next-generation neutron sources and as coolant of fast spectrum nuclear reactors that are developed to facilitate more efficient use of nuclear fuel as well as transmutation of long-lived nuclear waste. During the operation of such facilities, the heavy liquid metal will be activated by nuclear reactions. Additionally, fission product radionuclides may be introduced into the liquid metal from leaking fuel pins or by fission of the target nuclei in spallation. The chemical behaviour of these radioactive contaminants in the liquid metal - especially their immediate volatilization or volatilization of formed secondary compounds - may affect the safety of such facilities. The present article summarizes the activities of PSI's Laboratory of Radiochemistry towards a better understanding of the chemistry of potentially hazardous radionuclides in LBE and discusses aspects that need to be addressed in future to support the licensing of heavy liquid metal-based nuclear facilities.

Cesium and Strontium Contamination of Nuclear Plant Stainless Steel: Implications for Decommissioning and Waste Minimization.

Stainless steels can become contaminated with radionuclides at nuclear sites. Their disposal as radioactive waste would be costly. If the nature of steel contamination could be understood, effective decontamination strategies could be designed and implemented during nuclear site decommissioning in an effort to release the steels from regulatory control. Here, batch uptake experiments have been used to understand Sr and Cs (fission product radionuclides) uptake onto AISI Type 304 stainless steel under conditions representative of spent nuclear fuel storage (alkaline ponds) and PUREX nuclear fuel reprocessing (HNO3). Solution (ICP-MS) and surface measurements (GD-OES depth profiling, TOF-SIMS, and XPS) and kinetic modeling of Sr and Cs removal from solution were used to characterize their uptake onto the steel and define the chemical composition and structure of the passive layer formed on the steel surfaces. Under passivating conditions (when the steel was exposed to solutions representative of alkaline ponds and 3 and 6 M HNO3), Sr and Cs were maintained at the steel surface by sorption/selective incorporation into the Cr-rich passive film. In 12 M HNO3, corrosion and severe intergranular attack led to Sr diffusion into the passive layer and steel bulk. In HNO3, Sr and Cs accumulation was also commensurate with corrosion product (Fe and Cr) readsorption, and in the 12 M HNO3 system, XPS documented the presence of Sr and Cs chromates.

Correlation between Different Type of Caesium Carrier in The Radiocaesium Interception Potential Measurement for Forest Soils

Radiocaesium, especially 137Cs, is one of major heavy fission product radionuclide that has a relatively long half-life and acts as a dangerous persistent pollutant to the environment. It could be dispersed widely through the atmosphere during nuclear weapon test and reactor accident such as Fukushima Dai-Ichi Nuclear Power Plant (FDNPP) disaster in Japan. High retention of radiocaesium in the surface of forest floor surrounding Fukushima area is important issues to measure further potential risk of health and environment contamination. Radiocaesium Interception Potential (RIP) values are related to the sorption capacity of radioactive Cs in clay minerals, and in this study, we investigated the correlation between different type of Cs carrier to the RIP and their adsorption character in soil. The RIP values of all soil sample were varied from 27.27 to 522.66 mmol kg-1. The carrier effect on RIP was conducted using carrier 134Cs, carrier-free that contains 134Cs, 136Cs and 137Cs and 133Cs stable isotopes. Correlation between different type of carrier suggests a relatively lower RIP for stable caesium as a carrier. This phenomena could be caused by competitive adsorption among of caesium ions in the frayed edge sites of soil mineral. Organic carbon content and CEC also contributed to the RIP value. No significant difference found of C/N ratio and CEC values between deciduous and coniferous forest soil as they also have similarity of mineral content in soil.

