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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Half-life measurement of the 199-keV isomeric state in Ga 76

Background: Isomeric states in atomic nuclei are a sensitive probe of their underlying microscopic structure and can be used to study the evolution of shell structure far from stability. Recent studies have identified and provided detailed spectroscopy of isomers in neutron-rich nuclei with Z = 28-50. Isomeric states in the odd-odd gallium isotopes have been reported for all gallium isotopes from A = 72 to A = 80 with the exception of 76 Ga. Purpose: The purpose of this experiment was to observe short-lived isomeric states in the vicinity of 78 Ni. Methods: In-beam fragmentation of a 86 Kr primary beam at the National Superconducting Cyclotron Laboratory produced radioactive ions which were delivered to and deposited in a Ce Br 3 scintillator coupled to a position-sensitive photomultiplier tube. Beta-delayed γ rays were measured by ancillary HPGe clover and LaBr 3 detectors which surrounded the implantation detector. Results: The previously observed J π = 1 + , 199-keV level in 76 Ga, populated following the β decay of 76 Zn, was identified as isomeric with a half-life of 34(1) stat. (8) sys. ns. Shell-model calculations suggest this state is formed by the coupling of protons in negative-parity configurations to 1/2 - neutron configurations. Transition strengths assuming a ground-state spin of J = 2 and J = 3 were determined from the experimental data.

59 ≤ A ≤ 89↗
DOE OSTI2015

Annual Continuation And Progress Report For Low-Energy Nuclear Physics Research At Lawrence Livermore National Laboratory

(I)In this project, the Beta-­decay Paul Trap, an open-­geometry RFQ ion trap that can be instrumented with sophisticated radiation detection arrays, is used for precision β-­decay studies. Measurements of β-­decay angular correlations, which are sensitive to exotic particles and other phenomena beyond the Standard Model (SM) of particle physics that may occur at the TeV-­energy scale, are being performed by taking advantage of the favorable properties of the mirror 8 Li and 8 B β ± decays and the benefits afforded by using trapped ions. By detecting the β and two α particles emitted in these decays, the complete kinematics can be reconstructed. This allows a simultaneous measurement of the β-­n, β-­n-­α, and β-α correlations and a determination of the neutrino energy and momentum event by event. In addition, the 8 B neutrino spectrum, of great interest in solar neutrino oscillation studies, can be determined in a new way. Beta-­delayed neutron spectroscopy is also being performed on neutron-­rich isotopes by studying the β-­decay recoil ions that emerge from the trap with high efficiency, good energy resolution, and practically no backgrounds. This novel technique is being used to study isotopes of mass-­number A~130 in the vicinity of the N=82 neutron magic number to help understand the rapid neutron-­capture process (r-­process) that creates many of the heavy isotopes observed in the cosmos. (II)A year-long CHICO2 campaign at ANL/ATLAS together with GRETINA included a total of 10 experiments, seven with the radioactive beams from CARIBU and three with stable beams, with 82 researchers involved from 27 institutions worldwide. CHICO2 performed flawlessly during this long campaign with achieved position resolution matching to that of GRETINA, which greatly enhances the sensitivity in the study of nuclear γ-­ray spectroscopy. This can be demonstrated in our results on 144 Ba and 146 Ba where the octupole deformation is evident from the measured B(E3; 3 - →0 + ) strengths that significantly greater than the theoretical predictions. We anticipate that CHICO2 will continue to be a viable charged-­particle detector for the research need of the low-­energy nuclear physics community.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Observation of a $μs$ isomer in ${134\atop{49}}$ In $_{85}$: Proton-neutron coupling "southeast" of ${132\atop{50}}$ Sn $_{82}$

