Transuranium Nuclides Research Articles

Masses of transuranium nuclides measured with the PI-ICR technique at TRIGA-Trap

We have revisited the region of the actinides in the vicinity of the neutron number N=152 and conducted high-precision mass measurements using the newly implemented Phase-Imaging Ion-Cyclotron-Resonance (PI-ICR) technique. The masses of 244\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{244}$$\\end{document}Pu and 249\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{249}$$\\end{document}Cf were found to deviate by 5.4 and 2.9 combined sigmas, respectively, from our previous results published in 2014. This indicates the presence of systematic errors in the earlier measurements. Consequently, we decided to remeasure all the nuclides from our 2014 study, along with 248\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{248}$$\\end{document}Cm, to ensure accuracy and reliability. With our greatly improved apparatus, we have measured the masses of 244\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{244}$$\\end{document}Pu, 241\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{241}$$\\end{document}Am, 243\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{243}$$\\end{document}Am, 248\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{248}$$\\end{document}Cm, and 249\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{249}$$\\end{document}Cf, using 208\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{208}$$\\end{document}Pb and 238\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{238}$$\\end{document}U as mass references. The masses of these reference ions were recently determined with ultra-high precision at Pentatrap. Our results were implemented in the latest Atomic Mass Evaluation (AME), showing good consistency. The region related to the masses measured in this study, especially for isotopes near the N=152 deformed shell gap, is discussed in terms of two-neutron separation energies, first excited 2+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^+$$\\end{document} energy levels and their differentials, as well as δVpn\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta V_{pn}$$\\end{document} values, the average proton-neutron interaction of the most loosely bound two nucleons.

Atomic mass determination of uranium-238

The atomic mass of uranium-238 has been determined to be 238.050787618(15) u, improving the literature uncertainty by two orders of magnitude. It is obtained from a measurement of the mass ratio of U47+238 and Xe26+132 ions with an uncertainty of 3.5×10−12. The measurement was carried out with the Penning-trap mass spectrometer and was accompanied by a calculation of the binding energies EU and EXe of the 47 and 26 missing electrons of the two highly charged ions, respectively. These binding energies were determined using an multiconfiguration Dirac-Hartree-Fock method to be EU=39927(10) eV and EXe=8971.2(21) eV. The new mass value will serve as a reference for high-precision mass measurements in the heavy mass region of the nuclear chart up to transuranium nuclides. Published by the American Physical Society 2024

Simultaneous Determination of Transuranium Radionuclides in Urine by Tandem Quadrupole ICP-MS/MS with Mass-Shift Mode Combined with Chemical Separation.

The urine bioassay method for transuranium nuclides (237Np, 239,240,241Pu, 241Am, and 244Cm) is needed to quickly assess the potential internal contamination in emergency situations. However, in the case that the analysis of multiple radionuclides is required in the same sample, time-consuming/tedious sequential analytical procedures using multiple chromatographic separation resins would have to be employed for the separation of every single radionuclide. In this work, a rapid method for the simultaneous determination of transuranium nuclides in urine was developed by using triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS) combined with a single DGA resin column. The chemical behaviors of Np/Pu and Am/Cm on the DGA resin were consistent in 8-10 mol/L HNO3 and 0.005-0.02 mol/L NaNO2 when 242Pu and 243Am were selected as tracers for Np/Pu and Am/Cm yield monitoring. Based on their different reaction rates with O2, 237Np, 239,240,241Pu, 241Am, and 244Cm in the same solution were simultaneously measured by ICP-MS/MS in the same run. The elimination efficiency of 238U+ tailing (7.43 × 10-9), 238U1H16O2+/238U16O2+ (8.11 × 10-8) and cross contamination of 241Pu and 241Am (<1%) were achieved using 10.0 mL/min He-0.3 mL/min O2 even if the eluate was directly measured without any evaporation. The detection limits of transuranium nuclides were at the femtogram level, demonstrating the feasibility of ICP-MS/MS for simultaneous transuranic radionuclides urinalysis. The developed method was validated by analyzing the spiked urine samples.

Simultaneous Determination of Transuranium Radionuclides for Nuclear Forensics by Compact Accelerator Mass Spectrometry.

