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At least 577 records · Page 32

Beta decay and the origin of biologial chirality - New experimental results

The hypothetical connection developed by Vester and Ulbricht (1959), between the handedness of beta particles in radioactive decay and the (L) sign of biologial chirality is investigated in a radiolysis experiment. The experiment measured the predicted asymmetry in the formation triplet or 'ortho-' positronium (oPs) in amino acid enantiomers by low energy positrons under conditions of helicity reversal. The positrons were focused on amino acid powder samples. By measuring the time between positron arrival and emission of gamma rays, long-lived oPs were separated from other species. It is found that the asymmetry in leucine (0.8 x 10 to the -4th) is consistent with the theoretical prediction of 10 to the -6th. Neither the experimental limits nor the theoretical estimates are found to rule out a mechanism like that described by Vester and Ulbricht as the cause of the sign of the observed chiral polarization.

Van House, J.↗

How Can The SN-GRB Time Delay Be Measured?

The connection between SNe and GRBs, launched by SN 1998bw / GRB 980425 and clinched by SN 2003dh / GRB 030329-with the two GRBs differing by a factor of approximately 50000 in luminosity-so far suggests a rough upper limit of approximately 1-2 days for the delay between SN and GRB. Only four SNe have had nonnegligible coverage in close coincidence with the initial explosion, near the W shock breakout: two Qpe II, and two Type IC, SN 1999ex and SN 1998bw. For the latter, only a hint of the minimum between the UV maximum and the radioactivity bump served to help constrain the interval between SN and GRB. Swift GRB alerts may provide the opportunity to study many SNe through the UV breakout phase: GRB 980425 look dikes -apparently nearby, low- luminosity, soft-spectrum, long-lag GRBs-accounted for half of BATSE bursts near threshold, and may dominate the Swift yield near threshold, since it has sensitivity to lower energies than did BATSE. The SN to GRB delay timescale should be better constrained by prompt UV/optical observations alerted by these bursts. Definitive delay measurements may be obtained if long-lag bursters are truly nearby: The SNe/GRBs could emit gravitational radiation detectable by LIGO-II if robust non-axisymmetric bar instabilities develop during core collapse, and/or neutrino emission may be detectable as suggested by Meszaros et al.

Norris, J. P.↗

Alternative Liquid DSA Containers for Sludge Slurry Storage in the SRNL Shielded Cells

A pending revision of the Documented Safety Analysis (DSA) for the Savannah River National Laboratory (SRNL) defines “DSA containers” for liquid sludge slurries as containers not susceptible to a flashing spray release in a fire and requires that a list of DSA containers be maintained. High Level Waste (HLW) samples are typically received from the Savannah River Site (SRS) tank farm after retrieval from the storage tanks. Glass bottles are preferred for long-term storage of radioactive liquid sludge slurry samples but are not on the DSA container list. An evaluation has been conducted to identify vessel lids for the glass bottles that would vent prior to pressurization and liquid superheating in a fire event. Low melting Field’s Metal eutectic alloy with a melting point of 62 °C has been identified as a preferred material of construction for vessel lids for this application because the material is resistant to puncture and is expected to have good chemical compatibility and radiation stability in the shielded cells environment. A test vessel was designed to evaluate the alloy and confirm that it would melt before the water in the vessel reaches the boiling point. The tests confirmed: 1) that the reported melting point of the alloy was accurate, 2) that a top fashioned from this material will melt creating an open atmosphere in the vessel headspace prior to sample boiling under moderate and fast heating rates, and 3) that nonuniform heating of the bottle from the bottom also results in melting of the alloy prior to boiling. Based on the results, neither an engulfing fire with standing or toppled bottles or a fire producing localized heat at the vessel bottom would result in flashing spray conditions.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Phosphate (U-Th)/He Thermochronology of Apollo 14 Melt Breccia 14311