Modelling of the anti-neutrino production and spectra from a Magnox reactor

The anti-neutrino source properties of a fission reactor are governed by the production and beta decay of the radionuclides present and the summation of their individual anti-neutrino spectra. The fission product radionuclide production changes during reactor operation and different fissioning species give rise to different product distributions. It is thus possible to determine some details of reactor operation, such as power, from the anti-neutrino emission to confirm safeguards records. Also according to some published calculations, it may be feasible to observe different anti-neutrino spectra depending on the fissile contents of the reactor fuel and thus determine the reactor's fissile material inventory during operation which could considerable improve safeguards. In mid-2014 the University of Liverpool deployed a prototype anti-neutrino detector at the Wylfa R1 station in Anglesey, United Kingdom based upon plastic scintillator technology developed for the T2K project. The deployment was used to develop the detector electronics and software until the reactor was finally shutdown in December 2015. To support the development of this detector technology for reactor monitoring and to understand its capabilities, the National Nuclear Laboratory modelled this graphite moderated and natural uranium fuelled reactor with existing codes used to support Magnox reactor operations and waste management. The 3D multi-physics code PANTHER was used to determine the individual powers of each fuel element (8×6152) during the year and a half period of monitoring based upon reactor records. The WIMS/TRAIL/FISPIN code route was then used to determine the radionuclide inventory of each nuclide on a daily basis in each element. These nuclide inventories were then used with the BTSPEC code to determine the anti-neutrino spectra and source strength using JEFF-3.1.1 data. Finally the anti-neutrino source from the reactor for each day during the year and a half of monitored reactor operation was calculated. The results of the preliminary calculations are shown and limitations in the methods and data discussed.

Recovery of radio-cesium from actual high level liquid waste using solvents containing calix[4]arene-crown-6 ligands

This paper gives two methods, viz. a solvent extraction method and a hollow fiber contactor based liquid membrane method, for the separation of radio-cesium from actual high level liquid waste (HLLW) solutions using calix[4]arene-crown-6 based solvent systems. While the solvent extraction method involved calix[4]arene-bis-benzo-crwon-6 (CBC) in PTMS (phenyltrifluoromethyl sulphone), the hollow fiber supported liquid membrane method used a polysulphone fiber containing contactor and bis-octyl-benzo-calix[4]arene-mono-crown-6 (CMC) in 40% iso-decanol+60% n-dodecane. Both methods reported selective radio-cesium separation with almost no contamination from the associated fission product radionuclides. The radiolytic stability of the hollow fiber contactor was checked by keeping the contactor module in contact with the diluted HLLW for 50days. The second run carried out after 50days resulted in excellent reproducibility suggesting efficacy of this method for radioactive waste remediation.

The atmospheric transport of iodine‐129 from Fukushima to British Columbia, Canada and its deposition and transport into groundwater

AbstractThe Fukushima‐Daiichi nuclear accident (FDNA) released iodine‐129 (15.7 million year half‐life) and other fission product radionuclides into the environment in the spring and summer of 2011. 129I is recognized as a useful tracer for the short‐lived radiohazard 131I, which has a mobile geochemical behavior with potential to contaminate water resources. To trace 129I released by the FDNA reaching Canada, pre‐accident and post‐accident rain samples collected in Vancouver, on Saturna Island and from the National Atmospheric Deposition Program in Washington State were measured. Groundwater from the Abbotsford‐Sumas Aquifer was sampled to determine the fate of 129I that infiltrates below the root zone. Modeling of vadose zone transport was performed to constrain the travel time and retardation of 129I. The mean pre‐accident 129I concentration in rain was 31 × 106 atoms/L (n = 4). Immediately following the FDNA, 129I values increased to 211 × 106 atoms/L and quickly returned to near‐background levels. However, pulses of elevated 129I continued for several months. The increases in 129I concentrations from both Vancouver and Saturna Island were synchronized, and occurred directly after the initial release from the FDNA. The 129I in shallow (3H/3He age <1.4 years) Wassenaar et al. (2006) groundwater showed measurable variability through March 2013 with an average of 3.2 × 106 atoms/L (n = 32) that was coincident with modeled travel times for Fukushima 129I. The groundwater response and the modeling results suggest that 129I was partially attenuated in soil, which is consistent with its geochemical behavior; however, we conclude that the measured variability may be due to Fukushima 129I entering groundwater.

Determination of precise ¹³⁵Cs/¹³⁷Cs ratio in environmental samples using sector field inductively coupled plasma mass spectrometry.