Accelerator mass spectrometry (AMS) is one of the most sensitive techniques used to measure the long-lived actinides. This is particularly of interest for determination of ultra-trace transuranium nuclides and their isotopic fingerprints for nuclear forensics. In this work, a new method was developed for simultaneous determination of transuranium nuclides (Np, Pu, Am, and Cm isotopes) by using 300 kV AMS after a sequential chemical separation of each group of actinides. 242Pu and 243Am were utilized as tracers for Np/Pu and Am/Cm yield monitoring. The results show that the chemical behaviors of Np and Pu on the TK200 column and those of Am and Cm on the DGA column were very consistent in 8-9 mol/L of HNO3 and 0.015-0.03 mol/L of NaNO2 media during the radiochemical separation. The AMS detection efficiencies for transuranium nuclides were also evaluated. The detection limits for all radionuclides are below femtogram level and even in attogram level for Pu and Cm isotopes. The established method has been successfully applied to accurately measure various transuranium nuclides in a single actinide radionuclide solution, demonstrating its feasibility for nuclear forensic investigation.

Production of unknown neutron-rich transuranium isotopes 245–249Np, 248–251Pu, 248–254Am, and 252–254Cm in multinucleon transfer reactions

The production cross sections of unknown neutron-rich transuranium isotopes of elements Np, Pu, Am and Cm are investigated in multinucleon transfer (MNT) reactions based on the dinuclear system model with GEMINI code. The influence of the incident energy on the production of neutron-rich transuranium nuclei in actinide–actinide collisions is studied. The calculation results show that the final isotopic production cross sections are larger at 1.06–1.10 V cont than at other energies. Considering the high fissility of transuranium nuclides, 1.06 V cont is chosen as the optimal incident energy. The N/Z ratio equilibration mechanism in the nucleon transfer process is also studied in this work. The larger difference of N/Z ratio between projectile and target corresponds to larger neutron diffusion during the nucleon exchange process. The 238U beam with high N/Z ratio and neutron-rich actinide targets are good selections to produce neutron-rich transuranium nuclides. The production cross sections of unknown neutron-rich transuranium isotopes 245–249Np, 248–251Pu, 248–254Am, and 252–254Cm are predicted in 238U-induced actinide-based (249Bk, 249Cf, and 252Cf) MNT reactions. It is found that a large number of these unknown neutron-rich transuranium nuclei could be generated at the level of nb to μb in the reactions 238U + 249Bk and 238U + 252Cf. Our research indicates that the reaction 238U + 249Bk is a suitable projectile-target combination in the current experimental conditions and the reaction 238U + 252Cf could be a promising candidate to produce unknown neutron-rich transuranium nuclides in case that the 252Cf target were to be achieved in the future.

High-precision mass measurement of doubly magic 208\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{208}$$\\end{document}Pb

The absolute atomic mass of 208\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{208}$$\\end{document}Pb has been determined with a fractional uncertainty of 7×10-11\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$7\ imes 10^{-11}$$\\end{document} by measuring the cyclotron-frequency ratio R of 208\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{208}$$\\end{document}Pb41+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{41+}$$\\end{document} to 132\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{132}$$\\end{document}Xe26+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{26+}$$\\end{document} with the high-precision Penning-trap mass spectrometer Pentatrap and computing the binding energies EPb\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_{\ ext {Pb}}$$\\end{document} and EXe\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_{\ ext {Xe}}$$\\end{document} of the missing 41 and 26 atomic electrons, respectively, with the ab initio fully relativistic multi-configuration Dirac–Hartree–Fock (MCDHF) method. R has been measured with a relative precision of 9×10-12\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$9\ imes 10^{-12}$$\\end{document}. EPb\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_{\ ext {Pb}}$$\\end{document} and EXe\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_{\ ext {Xe}}$$\\end{document} have been computed with an uncertainty of 9.1 eV and 2.1 eV, respectively, yielding 207.976650571(14)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$207.976\\,650\\,571(14)$$\\end{document} u (u=9.3149410242(28)×108\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {u}=9.314\\,941\\,024\\,2(28)\ imes 10^{8}$$\\end{document} eV/c2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^2$$\\end{document}) for the 208\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{208}$$\\end{document}Pb neutral atomic mass. This result agrees within 1.2σ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1.2\\sigma $$\\end{document} with that from the Atomic-Mass Evaluation (AME) 2020, while improving the precision by almost two orders of magnitude. The new mass value directly improves the mass precision of 14 nuclides in the region of Z = 81–84 and is the most precise mass value with A>200\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$A>200$$\\end{document}. Thus, the measurement establishes a new region of reference mass values which can be used e.g. for precision mass determination of transuranium nuclides, including the superheavies.