Our ability to confidently characterize the impact history of the inner solar system is limited by discrepancies in radiometric dates and age interpretations for lunar rocks, impact melts, and recovered meteorites. It is therefore important to explore different thermally sensitive radiometric systems to unravel the timing and extent of the long term impact flux. Low-temperature thermochronology of lunar samples has the potential to provide more complementary geochronological datasets and further test dynamical models related to the evolution of the inner solar system (e.g., [1]). (U-Th)/He dating is based on the production of 4He atoms by radioactive alpha decay of U and Th (and to a lesser extent, Sm) in a crystal and the thermally activated volumetric diffusion of those 4He nuclides. At high temperatures, the crystal is an open system from which 4He can escape; at lower temperatures, 4He may be retained. This retention temperature depends on factors such as crystal structure and volume fraction of radiation damage in the crystal (e.g., [2, 3]), but is significantly lower for phosphate minerals compared to the diffusion of the radiogenic daughter products in other widely used chronometric systems (e.g., ~75°C in terrestrial apatite (U-Th)/He vs. ~500°C in apatite U-Th-Pb vs. ~900°C in zircon U-Th-Pb chronometry). Phosphate (U-Th)/He dating has been used to decipher peak temperatures and cooling rates related to terrestrial impact events (e.g., [4]). Pairing a low-temperature thermochronometer with higher-temperature approaches (i.e., a combined 207Pb-206Pb and (U-Th)/He approach), can therefore resolve multiple impact ages within a given sample or even grain. However, despite its potential, phosphate (U-Th)/He dating has not been reported on any lunar samples. Here we present the first lunar phosphate (U-Th)/He thermochronology on an Apollo 14 impact melt-breccia.

C A Diaz↗

Experimental validation of the mechanistic scale-up methodology of gas–solid spouted beds using radioactive particle tracking (RPT)

The very high-temperature reactors (VHTRs) are highly ranked among candidates of Generation IV of nuclear reactors due to their high efficiency, safety, the resistance to proliferation, and reliability. The VHTRs are preferentially fueled by Tristructural-isometric (TRISO) coated fuel particles which has fuel kernels of fissile material coated by four coating layers: a porous buffer pyrolysis carbon layer (buffer PyC), an inner dense pyrolysis carbon layer (IPyC), a silicon carbide layer (SiC) and an outer dense pyrolysis carbon layer (OPyC). The heart of the operation and safety of the VHTRs significantly depends on the reliability of the coating layers of TRISO particles to retain metallic and gaseous fission products within the particles. The technique used for coating TRISO particles are gas-solids spouted beds via chemical vapor deposition (CVD). Fabrication of high-quality low-defect TRISO fuel particles fuel at larger scale spouted beds is required to support the commercialization of the VHTRs. In this work, our new developed mechanistic scale-up methodology of gas-solids spouted beds based on matching the radial profile of gas-holdup has been demonstrated and validated using radioactive particle tracking (RPT). Two spouted beds of small and larger scales were used in the study. Three sets of conditions were carried out which include the conditions of the reference case in the large scale, conditions that provide similar gas holdup radial profile to that of the reference case and conditions that provided dissimilar gas holdup radial in the small-scale spouted beds. The results confirm the validation of the scale-up methodology in terms of the dimensionless values of the spout diameter, cumulative probability distribution of the solids particles penetration into the spout, fraction of cycle time in each region of the bed, the radial profiles of the dimensionless values of the root-mean-square particle velocities and solids eddy diffusivity. Finally, the results further advance the knowledge and understanding of the gas-solids spouted beds provide deeper insight into their solids dynamics and presenting important benchmarking data for validating computational fluid dynamics codes and models. At last, procedures are established for the implementation of the new scale-up methodology.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

Investigation of Process Emissions during Thermal Cutting of Clad Metals from the Nuclear Sector - 20183

