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Journal Articles

Measurement of the $^{235}$ U(n, f) cross section relative to the $^{6}$ Li(n, t) and $^{10}$ B(n, ) standards from thermal to 170 keV neutron energy range at n_TOF

Amaducci, S.*; Harada, Hideo; Kimura, Atsushi; 118 of others*

European Physical Journal A, 55(7), p.120_1 - 120_19, 2019/07

https://doi.org/10.1140/epja/i2019-12802-7

Times Cited Count：22 Percentile：90.38(Physics, Nuclear)

The $^{235}$ U(n, f) cross section was measured at n_TOF relative to $^{6}$ Li(n, t) and $^{10}$ B(n, ), in a wide energy range (25 meV170 keV) with 1.5% systematic uncertainty, making use of a stack of six samples and six silicon detectors placed in the neutron beam. The present results indicate that the cross section in the 918 keV neutron energy range is indeed overestimated by almost 5% in the recently released evaluated data files ENDF/B-VIII.0 and JEFF3.3. Furthermore, these new high-resolution data confirm the existence of resonance-like structures in the keV neutron energy region. From the present data, a value of 249.71.4(stat)0.94(syst) b eV has been extracted for the cross section integral between 7.8 and 11 eV, confirming the value of 247.53 b eV recently established as a standard.

Journal Articles

Benchmark tests of newly-evaluated data of $^{235}$ U for CIELO project using integral experiments of uranium-fueled FCA assemblies

Fukushima, Masahiro; Kitamura, Yasunori*; Yokoyama, Kenji; Iwamoto, Osamu; Nagaya, Yasunobu; Leal, L. C.*

Proceedings of International Conference on the Physics of Reactors; Unifying Theory and Experiments in the 21st Century (PHYSOR 2016) (USB Flash Drive), p.605 - 619, 2016/05

A nuclear data of $^{235}$ U has been recently evaluated for the CIELO (Collaborative International Evaluated Library Organization) project. We tested the newly-evaluated data of $^{235}$ U using integral experiments of the Fast Critical Assembly (FCA) performed at JAEA. We selected two integral data of uranium-fueled FCA assemblies; one is the sodium-void reactivity worth of FCA XXVII-1 assembly and the other is the criticalities of the seven assemblies of FCA IX. The benchmark tests support the evaluation done in the resonance regions. However, the $^{235}$ U capture cross section above the unresolved resonance range needs further investigation.

JAEA Reports

Evaluation of covariances for resolved resonance parameters of $^{235}$ U, $^{238}$ U, and $^{239}$ Pu in JENDL-3.2

Kawano, Toshihiko*; Shibata, Keiichi

JAERI-Research 2003-001, 36 Pages, 2003/02

JAERI-Research-2003-001.pdf:1.67MB

Evaluation of covariances for resolved resonance parameters of $^{235}U$ , $^{238}U$ , and $^{239}Pu$ was carried out. Although a large number of resolved resonances are observed for major actinides, uncertainties in averaged cross sections are more important than those in resonance parameters in reactor calculations. We developed a simple method which is to provide a covariance matrix for the resolved resonance parameters on the basis of uncertainties in the averaged cross sections. The method was adopted to evaluate the covariance data for some important actinides, and the results were compiled in the JENDL-3.2 covariance file.

JAEA Reports

Neutron and proton nuclear data evaluation for $^{235}$ U and $^{238}$ U at energies up to 250 MeV

Konobeyev, A. Y.; Fukahori, Tokio; Iwamoto, Osamu

JAERI-Research 2002-028, 69 Pages, 2002/12

JAERI-Research-2002-028.pdf:1.93MB

Basic features of nuclear data evaluation for uranium isotopes $^{235}$ U and 238U at intermediate energies are described. The coupled channel optical model was used to obtain total cross section, reaction cross section, angular distributions and transmission coefficients. The direct, pre-compound and evaporation models were used to describe neutron and charged particles emission from excited nuclei. The neutron data evaluated were combined with JENDL-3.3 data below 20 MeV to obtain a full data set in the whole energy range between 10 $^{-5}$ eV and 250 MeV. Evaluation of the proton data has been done at energies from 1 to 250 MeV

Journal Articles

Uncertainty analyses in the resolved resonance region of $^{235}U$ , $^{238}U$ , and $^{239}Pu$ with the Reich-Moore -matrix theory for JENDL-3.2

Kawano, Toshihiko*; Shibata, Keiichi

Journal of Nuclear Science and Technology, 39(8), p.807 - 815, 2002/08

https://doi.org/10.3327/jnst.39.807

Times Cited Count：6 Percentile：39.54(Nuclear Science & Technology)

A simple method to estimate covariances for resolved resonance parameters was developed. Although a large number of resolved resonances are observed for major actinides, uncertainties in averaged cross sections are more important than those in resonance parameters in reactor calculations. The method developed here is to derive a covariance matrix for the resolved resonance parameters which gives an appropriate uncertainty of the averaged cross sections. The method was adopted to evaluate the covariance data for $^{235}U$ , $^{238}U$ , and $^{239}Pu$ resonance parameters in JENDL-3.2,with the Reich-Moore R-matrix formula.

JAEA Reports