Assessment of TRU burning in a molten salt reactor moderated by zirconium hydride rods

Inventory reduction of transuranium (TRU) nuclides can effectively reduce the long-lived and high-level radioactive hazards in the spent nuclear fuel (SNF) from the current light water reactors (LWRs), which is of importance to the long-term development and deployment of nuclear energy. Considering its outstanding features such as excellent neutron spectrum, high fuel utilization and compact core structure, a molten salt reactor moderated by zirconium hydride rods (ZrH-MSR) is considered as one of the potential reactor types for TRU burning. In this work, several fuel salts and molten salt volume fractions (SVFs) are analyzed to assess the TRU burning capability in a ZrH-MSR. The fuel salt of 77.5 mol% LiF-22.5 mol% (ThF4 + TRUF3) is selected since it can meet the requirement of TRU solubility limit during 50 years operation and can achieve a high initial TRU loaded mass in the core to improve TRU burning capacity. The optimized SVF is 0.5, and the TRU burning rate and the Support factor can achieve about 28.76 kg/TWthh and 2.9, respectively. The TRU burning mass, TRU fuel utilization ratio and 233U production after 50 years operation are about 12.6 tons, 70.4 %, and 0.7 tons, respectively. The total TRU radiotoxicity after discharge is about 63.9 % smaller than that without burning. This optimized core is beneficial to get a high TRU burning rate to reduce the storage of TRU and to minimize the long-term radiotoxicity risk in a relatively short reactor life. The total temperature feedback coefficient can remain negative during the whole operation time, which ensures the safety of the ZrH-MSR.

FUEL-CYCLE SCENARIO TO REDUCE RADIOACTIVE WASTE FROM LIGHT-WATER REACTOR

It is important to reduce the amount of trans-uranium (TRU) produced from the existing nuclear power plants to realize sustainable nuclear energy since the some TRU nuclides remain for a long time and have high radioactivity and radiotoxicity. One of the promising solutions is to transmute the TRU nuclides to those with lesser radioactivity and radiotoxicity in the existing nuclear reactors. In the current scheme, the TRU nuclides are transmuted in fast reactors and/or accelerator-driven-systems, however, this scenario seems unpromising in Japan: after the Fukushima Daiichi accident, it is required to reduce the production of TRU nuclides from the light-water reactors. In the previous studies, a concept of FORSETI was investigated, and a nuclear-fuel cycle simulation code ATRUNCYS was developed to study the low TRU production scenario. The FORSETI concept consists of two types of fuels: 1) UO2 fuels with high-assay low-enriched-uranium, and 2) MOX fuels with highly fissile concentrated plutonium reprocessed from the FORSETI-UO2 fuels. The current paper focuses on the following two scenarios: a) once-recycled scenario with the current fuel design, and b) once-recycled scenario with the FORSETI concept. The two scenarios were compared by using the ATRUNCYS code where the simulation studies showed that the amount, radioactivity, and radiotoxicity of resulting waste can be decreased in the FORSETI concept: In the case 1), the production of TRU nuclides decreased in the UO2 fuel; In the case 2), the fission rate increased and neutron-capture reactions of 240Pu and 241Pu decreased in the MOX fuels.