Typically, reactor pressure vessels as well as steam generators comprising low alloyed steel with a cladding of stainless steel. Recently the permissible values for Cr (VI) in the air of the working areas have been reduced in Germany from 100 μg/m{sup 3} to 1 μg/m{sup 3} air. This results in the danger that even with low-alloy steel with claddings these limit values would be exceeded when using flame cutting technologies. In order to ensure compliance with the permissible limit values, exhaust gas systems with gas cleaning measures are provided. The process emission test shall replace the assumptions required for the design of these systems with measured values. NUKEM Technologies Engineering Services GmbH (NUKEM) has chosen autogenous flame cutting as an example of a thermal cutting system for process emission testing, as there are no proven values in the literature for the Cr (VI) and NiOx emissions produced. The autogenous flame cutting can be used for a variety of cutting tasks within decommissioning projects. In order to simulate the material to be cut, mock ups were generated and cut from information about the material specification for the reactor pressure vessel from existing nuclear power plants including possible claddings. The cutting length needed for analysis in the test will be maximum 100 mm. The airborne emissions from the thermal cutting process will be captured and analyzed as follows: - Dust emission: The generated particles will be collected by a hood equipped with strong suction device and suitable filter elements. The resulting filter is gravimetrically measured before and after the tests. - Particle Size Distribution: The airborne particle size distribution measurement will result in figures for the size and number of particles arising from the thermal cutting process. - Gas Analysis: The gas analysis enables the determination of e.g. CO{sub 2}, CO, O{sub 3}, NO, NO{sub 2}. - Cr (VI) and NiOx Analysis: For the Cr (VI) and NiOx analysis, samples of the filter residue will be taken. As a result Cr (VI) in relation to total Cr as well as the Ni content will be determined by ICP-optically emission spectroscopy and put in relation to the total dust amount. The process emissions test itself as well as the necessary gas analyses and spectroscopic analyses were carried out at the Institute of Materials Science (IW) of Leibniz Universitaet Hannover (LUH). The results of the process emission tests are used to confirm the design of the gas cleaning systems. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Modeling of life limiting phenomena in the discharge chamber of an electron bombardment ion thruster

An experimental facility to study the low energy sputtering of metal surfaces with ions produced by an ion gun is described. The energy of the ions ranged from 10 to 500 eV. Cesium ions with energies from 100 to 500 eV were used initially to characterize the operation of the ion gun. Next, argon and xenon ions were used to measure the sputtering yields of cobalt (Co), Cadmium (Cd), and Chromium (Cr) at an operating temperature of 2x10(exp -5) Torr. The ion current ranged from 0.0135 micro-A at 500 eV. The targets were electroplated on a copper substrate. The surface density of the electroplated material was approx. 50 micro-g/sq cm. The sputtered atoms were collected on an aluminum foil surrounding the target. Radioactive tracers were used to measure the sputtering yields. The sputtering yields of Cr were found to be much higher than those of Co and Cd. The yields of Co and Cd were comparable, with Co providing the higher yields. Co and Cd targets were observed to sputter at energies as low as 10 eV for both argon and xenon ions. The Cr yields could not be measured below 20 eV for argon ions and 15 eV for xenon ions. On a linear scale the yield energy curves near the threshold energies exhibit a concave nature.

Handoo, Arvind K.↗

Single-nucleon knockout cross sections for reactions producing resonance states at or beyond the drip line

Single-nucleon knockout cross sections from fast secondary beams of the proton-drip-line nuclei 9 C, 13 O, and 17 Ne on a 9 Be target have been studied with emphasis on the production of resonance states. These states were identified by their invariant mass, and resonances with two-, three-, and five-body exit channels were examined. The measured cross sections for these states were compared with eikonal-model predictions using shell-model or variational Monte Carlo spectroscopic factors. The experimental yields were found to be suppressed relative to the model predictions, especially when a well-bound neutron or proton is removed. This suppression exceeds that found systematically in measured inclusive cross sections to particle-bound final states. In neutron knockout from 9 C and 13 O projectiles, this suppression of the unbound ground-state residuals yield is a factor of two to three times larger than that found in the bound final-state studies. Modifications to the structure of these systems due to coupling of the shell-model configurations to the continuum is expected to contribute to this extra suppression, especially when the final state is a near-threshold resonance. Furthermore, other considerations including the role of nuclear dynamics may be required to explain all the observed trends.