In this paper, we report on the observation of a microsecond isomeric state in the single-proton-hole, three-neutron-particle nucleus 134 In . The nuclei of interest were produced by in-flight fission of a 238 U beam at the Radioactive Isotope Beam Factory at RIKEN. The isomer depopulates through a γ ray of energy 56.7(1) keV and with a half-life of $T_{1/2}$ = 3.5 (4) $μs$. Based on the comparison with shell-model calculations, we interpret the isomer as the $I^π$ = 5 - member of the $π0g{-1\atop{9/2}}Ⓧv1f{3\atop{7/2}}$ multiplet, decaying to the $I^π$ = 7 - ground state with a reduced-transition probability of $B (E$ 2; 5 - $\rightarrow$ 7 - = 0.53 (6) W. u. Observation of this isomer, and lack of evidence in the current work for a $I^π$ = 5 - isomer decay in 132 In , provides a benchmark of the proton-neutron interaction in the region of the nuclear chart “southeast” of 132 Sn , where experimental information on excited states is sparse.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Overview of PGSFR Project

The long-term plan for advanced SFR development was authorized by Korean Atomic Energy Commission (KAEC) in 2008 and updated in 2011, which will be carried out toward the construction of a SFR prototype plant called PGSFR (Prototype Gen-IV Sodium-cooled Fast Reactor) by 2028. The primary purpose of PGSFR is to demonstrate the technology reducing radioactive waste of spent nuclear fuel from nuclear power plants (NPP) in Korea. There are 24 NPPs in operation nationwide covering 30% of domestic electricity demand. The spent nuclear fuel is currently stored in the on-site storage pool of NPPs. Then, it has become a critical issue to ensure technical options to handle spent nuclear fuel in the long term basis to secure the sustainable operation of NPPs. PGSFR is a pool type sodium-cooled fast reactor with the power of 150 MWe or 400 MWth. PGSFR uses metallic fuel to make use of inherent safety characteristics of metallic fuel. The spent nuclear fuel will be processed using pyro-process to produce U-TRU-Zr fuel for PGSFR. But the initial core shall be loaded by low enriched U-Zr fuels. PGSFR has two intermediate loops with two intermediate heat exchangers (IHX) for each loop to deliver the generated heat from the core to power conversion system. There a steam generators producing super-heated steam in each loop. There are four decay heat removal circuits; two passive and two active ones. The reactor building is built on a seismic isolation base mat which can significantly mitigate seismic vibration of major components in the reactor building. The reactor building has a containment structure to isolate the reactor building under specific accident conditions and also provide structural integrity at the time of aircraft impact accident. PGSFR project is the national development program of Korea to construct the first SFR in Korea by 2028. The primary goal of PGSFR is the demonstration of reduction of radioactive waste from spent nuclear fuel by incineration in PGSFR. SFRA will flexibly cope with the licensing environment to minimize the uncertainty in licensing and safety concerns. The successful construction of PGSFR will bring Korean nuclear industry a step closer to guarantee the sustainable operation of NPPs nationwide and finally most importantly will solve the spent nuclear fuel issue of Korea. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Radiological Performance Modeling: Platform Comparison