Recent advances in sector field inductively coupled plasma mass spectrometry (ICP-SFMS) have led to significant sensitivity enhancements that expand the range of radionuclides measurable by ICP-MS. The increasing capability and performance of modern ICP-MS now allows analysis of medium-lived radionuclides previously undertaken using radiometric methods. A new generation ICP-SFMS was configured to achieve sensitivities up to 80,000 counts per second for a 1 ng/L (133)Cs solution, providing a detection limit of 1 pg/L. To extend this approach to environmental samples it has been necessary to develop an effective chemical separation scheme using ultrapure reagents. A procedure incorporating digestion, chemical separation and quantification by ICP-SFMS is presented for detection of the significant fission product radionuclides of cesium ((135)Cs and (137)Cs) at concentrations found in environmental and low level nuclear waste samples. This in turn enables measurement of the (135)Cs/(137)Cs ratio, which varies with the source of nuclear contamination, and can therefore provide a powerful dating and forensic tool compared to radiometric detection of (137)Cs alone. A detection limit in sediment samples of 0.05 ng/kg has been achieved for (135)Cs and (137)Cs, corresponding to 2.0 × 10(-3) and 160 mBq/kg, respectively. The critical issue is ensuring removal of barium to eliminate isobaric interferences arising from (135)Ba and (137)Ba. The ability to reliably measure (135)Cs/(137)Cs using a high specification laboratory ICP-SFMS now enables characterization of waste materials destined for nuclear waste repositories as well as extending options in environmental geochemical and nuclear forensics studies.

A SYSTEMS ASSESSMENT FOR THE KOREAN ADVANCED NUCLEAR FUEL CYCLE CONCEPT FROM THE PERSPECTIVE OF RADIOLOGICAL IMPACT

In this study, we compare the mass release rates of radionuclides (1) from waste forms arising from the KIEP-21 pyroprocessing system with (2) those from the directly-disposed pressurized-water reactor spent fuel, to investigate the potential radiological and environmental impacts. In both cases, most actinides and their daughters have been observed to remain in the vicinity of waste packages as precipitates because of their low solubility. The effects of the waste-form alteration rate on the release of radionuclides from the engineered-barrier boundary have been found to be significant, especially for congruently released radionuclides. The total mass release rate of radionuclides from direct disposal concept is similar to those from the pyroprocessing disposal concept. While the mass release rates for most radionuclides would decrease to negligible levels due to radioactive decay while in the engineered barriers and the surrounding host rock in both cases even without assuming any dilution or dispersal mechanisms during their transport, significant mass release rates for three fissionproduct radionuclides, 129 I, 79 Se, and 36 Cl, are observed at the 1,000-m location in the host rock. For these three radionuclides, we need to account for dilution/dispersal in the geosphere and the biosphere to confirm finally that the repository would achieve sufficient level of radiological safety. This can be done only after we have known where the repository site would be sited. The footprint of repository for the KIEP-21 system is about one tenth of those for the direct disposal.

Sorption of radioactive cesium and barium ions onto solid humic acid

In this study, the sorption behavior of two important fission product radionuclides ( 137Cs and 140Ba) onto sodium form of insolubilized humic acid (INaA) were investigated as a function of time, cation concentration and temperature, utilizing the radiotracer method. The sorption processes are well described by both Freundlich and Dubinin–Radushkevich type isotherms. Thermodynamic constants such as; free energy (Δ G ads), enthalpy (Δ H ads), entropy (Δ S ads) of adsorption were determined. It was found that Ba 2+ was adsorbed five times more than Cs + onto structurally modified humic acid and kinetic studies indicated that adsorption behavior of both ions obey the pseudo second order rate law. The effect of pH change on sorption was also examined. FTIR and solid-state carbon NMR ( 13CNMR) spectroscopic techniques were used to understand the structural changes during insolubilization process. Quantitative determination of adsorption sites was carried out using potantiometric titration.