6 ≤ A ≤ 19↗

Additional Analysis of the 2H-Evaporator Wall Scale Sample HTF-17-57

Savannah River National Laboratory previously analyzed scale samples from both the wall and cone sections of the 242-16H Evaporator prior to chemical cleaning. The samples were analyzed for uranium and plutonium isotopes required for a Nuclear Criticality Safety Assessment of the scale removal process. The analysis of the scale samples found the material to contain crystalline nitrated cancrinite and clarkeite and significant amounts of mercury. Savannah River Remediation subsequently requested additional analyses on the samples. Inspection of the sample bottles revealed that no sample remained of the cone scale (HTF-17-56) while approximately 4 g of the wall scale sample (HTF-17-57) remained. The wall sample was subsequently ground with a mortar and pestle, at which time it was discovered that the sample contained a significant amount of liquid, metallic mercury. The portion of the sample that was not mercury was approximately 3 g. This portion of the sample was analyzed to determine the concentrations of selected radionuclides. The following radionuclide concentrations were measured: <9.6E+02 dpm/g H-3, 2.9E+02 dpm/g C-14, 5.6E+03 dpm/g Tc-99, and 1.6E+02 dpm/g I-129. Blank samples were also analyzed to evaluate sample contamination from the Shielded Cells environment. All blank sample results were below detectable limits. Due to the limited sample size and the anticipated low levels of the target radionuclides, no replicate sample analysis was conducted.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

An Assessment of the Nevada Test Site for Low-Level Waste Management

This report presents a summary of description information, facilities, and operating practices at the Nevada Test Site. It is concluded that NTS is not only a feasible location for surface and near-surface storage of low-level wastes, but also a potential site for underground storage of higher level wastes.

052002* -- Nuclear Fuels-- Waste Disposal & Storag↗

Relationship Between the Marginal Probability of Failure for a CPP Test and the Recommended Corrosion Control Requirements for Hanford Double Shell Waste Tanks

The Hanford Site in Washington State currently stores millions of gallons of radioactive waste in underground, carbon steel, double shell tanks (DSTs) that were constructed between 1968 and 1986. A chemistry control and monitoring program has been established mitigate corrosion in order to extend the service life for the DSTs. The current waste temperatures in the DSTs are at historical lows (i.e., typically less than 50 °C). The previous chemistry control requirements were determined for conditions at temperatures significantly higher. SRNL undertook a statistically based investigation of the role of nitrate and halide ion (i.e., chloride and fluoride) induced pitting corrosion. The objective was to develop a comprehensive waste chemistry envelope for the simultaneous minimization of the pitting and SCC risks caused by halide and nitrate ions at the lower temperature conditions. On the basis of these tests, new chemistry control requirements were proposed and have since been implemented for pitting corrosion control.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Measurement of the gas gain and understanding the gas flow in the Mu2e Tracker

The Mu2e experiment will search for the charged-lepton flavor violating (CLFV) neutrinoless conversion of a negative muon into an electron in the field of an Aluminum nucleus µ − N → e − N. The signature of this process is the emission of a monochromatic electron with an energy of 104.97 MeV. The Mu2e Tracker is a low mass straw tube detector, whose aim is to measure the position and the momentum of the electron. In past measurements, high values of currents were found in some panels of the Tracker in absence of any radioactive sources. In this report new measurements of currents, that were taken with the panel MN084 of the Mu2e Tracker are described. Moreover, the addition of a small amount of water vapour in the gas mixture and the influence of the environmental conditions on the currents of the panel are studied.

47 OTHER INSTRUMENTATION↗

Charge transfer efficiency measurements at low signal levels on STIS/SOHO TK1024 CCD's

Charge transfer efficiency (CTE) test methods are reviewed, and the results and conclusions of the tests are given. The test methods have been utilized to describe the CTE characteristics of the Tektronix 1024 by 1024 CCD to optimize low dark current, low readout noise, and high CTE at low signal levels. CTE modelling is described, and three test methods are set forth and compared. The Fe-55 X-ray response method utilizes the response of a CCD to X-ray photons from the radioactive source Fe-55. The extended pixel edge response method employs the measurement of the charge lost to successive pixels by a known initial signal as it is shifted through the array. The charge injection method consists of charge injection through the output amplifier reset transistor. These measurements were performed on several devices with known CTEs. The CTEs are found to be in agreement for the three methods, making application and test requirements the principal criteria for their use.

