scholarly journals Fission fragments observables measured at the LOHENGRIN spectrometer

2020 ◽  
Vol 239 ◽  
pp. 05017
Author(s):  
S. Julien-Laferrière ◽  
L. Thombansen ◽  
G. Kessedjian ◽  
A. Chebboubi ◽  
O. Serot ◽  
...  
Keyword(s):  
Neutron Emission ◽  
Evaluation Process ◽  
Nuclear Data ◽  
Nuclear Fission ◽  
Experimental Program ◽  
Spent Fuel ◽  
Ionic Charge ◽  
Fission Fragments ◽  
Common Effort ◽  
Fission Yields

Nuclear fission yields are key data for reactor studies, such as spent fuel inventory or decay heat, and for understanding fission process. Despite a significant effort allocated to measure fission yields during the last decades, the recent evaluated libraries still need improvements in particular in the reduction of the uncertainties. Moreover, some discrepancies between these libraries must be explained. Additional measurements provide complementary information and estimations of experimental correlations, and new kinds of measurements enable to test the models used during the nuclear data evaluation process. A common effort by the CEA, the LPSC and the ILL aims at tackling these issues by providing precise measurements of isotopic and isobaric fission yields with the related variance-covariance matrices. Additionally, the experimental program involves a large range of observables requested by the evaluations, such as kinetic energy dependency of isotopic yields and odd-even effect in order to test the sharing of total excitation energy and the spin generation mechanism. Another example is the complete range of isotopic distribution per mass that allows the determination of the charge polarization, which has to be consistent for complementary masses (pre-neutron emission). For instance, this information is the key observable for the evaluation of isotopic yields. Finally, ionic charge distributions are indirect measurements of nanosecond isomeric ratios as a probe of the nuclear de-excitation path in the (E*, J, π) representation. Measurements for thermal neutron induced fission of 241 Pu have been carried out at the ILL in Grenoble, using the LOHENGRIN mass spectrometer. Methods, results and comparison to models calculations will be presented corresponding to a status on fission fragments observables reachable with this facility.

scholarly journals Status of fission fragment observables measured with the LOHENGRIN spectrometer

2019 ◽  
Vol 211 ◽  
pp. 04004 ◽  
Author(s):  
S. Julien-Laferrière ◽  
L. Thombansen ◽  
G. Kessedjian ◽  
A. Chebboubi ◽  
O. Serot ◽  
...  
Keyword(s):  
Fission Fragment ◽  
Isomeric Ratio ◽  
Nuclear Data ◽  
Nuclear Fission ◽  
Experimental Program ◽  
Spent Fuel ◽  
Reactor Physics ◽  
Model Calculations ◽  
Common Effort ◽  
Fission Yields

Nuclear fission yields are key parameters to evaluate reactor physics observables, such as fuel inventory, decay heat, spent fuel radiotoxicity, criticality but also for understanding the fission process. Despite a significant effort allocated to measure fission yields during the last decades, the recent evaluated libraries still need improvements in particular in the description of the uncertainties with the associated correlations. Additional kinds of measurements provide complementary information in order to test the models used in the nuclear data evaluation. Moreover, some discrepancies between these libraries must be explained. A common effort by the CEA, the LPSC and the ILL aims at tackling these issues by providing precise measurement of isotopic and isobaric fission yields with the related variance-covariance matrices. Nevertheless, the experimental program represents itself a large range of observables requested by the evaluations: isotopic yields, nuclear charge polarization, odd-even effect, isomeric ratio and their dependency with fission fragment kinetic energy as a probe of the nuclear de-excitation path in the (E*, Jπ) representation. Measurements for thermal neutron induced fission of 241Pu have been carried out at the Institut Laue Langevin using the LOHENGRIN mass spectrometer. Experimental program, observables reachable, results and comparison to model calculations are shown.