Feasibility study on burnable absorber for FORSETI to reduce productions of Pu238 and Pu241

ABSTRACTTo reduce the radiotoxicity of transuranium nuclides, Fuel cycle Of light water Reactor with Surplus Enriched Uranium for Transuranium-production Inhibition (FORSETI) has been studied. Since the potential radiotoxicity in spent fuel of FORSETI is mainly due to Pu238 and Pu241, the present study discusses the inclusion in FORSETI of a burnable absorber to reduce productions of these nuclides. Impacts of burnable absorbers on reaction rates related to productions of Pu238 and Pu241 are investigated by Monte Carlo calculations. The results show that Dy162, Er162, and Hf179 can reduce the production of Pu238 by suppressing the capture reaction of U236, and Hf177 can reduce the production of Pu241 by suppressing the capture reaction of Pu240. By comparing cross sections and capture reaction rates, it is confirmed that the suppression is mainly caused by the overlap of the resonances. Results of depletion calculations show that Dy162 and natural dysprosium suppress the production of Pu238, and Hf177 and natural hafnium suppress the production of Pu241. The present study concluded that Dy162 and natural dysprosium are candidates of the burnable absorber for FORSETI since they are suitable for further reduction of the potential radiotoxicity of transuranium nuclides through 50 years after discharge.

Uranium-based TRU multi-recycling with thermal neutron HTGR to reduce environmental burden and threat of nuclear proliferation

ABSTRACT To reduce environmental burden and threat of nuclear proliferation, multi-recycling fuel cycle with high temperature gas-cooled reactor has been investigated. Those problems are solved by incinerating trans-uranium (TRU) nuclides, which is composed of plutonium and minor actinoid, and there is concept to realize TRU incineration by multi-recycling with fast breeder reactor. In this study, multi-recycling is realized even with a thermal reactor by feeding fissile uranium from outside of the fuel cycle instead of breeding fissile nuclide. In this fuel cycle, recovered uranium and natural uranium are enriched and mixed with recovered TRU to fabricate fresh fuels. The fuel cycle was designed for a gas turbine high temperature reactor (GTHTR300). Reprocessing is assumed as existing reprocessing with four-group partitioning technology. As a result, the TRU nuclides excluding neptunium can be recycled by the proposed cycle. The duration of potential toxicity decaying to natural uranium level can be reduced to approximately 300 years, and the footprint of repository for high-level waste can be reduced by 99.7% compared with the standard case. Surplus plutonium is not generated by this cycle. Moreover, incineration of TRU from light water reactor cycle can be performed in this cycle.

Nucleosynthesis of Heavy Elements in Thermonuclear Explosions 'Mike', 'Par' and 'Barbell'

The formation of transuranium nuclides in pulsed neutron fluxes of thermo-nuclear explosions is investigated in the kinetic model of the astrophysical r-process, taking into account time dependence of the external parameters and including the processes accompanying the β-decay of neutron-rich nuclei. Time-dependent neutron fluxes in the interval ∼ 10−6 s were modeled within the developed adiabatic binary model. Probabilities of β-delayed processes were calculated using the microsco-pic theory of finite Fermi systems. Calculations of the yields of transuranium nuclides Y(A) are made for three experimental USA thermonuclear explosions ”Mike” (Y

Production of Transuranium Nuclides in Pulsed Neutron Fluxes from Thermonuclear Explosions

The production of transuranium nuclides in pulsed neutron fluxes from thermonuclear explosions has been studied within the kinetic model of the astrophysical r-process taking into account the time dependence of external parameters and processes accompanying the beta decay of neutron-rich nuclei. Neutron fluxes depending on the time in the range of ~10–6 s have been simulated within the developed adiabatic binary model. The probabilities of beta-delayed processes have been calculated within the microscopic theory of finite Fermi systems. The yields of transuranium nuclides Y(A) have been calculated for three experimental thermonuclear explosions Mike (YM), Par (YP), and Barbel (YB) (United States). The rms deviations of the calculations from experimental data are 91, 33, and 29% for YM, YP, and YB, respectively. These deviations are much smaller than those for other known calculations and are comparable with the proposed exponential approximation ensuring rms deviations of 56, 86.8, and 60.2% for YM, YP, and YB, respectively. The even–odd anomaly in the observed yields of heavy nuclei is explained by the dominant effect of processes accompanying the beta decay of heavy neutron-rich isotopes.

