Predictions of strontium accommodation in A2B2O7 pyrochlores

2002 ◽  
Vol 17 (8) ◽  
pp. 2041-2047 ◽  
Author(s):  
Mohsin Pirzada ◽  
Robin W. Grimes ◽  
John Maguire ◽  
Kurt Sickafus
Keyword(s):  
Oxygen Vacancy ◽  
Fission Product ◽  
Computer Simulations ◽  
Relative Equilibrium ◽  
Fission Products ◽  
Defect Clusters ◽  
Relative Ability ◽  
Host Materials ◽  
Product Ions ◽  
Energy Maps

A2B2O7 pyrochlore oxides are being considered as potential host materials for the immobilization of fission products. It is therefore important to establish the relative ability of these compounds to accommodate fission product ions. We address this issue by using computer simulations to predict the structures and relative equilibrium energies associated with solution of Sr2+ over an extensive compositional range. Results indicate that strontium is accommodated via substitution for A host cations with oxygen vacancy compensation. This results in a nonstoichiometric composition. Optimum compositions and defect clusters structures are identified by constructing contour energy maps.

scholarly journals Separation of Lanthanide Isotopes from Mixed Fission Product Samples

Separations ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 104
Author(s):  
Leah M. Arrigo ◽  
Jun Jiang ◽  
Zachary S. Finch ◽  
James M. Bowen ◽  
Staci M. Herman ◽  
...  
Keyword(s):  
Fission Product ◽  
Fission Products ◽  
Nuclear Data ◽  
Product Analysis ◽  
Data Production ◽  
Thermal Irradiation ◽  
Nuclear Events ◽  
Lanthanide Separation ◽  
Enriched Uranium ◽  
Fission Yields

The measurement of radioactive fission products from nuclear events has important implications for nuclear data production, environmental monitoring, and nuclear forensics. In a previous paper, the authors reported the optimization of an intra-group lanthanide separation using LN extraction resin from Eichrom Technologies®, Inc. and a nitric acid gradient. In this work, the method was demonstrated for the separation and quantification of multiple short-lived fission product lanthanide isotopes from a fission product sample produced from the thermal irradiation of highly enriched uranium. The separations were performed in parallel in quadruplicate with reproducible results and high decontamination factors for 153Sm, 156Eu, and 161Tb. Based on the results obtained here, the fission yields for 144Ce, 153Sm, 156Eu, and 161Tb are consistent with published fission yields. This work demonstrates the effectiveness of the separations for the intended application of short-lived lanthanide fission product analysis requiring high decontamination factors.

THE IDENTIFICATION AND HALF LIVES OF FISSION-PRODUCT Rb92 AND Rb93

1960 ◽  
Vol 38 (12) ◽  
pp. 1614-1622 ◽  
Author(s):  
K. Fritze ◽  
T. J. Kennett
Keyword(s):  
Fission Product ◽  
Decay Rate ◽  
Half Life ◽  
Fission Products ◽  
Strontium Isotopes ◽  
A Value ◽  
Γ Ray ◽  
Rubidium Isotopes

The existence of two new rubidium isotopes, Rb92 and Rb93, has been established and their half lives measured. The half lives of these short-lived fission products were determined using a technique of timed precipitations. The values obtained for Rb92 and Rb93 were 5.3 ± 0.5 sec and 5.6 ± 0.5 sec respectively. The half lives of the strontium and yttrium daughters were also determined. The strontium isotopes were studied by observing the decay rate of a characteristic γ-ray peak. For Sr92, the decay of the 1.37-Mev line gave a value of 2.71 ± 0.02 hr. A γ-ray peak at 590 kev, which was found to be associated with Sr93, decayed with a half life of 7.54 ± 0.06 min. The half lives of the yttrium daughters were determined by β counting. The values found for Y92 and Y93 were 3.53 ± 0.02 hr and 10.1 ± 0.1 hr respectively.

scholarly journals A Safety Re-Evaluation of the AVR Pebble Bed Reactor Operation and Its Consequences for Future HTR Concepts

2008 ◽  
Author(s):  
Rainer Moormann
Keyword(s):  
Fission Product ◽  
End Of Life ◽  
Fission Products ◽  
Normal Operation ◽  
Primary Circuit ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Hot Gas ◽  
Design Basis ◽  
Gas Tight