Effects of ionizing radiation on the hollandite structure-type: Ba0.85Cs0.26Al1.35Fe0.77Ti5.90O16

The hollandite structure-type has received considerable attention as a nuclear waste form for the incorporation of radioactive 135Cs and 137Cs, both of which are important fission product radionuclides in the high-level nuclear waste generated by the reprocessing of used nuclear fuel. A critical concern has been the effects of high doses of ionizing radiation from incorporated Cs on the long-term structural stability of the hollandite structure. Optimization of the synthesis conditions has resulted in the hollandite stoichiometry of Ba0.85Cs0.26Al1.35Fe0.77Ti5.90O16. To evaluate the effect of Cs-beta-decay on this stoichiometry, we have simulated the ionizing radiation using 200 kV electron beam using transmission electron microscopy (TEM) at 298 and 573 K. Complete amorphization was achieved at doses of 1.1 × 1014 and 1.8 × 1014 Gy at temperatures of 298 and 573 K, respectively. Electron energyloss spectroscopy (EELS) of the Cs M-edge revealed the selective loss of Cs at the maximum doses. Hollandite irradiated using gamma rays, ~106 Gy, which has defects associated with the formation of Ti3+ and O2̅ had a dissolution rate similar to that of the pristine hollandite, suggesting that the initial stage of defect formation does not influence chemical durability. Because the accumulated dose in the hollandite with 5 wt% of radioactive 137Cs2O is estimated to be ~2.0 × 1010 Gy after 500 years, the hollandite structure should be stable under the conditions anticipated for geologic disposal.

Deterministic Assessment for Environmental Impact of Yucca Mountain Repository Measured by Radiotoxicity

Environmental impact of the Yucca Mountain Repository (YMR) has been quantitatively and deterministically evaluated in terms of the radiotoxicity of transuranic (TRU) and fission-product radionuclides existing in the environment after released from failed packages. Inventory abstraction has been made based on the data published in Final Environmental Impact Statement by US Department of Energy (DOE). Mathematical model and computation code have been developed based on analytical solutions. Environmental impact from the commercial spent nuclear fuel (CSNF) packages is about 90% of the total impact including the contribution from defense waste (DW) packages. Impacts due to isotopes of Cm, Am, Pu and Np, and their decay daughters are dominant, compared with those from fission-product nuclides. Numerical results show that reduction of the TRU nuclides by a factor of 100 makes the impact from CSNF smaller than that from DW.

Environmental Impact of Yucca Mountain Repository in the Case of Canister Failure

Mathematical models and a computation code have been developed for total release of transuranic (TRU) and fission product radionuclides from waste packages in the Yucca Mountain Repository (YMR) into the surrounding geosphere in the case of simultaneous package failure. The total amount of these radionuclides in the geosphere, which is called the environmental impact in this paper, has been expressed in terms of radiotoxicity. Inventory abstraction has been made, based on the data provided in the Final Environmental Impact Statement published by the U.S. Department of Energy. Various types of waste packages in the YMR have been abstracted into commercial spent nuclear fuel (CSNF) and defense waste. For defense waste, co-disposal and naval spent fuel have been abstracted separately. Numerical results show that within the total environmental impact, contribution from the defense waste packages is about 10%, which is close to the fraction of the repository capacity allocated for defense waste. Impacts due to isotopes of TRU and their decay daughters are dominant, compared with those from fission product nuclides. If the mass of TRU nuclides to be disposed of in the repository were reduced by a factor of 100, the impact from CSNF would become smaller than that from defense waste.

Uranium Mineralogy and Neptunium Mobility

Research Article| December 01, 2006 Uranium Mineralogy and Neptunium Mobility Peter C. Burns; Peter C. Burns Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA E-mail: pburns@nd.edu Search for other works by this author on: GSW Google Scholar Amanda L. Klingensmith Amanda L. Klingensmith Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Peter C. Burns Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA E-mail: pburns@nd.edu Amanda L. Klingensmith Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA Publisher: Mineralogical Society of America First Online: 09 Mar 2017 Online ISSN: 1811-5217 Print ISSN: 1811-5209 © 2006 by the Mineralogical Society of America Elements (2006) 2 (6): 351–356. https://doi.org/10.2113/gselements.2.6.351 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Peter C. Burns, Amanda L. Klingensmith; Uranium Mineralogy and Neptunium Mobility. Elements 2006;; 2 (6): 351–356. doi: https://doi.org/10.2113/gselements.2.6.351 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyElements Search Advanced Search Abstract Spent nuclear fuel, mainly UO2, is chemically unstable under oxidizing conditions. Alteration occurs by oxidation and hydration and can be rapid and substantial. Uranyl minerals, containing U6+, form when commercial spent fuel is altered in a moist, oxidizing environment. During the alteration and dissolution of the UO2, fission-product radionuclides and transuranium elements are released. Uranyl minerals that form locally as alteration products in a geologic repository may incorporate many of these radionuclides, thereby immobilizing them for lengthy periods and thus improving the long-term performance of the repository. Here we discuss one very important radionuclide, 237Np (half-life = 2.14 million years), and focus on mineralogical studies that probe the potential impact of uranyl minerals on neptunium mobility. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Today's epidemics in children: Possible relations to environmental pollution and suggested preventive measures

