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Journal Articles

An Estimation method for an unknown covariance in cross-section adjustment based on unbiased and consistent estimator

Maruyama, Shuhei; Endo, Tomohiro*; Yamamoto, Akio*

Journal of Nuclear Science and Technology, 60(11), p.1372 - 1385, 2023/11

Journal Articles

Covariance of resonance parameters ascribed to systematic uncertainties in experiments

Endo, Shunsuke; Kimura, Atsushi; Nakamura, Shoji; Iwamoto, Osamu; Iwamoto, Nobuyuki; Rovira Leveroni, G.

EPJ Web of Conferences, 281, p.00012_1 - 00012_5, 2023/03

Journal Articles

Great achievements of M. Salvatores for nuclear data adjustment study with use of integral experiments

Yokoyama, Kenji; Ishikawa, Makoto*

Annals of Nuclear Energy, 154, p.108100_1 - 108100_11, 2021/05

 Times Cited Count:1 Percentile:19.33(Nuclear Science & Technology)

In the design of innovative nuclear reactors such as fast reactors, the improvement of the prediction accuracies for neutronics properties is an important task. The nuclear data adjustment is a promising methodology for this issue. The idea of the nuclear data adjustment was first proposed in 1964. Toward its practical application, however, a great deal of study has been conducted over a long time. While it took about 10 years to establish the theoretical formulation, the research and development for its practical application has been conducted for more than half a century. Researches in this field are still active, and the fact suggests that the improvement of the prediction accuracies is indispensable for the development of new types of nuclear reactors. Massimo Salvatores, who passed away in March 2020, was one of the first proposers to develop the nuclear data adjustment technique, as well as one of the great contributors to its practical application. Reviewing his long-time works in this area is almost the same as reviewing the history of the nuclear data adjustment methodology. The authors intend that this review would suggest what should be done in the future toward the next development in this area. The present review consists of two parts: a) the establishment of the nuclear data adjustment methodology and b) the achievements related to practical applications. Furthermore, the former is divided into two aspects: the study on the nuclear data adjustment theory and the numerical solution for sensitivity coefficient that is requisite for the nuclear data adjustment. The latter is separated to three categories: the use of integral experimental data, the uncertainty quantification and design target accuracy evaluation, and the promotion of nuclear data covariance development.

Journal Articles

Estimation method of systematic uncertainties in Monte Carlo particle transport simulation based on analysis of variance

Hashimoto, Shintaro; Sato, Tatsuhiko

Journal of Nuclear Science and Technology, 56(4), p.345 - 354, 2019/04

 Times Cited Count:4 Percentile:43.56(Nuclear Science & Technology)

Particle transport simulations based on the Monte Carlo method have been applied to shielding calculations. Estimation of not only statistical uncertainty related to the number of trials but also systematic one induced by unclear physical quantities is required to confirm the reliability of calculated results. In this study, we applied a method based on analysis of variance to shielding calculations. We proposed random- and three-condition methods. The first one determines randomly the value of the unclear quantity, while the second one uses only three values: the default value, upper and lower limits. The systematic uncertainty can be estimated adequately by the random-condition method, though it needs the large computational cost. The three-condition method can provide almost the same estimate as the random-condition method when the effect of the variation is monotonic. We found criterion to confirm convergence of the systematic uncertainty as the number of trials increases.

Journal Articles

Comparative study on prediction accuracy improvement methods with the use of integral experiments for neutronic characteristics of fast reactors

Yokoyama, Kenji; Kitada, Takanori*

Proceedings of 2018 International Congress on Advances in Nuclear Power Plants (ICAPP 2018) (CD-ROM), p.1221 - 1230, 2018/04

no abstracts in English

Journal Articles

Dimension-reduced cross-section adjustment method based on minimum variance unbiased estimation

Yokoyama, Kenji; Yamamoto, Akio*; Kitada, Takanori*

Journal of Nuclear Science and Technology, 55(3), p.319 - 334, 2018/03

 Times Cited Count:8 Percentile:65.17(Nuclear Science & Technology)

