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DOE OSTI2014

Nuclear Data Sheets for A = 129

The experimental nuclear spectroscopic data for known nuclides of mass number 129 (Ag, Cd, In, Sn, Sb, Te, I, Xe, Cs, Ba, La, Ce, Pr, Nd, Pm, Sm) have been evaluated and presented together with adopted properties for levels and γ rays. This evaluation represents a revision of the previous one 18 years ago by Y. Tendow (1996Te01). Extensive new data have become available for many nuclides in the intervening years, although, no data are available for excited states in {sup 129}Pm and {sup 129}Sm, and for {sup 129}Ag and {sup 129}Cd, only limited information is available for the g.s. and isomers. The decay schemes of {sup 129}Ag, {sup 129}Pm and {sup 129}Sm are unknown, and those for {sup 129}Cd, {sup 129}In, {sup 129}Ce, {sup 129}Pr and {sup 129}Nd are incomplete. Many γ rays and extended level schemes have been reported for the ground state and isomer decays of {sup 129}Ba to {sup 129}Cs, yet the adopted set of intensities in this evaluation originate from a brief paper in an annual laboratory report. There remain several unplaced gamma rays, coupled with ambiguity about division of intensities amongst the two activities of {sup 129}Ba with nearly the same half-lives. Isomerism is expected in {sup 129}Pr, but there is no confirmed identification. Low-lying level structure in {sup 129}Nd, including identification of a possible third long-lived isomer in this nuclide, remains uncertain. The spin-parity assignments of (5/2+) for the ground state and (7/2−) for an isomer at 107.6 keV in {sup 129}Ce are assigned based on strong support from systematics and band configurations, yet this result is in contradiction with the quadrupole interaction hyperfine structure measurement which favors 9/2− over 7/2− for the isomer, consequently 7/2+ for the ground state. Direct measurements of spins of ground state and isomer of {sup 129}Ce are needed to settle this issue. Confirmed spins and parities of the ground state and isomer of {sup 129}La are also lacking. Assignments in this work are mainly based on systematics of h{sub 11/2} decoupled structures. A direct measurement of ground state spin of {sup 129}La will also be desirable. Recommended data presented in this work supersede those in previous NDS evaluations of A=129 nuclides published by 1996Te01, 1983Ha46 and 1972Ho55.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI1992

Nuclear Safety [Vol. 33, No. 1, January-March 1992]

Nuclear Safety is a review journal that covers significant developments in the field of nuclear safety. Its scope includes the analysis and control of hazards associated with nuclear energy, operations involving fissionable materials, and the products of nuclear fission and their effects on the environment. Primary emphasis is on safety in reactor design, construction, and operation; however, the safety aspects of the entire fuel cycle, including fuel fabrication, spent-fuel processing, nuclear waste disposal, handling of radioisotopes, and environmental effects of these operations, are also treated. Table of Contents for this issue follows. GENERAL SAFETY CONSIDERATIONS: 1 Technical Note: A New Approach to Fission Reactor Safety, Yu. V. Petrov; 5 Erratum; ACCIDENT ANALYSIS: 6 Analysis and Modeling of Fission Product Release from Various Uranium-Aluminum Plate-Type Reactor Fuels, R. P. Taleyarkhan; CONTROL AND INSTRUMENTATION: 23 Applications of a Surveillance and Diagnostics Methodology Using Neutron Noise From a Pressurized-Water Reactor, R. T. Wood, L. F. Miller, and R. B. Perez; DESIGN FEATURES: 36 Westinghouse Advanced Passive 600 Plant, B. A. McIntyre and R. K. Beck; 47 System 80+™ PWR Safety Design, C. W. Bagnal, R. A. Matzie, and R. S. Turk; ENVIRONMENTAL EFFECTS: 58 The MATS Experiments—Mesoscale Atmospheric Transport Studies at the Savannah River Site, A. H. Weber, S. Berman, R. J. Kurzeja, and R. P. Addis; 75 Book Review: Environmental Radioactivity in the European Community 1984-1985-1986, C. A. Little; WASTE AND SPENT FUEL MANAGEMENT: 76 Activities Related to Waste and Spent Fuel Management, M. D. Muhlheim and E. G. Silver; OPERATING EXPERIENCES: 87 Aging Assessment of BWR Control Rod Drive Systems, R. H. Greene; 100 Reactor Shutdown Experience, Compiled by J. W. Cletcher; 103 Selected Safety-Related Events, Compiled by G. A. Murphy; 110 Operating U.S. Power Reactors, Compiled by M. D. Muhlheim and E. G. Silver; RECENT DEVELOPMENTS: 129 General Administrative Activities, Compiled by M. D. Muhlheim and E. G. Silver; 139 Reports, Standards, and Safety Guides, D. S. Queener; 143 Proposed Rule Changes as of Sept. 30 1991; ANNOUNCEMENTS: 128 Harvard School of Public Health Announces Short Courses; 128 16th Biennial ANS Topical Meeting on Reactor Operating Experience: Present and Future Technologies—Applying Lessons Learned (Call for Papers); 147 The Authors; 150 Indexes to Nuclear Safety, Volume 32; 154 Errata.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI1992