Zapadnoe Uranium Mill Tailings Site, Pridneprovsky Chemical Plant Ukraine: Two exposure scenarios were utilized to develop performance assessment models in GoldSim and NORMALYSA. The first scenario is an onsite worker exposed to radioactivity through external ground irradiation as well as radon and radioactive dust inhalation. The second being an offsite Resident 300 years after institutional control exposed through the ingestion of garden vegetables irrigated by contaminated ground water, ingestion of fish from Konoplyanka River, and agricultural activities in contaminated garden. NORMALYSA utilizes a modular interface to connect extensive pre-created modules to develop contaminant transport and risk assessment models for safety assessments and performance assessments at NORM and legacy sites. Developed by Facilia AB, the program was tested with the creation of the Zapadnoe model under the International Atomic Energy Agency MODARIA Il Working Group 1 (WG1). Default values are provided for input parameters where site specific data and distributions lack. Probabilistic simulations and inputs are limited to parameters with assigned Gaussian probability functions. Similar results for transient worker inhalation dose were found in comparison with the Zapadnoe GoldSim model. However, the NORMALYSA model has results larger by an order of magnitude for external radiation in the transient worker and for aquatic food ingestion, inhalation, and garden food ingestion to the resident. Performance Assessment Modeling: Radiological performance models promote good management and support in remediation and environmental decision making by optimizing radioactive waste disposal site performance. a performance assessment model of the Zapadnoe uranium mill tailings site and a model for calculating authorized limits at Los Alamos National Laboratory are created to demonstrate and highlight the respective capabilities of three modeling platforms: GoldSim, NORMALYSA, and RESRAD-Onsite. GoldSim is a general-purpose modeling platform with the ability to simulate site-specific FT radionuclide transport and risk assessment using a graphical interface to create and link elements that act as indivisible building blocks of the model. The Zapadnoe performance assessment model created in GoldSim is composed of input parameters collected from site specific parameters from WG1 as well as standard assumptions seen in the Generic PA Model from Neptune and Company. The multivariate Zapadnoe simulation contains both deterministic and probabilistic simulation capabilities with the ability to quantitatively represent the uncertainty and associated risks of the site via the Monte Carlo simulation method. Model parameters, documentation, and assumptions are built directly into the model creating a transparent, reproducible, and more purposeful site specific model. To demonstrate this, an ingestion of water pathway was included in addition to the exposure pathways included in the NORMALYSA model. GoldSim offers a wide variety of probability distributions to choose from as well as many tools to visualize the uncertainty of the models and explore which pathways and radionuclides dominate dose. In contrast to the NORMALYSA model, the GoldSim model uses dynamic simulation to calculate tritium concentrations. Authorized limits support the evaluation of radiological health effects from radionuclides present in bulk contaminated soil in order to assist in the process of clearing land for release under different uses. Calculations of authorized limits in RESRAD-Onsite and GoldSim models support the evaluation for 15 radionuclides using a residential exposure scenario, indoor and outdoor inhalation of dust and vapor phase radionuclides (tritium), incidental soil ingestion, and ingestion grown fruits and Vegetables. RESRAD-Onsite, developed by Argonne National Laboratory is a dedicated computer code for calculating radiation doses and cancer risks to an individual located on top of radioactively contaminated soils. It can also be used to provide guidelines for deriving radionuclide soil levels corresponding to a specific dose criterion. The menu driven user interface facilitates selection of radionuclides and soil concentrations, as well as defines parameter values related to materials, environmental factors, and exposure pathways. The program contains radionuclide-specific data such as dose conversion factors and risk coefficients, as well as soil-water partition coefficients and transfer factors for biotic media. The GoldSim model successfully emulates the RESRAD-Onsite code using identical radiological decay and ingrowth factors, radiation dose conversion factors, and other input parameters. DE EEDE ETS Each model supports dynamic modeling of radionuclide ingrowth and decay over time, and integrate this capability with the transport of radionuclides in the environment via processes such as advection and/or diffusion in fluids, or within porous solid media, The applicability of each program is heavily dependent on project context. In the context of developing Authorized Limits, RESRAD-Onsite may be a more desirable option as it was developed for this particular application. For simple disposal or legacy sites or sites that do not need site-specific model structure, NORMALYSA may be a desirable modeling platform, GoldSim can be used to model any problem for which RESRAD or NORMALYSA is applicable, but its strength lies in its flexibility, analytical, and probabilistic capabilities.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Effectiveness of actinide management in fast reactors over a finite recycling period - 15123