Orbock, J. D.↗

Small to Full Height Scale Comparisons of Cesium Ion Exchange Performance with Crystalline Silicotitanate

The U.S. Department of Energy’s (DOE) Hanford Site houses 56 million gallons of high-level radioactive waste generated from plutonium production from 1944 to 1988. The supernatant waste, currently stored in underground tanks, is intended to be vitrified following filtration and 137 Cs removal at the Hanford Waste Treatment and Immobilization Plant (WTP) Low-Activity Waste (LAW) Vitrification Facility. The WTP Pretreatment Facility will not be operational for several years. The Tank Side Cesium Removal (TSCR) system is a technology demonstration that will remove cesium from tank waste supernate to support directly feeding LAW to the vitrification facility. The 137 Cs removal is important to meet the WTP LAW contract specification and ultimately for creating a contact-handled waste form. The waste acceptance criteria (WAC) limit for the WTP LAW Facility is <3.18E-5 Ci 137 Cs per mole Na. The TSCR system is skid mounted and employs two key technologies: dead end filtration for solids removal and ion exchange (IX) for cesium removal. Filtration is necessary to protect the functionality of the IX columns. The IX process utilizes sodium form crystalline silicotitanate (CST) IX media produced by UOP Honeywell, LLC (Des Plaines, IL) under the product name IONSIV R9140-B, 18 x 50 mesh, in a lead-lag-polish column configuration. Each column contains a CST bed height of 92 inches and a volume of approximately 157 gallons of CST IX media. The full-scale TSCR operation will run at a residence time of 1.9 bed volumes (BV)/h, which results in a superficial velocity of 7.3 cm/min and a flowrate of ~5 gal/min. Column testing at small (2.5% of the full bed height), medium (12% of the full bed height), and full-height scales has been previously conducted to evaluate process variables and scale up performance of Cs exchange onto the CST. Cesium load performances from various sieve cuts at the small scale indicated that a 30-mesh sieve cut be tested to determine if it better reflects the 12% and full-height column performances at the small scale. Two process flowrates were tested in the small-column configuration with <30-mesh CST and simulant solutions. These tests were compared to full-height column tests at the same residence times to assess CST particle size effect on column scaling. Table S.1 summarizes the observed column performance determined for the two flowrates juxtaposed to the previous work with 5.6 M Na simulant at higher scales (used as benchmarks). The WAC breakthroughs between the small and full-height tests at 1.3 BV/h differed by ~59 BVs. The WAC breakthroughs for small, medium, and full-height tests at 1.8 BV/h were consistent at 240 BVs. The 50% Cs breakthroughs were nominally equivalent for all column tests. The common transition zones and onsets of Cs breakthrough at the 1.8 BV/h tests indicated that the Cs mass transfers were equivalent and thus the <30-mesh CST Cs load performance at the small scale successfully modeled that of the full-height system. It is recommended that the <30-mesh CST be used in subsequent 10-mL CST bed tests.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

KOMPASS: Compaction of crushed salt for the safe containment

In Germany, rock salt formations are a possible host rock taken into account for the safe disposal of heat-emitting radioactive waste. With respect to crushed salt will be used in the repository for backfilling of open cavitied (using dry material). With time, the crushed salt will be compacted by the convergence of the host rock and reaches porosities comparable with the rock salts. The compaction behaviour of crushed salt has been investigated within the last 40 years, however, its behaviour at low porosities and the resulting low permeabilities becomes relevant with the introduction of the approach of the containment providing rock zone. In the current state, the database and process understanding have some important gaps in knowledge referring the material behaviour, existing laboratory and numerical models, especially for the porosity range. The objective of this project was the development of methods and strategies for the reduction of deficits in the prediction of crushed salt compaction leading to an improvement of the prognosis quality. It includes the development of experimental methods for determining crushed salt properties in the range of low porosities, the enhancement of process understanding and the investigation and development of existing numerical models.