ELISe: A NEW FACILITY FOR UNPRECEDENTED EXPERIMENTAL NUCLEAR FISSION STUDIES

2009 ◽  
Vol 18 (04) ◽  
pp. 767-772 ◽  
Author(s):  
J. TAIEB ◽  
G. BELIER ◽  
A. CHATILLON ◽  
T. GRANIER ◽  
A. KELIC ◽  
...  
Keyword(s):  
Inverse Kinematics ◽  
Total Mass ◽  
Nuclear Fission ◽  
Experimental Program ◽  
Fission Process ◽  
Fission Fragments ◽  
Charge Resolution ◽  
New Facility

A novel experimental program aiming to study the properties of fragments and neutrons emitted in the fission process has been initiated. The experiment will be held at the ELISe electron-ion collider to be constructed at GSI, Darmstadt in the framework of the FAIR extension of the facility. The experiment will take advantage of the inverse kinematics allowing, in particular, a total mass and charge resolution for all fission fragments.

Field Examples of Waste Assay Solutions for Curium-Contaminated Wastes

2009 ◽  
Author(s):  
Patrick M. J. Chard ◽  
Stephen Croft ◽  
Ian G. Hutchinson ◽  
Tom W. Turner ◽  
Ann Ross ◽  
...  
Keyword(s):  
Spontaneous Fission ◽  
Neutron Emission ◽  
Nuclear Data ◽  
Fission Neutron ◽  
Nuclear Material ◽  
Spent Fuel ◽  
Coincidence Counting ◽  
Plant Operations ◽  
Technical Solutions

Passive neutron coincidence counting is a mature technique for the assay of Pu in nuclear material. It is widely deployed in safeguards and waste inventory verification applications. The presence of 242Cm and 244Cm in spent fuel wastes, often poses a severe challenge owing to the relatively short spontaneous fission half-life for these isotopes and the subsequent prolific spontaneous fission neutron emission. This is a well documented problem, compounded by the fact that for most waste assay applications, neutron assay techniques are not capable of distinguishing between these Cm isotopes and the even isotopes of Pu, which are normally of interest in waste assay applications. Therefore the presence of even small quantities of these isotopes can result in gross over-estimation of the Pu inventory, if an appropriate correction is not made. Previous theoretical studies carried out recently have illustrated the potential magnitude of the problem, with reference to the fundamental nuclear data and typical isotopic compositions of wastes. Neutron multiplicity counting can, in principle, differentiate between isotopes that undergo spontaneous fission, however in practice the uncertainties in waste assay are such that this is rarely beneficial. More practical “compensation” techniques use combinations of different assay techniques (for example passive and active neutron counting) and knowledge of the actinide ratios in the waste stream fingerprint. In this paper we describe various waste assay applications as case studies. For each example we describe the nature of the challenge and show how solutions have been developed for applications where the presence of curium has caused problems. We describe the technical solutions, showing the limitations and assumptions of each. We also emphasise the role of robust Quality Assurance procedures, to ensure that the techniques are implemented reliably and with predictable outcomes. Finally, we describe the benefits that have been realised for the plant operations teams, with regard to improved measurement accuracy, avoidance of false over-estimation of the Pu inventory and subsequent improvement in plant throughput.

INDEPENDENT YIELDS OF 124Sb AND 126sb IN THERMAL NEUTRON INDUCED FISSION AND THEIR IMPLICATION ON THE EMPIRICAL Zp FUNCTION

1965 ◽  
Vol 43 (9) ◽  
pp. 2493-2507 ◽  
Author(s):  
P. O. Strom ◽  
G. R. Grant ◽  
A. C. Pappas
Keyword(s):  
Thermal Neutron ◽  
Charge Distribution ◽  
Distribution Curve ◽  
Neutron Emission ◽  
Shell Effect ◽  
Shell Effects ◽  
Fission Fragments ◽  
Induced Fission ◽  
Fission Yields ◽  
Proton Shell

The independent fission yields in thermal neutron induced fission of 235U have been measured to be (9.5 ± 1.4)•10−6% and (1.04 ± 0.17)•10−3% for 124gSb and 126gSb, respectively. The total independent yields for all isomers of these nuclides are estimated to be (1.2 ± 0.2)•10−5% for 124Sb and (3.7 ± 0.6)•10−3% for 126Sb using a Huizenga–Vandenbosch approach for estimating population of isomeric states.These data do not seem to support a 50 proton shell effect on the Zp function, using the "unique" charge distribution curve of Wahl. A revised Wahl plot based on recent information on neutron emission from individual fission fragments is given and discussed in view of shell effects in fission. It is shown that the effect of the Zp function of the 50 proton shell is very small.