Long-lived nuclear waste primarily consists of transuranic (TRU) isotopes. Full recycling of TRU isotopes can, in theory, lead to a reduction in repository radiotoxicity to reference levels in as little as ∼500 years provided reprocessing and fuel fabrication losses are limited. However, over a limited time frame, the radiotoxicity of the 'final' core can dominate over reprocessing losses, leading to a much lower reduction in radiotoxicity compared to that achievable at equilibrium. In this paper, the fuel cycle code ORION is used to model the recycle of light water reactor (LWR)-produced TRUs in sodium-cooled fast reactors (SFRs). With full actinide recycling, at least 6 generations of SFRs are required in a gradual phase-out of nuclear power to achieve transmutation performance approaching the theoretical equilibrium performance. Break-even SFRs are much less effective from a point of view of reducing waste radiotoxicity. Thorium (Th)-burner fuel cycles are found to result in slightly lower radiotoxicity than U-burner fuel cycles for the same number of generations. Closed break-even Th fuel cycles require ∼3 generations of operation before their waste radiotoxicity benefits result in decay to the reference level in ∼1000 years, provided that Pa is recycled. While this is a very long time frame, it is substantially better than the time frame required by other strategies. The integrated decay heat over the scenario time frame is substantially higher for break-even Th-SFRs than break-even U-SFRs as a result of much higher {sup 90}Sr production. As decay heat affects repository sizing, this weakens the argument for the Th cycle. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Intrinsic electric quadrupole moment of the K π = 8 - isomeric state in Hf 178

The lifetime of the 9 - state in the rotational band based on the 4.0 s, K π = 8 - , isomeric state ( 178 Hf m 1 ) from the decay of the 31-yr isomer ( 178 Hf m 2 ) was determined to be 99(2) ps by means of the fast-timing technique using two LaBr 3 (Ce) scintillators. The δ (E2/M1) mixing ratios of the ΔI = 1 γ rays depopulating levels in this band were deduced from γ-γ angular correlations by using a 178 Hf m 2 radioactive source located at the center of the Gammasphere HPGe detector array. The new results, together with previous spectroscopic information, provide a different way to extract the intrinsic quadrupole moment of Q 0 = 6.45 (14) eb for the 178 Hf m 1 band. A possible explanation for the reduction of the 178 Hf m 1 nuclear charge radius is presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Nuclear Considerations for the Application of Lanthanum Telluride in Future Radioisotope Power Systems

Thermoelectric-based radioisotope power systems (RPSs) produced in the United States convert the heat generated by the radioactive emission of alpha particles from plutonium dioxide ( 238 puO 2 ) into electricity by means of the Seebeck effect [1]. Certain designs for thermoelectric convertors propose the use of lanthanum telluride (La 3 Te 4 ) materials due to their significant conversion capabilities [2]. The generation of neutrons from spontaneous fission and alpha-neutron (α,n) reactions is also associated with the decay of 238 PuO 2 . A portion of these neutrons will interact with the thermoelectric materials and induce trace amounts of transmutation reactions in various lanthanum and tellurium isotopes. While very small quantities of several transmutation products are predicted, the most significant reaction channels are expected to produce trace amounts of iodine which will accumulate over time. Although iodine is classified as a halogen, it is the least reactive of the halogens, and as such, it is the most likely to be able to chemically convert back into the molecule I 2 . Since I 2 is a gas at RPS temperatures, it may be possible for iodine to attack other components in the thermoelectric cavity of an RPS system. Iodine reacts easily with metals to produce a wide variety of salts. This behavior could affect the performance of La 3 Te 4 thermoelectric devices, particularly the segmented architectures that include multiple sets of bonding and metallization layers. In this type of architecture, several segments of different thermoelectric materials are joined to increase the average thermoelectric figure of merit over a relatively large temperature gradient. It is plausible that sophisticated bonding/metallization layers could be required to join the segment interfaces to each other and to the cold- and hot-shoe materials. The long-term stability and performance of these segmented material combinations could degrade as a result of the potential formation and reactions of metal-iodide compounds at the segment interfaces. This paper (1) investigates the degree to which, if any, this process may threaten potential La 3 Te 4 thermoelectric technologies, (2) presents calculations of the amount of iodine generated over the operational life of a radioisotope thermoelectric generator design, and (3) discusses the potential effects of the resulting material's chemical reactions in a segmented couple-level architecture containing La 3 Te 4 . Conclusions drawn from combined particle transport, transmutation, and thermochemical calculations for La 3 Te 4 thermoelectric materials undergoing a notional 20-year mission scenario suggest that there is no significant potential for transmutation-induced thermoelectric (TE) performance degradation.