Nuclear Safety [Vol. 33, No. 1, January-March 1992]

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2016

FY-2016 Methyl Iodide Higher NOx Adsorption Test Report

Deep-bed methyl iodide adsorption testing has continued in Fiscal Year 2016 under the Department of Energy (DOE) Fuel Cycle Technology (FCT) Program Offgas Sigma Team to further research and advance the technical maturity of solid sorbents for capturing iodine-129 in off-gas streams during used nuclear fuel reprocessing. Adsorption testing with higher levels of NO (approximately 3,300 ppm) and NO2 (up to about 10,000 ppm) indicate that high efficiency iodine capture by silver aerogel remains possible. Maximum iodine decontamination factors (DFs, or the ratio of iodine flowrate in the sorbent bed inlet gas compared to the iodine flowrate in the outlet gas) exceeded 3,000 until bed breakthrough rapidly decreased the DF levels to as low as about 2, when the adsorption capability was near depletion. After breakthrough, nearly all of the uncaptured iodine that remains in the bed outlet gas stream is no longer in the form of the original methyl iodide. The methyl iodide molecules are cleaved in the sorbent bed, even after iodine adsorption is no longer efficient, so that uncaptured iodine is in the form of iodine species soluble in caustic scrubber solutions, and detected and reported here as diatomic I2. The mass transfer zone depths were estimated at 8 inches, somewhat deeper than the 2-5 inch range estimated for both silver aerogels and silver zeolites in prior deep-bed tests, which had lower NOx levels. The maximum iodine adsorption capacity and silver utilization for these higher NOx tests, at about 5-15% of the original sorbent mass, and about 12-35% of the total silver, respectively, were lower than for trends from prior silver aerogel and silver zeolite tests with lower NOx levels. Additional deep-bed testing and analyses are recommended to expand the database for organic iodide adsorption and increase the technical maturity if iodine adsorption processes.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2024

Influence of elevated temperature and oxygen on the capture of radioactive iodine by silver functionalized silica aerogel

Reprocessing is considered a competent strategy for spent nuclear fuel management, yet radioiodine ( 129 I) is emitted in reprocessing off-gas as a hazardous byproduct. Silver functionalized silica aerogel (Ag 0 -aerogel), a promising iodine capture material, experiences a reduction in its capacity after prolonged exposure to off-gas components at elevated temperatures, a phenomenon termed as aging. To fully understand this process, we isolated the contribution of each aging factor, exposing Ag 0 -aerogel samples to N 2 and dry air gas streams, respectively, at 150 °C for different time periods. Aged samples were loaded with I 2 to examine the capacity change and comprehensively characterized to investigate the evolution of their properties. Results show that temperature alone did not alter Ag 0 -aerogel's capacity but triggered Ag 0 nanoparticles sintering and generated organic sulfur species. The presence of O 2 reduced the capacity by ~20 %, causing (i) formation of silver sulfide (Ag 2 S) crystals and (ii) oxidation of Ag-thiolate (Ag-S-r) to Ag sulfonate (Ag-SO 3 -r). Given that Ag 2 S readily adsorbs I 2 , the formation of Ag-SO 3 -r is the major inhibitor for iodine adsorption. This hypothesis was supported by density functional theory (DFT) simulations. These findings unraveled key mechanisms of Ag 0 -aerogel aging, which are useful in the development of materials that withstand realistic spent-nuclear-fuel-reprocessing off-gas conditions.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2018

