Jun-ichi Katakura

JENDL-4.0 : A New Library for Nuclear Science and Engineering

The fourth version of the Japanese Evaluated Nuclear Data Library has been produced in cooperation with the Japanese Nuclear Data Committee. In the new library, much emphasis is placed on the improvements of fission product and minor actinoid data. Two nuclear model codes were developed in order to evaluate the cross sections of fission products and minor actinoids. Coupled-channel optical model parameters, which can be applied to wide mass and energy regions, were obtained for nuclear model calculations. Thermal cross sections of actinoids were carefully examined by considering experimental data or by the systematics of neighboring nuclei. Most of the fission cross sections were derived from experimental data. A simultaneous evaluation was performed for the fission cross sections of important uranium and plutonium isotopes above 10 keV. New evaluations were performed for the thirty fissionproduct nuclides that had not been contained in the previous library JENDL-3.3. The data for light elements and structural materials were partly reevaluated. Moreover, covariances were estimated mainly for actinoids. The new library was released as JENDL-4.0, and the data can be retrieved from the Web site of the JAEA Nuclear Data Center.

INTERNATIONAL CO-OPERATION IN NUCLEAR DATA EVALUATION

The OECD Nuclear Energy Agency (NEA) is organising a co-operation between the major nuclear data evaluation projects in the world. The co-operation involves the US ENDF project, the Western European JEFF project, the Japanese JENDL project, and, through collaboration with the IAEA, the Russian BROND project, the Chinese CENDL project and the IAEA FENDL project. The Korean data evaluation effort at KAERI presently has observer status within the co-operation. A Working Party comprised of 16 core members meets annually to discuss progress within each evaluation project and to assess common needs for nuclear data improvements. These needs are then addressed by initiating joint evaluation and/or measurement efforts. The work is performed in specially established subgroups, consisting of experts from the different evaluation projects. The results of these subgroups are published in reports issued by the NEA. Fourteen such reports have so far been issued. Present activities cover the following subjects: • Nuclear data standards. • Fission neutron spectra. • Activation cross-sections. • Evaluation and processing of covariance data. • Assessment of evaluations for the bulk of fission products. In addition to the previously mentioned short-term task-oriented subgroups, the Working Party has also established three longer-term subgroups dealing with: • Nuclear model codes. • Evaluated data formats and processing. • High priority requests for nuclear data. The paper will briefly review the achievements of the co-operation, present ongoing activities and reflect on ideas for future activities and challenges in the field of evaluated nuclear data.

On the design of a remotely-deployed detection system for reactor assessment at Fukushima Daiichi

The premise behind this research is the design of a system that will allow fuel debris characterisation at Fukushima Daiichi. The precise location of the debris is not known for example as to whether it remains within the reactor pressure vessel or it has leaked through into the base of the pedestal below, additionally the state of the fuel is also in question as to whether this has corroded from within its encasing or if it is intact. The most likely scenario is a combination of all four of these situations. The flooding of the reactor floors immediately following the Fukushima accident adds an extra element of complexity for the detection system requiring it to be submersible and to hold any detector system in water tight confinement. The research carried out has involved extensive modifications to a previously-designed low-cost small-scale AVEXIS submersible inspection vehicle and the incorporation of a variety of radiation detectors. The latter has been designed to allow for mapping and determination of the situation that is present within the primary containment vessels. The challenges addressed with the detection system arise from the high dose rates that have been recorded around the reactor pressure vessels which can be as high as 1000 Gy/hr. In such a harsh environment not only will the radiation detectors struggle to operate but the components that make up the remote-operated vehicle are also likely to suffer radiation damage after only a relatively short period of time. The research presented here evaluates the components currently incorporated into the AVEXIS system in terms of their radiation tolerability as well as presenting the combination of detectors to be used in the remote probe for the investigation of the fuel debris.

International Cooperation in Nuclear Data Evaluation

The OECD Nuclear Energy Agency (NEA) is organising a co-operation between the major nuclear data evaluation projects in the world. The co-operation involves the ENDF, JEFF, and JENDL projects, and, owing to the collaboration with the International Atomic Energy Agency (IAEA), also the Russian BROND and the Chinese CENDL projects. The Working Party on international nuclear data Evaluation Cooperation (WPEC), comprised of about 20 core members, manages this co-operation and meets annually to discuss progress in each evaluation project and also related experimental activities. The WPEC assesses common needs for nuclear data improvements and these needs are then addressed by initiating joint evaluation efforts. The work is performed in specially established subgroups, consisting of experts from the participating evaluation projects. The outcome of these subgroups is published in reports, issued by the NEA. Current WPEC activities comprise for example a number of studies related to nuclear data uncertainties, including a review of methods for the combined use of integral experiments and covariance data, as well as evaluations of some of the major actinides, such as {sup 235}U and {sup 239}Pu. This paper gives an overview of current and planned activities within the WPEC.

Status of the JENDL Project

Activities on the general‐purpose and special‐purpose files of JENDL are described. Evaluation work for the general‐purpose file JENDL‐4 has started in order to provide users with high‐quality data. Part of the JENDL High Energy File and the JENDL Photonuclear Data File were released this year. Nuclear model codes are developed so as to make evaluations efficiently. The nuclear data utilization system is being created to disseminate JENDL data.

International Chart Of The Nuclides – 2001

The International Chart of Nuclides – 2001 has been developed taking into account the data obtained in 1998 -2001. Unlike widespread nuclide charts the present Chart of Nuclides contains EVALUATED values of the main characteristics. These values are supplied with the standard deviations.

Development of JENDL FP Decay Data File 2000

JENDL FP Decay Data File 2000 has been developed as a special purpose file of JENDL. The file contains various decay data of fission product nuclides needed for the analyses of FP accumulation, decay heat, aggregate beta- and gamma-ray spectra and so on in a nuclear reactor. The number of unstable nuclides including isomeric states is 1087.