Calculation of Low-Energy Reactor Neutrino Spectra for Reactor Neutrino Experiments

Background: Nuclear reactors produce a great number of antielectron neutrinos mainly from beta-decay chains of fission products. Such neutrinos have energies mostly in MeV range. We are interested in neutrinos in a region of keV, since they may take part in special weak interactions. We calculate reactor antineutrino spectra especially in the low energy region. In this work we present neutrino spectrum from a typical pressurized water reactor (PWR) reactor core. Materials and Methods: To calculate neutrino spectra, we need information about all generated nuclides that emit neutrinos. They are mainly fission fragments, reaction products and trans-uranium nuclides that undergo negative beta decay. Information in relation to trans-uranium nuclide compositions and its evolution in time (burn-up process) were provided by a reactor code MVP-BURN. We used typical PWR parameter input for MVP-BURN code and assumed the reactor to be operated continuously for 1 year (12 months) in a steady thermal power (3.4 GWth). The PWR has three fuel compositions of 2.0, 3.5 and 4.1 wt% 235U contents. For preliminary calculation we adopted a standard burn-up chain model provided by MVP-BURN. The chain model treated 21 heavy nuclides and 50 fission products. The MVB-BURN code utilized JENDL 3.3 as nuclear data library. Results and Discussion: We confirm that the antielectron neutrino flux in the low energy region increases with burn-up of nuclear fuel. The antielectron-neutrino spectrum in low energy region is influenced by beta emitter nuclides with low Q value in beta decay (e.g. 241Pu) which is influenced by burp-up level: Low energy antielectron-neutrino spectra or emission rates increase when beta emitters with low Q value in beta decay accumulate Conclusion: Our result shows the flux of low energy reactor neutrinos increases with burn-up of nuclear fuel.

Direct high-precision mass measurements onAm241,243,Pu244, andCf249

The absolute masses of four long-lived transuranium nuclides, $^{241,243}\mathrm{Am}$, $^{244}\mathrm{Pu}$, $^{244}\mathrm{Pu}$, and $^{249}\mathrm{Cf}$, in the vicinity of the deformed $N=152$ neutron shell closure have been measured directly with the Penning-trap mass spectrometer TRIGA-TRAP. Our measurements confirm the AME2012 mass values of $^{241,243}\mathrm{Am}$ and $^{244}\mathrm{Pu}$ within one standard deviation, which were indirectly determined, by decay spectroscopy studies. In the case of the $^{249}\mathrm{Cf}$ mass, a discrepancy of more than three standard deviations has been observed, affecting absolute masses even in the superheavy element region. The implementation of the mass values into the AME2012 network yields a reduced mass uncertainty for 84 nuclides, particularly for $^{244}\mathrm{Pu}$ and its strongly correlated $\ensuremath{\alpha}$ decay chains.

Evaluating the yield of transuranium nuclides with masses of up to A = 270 via pulsed nucleosynthesis

A model of the creation of transuranium isotopes of up to A = 270 under conditions of pulse nucleosynthesis in a neutron flux with densities of up to ∼1025 neutron cm−2 is considered. The pulse process allows us to divide it in time into two stages: the process of multiple neutron captures (t < 10−6 s) and the subsequent β-decay of neutron-excess nuclei. The modeling of the transuranium yields takes into account the adiabatic character of the process, the probability of delayed fission, and the emission of delayed neutrons. A target with a binary composition of 238U and 239Pu, 248Cm, and 251Cf isotopes is used to predict the yields of heavy and superheavy isotopes.

Analysis of radionuclide wash-off from river basins

The concept of the rate of transport of exchange and non-exchange forms of radionuclides over river catchment is introduced. On this basis, a differential transport equation is proposed for finding the radionuclide content in soil and radionuclide flow into a river with nonuniform contamination of the catchment area. The time dependence of the radionuclide wash-off time constant is determined from the measurements. It is found that transport is slow, so that radionuclide decay plays a large role. A large fraction of the radionuclides, aside from the long-lived transuranium nuclides, decays within the catchment area and does not enter the river. The flow into the river is largely determined by the radionuclide content near river edge. Examples of calculations of radionuclide flow into a river and bukhta are presented.