Preparation of Four Large-format Hot Isostatically Pressed I-AgZ Waste Form Samples for Performance Testing

Hot isostatic pressing (HIP) is being considered as a process to directly convert 129 I-bearing materials to a durable radiological waste form. Zeolites, specifically silver-exchanged mordenite (AgZ), have been studied extensively as potential radioactive iodine sorbents and will contain 129 I as chemisorbed AgI, a relatively insoluble compound with a high melting point. Oak Ridge National Laboratory has conducted several recent studies on the HIP of both I–AgZ and other iodine-bearing zeolites, resulting in an inventory of samples prepared with a suite of zeolites with varied iodine incorporation methods, pressing conditions, and sizes. These samples have been made available to researchers at other national laboratories in support of test method development to assess the stability of heterogenous iodine-bearing waste forms. The work described here generated four large-format HIPed I–AgZ samples. These samples are 1.5 in. diameter and 2 in. length and contain 49 g of I–AgZ. Two samples were prepared at an iodine loading of 64 mg I/g I– AgZ, and two samples were prepared at an iodine loading of 135 mg I/g I–AgZ. These two sets of duplicate samples will be made available upon request in support of iodine waste form durability method development efforts.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2016

Silver-based getters for 129I removal from low-activity waste

Abstract A prominent radionuclide of concern in nuclear wastes,

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2016

Preparation of NO 2 -Aged Silver-Functionalized Silica-Aerogel and Silver Mordenite Samples

Reprocessing used nuclear fuel can result in the volatilization of radioactive gaseous species, including 129 I, into the various process off-gas streams. In order to comply with US regulatory requirements, plant off-gas streams must be treated to remove the iodine prior to discharging the off-gas into the environment. The performance of available gas removal methods depends not only on the concentration of the volatile radioisotope of interest, but also on other constituents that could be present in the reprocessing off-gas streams. Some of the constituents, such as NOx produced during fuel dissolution, are known to have deleterious effects on the capture performance of silver-based sorbents used for iodine removal. Commercially available reduced silver mordenite (AgZ) has an iodine saturation concentration of 7.0-9.0 wt%, and its iodine sorption capacity is reduced by 20-50% as a result of NO2 aging. Silverfunctionalized silica aerogel (AgAerogel), an alternative for iodine capture, has an initial iodine saturation of 29.0 wt% and its iodine capacity is only reduced by 15% from NO2 aging. Understanding the differences in aging behavior between AgZ and AgAerogel is critical to determining the behavior of these sorbents under realistic off-gas conditions. To assist in future technical studies on this topic, samples of both AgZ and AgAerogel were aged with NO2. In the experiment, 10.2190 g of AgZ and 10.1771 g of AgAerogel were exposed to a static 0.75% NO 2 /dry air blend for a period of 28 days. The samples were then removed and stored under argon until needed for future experiments.=

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2017

Hot Isostatic Pressing of Engineered Forms of I-AgZ

Hot isostatic pressing (HIP) is being considered for direct conversion of 129 I-bearing materials to a radiological waste form. The removal of volatile radioactive 129 I from the off-gas of a nuclear fuel reprocessing facility will be necessary to comply with regulatory requirements regarding reprocessing facilities sited within the United States, and any iodine-containing media or solid sorbents generated by offgas abatement will require disposal. Zeolite minerals such as silver-exchanged mordenite (AgZ) have been studied as potential iodine sorbents and will contain 129 I as chemisorbed AgI. Oak Ridge National Laboratory (ORNL) has conducted several recent studies on the HIP of both iodine-loaded AgZ (I-AgZ) and other iodine-bearing zeolite minerals. The goal of these research efforts is to achieve a stable, highly leach resistant material that is reduced in volume as compared to bulk iodine-loaded I-AgZ. Through the use of HIP, it may be possible to achieve this with the addition of little or no additional materials (waste formers). Other goals for the process include that the waste form will be tolerant to high temperatures and pressures, not chemically hazardous, and that the process will result in minimal secondary waste generation. This document describes the preparation of 27 samples that are distinct from previous efforts in that they are prepared exclusively with an engineered form of AgZ that is manufactured using a binder. Iodine was incorporated solely by chemisorption. This base material is expected to be more representative of an operational system than were samples prepared previously with pure minerals.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2024