Crushed salt compaction↗

Low Level Calibration of Liquid Scintillation Counting

Liquid Scintillation Counting (LSC) is an analytical laboratory method that quantifies the concentrations of alpha and beta emitting isotopes. The LSC method can be utilized for the detection of tritium, both environmentally and at nuclear facilities. Most LSC samples are aqueous-based and prepared as a radioactive sample dissolved or suspended in a high efficiency scintillation cocktail that converts radioactive energy into light pulses. When placed in counting vials, the liquid scintillation cocktail allows for optical coupling in which energy is released from the samples radioactive decay, and transferred to the scintillator. That energy is then absorbed to produce excited electrons that fall back to their ground-state and emit a pulse of light that is detected by the liquid scintillation analyzers photomultiplier tubes. Quench is a signal attenuation due to physical, chemical, or color interferences. To compensate for quench, quench standards of a known concentration are implemented at increasing increments of quench per vial to create a quench curve. Quench standards can be purchased pre-made or customized from the manufacturer, however, there are several issues that arise from purchasing the pre-made quench standards. The main issues with ordering pre-made quench standards is that they use higher count values, between 30,000 and 250,000 disintegrations per minute (dpm) of tritium per vial and only come in glass vials. Using higher counting standards in glass vials makes it hard to see lower concentrations in plastic vials. Additionally, when using higher energy standards the accuracy of the calibration readings tend to be lower. On the other hand, making a set of quench standards in-house allows for the customization of the dpm concentration to roughly 1,500-3,000 and preparation in plastic vials. This allows for lower activity readings that results in closer precision of the samples' true concentration. Technical Objectives: Create a quench curve and calibrate the LSA for tritium. Verify the calibration of the quench curve prior to cross sample runs. Check calibration against Quality Control (QC) reference value. Conclusion: a tritium quench curve calibration was performed using a scintillation cocktail with ultima gold (AB and AB/F), acetone (only with AB), and water (only with AB/F). By performing the tritium quench curve calibration, the counting efficiency was correlated to various levels of quench. Calibration checks with quality control standards were also performed to verify that the calibration was correct. The observed results provided acceptable values that matched the quality control standard reference values with an acceptable uncertainty. The next step will be fine tuning and cross comparison checks with legacy instrumentation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

New transitions and levels for 163 Tb obtained from β-decay studies

Transitions in 163 Tb following β decay of 163 Gd were obtained as part of investigations of γ rays emitted following 163 Euβ decay to 163 Gd. In this work, detailed analysis of the low-energy structure of 163 Tb has been carried out with these data to expand previous β-decay studies and reactions studies of levels in 163 Tb. Data were collected at the LeRIBSS station of the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory with an array of four Clover HPGe detectors for γ rays and two plastic scintillators for β detection. The γ rays were identified as belonging to 163 Gd and 163 Tb via mass selection and γ-γ-β, γ-γ, or γ-x-ray coincidence. In total, 38 new γ-ray transitions were observed in 163 Tb from 15 newly identified levels and 12 previously identified levels. Potential energy surface calculations were performed which support a rigid prolate deformation. Previously identified unplaced transitions in 163 Tb have been placed within the level scheme of 163 Tb and additional states and transitions have been identified.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

West Valley Demonstration Project (WVDP) Annual Site Environmental Report (ASER) for Calendar Year 2023

The report, prepared for the U.S. Department of Energy West Valley Demonstration Project office (DOE-WVDP), summarizes the environmental protection program at the WVDP for calendar year (CY) 2023. Monitoring and surveillance of the facilities used by the DOE are conducted to verify protection of public health and safety and the environment. The report is a key component of DOE’s effort to keep the public informed of environmental conditions at the WVDP. The quality assurance protocols applied to the environmental monitoring program ensure the validity and accuracy of the monitoring data. In addition to demonstrating compliance with environmental laws, regulations, and directives, evaluation of data collected in 2023 continued to indicate that WVDP activities pose no threat to public health or safety, or to the environment.

Record of Decision↗