scholarly journals Data assimilation of post-irradiation examination data for fission yields from GEF

2020 ◽  
Vol 6 ◽  
pp. 52
Author(s):  
Daniel Siefman ◽  
Mathieu Hursin ◽  
Henrik Sjostrand ◽  
Georg Schnabel ◽  
Dimitri Rochman ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Marginal Likelihood ◽  
Fission Products ◽  
Nuclear Data ◽  
Optimization Method ◽  
Model Parameters ◽  
Spent Fuel ◽  
Post Irradiation ◽  
Relative Standard ◽  
Fission Yields

Nuclear data, especially fission yields, create uncertainties in the predicted concentrations of fission products in spent fuel which can exceed engineering target accuracies. Herein, we present a new framework that extends data assimilation methods to burnup simulations by using post-irradiation examination experiments. The adjusted fission yields lowered the bias and reduced the uncertainty of the simulations. Our approach adjusts the model parameters of the code GEF. We compare the BFMC and MOCABA approaches to data assimilation, focusing especially on the effects of the non-normality of GEF’s fission yields. In the application that we present, the best data assimilation framework decreased the average bias of the simulations from 26% to 14%. The average relative standard deviation decreased from 21% to 14%. The GEF fission yields after data assimilation agreed better with those in JEFF3.3. For Pu-239 thermal fission, the average relative difference from JEFF3.3 was 16% before data assimilation and after it was 12%. For the standard deviations of the fission yields, GEF’s were 100% larger than JEFF3.3’s before data assimilation and after were only 4% larger. The inconsistency of the integral data had an important effect on MOCABA, as shown with the Marginal Likelihood Optimization method. When the method was not applied, MOCABA’s adjusted fission yields worsened the bias of the simulations by 30%. BFMC showed that it inherently accounted for this inconsistency. Applying Marginal Likelihood Optimization with BFMC gave a 2% lower bias compared to not applying it, but the results were more poorly converged.

Fission Products Particular Peak Measurement for UO2-Gd2O3-MOX γ-Scanning Renormalization in 100% MOX ABWR Mock-Up Cores

2004 ◽  
Author(s):  
P. Blaise ◽  
S. Cathalau ◽  
N. Thiollay ◽  
P. Fougeras ◽  
V. Laval ◽  
...  
Keyword(s):  
Radioactive Decay ◽  
Fission Products ◽  
Nuclear Data ◽  
Scaling Factor ◽  
Experimental Program ◽  
Fission Rate ◽  
Good Consistency ◽  
Different Sources ◽  
Fission Yields ◽  
Systematical Uncertainty

This paper presents the principles of the peak check measurements by gamma spectrometry. One details the main equations used for the analysis of the raw data as the calculation of the different sources of uncertainties and their propagation on the result. The method is illustrated with actual examples from the French-Japanese BASALA ABWR 100% MOX experimental program. • For each individual fission rate, the systematical uncertainty due to the radioactive decay data is smaller than the statistical uncertainty due to the counting process. • The main part of the final uncertainty on the scaling factor is brought by the systematical uncertainty on the average fission yields. This study enables to propose some recommendations for fission products and nuclear data evaluation used. • Only the analysis of the 140La peak at 1596 keV leads to acceptable uncertainties on the fission rate maps renormalization, with a good consistency with the integral γ-scanning results. • The JEF-2.2 evaluation on the fission yields and their associated uncertainties seems more realistic than the ENDF/B-6 and is recommended for the scaling factor analysis.

scholarly journals Data assimilation of post irradiation examination experiments to adjust fission yields

2020 ◽  
Vol 239 ◽  
pp. 13004
Author(s):  
Daniel Siefman ◽  
Mathieu Hursin ◽  
Andreas Pautz
Keyword(s):  
Data Assimilation ◽  
Fission Product ◽  
Fission Products ◽  
Nuclear Data ◽  
Relative Difference ◽  
Model Parameters ◽  
Spent Fuel ◽  
Post Irradiation ◽  
Relative Standard ◽  
Fission Yields