Synthesis and Characterization of Silver-Modified Nanoporous Silica Materials for Enhanced Iodine Removal

In aquatic environments, the presence of iodine species, including radioactive isotopes like 129 I and I 2 , poses significant environmental and health concerns. Iodine can enter water resources from various sources, including nuclear accidents, medical procedures, and natural occurrences. To address this issue, the use of natural occurring nanoporous minerals, such as zeolitic materials, for iodine removal will be explored. This study focuses on the adsorption of iodine by silver-modified zeolites (13X-Ag, 5A-Ag, Chabazite-Ag, and Clinoptilolite-Ag) and evaluates their performance under different conditions. All materials were characterized using scanning electron microscopey (SEM), energy-dispersive X-ray spectroscopy (EDS), powdered X-ray diffraction (P-XRD), Fourier-transform infrared spectrometry (FTIR), and nitrogen adsorption studies. The results indicate that Chabazite-Ag exhibited the highest iodine adsorption capacity, with an impressive 769 mg/g, making it a viable option for iodine removal applications. 13X-Ag and 5A-Ag also demonstrated substantial adsorption capacities of 714 mg/g and 556 mg/g, respectively, though their behavior varied according to different models. In contrast, Clinoptilolite-Ag exhibited strong pH-dependent behavior, rendering it less suitable for neutral to slightly acidic conditions. Furthermore, this study explored the impact of ionic strength on iodine adsorption, revealing that Chabazite-Ag is efficient in low-salinity environments with an iodine adsorption capacity of 51.80 mg/g but less effective in saline conditions. 5A-Ag proved to be a versatile option for various water treatments, maintaining its iodine adsorption capacity across different salinity levels. In contrast, Clinoptilolite-Ag exhibited high sensitivity to ionic competition, virtually losing its iodine adsorption ability at a NaCl concentration of 0.1 M. Kinetic studies indicated that the pseudo-second-order model best describes the adsorption process, suggesting chemisorption mechanisms dominate iodine removal. Chabazite-Ag exhibited the highest initial adsorption rate with a k 2 value of 0.002 mg g -1 h -1 , emphasizing its superior adsorption capabilities. Chabazite and Clinoptilolite, naturally occurring minerals, provide eco-friendly solutions for iodine adsorption. Chabazite superior iodine removal highlights its value in critical applications and its potential for addressing pressing environmental challenges.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2017

Evaluation of Iodine Remediation Technologies in Subsurface Sediments (Interim Status Report)

Isotopes of iodine were generated during plutonium production from nine production reactors at the U.S. Department of Energy Hanford Site. The long half-life 129 I generated at the Hanford Site during reactor operations was 1) stored in single-shell and double-shell tanks, 2) discharged to liquid disposal sites (e.g., cribs and trenches), 3) released to the atmosphere during fuel reprocessing operations, or 4) captured by off-gas absorbent devices (silver reactors) at chemical separations plants (PUREX, B-Plant, T-Plant, and REDOX). Releases of 129 I to the subsurface have resulted in several large, though dilute, plumes in the groundwater, including the plume in the 200-UP-1 operable unit. There is also 129 I remaining in the vadose zone beneath disposal or leak locations. Because 129 I is an uncommon contaminant, relevant remediation experience and scientific literature are limited. Iodine cannot be degraded/transformed to a less toxic form. Therefore, the primary metric for remediation is changing the fate and transport properties in a way that works to decrease radioiodine concentrations in groundwater. To this end, targeted laboratory experiments were conducted to provide proof-of-principle screening of remedial options and to evaluate scale-up and performance elements. The evaluation of different iodine remediation technologies will occur over multiple years and fall into three different categories: 1) geochemical/biological sequestration, 2) microbial volatilization, and 3) enhanced pump-and-treat. This report provides status on two in situ sequestration methods (apatite and iron oxides) and two methods examining enhanced pump-and-treat.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2016

Rod-shaped silica particles derivatized with elongated silver nanoparticles immobilized within mesopores