Smith, Michael↗
DOE OSTI2016

Gaseous time projection chambers for rare event detection: results from the T-REX project. I. Double beta decay

As part of the T-REX project, a number of R and D and prototyping activities have been carried out during the last years to explore the applicability of gaseous Time Projection Chambers (TPCs) with Micromesh Gas Structures (Micromegas) in rare event searches like double beta decay, axion research and low-mass WIMP searches. In both this and its companion paper, we compile the main results of the project and give an outlook of application prospects for this detection technique. While in the companion paper we focus on axions and WIMPs, in this paper we focus on the results regarding the measurement of the double beta decay (DBD) of {sup 136}Xe in a high pressure Xe (HPXe) TPC. Micromegas of the microbulk type have been extensively studied in high pressure Xe and Xe mixtures. Particularly relevant are the results obtained in Xe + trimethylamine (TMA) mixtures, showing very promising results in terms of gain, stability of operation, and energy resolution at high pressures up to 10 bar. The addition of TMA at levels of ∼ 1% reduces electron diffusion by up to a factor of 10 with respect to pure Xe, improving the quality of the topological pattern, with a positive impact on the discrimination capability. Operation with a medium size prototype of 30 cm diameter and 38 cm of drift (holding about 1 kg of Xe at 10 bar in the fiducial volume, enough to contain high energy electron tracks in the detector volume) has allowed to test the detection concept in realistic experimental conditions. Microbulk Micromegas are able to image the DBD ionization signature with high quality while, at the same time, measuring its energy deposition with a resolution of at least a ∼ 3% FWHM @ Q{sub ββ}. This value was experimentally demonstrated for high-energy extended tracks at 10 bar, and is probably improvable down to the ∼ 1% FWHM levels as extrapolated from low energy events. In addition, first results on the topological signature information (one straggling track ending in two blobs) show promising background discrimination capabilities out of reach of other experimental implementations. Moreover, microbulk Micromegas have very low levels of intrinsic radioactivity, and offer cost-effective scaling-up options. All these results demonstrate that Micromegas-read HPXe TPC remains a very competitive technique for the next generation DBD experiments.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Thermal Analysis of Disposal of High-Level Nuclear Waste in a Generic Bedded Salt repository using the Semi-Analytical Method.

An example case is presented for testing analytical thermal models. The example case represents thermal analysis of a generic repository in bedded salt at 500 m depth. The analysis is part of the study reported in Matteo et al. (2016). Ambient average ground surface temperature of 15°C, and a natural geothermal gradient of 25°C/km, were assumed to calculate temperature at the near field. For generic salt repository concept crushed salt backfill is assumed. For the semi-analytical analysis crushed salt thermal conductivity of 0.57 W/m-K was used. With time the crushed salt is expected to consolidate into intact salt. In this study a backfill thermal conductivity of 3.2 W/m-K (same as intact) is used for sensitivity analysis. Decay heat data for SRS glass is given in Table 1. The rest of the parameter values are shown below. Results of peak temperatures at the waste package surface are given in Table 2.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2026

Spent Nuclear Fuel and Reprocessing Waste Inventory

This report provides information on the inventory of spent nuclear fuel (SNF) in the United States located at Nuclear Power Reactor (NPR) and Independent Spent Fuel Storage Installation (ISFSI) sites, as well as SNF and reprocessing waste located at U.S. Department of Energy (DOE) sites and other research and development (R&D) centers as of the end of calendar year 2024. Actual quantitative values for current inventories are provided along with inventory forecasts derived from examining different future nuclear power generation scenarios, based on information available and assumptions made at the time the scenarios were developed. The report also includes select information on the characteristics associated with the wastes examined (e.g., type, packaging, heat generation rate, decay curves).