Accumulation of uranium, transuranium and fission products on stainless steel surfaces II. Sorption studies in a laboratory model system

Within the frame of a joint project, the accumulation of the uranium and transuranium (TRU) species on some structural materials used at Soviet made VVER-type pressurized water reactors (such as heat exchanger tube of steam generators and stainless steel canister material) has been studied. The experiments were carried out in a laboratory model system. During the sorption studies, boric acid coolants provided by the Paks Nuclear Power Plant (Paks NPP) were circulated for a period of 30 h. Solution and tube samples obtained in the course of above experiments were analyzed by independent methods (α- and γ-spectrometry, ICP-MS, SEM-EDX, voltammetry and XPS). The experimental results reveal that: (i) the surface excess of the TRU nuclides studied is extremely low (less than 1% of a monolayer coverage); (ii) the surface excess of uranium species measured on the SG tube surfaces is significantly higher, after 30 h sorption period (Γsample = 1.0 μg cm−2 U ≅ 3.7 × 10−9 mol cm−2 UO2) exceeds a monolayer coverage; (iii) the mechanistic features of the contamination processes (specific or non-specific adsorption, deposition of colloidal and/or disperse particles) depend decisively upon the nature of the studied radionuclides and the chemical structure and composition of the oxide layer formed on stainless steel surfaces.

Further results in search for transuranium elements in effluents discharged to air from nuclear power plants.

In this work we present data on transuranium nuclides 238Pu, 239,240Pu, 241Am, 242Cm and 244Cm in effluents discharged to air (activity concentrations and annually discharged activities of individual radionuclides) from 7 stacks in 2004–2009. In the effluents discharged to air from one stack low activities of transuranium nuclides were observed throughout the studied period. Transuranium nuclides had been discharged to air from this stack also in previous years since 1996 when defect in the cladding of a fuel element and consequent contamination of the primary circuit occurred. In the effluents discharged to air from another stack transuranium nuclides were observed only in some monitoring periods of studied years. We could not prove the presence of transuranium nuclides in the effluents of the other stacks up to 2006. The transuranium nuclides in discharged effluents were registered in the second half-year of 2006. In 2007–2008 especially low activities of 241Am were found in these effluents.

Accumulation of uranium, transuranium and fission products on stainless steel surfaces. I. A comprehensive view of the experimental parameters influencing the extent and character of the contamination

The surface contamination by uranium and transuranium (Pu, Am, Cm) nuclides in the primary circuit of pressurized water nuclear reactors is a fairly complex problem as (i) different chemical forms (molecular, colloidal and/or disperse) of these atoms can be present in the boric acid coolant, and (ii) only limited information about the extent, kinetics and mechanism of uranium and transuranium (TRU) accumulation on constructional materials is available in the literature. A comprehensive program has been initiated in order to study the accumulation of uranium and TRU species on some structural materials used at Soviet made VVER-type pressurized water reactors (such as heat exchanger tube of steam generators and stainless steel canister material). This paper, which is the first part of a series of two, provides a comprehensive view on the main experimental parameters influencing the extent and character of the surface contamination by uranium and TRU nuclides. Specifically, we give a brief summary of relevant literature data on the chemistry of uranium and TRU elements and review the dominant chemical forms and their relative sorbability on austenitic stainless steel and Zr(Nb) alloy surfaces. Moreover, some findings on the distribution of uranium, plutonium, americium, and curium species in a model solution of boric acid coolant obtained by the VisualMINTEQ computer code are also presented and discussed.

Identification and characterisation of radioactive particles in salt marsh sediments

Radionuclides from authorized low level radioactive effluent discharges from the nuclear fuel reprocessing plant at Sellafield, UK, are present in the Irish Sea sediments. The distribution of radionuclides in salt marsh sediment profiles can be related to the discharge history from Sellafield. Radioactive particles, from the intertidal salt marsh sediments in the Esk estuary (10 km from Sellafield), have been isolated and investigated. Autoradiography and heavy liquid density separation were used to find and isolate these particles. Scanning electron microscopy, combined with energy dispersive X-ray analysis (SEM-EDX), was used to obtain information on the morphology and elemental composition of the particles, and alpha spectrometry for radionuclide composition. Particles are typically 1 — 20 μm size. Elemental analysis suggests that they are composed mainly of uranium. Alpha spectrometry shows that they have been irradiated, and transuranium nuclides (Pu, Am, Cm) can be identified in them.