Silver-derivatized silica particles possessing a non-spherical morphology and surface plasmon resonance properties have been achieved. Nanometer-sized silica rods with uniformly sized mesopore channels were prepared first making use of alkyltrimethyl ammonium surfactants as porogens and the 1:0.10 tetraethyl orthosilicate (TEOS) : 3-aminopropyltriethoxysilane (APTES) mixture as a silicon source. Silica rods were subsequently functionalized by introducing elongated silver nanoparticles within the intra-particle mesopores thanks to the AgNO{sub 3} reduction procedure based on the action of hemiaminal groups previously located on the mesopore walls. The textural and structural features of the samples were inferred from the combined characterization studies including SEM and TEM microscopy, nitrogen adsorption-desorption at 77 K, powder XRD in the small- and wide-angle region, as well as UV–visible spectroscopy. {sup 129}Xe NMR spectroscopy appeared particularly useful to obtain a correct information about the porous structure of rod-shaped silica particles and the silver incorporation within their intra-particle mesopores. - Highlights: • Mesoporous monodisperse submicron-sized silica rods were achieved. • Silver nanoparticles were located lengthwise within the intra-particle mesopores. • Textural and plasmonic properties of particles studied by {sup 129}Xe NMR and UV–Vis.

36 MATERIALS SCIENCE↗

NASA NTRS1980

Cycles till failure of silver-zinc cells with competing failure modes - Preliminary data analysis

The data analysis of cycles to failure of silver-zinc electrochemical cells with competing failure modes is presented. The test ran 129 cells through charge-discharge cycles until failure; preliminary data analysis consisted of response surface estimate of life. Batteries fail through low voltage condition and an internal shorting condition; a competing failure modes analysis was made using maximum likelihood estimation for the extreme value life distribution. Extensive residual plotting and probability plotting were used to verify data quality and selection of model.

Sidik, S. M.↗

DOE OSTI2023

Enhanced Iodine Capture Using a Postsynthetically Modified Thione–Silver Zeolitic Imidazole Framework

Efficient management of radionuclides that are released from various processes in the nuclear fuel cycle is of significant importance. Among these nuclides, radioactive iodine (mainly 129 I and 131 I) is a major concern due to the risk it poses to the environment and to human health; thus, the development of materials that can capture and safely store radioactive iodine is crucial. Herein, a novel silver-thione-functionalized zeolitic imidazole framework (ZIF) was synthesized via post-synthetic modification and assessed for its iodine uptake capabilities alongside the parent ZIF-8 and intermediate materials. A solvent-assisted ligand exchange procedure was used to replace the 2-methylimidazole linkers in ZIF-8 with 2-mercaptoimidazole, forming the intermediate compound ZIF-8=S, which was reacted with AgNO 3 to yield the ZIF-8=S-Ag + composite for iodine uptake. Despite possessing the lowest BET surface area of the derivatives, the Ag-functionalized material demonstrated superior I 2 adsorption in terms of both maximum capacity (550 g I 2 /mol) and rapid kinetics (50% loading achieved in 5 hrs, saturation in 50 hrs) compared to our pristine ZIF-8, which reached 450 g I 2 /mol after 150 hours and 50% loading in 25 hours. This improvement is attributed to the presence of the Ag + ions, which provide a strong chemical driving force to form stable Ag-I species. In conclusion, the results of this study contribute to a broader understanding of the strategies that can be employed to engineer adsorbents with robust iodine uptake behavior.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Sustainable Remediation of Radionuclides By a Common Sense Approach to Enhanced Attenuation - 16441