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

First study of the $^{139}\text{Ba}(n,y)^{140}\text{Ba}$ reaction to constrain the conditions for the astrophysical $\mathcal{i}$ process

New astronomical observations point to a nucleosynthesis picture that goes beyond what was accepted until recently. The intermediate “i” process was proposed as a plausible scenario to explain some of the unusual abundance patterns observed in metal-poor stars. The most important nuclear physics properties entering i-process calculations are the neutron-capture cross sections and they are almost exclusively not known experimentally. In this report we provide the first experimental constraints on the 139 Ba(n,γ) 140 Ba reaction rate, which is the dominant source of uncertainty for the production of lanthanum, a key indicator of i-process conditions. This is an important step towards identifying the exact astrophysical site of stars carrying the i-process signature.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Calculation of the dose load during dismantling of large components in the process of decommissioning of nuclear installations

The paper is focused on the decommissioning process from the point of view of steam generator dismantling. A brief description of the steam generator (used in nuclear power plants with VVER 440 type reactor) and used computer code VISIPLAN 3D ALARA are given. The main part deals with the created model and dismantling strategy together with variable input parameters - decay time and decontamination. The obtained results - external exposure of workers and the influence of time and pre-dismantling decontamination - are studied. Also detailed analyses of every dismantling step considered are presented. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Modeling of ATR Fuel in DOE Standard Canisters with Helium Backfill

One pathway for road-ready and final disposition packaging configurations for the aluminum-clad spent nuclear fuel (ANSF) fuel is storage within helium backfilled sealed Department of Energy (DOE) standard canisters. The typical packaging configuration for the 15-foot DOE standard canisters places 10 advance test reactor (ATR) elements a basket, and three baskets are loaded within each DOE canister. During in-reactor operations and cooling pond storage conditions, oxyhydroxide layers form on the surface of the aluminum clad fuel. These layers produce hydrogen gas over time due to the fuel’s radiation field. As part of the packing procedure, the ATR fuel should be dried to remove any residual physio-/chemi- sorbed water bound to the surface. A 50-year CFD model of the DOE canister packaged with fuel was developed to provide a temperature profile for coupled chemical modeling of the conditions within the canister. The results of this modeling include results at fully saturated and fully dried fuel cladding conditions. In the associated experimental work, radiolysis experiments tests were completed in a helium environment, and G-values for the radiolytic production of hydrogen from the oxyhydroxide layers were provided. That reaction was coupled with the thermal profiles and gas-phase reactions to develop a 50-year model of the conditions within a sealed DOE canister with ATR fuel. For a nominal scenario of stored ATR fuel, after 50 years the model results give a 1.36 atm total pressure, 7% mole percent hydrogen, for the upper decay heat, 1.51 atm total pressure, 16% mole percent hydrogen, and for upper decay heat with undried fuel 2.6 atm total pressure, 15% mole percent hydrogen. No case modeled yields significant oxygen, and for the lower decay heat case that is modeled, hydrogen concentrations are under the 4% flammability limit after 50 years of storage. The modeled pressures for all cases modeled are below the pressure limit for the DOE standard sealed canister.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1987

Radiogenic heating of comets by 26Al and implications for their time of formation

The effect of radiogenic heating on the thermal evolution of spherical icy bodies with radii 1 km < R < 100 km was investigated. The radioisotopes considered were 26Al, 40K, 232Th, 235U, and 238U. Except for the 26Al abundance, which was varied, the other initial abundances were kept fixed, at values derived from those of chondritic meteorites and corresponding to a gas-to-dust ratio of 1. The initial models were homogeneous and isothermal (To = 10 K) amorphous ice spheres, in a circular orbit at 10(4) AU from the Sun. The main object of this study was to examine the conditions under which the transition temperature from amorphous into cubic ice (Ta = 137 K) would be reached. It was shown that the influence of the short-lived radionuclide 26Al dominates the effect of other radioactive species for bodies of radii up to approximately 50 km. Consequently, if we require comets to retain their ice in amorphous form, as suggested by observations, an upper limit of approximately 4 x 10(-9) is obtained for the initial 26Al abundance in comets, a factor of 100 lower than that of the inclusions in the Allende meteorite. A lower limit for the formation time of comets may thus be derived. The possibility of a coexistence of molten cometary cores and extended amorphous ice mantles is ruled out. Larger icy spheres (R > 100 km) reached Ta even in the absence of 26Al, due to the decay of the other radionuclides. As a result, a crystalline core formed whose relative size depended on the composition assumed. Thus the outermost icy satellites in the solar system, which might have been formed of ice in the amorphous state, have probably undergone crystallization and may have exhibited eruptive activity when the gas trapped in the amorphous ice was released (e.g., Miranda).