The AVR pebble bed reactor (46 MWth) was operated 1967–1988 at coolant outlet temperatures up to 990°C. Also because of a lack of other experience the AVR operation is a basis for future HTRs. This paper deals with insufficiently published unresolved safety problems of AVR and of pebble bed HTRs. The AVR primary circuit is heavily contaminated with dust bound and mobile metallic fission products (Sr-90, Cs-137) which create problems in current dismantling. The evaluation of fission product deposition experiments indicates that the end of life contamination reached several percent of a single core inventory. A re-evaluation of the AVR contamination is performed in order to quantify consequences for future HTRs: The AVR contamination was mainly caused by inadmissible high core temperatures, and not — as presumed in the past — by inadequate fuel quality only. The high AVR core temperatures were detected not earlier than one year before final AVR shut-down, because a pebble bed core cannot be equipped with instruments. The maximum core temperatures were more than 200 K higher than precalculated. Further, azimuthal temperature differences at the active core margin were observed, as unpredictable hot gas currents with temperatures > 1100°C. Despite of remarkable effort these problems are not yet understood. Having the black box character of the AVR core in mind it remains uncertain whether convincing explanations can be found without major experimental R&D. After detection of the inadmissible core temperatures, the AVR hot gas temperatures were strongly reduced for safety reasons. Metallic fission products diffuse in fuel kernel, coatings and graphite and their break through takes place in long term normal operation, if fission product specific temperature limits are exceeded. This is an unresolved weak point of HTRs in contrast to other reactors and is particularly problematic in pebble bed systems with their large dust content. Another disadvantage, responsible for the pronounced AVR contamination, lies in the fact that activity released from fuel elements is distributed in HTRs all over the coolant circuit surfaces and on graphitic dust and accumulates there. Consequences of AVR experience on future reactors are discussed. As long as pebble bed intrinsic reasons for the high AVR temperatures cannot be excluded they have to be conservatively considered in operation and design basis accidents. For an HTR of 400 MWth, 900°C hot gas temperature, modern fuel and 32 fpy the contaminations are expected to approach at least the same order as in AVR end of life. This creates major problems in design basis accidents, for maintenance and dismantling. Application of German dose criteria on advanced pebble bed reactors leads to the conclusion that a pebble bed HTR needs a gas tight containment even if inadmissible high temperatures as observed in AVR are not considered. However, a gas tight containment does not diminish the consequences of the primary circuit contamination on maintenance and dismantling. Thus complementary measures are discussed. A reduction of demands on future reactors (hot gas temperatures, fuel burn-up) is one option; another one is an elaborate R&D program for solution of unresolved problems related to operation and design basis accidents. These problems are listed in the paper.

scholarly journals Np-237 incineration study in various beams in ADS setup QUINTA

Nukleonika ◽  
2018 ◽  
Vol 63 (1) ◽  
pp. 17-22 ◽  
Author(s):  
Stanisław Kilim ◽  
Elżbieta Strugalska-Gola ◽  
Marcin Szuta ◽  
Marcin Bielewicz ◽  
Sergej I. Tyutyunnikov ◽  
...  
Keyword(s):  
Fission Product ◽  
Proton Beam ◽  
Neutron Capture ◽  
Gamma Ray ◽  
Fission Products ◽  
Neutron Field ◽  
Gamma Ray Spectrometry ◽  
Driven System ◽  
Accelerator Driven System

Abstract Neptunium-237 samples were irradiated in a spallation neutron field produced in accelerator-driven system (ADS) setup QUINTA. Five experiments were carried out on the accelerators at the JINR in Dubna - one in carbon (C6+), three in deuteron, and one in a proton beam. The energy in carbon was 24 GeV, in deuteron 2, 4 and 8 GeV, respectively, and 660 MeV in the proton beam. The incineration study method was based on gamma-ray spectrometry. During the analysis of the spectra several fission products and one actinide were identified. Fission product activities yielded the number of fissions. The actinide (Np-238), a result of neutron capture by Np-237, yielded the number of captures. The main goal of this work was to find out if and how the incineration rate depended on parameters of the accelerator beam.

scholarly journals Fission Product Yield Measurements from Neutron-Induced Fission of 235,238 U and 239Pu