Development of in situ and relatively passive remedies for treatment of groundwater contaminated by metals and radionuclides is becoming more important because of the difficulty and cost - both to the environment and financially -- of removing these types of contaminants from the subsurface by pump-and-treat or excavation. In situ technologies rely on reactions that tend to remove contaminants from groundwater by partitioning them to solid phases in the aquifer. Monitored natural attenuation (MNA) relies solely on natural reactions to achieve remedial goals. Enhanced attenuation (EA) uses engineered approaches to supplement remediation when MNA is not sufficient to meet remedial goals. Both approaches leave contaminants in the subsurface and require a high burden of proof that contaminants will not be mobilized and become a risk in the future. Proof of the sustained effectiveness of an EA remedy is made much easier by strategic design. In multi-contaminant plumes, it is important to prioritize contaminants according to the risk they pose, with the recognition that one remedy rarely treats all contaminants. The goal for the engineered portion of the remedy should be maximum risk reduction with minimal engineering. Natural attenuation or negotiated alternate concentration levels will often allow low risk contaminants to go untreated. Whenever possible, the remedy should be consistent with the geochemical evolution of the waste site, insuring that the treated immobilized contaminants are likely to remain relatively immobile for long time frames. Finally, use what nature provides geologically, hydrologically, geochemically, or microbiologically in the remedy design. One of the impediments faced by waste site managers in implementing EA remedies is paralysis by perceived complexity. There are things that must be known to design an effective EA remedy, but there is always the temptation to know everything to eliminate the possibility of failure. Furthermore, there are plenty of people warning of failure if all is not known and they are usually willing to help the design team know all, for a price. Yet, the price of trying to eliminate all risk is never implementing an innovative remedy. All parties involved -- scientists/engineers, waste site managers, regulators and stakeholders must assume some degree of risk to deploy an EA remedy. If all parties are to assume some risk, then trust built through close communication from the start is required. The U.S. Department of Energy Office of Environmental Management has funded an applied field research initiative for several years focused, in part, on developing EA remedies for metals and radionuclides using these guiding principles. This approach to EA remedies grew out of developing and deploying a remediation strategy to replace a pump-and-treat system at the F-Area Seepage Basins on the Savannah River Site. The pump-and-treat system was energy intensive, produced several thousand cubic feet of solid radioactive waste per year, and cost $ 1 million per month to operate. The EA remedy that replaced the pump-and-treat is energy efficient, produces no waste, and costs approximately $1 million per year to maintain. At the F-Area Seepage Basins approximately 7 billion liters of low level radioactive waste solutions were disposed in three unlined basins resulting in contaminated groundwater containing various radionuclides and other contaminants. The primary contaminants of concern are tritium, strontium-90, uranium, and iodine-129. Other key features of the contaminant plume are its acidic nature with pH values as low as 3.2, its vertical stratification in the water table aquifer, and the tendency of the most contaminated portions to follow troughs in the top of the clay separating the upper aquifer zone from the lower aquifer zone. The geology was exploited by installing a funnel-and-gate system into the clay with the barrier portion blocking contaminant flow paths in the troughs in the clay. This forces the most contaminated water to flow through the gates where it encounters an in situ treatment zone created by periodic injections of alkaline solution. The flux of tritium has been reduced significantly by the barrier walls. Strontium-90 and uranium are treated by enhanced sorption in the circum-neutral pH treatment zone, consistent with natural geochemical evolution of the waste site from acidic to more neutral pH. An additional in situ treatment zone was created up-gradient of the one of the gates to treat iodine-129. Sub-micrometer diameter silver chloride particles were injected into the aquifer by direct push methods to create the treatment zone. In the laboratory and in a field pilot test the poorly soluble silver chloride particles reacted with iodide to form much less soluble silver iodide. Evaluation of the effectiveness of the silver chloride is ongoing. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2019

Iodine Retention of Long-chain Organic Iodides on Silver-based Sorbents under DOG and VOG Conditions

The aqueous reprocessing of used nuclear fuel releases four key volatile radionuclides ( 3 H, 14 C, 85 Kr, and 129 I) from the used fuel into the off-gas streams of a reprocessing facility. Some semi-volatile radionuclides such as 106 Ru may also be released into the gas streams. Compliance with US regulations may require removal of these radionuclides from the off-gas streams before their discharge to the environment (Jubin et al. 2017). Iodine is released during multiple unit operations within a plant and can be found in gas streams such as the shear off-gas, dissolver off-gas, vessel off-gas (VOG), and waste solidification off-gas. To achieve DFs >1,000, treatment of the plant off-gas streams must include, at minimum, removal of both the dissolver off-gas and VOG. A 2015 analysis showing that the speciation of iodine in the VOG is primarily composed of organic alkyl iodides and that abatement technology for organic iodides is not well developed has produced increased interest in removing iodine from VOG. The lack of knowledge surrounding iodine removal from the VOG prompted the Office of Nuclear Energy within the US Department of Energy to initiate experimental efforts targeted at understanding organic iodide removal from prototypic VOG streams. In 2018 a joint test plan was developed and issued by Oak Ridge National Laboratory and Idaho National Laboratory. This test plan is intended to guide a multiyear experimental effort that will provide substantial amounts of information about the removal of organic iodides from VOG streams. This document reports on the progress of Idaho National Laboratory and Oak Ridge National Laboratory in the execution of the joint test plan as of the end of fiscal year 2019. Silver-based sorbents are the primary removal technology being characterized, and this report includes data on iodine adsorption by reduced silver-exchanged mordenite (also called silver-exchanged zeolite [AgZ]) (as a baseline iodine sorbent) and silver-functionalized silica aerogel (AgAero or Ag Aerogel) (as an advanced iodine sorbent). Conclusions are preliminary in nature and reflect the ongoing execution of the test plan through close collaboration between the two laboratories.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2014

