Reference database for photon strength functions

Goriely, S.*; Dimitriou, P.*; Wiedeking, M.*; Belgya, T.*; Firestone, R.*; Kopecky, J.*; Krtika, M.*; Plujko, V.*; Schwengner, R.*; Siem, S.*; et al.

European Physical Journal A, 55(10), p.172_1 - 172_52, 2019/10

https://doi.org/10.1140/epja/i2019-12840-1

3rd RCM on Updating the Photonuclear Data Library and Generating a Reference Database for Photon Strength Functions

Utsunomiya, Hiroaki*; Iwamoto, Nobuyuki; Kawano, Toshihiko*

Kaku Deta Nyusu (Internet), (122), p.26 - 32, 2019/02

http://www.aesj.or.jp/~ndd/ndnews/pdf122/No122-06.pdf

no abstracts in English

CIELO collaboration summary results; International evaluations of neutron reactions on uranium, plutonium, iron, oxygen and hydrogen

Chadwick, M. B.*; Capote, R.*; Trkov, A.*; Herman, M. W.*; Brown, D. A.*; Hale, G. M.*; Kahler, A. C.*; Talou, P.*; Plompen, A. J.*; Schillebeeckx, P.*; et al.

Nuclear Data Sheets, 148, p.189 - 213, 2018/02

https://doi.org/10.1016/j.nds.2018.02.003

The CIELO collaboration has studied neutron cross sections on nuclides that significantly impact criticality in nuclear facilities - U, U, Pu, Fe, O and H - with the aim of improving the accuracy of the data and resolving previous discrepancies in our understanding. This multi-laboratory pilot project, coordinated via the OECD/NEA Working Party on Evaluation Cooperation (WPEC) Subgroup 40 with support also from the IAEA, has motivated experimental and theoretical work and led to suites of new evaluated libraries that accurately reflect measured data and also perform well in integral simulations of criticality. This report summarizes our results and outlines plans for the next phase of this collaboration.

The CIELO collaboration; Progress in international evaluations of neutron reactions on Oxygen, Iron, Uranium and Plutonium

Chadwick, M. B.*; Capote, R.*; Trkov, A.*; Kahler, A. C.*; Herman, M. W.*; Brown, D. A.*; Hale, G. M.*; Pigni, M.*; Dunn, M.*; Leal, L.*; et al.

EPJ Web of Conferences, 146, p.02001_1 - 02001_9, 2017/09

https://doi.org/10.1051/epjconf/201714602001

The CIELO collaboration has studied neutron cross sections on nuclides (O, Fe, U and Pu) that significantly impact criticality in nuclear technologies with the aim of improving the accuracy of the data and resolving previous discrepancies in our understanding. This multi-laboratory pilot project, coordinated via the OECD/NEA Working Party on Evaluation Cooperation (WPEC) Subgroup 40 with support also from the IAEA, has motivated experimental and theoretical work and led to suites of new evaluated libraries that accurately reflect measured data and also perform well in integral simulations of criticality.

Toward advancement of nuclear data research in the resonance region

Kunieda, Satoshi; Shibata, Keiichi; Fukahori, Tokio; Kawano, Toshihiko*; Paris, M.*; Hale, G.*

JAEA-Conf 2015-003, p.33 - 38, 2016/03

https://doi.org/10.11484/jaea-conf-2015-003

We present recent progress of nuclear data evaluation method in the resolved resonance range. Our multi-channel R-matrix code now includes photon-channel and computational capability of charged-particle elastic scattering. We also present the physical constraint from the theory in the analysis of experimental data. Example analysis results are shown for Be and O compound system. Finally, perspectives are discussed toward the advancement of nuclear data in the resonance region including those for medium-heavy nuclei.

Estimation of neutron cross-sections for O up to 5.2 MeV through R-matrix analysis

Kunieda, Satoshi; Kawano, Toshihiko*; Paris, M.*; Hale, G. M.*; Shibata, Keiichi; Fukahori, Tokio

NEA/NSC/DOC(2014)13 (Internet), p.33 - 39, 2014/07

https://www.oecd-nea.org/science/docs/2014/nsc-doc2014-13.pdf#page=35

There still remain differences among measured data, which makes the evaluated cross-sections uncertain, and which consequently affects some integral calculation. O is one of the important nuclei in the nuclear application, but such kinds of issues appears in elastic-scattering and (n,) reaction cross-sections. Purpose of this study is to solve those issues as they are common concerns in the world. We present estimated cross sections and their covariance data which are "physically" constrained by the R-matrix theory. The differences between the estimated and the measured cross-sections will be also discussed.

The CIELO Collaboration; Neutron reactions on H, O, Fe, U, and Pu

Chadwick, M. B.*; Dupont, E.*; Bauge, E.*; Blokhin, A.*; Bouland, O.*; Brown, D. A.*; Capote, R.*; Carlson, A. D.*; Danon, Y.*; De Saint Jean, C.*; et al.