Facts and hypotheses on the relationship between some children's diseases or disorders and external stressors during the developmental stage of a child, both prenatally and postnatally are described in literature. In this paper the following changes in patterns and causes of the main childhood illnesses are summarized and recommendations for actions are made. Prematurity. Intra-uterine growth restriction. Testicular dysgenesis syndrome. Type I and Type II diabetes. Asthma, atopy and hay fever. Autism. Attention deficit hyperactivity disorder (ADHD). Learning disabilities. Cancer. Obesity. Hearing problems. Literature provides a growing amount of information on changing patterns in childhood diseases. The following recommendations for action are formulated: Immediate research on endocrine disrupters in relation to prematurity. Diabetes: avoid Maillard Compounds in liquid baby food and in food in general: promote breastfeeding. Asthma: avoid exposure to smoking, the use of chemical household products, dioxin and dioxin-like chemicals, and avoid air pollution with high levels of particulate matter, especially around conception, during pregnancy and in the first years of life. Autism: more research on incidence and causes. ADHD and learning disabilities: more research on prevalence and causes. Preventions: 1) preconception counselling to avoid potentially harmful substances; 2) controlling and further lowering levels of polychlorinated biphenyls, lead and methyl mercury. Cancer: promote breastfeeding, carry out research into effects of foetal exposure to internal fission-product radionuclides. Obesity: stop smoking in pregnancy, avoid parental obesity, longer night sleep. Hearing problems: lower noise levels in discothèques, promote the day-evening-night level to avoid noise (longer night sleep).

Radioactive nuclides as tracers of environmental processes

Relatively short-lived radioactive nuclides of cosmogenic origin, such as7Be (T1/2=53.3 d),32P (14.3 d),33P (25.3 d),35S (87.4 d) as well as22Na (2.6 y) have come to be recognized as potential tools to trace environmental processes, such as precipitation, washout (precipitation scavenging), resuspension, atmospheric particle deposition and deposition patterns of airborne contaminants, aerosol deposition and aerosol trapping by above ground vegetation (air-to-vegetation transfer). Of the above radionuclides,7Be as well as210Pb of terrestrial origin and137Cs, a fission product radionuclide, are commonly used for determining the atmospheric particle deposition parameters. It was found that the deposition velocity of7Be-associated aerosol particles varied from 0.3 to 0.8 cm. s-1(average 0.5 cm. s-1), the washout ratio for7Be varied from 103 to 375 (average 144), the resuspension factor for the7Be-associated particles varied from 1.6. 10-4to 4.2. 10-4m-1(average 2.3. 10-4m-1) and the air-to-vegetation transfer rate for7Be varied from 5258 to 16180 m3.kg-1(average 9856 m3.kg-1) for grass, gramineae or poaceae the species. For the137Cs-associated aerosol particles the deposition velocity varied from 1.3 to 6.3 cm. s-1(average 3.4 cm. s-1), the washout ratio for137Cs varied from 284 to 3810 (average 1295), the resuspension factor for the137Cs-associated aerosol particles varied from 0.1. 10-4to 1.2. 10-4m-1(average 0.6. 10-4m-1) and the air-to-vegetation transfer rate for137Cs varied from 39638 to 345279 m3.kg-1(average 181197 m3.kg-1) for grass, gramineae or poaceaethe species.