A new formulation of the cross-section adjustment methodology with the dimensionality reduction technique has been derived. This new formulation is proposed as the dimension reduced cross-section adjustment method (DRCA). Since the derivation of DRCA is based on the minimum variance unbiased estimation (MVUE), an assumption of normal distribution is not required. The result of DRCA depends on a user-defined matrix that determines the dimension reduced feature subspace. We have examine three variations of DRCA, namely DRCA1, DRCA2, and DRCA3. Mathematical investigation and numerical verification have revealed that DRCA2 is equivalent to the currently widely used cross-section adjustment method. Moreover, DRCA3 is found to be identical to the cross-section adjustment method based on MVUE, which has been proposed in the previous study.

Journal Articles

Methods and approaches to provide feedback from nuclear and covariance data adjustment for improvement of nuclear data files

Palmiotti, G.*; Salvatores, M.*; Yokoyama, Kenji; Ishikawa, Makoto

NEA/NSC/R(2016)6 (Internet), 42 Pages, 2017/05

Journal Articles

Model verification and validation procedure for a neutronics design methodology of next generation fast reactors

Ohgama, Kazuya; Ikeda, Kazumi*; Ishikawa, Makoto; Kan, Taro*; Maruyama, Shuhei; Yokoyama, Kenji; Sugino, Kazuteru; Nagaya, Yasunobu; Oki, Shigeo

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 10 Pages, 2017/04

Journal Articles

An Integrated approach to source term uncertainty and sensitivity analysis for nuclear reactor severe accidents

Zheng, X.; Ito, Hiroto; Tamaki, Hitoshi; Maruyama, Yu

Journal of Nuclear Science and Technology, 53(3), p.333 - 344, 2016/03


 Times Cited Count:9 Percentile:66.04(Nuclear Science & Technology)

Journal Articles

Estimation of covariance matrices for nuclear data of $$^{237}Np$$, $$^{241}Am$$ and $$^{243}Am$$

Nakagawa, Tsuneo

Journal of Nuclear Science and Technology, 42(11), p.984 - 993, 2005/11

 Times Cited Count:9 Percentile:53.45(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Status of the JENDL project

Shibata, Keiichi; Nakagawa, Tsuneo; Fukahori, Tokio; Ichihara, Akira; Iwamoto, Osamu; Otsuka, Naohiko*; Katakura, Junichi

AIP Conference Proceedings 769, p.171 - 176, 2005/05

The presentation deals with the activities on JENDL. JENDL-4 is being developed as a general purpose library. This library will include charged-particle and photon induced reaction data as well as spontaneous fission data for a limited number of nuclei in addition to neutron induced reaction data. The maximum incident energy can be extended to higher values than 20 MeV depending on data needs. Key subjects are improvements of accuracy of minor actinide and FP data, evaluations of covariances and so on. Quality assurance is regarded as important for JENDL-4. As special purpose files, we released the JENDL High Energy File and Photonuclear Data File this year. For the development of ADS, the Actinide File is being made. Furthermore,covariance data for some nuclei are also evaluated for ADS. Nuclear model codes are developed in order to reflect recent advances in nuclear theory on data evalulations. For users' covenience, we are working on the development of the Combined System for Nuclear Data Utilization, Circulaiton and Transfer.

Journal Articles

Uncertainty analyses of neutron cross sections for $$^{235}$$U in the resonance region

Shibata, Keiichi

Journal of Nuclear Science and Technology, 42(1), p.130 - 133, 2005/01

 Times Cited Count:7 Percentile:45.17(Nuclear Science & Technology)

Covariances of neutron cross sections for $$^{235}$$U were evaluated in the resonance region to estimate the accuracy of various design calculations. Energy-averaged cross-section covariances were deduced from available measurements by using the least-square method. The data obtained were combined with the $$^{235}$$U data of JENDL-3.3 in order to complete uncertainty infomation required by users.