Nuclear Data Sheets, 118, p.1 - 25, 2014/04

https://doi.org/10.1016/j.nds.2014.04.002

CIELO (Collaborative International Evaluated Library Organization) provides a new working paradigm to facilitate evaluated nuclear reaction data advances. It brings together experts from across the international nuclear reaction data community to identify and document discrepancies among existing evaluated data libraries, measured data, and model calculation interpretations, and aims to make progress in reconciling these discrepancies to create more accurate ENDF-formatted files. The focus will initially be on a small number of the highest-priority isotopes, namely H, O, Fe, U, and Pu. This paper identifies discrepancies between various evaluations of the highest priority isotopes. The evaluated data for these materials in the existing nuclear data libraries are reviewed, and some integral properties are given. The paper summarizes a program of nuclear science and computational work needed to create the new CIELO nuclear data evaluations.

Clustering pre-equilibrium model analysis for nucleon-induced alpha-particle spectra up to 200 MeV

Kunieda, Satoshi; Kawano, Toshihiko*; Chadwick, M. B.*; Fukahori, Tokio; Watanabe, Yukinobu*

EPJ Web of Conferences, 21, p.09003_1 - 09003_8, 2012/02

https://doi.org/10.1051/epjconf/20122109003

The clustering exciton model of Iwamoto and Harada is applied to the analysis of pre-equilibrium energy spectra for medium-to-heavy nuclei up to 200 MeV. In this work, we calculate alpha-particle formation factors without any approximations that appear in the original model. The clustering process is also considered in both the primary and second pre-equilibrium emissions. We optimize the exciton and the clustering model parameters simultaneously by looking at the experimental and energy spectra. The experimental alpha-particle spectra are well reproduced with a unique set of clustering model parameters, which is independent of incident neutrons/protons. The present analysis also implies that the clustering model parameter is not so different between the medium and heavy nuclei. Our calculations reproduce experimental data generally well up to the incident energy of 150 MeV, but underestimations are seen above this energy.

Direct and semi-direct capture in low-energy (,) reactions of neutron-rich tin isotopes and its implications for -process nucleosynthesis

Chiba, Satoshi; Koura, Hiroyuki; Hayakawa, Takehito; Maruyama, Toshiki; Kawano, Toshihiko*; Kajino, Toshitaka*

Physical Review C, 77(1), p.015809_1 - 015809_7, 2008/01

https://doi.org/10.1103/PhysRevC.77.015809

We calculate the direct and semi-direct (DSD) components of the neutron capture cross sections for a series of tin isotopes and compare them with the Hauser-Feshbach (HF) contribution in the energy region of astrophysical interests. It was found that the HF component, which is known to be dominant for isotopes in the vicinity of the stability line, drops off rapidly for isotope Sn and toward more neutron-rich ones, while the DSD component decreases only smoothly. As a consequence, the direct portion of the DSD component comes to give the largest contribution to the total (,) cross section below a few MeV. Therefore, the direct capture process modifies the astrophysical (,) reaction rates for these neutron-rich isotopes to a great extent. The reason of the difference in the isotopic dependence between the HF and DSD components is discussed, and its implication for the -process nucleosynthesis is given.

Report of investigation on malfunction of reserved shutdown system in HTTR

Hamamoto, Shimpei; Iigaki, Kazuhiko; Shimizu, Atsushi; Sawahata, Hiroaki; Kondo, Makoto; Oyama, Sunao; Kawano, Shuichi; Kobayashi, Shoichi; Kawamoto, Taiki; Suzuki, Hisashi; et al.

JAEA-Technology 2006-030, 58 Pages, 2006/03

JAEA-Technology-2006-030.pdf:10.69MB

During normal operation of High Temperature engineering Test Reactor (HTTR) in Japan Atomic Energy Agency (JAEA), the reactivity is controlled by the Control Rods (CRs) system which consists of 32 CRs (16 pairs) and 16 Control Rod Drive Mechanisms (CRDMs). The CR system is located in stand-pipes accompanied by the Reserved Shutdown System (RSS). In the unlikely event that the CRs fail to be inserted, the RSS is provided to insert BC/C pellets into the core. The RSS shall be designed so that the reactor should be held subcriticality from any operation condition by dropping in the pellets. The RSS consists of BC/C pellets, hoppers which contain the pellets, electric plug, driving mechanisms, guide tubes and so on. In accidents when the CRs cannot be inserted, an electric plug is pulled out by a motor and the absorber pellets fall into the core by gravity. A trouble, malfunction of one RSS out of sixteen, occurred during a series of the pre-start up checks of HTTR on February 21, 2005. We investigated the cause of the RSS trouble and took countermeasures to prevent the issue. As the result of investigation, the cause of the trouble was attributed to the following reason: In the motor inside, The Oil of grease of the multiplying gear flowed down from a gap of the oil seal which has been deformed and was mixed with abrasion powder of brake disk. Therefore the adhesive mixture prevented a motor from rotating.