Preparation of calibrated reference sources containing "fresh" fission products

NPL was recently asked to provide reference sources containing g-ray emitting fission product radionuclides, with certification completed within 50 days of the irradiation. Furthermore, the reference sources were to contain fission products, but no fissile material. The samples in the first reference source were to contain a mixture of fission products with only the 235U removed, leaving the fission products as 'undisturbed' as possible. A number of radionuclides were reported in this sample and included: 91Y, 95Zr, 95mNb, 95gNb, 99Mo, 99mTc, 103Ru, 106Ru, 127Sb, 129mTe, 129gTe, 131I,132Te, 132I, 137Cs, 140Ba, 140La, 141Ce, 144Ce, and147Nd. Of these nuclides, NPL provided certified values for 91Y, 95Zr, 95mNb, 95gNb, 99Mo, 99mTc, 103Ru, 106Ru, 132Te, 132I, 137Cs, 140Ba, 140La, 141Ce, 144Ce, and 147Nd. The second reference source focused on a smaller subset of radionulides: 95Zr, 99Mo, 103Ru, 106Ru, 140Ba, and 155Eu, although 95gNb, 99mTc, 132I and 140La were present as daughter radionuclides and 91Y, 127Sb, 129mTe, 129gTe, 131I, 132Te, 137Cs, 152Eu and 154Eu were present as impurities. This paper describes the preparation of these sources, based on a combination of cation- and anion-exchange chromatography with selective precipitation. The separation techniques were used to (1) produce the 'fresh' fission product mixture from irradiated 235U, and (2) isolate the specific set of radionuclides in the second exercise from mixtures containing irradiated 235U and fission products. To enable accurate assay of parent-daughter systems, integrated ingrowth and decay equations were derived from original Bateman equations and tested by observing the 140Ba-140La system over time.

Sorption of fission product radionuclides,137Cs and90Sr, by Savannah River Site sediments impregnated with colloidal silica

SummaryPermeation grouting with colloidal silica gel is a potentially effective means for creating hydraulic barriers to prevent the advective migration of radioactive contaminants in shallow permeable sediments. However, the effectiveness of silica gel grouted barriers in controlling transport of fission product radionuclides through sorption and diffusion is unknown. To resolve this question, static-batch sorption measurements with Cs+and Sr2+were conducted at ambient temperature (23 °C) and for times up to 96 days on silica gel and on two kaolinitic sediments from the Savannah River Site in South Carolina. Sorption experiments on the latter were conducted both in the presence and in the absence of silica gel. Cesium and strontium concentrations were varied between 10-3to 10-8M (mol/L) and 10-4to 10-8M, respectively. The pH values after one day varied for each experiment and ranged from 3.6 to 6.6. The pH of the solutions were, however, buffered by the sediments and/or silica gel, and changed little over the duration of the experiments. The fraction of both cesium and strontium retained on the solids increased with decreasing radioelement concentration. The sorption data were fitted to the Freundlich isotherm model.

Development of Zirconium/Magnesium Phosphate Composites for Immobilization of Fission Products

Novel chemically bonded phosphate ceramics have been investigated for the capture and stabilization of volatile fission‐product radionuclides. We have used low‐temperature processing to fabricate zirconium phosphate and zirconium/magnesium phosphate composites. A zirconium/magnesium phosphate composite has been developed and shown to stabilize ash waste that has been contaminated with a radioactive surrogate of the 137Cs and 90Sr species. Excellent retention of cesium in the phosphate matrix system was observed in both short‐ and long‐term leaching tests. The retention factor determined by the USEPA Toxicity Characteristic Leaching Procedure was one order of magnitude better for cesium than for strontium. The effective diffusivity, at room temperature, for cesium and strontium in the waste forms was estimated to be as low as 2.4 × 10−13 and 1.2 ×10−11 cm2/s, respectively. This behavior was attributed to the capture of cesium in the layered zirconium phosphate structure via an intercalation ion‐exchange reaction, followed by microencapsulation. However, strontium is believed to be precipitated out in its phosphate form and subsequently microencapsulated in the phosphate ceramic. The performance of these final waste forms, as indicated by the compression strength and the durability in aqueous environments, satisfies the regulatory criteria.