Iodine Standard Materials: Preparation and Inter-Laboratory Comparisons

The Idaho National Laboratory is preparing to enter the community of AMS practioners who analyze for 129Iodine. We expect to take delivery of a 0.5 MV compact accelerator mass spectrometry system, built by NEC, in the early summer of 2014. The primary mission for this instrument is iodine; it is designed to analyze iodine in the +3 charge state. As part of the acceptance testing for this instrument, both at NEC and on-site in our laboratory, some sort of standard or reference material is needed to verify performance. Appropriate standard materials are not readily available in the commercial marketplace. Small quantities can sometimes be acquired from other laboratories already engaged in iodine analyses. In the longer-term, meaningful quantities of standard materials are needed for routine use in analyses, and for quality control functions1. We have prepared some standard materials, starting with elemental Woodward iodine and NIST SRM 3231 [Iodine-129 Isotopic Standard (high level)] 10-6 solution. The goal was to make mixtures at the 5x10-10, 5x10-11, 5x10-12 ratio levels, along with some unmodified Woodward, in the chemical form of silver iodide. Approximately twenty grams of each of these mixtures were prepared. The elemental Woodward iodine was dissolved in chloroform, then reduced to iodide using sodium bisulfite in water. At this point the NIST spike material was added, in the form of sodium iodide. The mixed iodides were oxidized back to iodine in chloroform using hydrogen peroxide. This oxidation step was essential for isotopic equilibration of the 127 and 129 atoms. The iodine was reduced to iodide using sodium bisulfite as before. Excess sulfites and sulfates were precipitated with barium nitrate. After decanting, silver nitrate was used to precipitate the desired silver iodide. Once the silver iodide was produced, the material was kept in darkness as much as possible to minimize photo-oxidation. The various mixtures were synthesized independently of each other; there were no serial dilutions involved. Aliquots of these four materials have been submitted to five established AMS laboratories where iodine analyses are routinely performed: ETH (Zurich), CNA (Seville), PRIME (Purdue), LLNL (California), and Isotrace (Toronto.) Results from four of these laboratories have been received; in general they indicate that the desired 129/127 ratios have been achieved. We will discuss the results of this informal round-robin exercise. If the installation of the instrument in Idaho goes well, we may have some very preliminary results from the new system. An integral part of data reporting is the approach to data reduction. Accordingly, there will also be some discussion of various philosophies of data handling in regard to the use of standards to adjust data, and background subtraction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Quantify the Extent of Physisorption on Silver Based Sorbents under VOG Conditions

US regulations govern release limits for volatile radionuclides contained in the gaseous effluents of used nuclear fuel reprocessing facilities. Of the four volatile radionuclides that are most restricted by the release limits ( 3 H, 14 C, 85 Kr, and 129 I), 129 I will require the greatest degree of abatement. Within a reprocessing facility, the vessel off-gas stream will likely contain 1%–5% of the total iodine at parts per billion (ppb) concentrations. Studies conducted by the authors have now investigated both I 2 and methyl iodide (CH 3 I) adsorption by two silver-bearing sorbents, hydrogen-reduced silver-exchanged mordenite (Ag 0 Z) and silver functionalized aerogel (AgAerogel) at a range of concentrations up to 1,000 ppb. Throughout this suite of tests, and particularly in the case of CH3I adsorption tests, there was a significant discrepancy in the amount of iodine recovered on sorbent beds compared to the amount of iodine that was believed to be delivered to the test system.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