JAEA Reports

Evaluations of heavy nuclide data for JENDL-3.3

Kawano, Toshihiko*; Matsunobu, Hiroyuki*; Murata, Toru*; Zukeran, Atsushi*; Nakajima, Yutaka*; Kawai, Masayoshi*; Iwamoto, Osamu; Shibata, Keiichi; Nakagawa, Tsuneo; Osawa, Takaaki*; et al.

JAERI-Research 2003-026, 53 Pages, 2003/12


New evaluations of neutron nuclear data for Uranium, Plutonium, and Thorium isotopes which are essential for applications to nuclear technology were carried out for the Japanese Evaluated Nuclear Data Library, JENDL-3.3. The objectives of the current release of JENDL were to fix several problems which have been reported for the previous version, to improve the accuracy of the data, and to evaluate covariances for the important nuclides. Quantities in JENDL-3.2 were extensively re-evaluated or replaced by more reliable values. The heavy nuclide data in JENDL-3.3 were validated with several benchmark tests, and it was reported that the current release gave a good prediction of criticalities.

Journal Articles

3-D shielding calculation method for 1-MW JSNS

Maekawa, Fujio; Tamura, Masaya

Proceedings of ICANS-XVI, Volume 3, p.1051 - 1058, 2003/07

A three-dimensional (3-D) shielding calculation model for MCNPX was produced for shielding design of 1-MW JSNS. The model included simplified target-moderator-reflector assembly, helium-vessel and neutron beam extraction pipes, shutters, shield blocks, gaps and void spaces between these components, and so on, and could treat streaming effects precisely. The particle splitting and kill method with cell importance parameters was adopted as a variance reduction method. The cell importance parameters for such a large target station of about 15 m in diameter and 12 m in hight in which neutron fluxes attenuated more than 12 orders of magnitude could be determined appropriately by automated iteration calculations. This calculation procedure enabled detailed 3-D shielding design calculations for the whole target station in a short time, i.e., within 2 days, and contributed for progress of shielding designs of JSNS.

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


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.

Journal Articles

Evaluation of shutdown $$gamma$$-ray dose rates around the duct penetration by three-dimensional Monte Carlo decay $$gamma$$-ray transport calculation with variance reduction method

Sato, Satoshi; Iida, Hiromasa; Nishitani, Takeo

Journal of Nuclear Science and Technology, 39(11), p.1237 - 1246, 2002/11

 Times Cited Count:27 Percentile:83.49(Nuclear Science & Technology)

no abstracts in English

Journal Articles

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

Kawano, Toshihiko*; Shibata, Keiichi

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

 Times Cited Count:5 Percentile:34.78(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

JENDL Dosimetry File 99 (JENDL/D-99)

Kobayashi, Katsuhei*; Iguchi, Tetsuo*; Iwasaki, Shin*; Aoyama, Takafumi*; Shimakawa, Satoshi; Ikeda, Yujiro; Odano, Naoteru; Sakurai, Kiyoshi; Shibata, Keiichi; Nakagawa, Tsuneo; et al.

JAERI 1344, 133 Pages, 2002/01


The JENDL Dosimetry File 99 (JENDL/D-99) has been prepared for determinations of neutron flux/fluence and energy spectrum at specific neutron fields. This file contains data for 67 reactions with 47 nuclides. Cross sections for 33 major dosimetry reactions and their covariance data were simultaneously generated and the other 34 reaction data were mainly adopted from the first version, JENDL/D-91. The GMA code was mainly used for most of the evaluation procedures by referring the basic experimental data in EXFOR. The resultant data are given in the neutron energy region below 20 MeV in both of point-wise and group-wise files in the ENDF-6 format. In order to confirm reliability of the data, several integral tests have been carried out: comparison with the data in IRDF-90V2 and average cross sections measured in fission neutron fields, fast/thermal reactor spectra, DT neutron fields and Li(d,n) neutron fields. The contents of JENDL/D-99 and the results of the integral tests are described in this report. All of the dosimetry cross sections are shown in a graphical form in the Appendix.

Journal Articles

Core calculation of the JMTR using MCNP

Nagao, Yoshiharu

JAERI-Conf 2000-018, p.156 - 167, 2001/01

no abstracts in English

36 (Records 1-20 displayed on this page)