2020 ◽  
Vol 232 ◽  
pp. 03006
Author(s):  
M. A. Stoyer ◽  
A. P. Tonchev ◽  
J. A. Silano ◽  
M. E. Gooden ◽  
J. B. Wilhelmy ◽  
...  
Keyword(s):  
Fission Product ◽  
Nuclear Physics ◽  
Fission Products ◽  
Product Yield ◽  
Tandem Accelerator ◽  
Precision Data ◽  
High Precision Data ◽  
Induced Fission ◽  
The Impact ◽  
Fission Yields

Fission product yields (FPY) are one of the most fundamental quantities that can be measured for a fissioning nucleus and are important for basic and applied nuclear physics. Recent measurements using mono-energetic and pulsed neutron beams generated using Triangle Universities Nuclear Laboratory’s tandem accelerator and employing a dual fission chamber setup have produced self-consistent, high-precision data critical for testing fission models for the neutron-induced fission of 235,238U and 239Pu between neutron energies of 0.5 to 15.0 MeV. These data have elucidated a low-energy dependence of FPY for several fission products using irradiations of varying lengths and neutron energies. This paper will discuss new measurements just beginning utilizing a RApid Belt-driven Irradiated Target Transfer System (RABITTS) to measure shorterlived fission products and the time dependence of fission yields, expanding the measurements from cumulative towards independent fission yields. The uniqueness of these FPY data and the impact on the development of fission theory will be discussed.

Effect of Americium and Simulated Fission Products Addition on Oxygen Potential of Uranium-Plutonium Mixed Oxide Fuels

2009 ◽  
Vol 1215 ◽  
Author(s):  
Kosuke Tanaka ◽  
Masahiko Osaka ◽  
Ken Kurosaki ◽  
Hiroaki Muta ◽  
Masayoshi Uno ◽  
...  
Keyword(s):  
Thermogravimetric Analysis ◽  
Fission Product ◽  
Mixed Oxide ◽  
Oxygen Potential ◽  
Fission Products ◽  
Mox Fuel ◽  
Uranium Plutonium

AbstractThe oxygen potentials at 1273 K of mixed oxide (MOX) fuels with Am and 26 kinds of fission product elements (FPs), simulating low-decontaminated MOX fuel and high burn-up of up to 250 GWd/t, have been measured by using thermogravimetric analysis (TGA). The oxygen potentials for simulated low-decontaminated MOX fuels were higher than the fuels without FPs and increased with increasing simulated burn-up.

CORBA AND MPI-BASED “BACKBONE” FOR COUPLING ADVANCED SIMULATION TOOLS

2014 ◽  
Vol 3 (2) ◽  
pp. 83-90 ◽  
Author(s):  
M. Seydaliev ◽  
D. Caswell
Keyword(s):  
Fission Product ◽  
Computer Simulations ◽  
Message Passing ◽  
Message Passing Interface ◽  
Nuclear Reactor ◽  
Atmospheric Dispersion ◽  
Safety Analysis ◽  
Severe Accident ◽  
Nuclear Reactor Safety ◽  
Exchange Data

There is a growing international interest in using coupled, multidisciplinary computer simulations for a variety of purposes, including nuclear reactor safety analysis. Reactor behaviour can be modeled using a suite of computer programs simulating phenomena or predicting parameters that can be categorized into disciplines such as Thermalhydraulics, Neutronics, Fuel, Fuel Channels, Fission Product Release and Transport, Containment and Atmospheric Dispersion, and Severe Accident Analysis. Traditionally, simulations used for safety analysis individually addressed only the behaviour within a single discipline, based upon static input data from other simulation programs. The limitation of using a suite of stand-alone simulations is that phenomenological interdependencies or temporal feedback between the parameters calculated within individual simulations cannot be adequately captured. To remove this shortcoming, multiple computer simulations for different disciplines must exchange data during runtime to address these interdependencies. This article describes the concept of a new framework, which we refer to as the “Backbone,” to provide the necessary runtime exchange of data. The Backbone, currently under development at AECL for a preliminary feasibility study, is a hybrid design using features taken from the Common Object Request Broker Architecture (CORBA), a standard defined by the Object Management Group, and the Message Passing Interface (MPI), a standard developed by a group of researchers from academia and industry. Both have well-tested and efficient implementations, including some that are freely available under the GNU public licenses. The CORBA component enables individual programs written in different languages and running on different platforms within a network to exchange data with each other, thus behaving like a single application. MPI provides the process-to-process intercommunication between these programs. This paper outlines the different CORBA and MPI configurations examined to date, as well as the preliminary configuration selected for coupling 2 existing safety analysis programs used for modeling thermal–mechanical fuel behavior and fission product behavior respectively. In addition, preliminary work in hosting both the Backbone and the associated safety analysis programs in a cluster environment are discussed.