Non-NASA Center↗
DOE OSTI2022

Search for Majorana neutrinos exploiting millikelvin cryogenics with CUORE

The possibility that neutrinos may be their own antiparticles, unique among the known fundamental particles, arises from the symmetric theory of fermions proposed by Ettore Majorana in 1937. Given the profound consequences of such Majorana neutrinos, among which is a potential explanation for the matter–antimatter asymmetry of the universe via leptogenesis, the Majorana nature of neutrinos commands intense experimental scrutiny globally; one of the primary experimental probes is neutrinoless double beta (0νββ) decay. Here we show results from the search for 0νββ decay of 130 Te, using the latest advanced cryogenic calorimeters with the CUORE experiment3. CUORE, operating just 10 millikelvin above absolute zero, has pushed the state of the art on three frontiers: the sheer mass held at such ultralow temperatures, operational longevity, and the low levels of ionizing radiation emanating from the cryogenic infrastructure. We find no evidence for 0νββ decay and set a lower bound of the process half-life as 2.2 × 10 25 years at a 90 percent credibility interval. We discuss potential applications of the advances made with CUORE to other fields such as direct dark matter, neutrino and nuclear physics searches and large-scale quantum computing, which can benefit from sustained operation of large payloads in a low-radioactivity, ultralow-temperature cryogenic environment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

An Updated Picture of Presolar History from Short-lived Radioactive Isotopes and Inferences on the Birth of the Sun

We examine the origin of the short-lived radionuclides (SLRs; defined as having half-lives between 0.1 and 100 Ma) present in the early solar system (ESS) by investigating how predictions of their abundances in the interstellar medium (ISM) from steady-state equilibrium relate to their ESS values. For this, we take into account the non-negligible time t iso elapsed between the isolation of the presolar molecular cloud and the formation of the ESS, during which the SLRs decayed freely. We also consider the alternative scenario in which the presolar molecular cloud remained partially mixed with the ISM, with a mixing timescale t mix . We find that the ESS abundances of 107 Pd and 182 Hf produced by slow neutron captures (s-process) and of 53 Mn and 60 Fe produced by explosive nucleosynthesis can be consistently explained within these scenarios. Their required tiso is 9–12 Ma and their required tmix is 11–14 Ma (with one potential exception of t mix = 38 Ma), depending on galactic uncertainties, such as the galactic star formation history and efficiency and the star-to-gas mass ratio. Another s -process SLR, 205 Pb, has a more uncertain ESS value and falls within only some of these time values. The same applies to the SLRs produced by the p -process ( 92 Nb and 146 Sm), depending on the latter’s half-life. In agreement with previous studies, we find that the ESS abundances of the rapid neutron-capture isotopes ( 129 I, 244 Pu, and 247 Cm) and of the most short-lived radionuclides ( 26 Al, 36 Cl, and 41 Ca) cannot be explained by assuming steady-state equilibrium in the ISM.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

The half-life of {sup 131g,m}Te

In this work, the half-lives of {sup 131m}Te and {sup 131g}Te were measured. Radioactive sources of {sup 131}Te were obtained using the {sup 130}Te(n,{gamma}){sup 131}Te nuclear reaction. These nuclear parameters have been determined with a better confidence and accuracy than previously available: 18.89 {+-} 0.11 min and 33.18 {+-} 0.13 h, respectively. These results are quite helpful for new calculations that attempt to describe the low-lying levels in {sup 131}I from the decay of {sup 131g,m}Te.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