Nuclear data, especially fission yields, create uncertainties in the predicted concentrations of fission products in spent fuel. Herein, we present a new framework that extends data assimilation methods to burnup simulations by using data from post-irradiation examination experiments. The adjusted fission yields improve the bias and reduce the uncertainty of predicted fission product concentrations in spent fuel. Our approach modifies fission yields by adjusting the model parameters of the code GEF with post-irradiation examination experiments. We used the BFMC data assimilation method to account for the non-normality of GEF's fission yields. In the application that we present, the assimilation decreased the average bias of the predicted fission product concentrations from 26% to 15%. The average relative standard deviation decreased from 21% to 14%. The GEF fission yields after data assimilation agreed better with those in ENDF/B-VIII.O. For Pu-239 thermal fission, the average relative difference from ENDF/B-VIII.O was 16% before data assimilation and 11% after. For the standard deviations of the fission yields, GEF's were, on average, 16% larger than those from ENDF/B-VIII.O before data assimilation and 15% smaller after.

scholarly journals Velocity fluctuations of fission fragments

2016 ◽  
Vol 25 (02) ◽  
pp. 1650009
Author(s):  
Felipe J. Llanes-Estrada ◽  
Belén Martínez Carmona ◽  
Jose L. Muñoz Martínez
Keyword(s):  
Velocity Distribution ◽  
Potential Barrier ◽  
Neutron Emission ◽  
Nuclear Fission ◽  
Collective Variable ◽  
Effective Theory ◽  
Spectral Measurements ◽  
Velocity Fluctuations ◽  
Fission Fragments ◽  
Nuclear Temperature

We propose event by event velocity fluctuations of nuclear fission fragments as an additional interesting observable that gives access to the nuclear temperature in an independent way from spectral measurements and relates the diffusion and friction coefficients for the relative fragment coordinate in Kramers-like models (in which some aspects of fission can be understood as the diffusion of a collective variable through a potential barrier). We point out that neutron emission by the heavy fragments can be treated in effective theory if corrections to the velocity distribution are needed.

scholarly journals Prompt fission neutron emission in the reaction 235U(n,f)

2018 ◽  
Vol 169 ◽  
pp. 00004 ◽  
Author(s):  
Alf Göök ◽  
Franz-Josef Hambsch ◽  
Stephan Oberstedt
Keyword(s):  
Fission Fragment ◽  
Ionization Chamber ◽  
Neutron Emission ◽  
Nuclear Data ◽  
Fission Neutron ◽  
Fission Fragments ◽  
Position Sensitive ◽  
Prompt Fission ◽  
Prompt Fission Neutron ◽  
Reaction 235U

Experimental activities at JRC-Geel on prompt fission neutron (PFN) emission in response to OECD/NEA nuclear data requests are presented in this contribution. Specifically, on-going investigations of PFN emission from the reaction 235U(n,f) in the region of the resolved resonances, taking place at the GELINA facility, are presented. The focus of this contribution lies on studies of PFN correlations with fission fragment properties. The experiment employs a scintillation detector array for neutron detection, while fission fragment properties are determined via the double kinetic energy technique using a position sensitive twin ionization chamber. This setup allows us to study several correlations between properties of neutron and fission fragments simultaneously. Results on PFN correlations with fission fragment properties from the present study differ significantly from earlier studies on this reaction, induced by thermal neutrons.

scholarly journals High-precision measurement of isotopic fission yields of 236U*

2018 ◽  
Vol 193 ◽  
pp. 02001
Author(s):  
L. Audouin ◽  
J. Taieb ◽  
A. Chatillon ◽  
L. Grente ◽  
G. Boutoux ◽  
...  
Keyword(s):  
High Precision ◽  
Precision Measurement ◽  
Inverse Kinematics ◽  
Nuclear Data ◽  
Secondary Beam ◽  
High Precision Measurement ◽  
Fission Fragments ◽  
Data Libraries ◽  
Nuclear Data Libraries ◽  
Fission Yields

We report on the second SOFIA experiment, dedicated to the fission yields of 236U*, analog to 235U(n,f). The measurement is based on the inverse kinematics method, using a relativistic, secondary beam of 236U. Both fission fragments are identified in mass and charge in the SOFIA recoil spectrometer. The obtained isotopic yields are compared with existing spectroscopy measurements and the elemental yields are used to discuss the treatment of the even-odd effect with energy in nuclear data libraries.

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