Implementation of A Gibbs Energy Minimizer In A Fission-Product Release Computer Program

2013 ◽  
Vol 2 (1) ◽  
pp. 39-48
Author(s):  
D.H. Barber
Keyword(s):  
Computer Program ◽  
Fission Product ◽  
Nuclear Physics ◽  
Noble Gas ◽  
Safety Margin ◽  
Fission Products ◽  
Nuclear Accidents ◽  
The Public ◽  
Product Release ◽  
Core Cooling

SOURCE 2.0 is the Canadian computer program for calculating fractional release of fission products from the UO2 fuel matrix. In nuclear accidents, fission-product release from fuel is one of the physical steps required before radiation dose from fission products can affect the public. Fission-product release calculations are a step in the analysis path to calculating dose consequences to the public from postulated nuclear accidents. SOURCE 2.0 contains a 1997 model of fission-product vaporization by B.J. Corse et al. based on lookup tables generated with the FACT computer program. That model was tractable on computers of that day. However, the understanding of fuel thermochemistry has advanced since that time. Additionally, computational resources have significantly improved since the time of the development of the Corse model and now allow incorporation of the more-rigorous thermodynamic treatment. Combining the newer Royal Military College of Canada (RMC) thermodynamic model of irradiated uranium dioxide fuel, a new model for fission-product vaporization from the fuel surface, a commercial user-callable thermodynamics subroutine library (ChemApp), an updated nuclide list, and updated nuclear physics data, a prototype computer program based on SOURCE IST 2.0P11 has been created that performs thermodynamic calculations internally. The resulting prototype code (with updated and revised data) provides estimates of 140La releases that are in better agreement with experiments than the original code version and data. The improvement can be quantified by a reduction in the mean difference between experimental and calculated release fractions from 0.70 to 0.07. 140La is taken to be representative of “low-volatile” fission products. To ensure that the existing acceptable performance for noble gases and volatile fission products is not adversely affected by the changes, comparisons were also made for a representative noble gas, 85Kr, and a representative volatile fission-product, 134Cs. These nuclides have the largest dataset in the SOURCE 2.0 validation test suite. This improvement provides increased confidence in the safety margin for equipment qualification in Loss-of-Coolant Accidents with Loss of Emergency Core Cooling.

Characterization of the influence of fission product doping on the anodic reactivity of uranium dioxide

2007 ◽  
Vol 85 (10) ◽  
pp. 702-713 ◽  
Author(s):  
Heming He ◽  
Peter G Keech ◽  
Michael E Broczkowski ◽  
James J Noël ◽  
David W Shoesmith
Keyword(s):  
Raman Spectroscopy ◽  
Fission Product ◽  
Uranium Dioxide ◽  
Photoelectron Spectroscopy ◽  
Fission Products ◽  
Nuclear Fission ◽  
Lattice Contraction ◽  
Cubic Symmetry ◽  
X Ray ◽  
Dopant Level

The influence of fission product doping on the structure, composition, and electrochemical reactivity of uranium dioxide has been studied using X-ray diffractometry (XRD), scanning electron microscopy (SEM/EDX), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Experiments were conducted on SIMFUEL specimens with simulated burn-ups (increasing doping levels) of 1.5, 3.0, and 6.0 atom%. As the dopant level increased, the lattice contracted, suggesting the dominant formation of dopant-oxygen vacancy clusters. The smaller than expected lattice contraction can be attributed to the segregation of Zr (one of eleven added dopants) to ABO3 perovskite-type phases that SEM/EDX shows also contain Ba, Ce, and possibly some U. Raman spectroscopy shows that doping leads to a loss of cubic symmetry, possibly associated with tetragonal distortions. Raman mapping confirms this loss of cubic symmetry and suggests the specimen is not uniformly doped. Electrochemical experiments show that these distortions lead to a decrease in the oxidative dissolution rate of the UO2 with increased doping density.Key words: UO2, X-ray diffraction, electrochemistry, Raman spectroscopy, nuclear fission products.

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