[en] A compilation of references is presented for fission reactions induced by neutrons, protons, deuterons, alpha particles, ³He ions, some heavier charged particles and photons. The energy ranges for the collected references are for neutrons from essentially 14 MeV up to 1 GeV. For charged particles the energy range is from the coulomb barrier up to a few hundred MeV. For photon induced fission the energy range (endpoint of Bremsstrahlung) is from the fission barrier up to about 100 MeV. In addition to the printed version, the compilation is also provided as a Microsoft Word file on the attached CD-ROM to permit electronic processing. References are given for fission reactions induced by neutrons, protons, deuterons, alpha particles, ³He ions, some heavier charged particles and photons. The energy ranges for these references are for neutrons from essentially 14 MeV up to 1 GeV (a few cases of mono-energetic neutrons below 14 MeV are also included). For charged particles the energy range is from the energy required to overcome the coulomb barrier to a few hundred MeV. For photon induced fission the energy range (endpoint of Bremsstrahlung) is from the fission barrier up to about 100 MeV. In addition, some references are given that are concerned with the new technique of fission in inverse kinematics. It should be stressed that the present listing concentrates on the exotic high energy reactions mentioned, and does not cover the well studied fission reactions induced, for example, by neutrons (thermal, reactor spectrum, 14 MeV), spontaneous fission, etc. Ample information on the product yields from these classical fission reactions may be found on web page http://ie.lbl.gov/fission.html . In order to facilitate the use of this listing, a grouping has been made according to the species that induces fission. Furthermore, within each type of fission reaction a differentiation is made according to the type of fission yields obtained (mass yields or independent yields of single nuclides, yields of single isomeric states, yields of neutrons (prompt and delayed), and yields of light charged particles (ternary fission)). The listing is based on a small databank that will be made available to interested users on request to the author. This databank contains a collection of the original publications, along with more information than the present listing; for instance, in many cases the database contains the abstracts of the respective papers. Interrogation of the databank is based on a program available commercially and access can only be achieved after installation of this program (EndNote 2 by Niles and Associates, USA). An electronic search for desired references, author names and titles of articles can also be undertaken through provision of the list of references contained on the CD-ROM attached to this publication

[en] The Chinese reference fission yield file has been established, in which all experimental data available at the time of evaluation were considered. The data were processed using the AVERAG codes for calculating weighted averages, and ZOTT for the simultaneous evaluation of experimental input data. Our evaluated data were compared with those from ENDF/B-VI, JEF-2, JENDL-3 and CENDL/ FY. The data were updated and improved, and uncertainties were considerably reduced in comparison with JEF-2 and CENDL/FY. (author)

[en] Brief descriptions of the most important features of the systematics and models used in the benchmark calculations are given in Section 5.1.3 for a better understanding of the results and analyses. Participants have also provided full accounts of their work in their individual contributions to this report, along with more detailed descriptions of the benchmark exercise and results. All participants contributed to the developments achieved during this CRP through fruitful discussions at project meetings, constructive critiques and the formulation of useful ideas towards the solutions of problems. (author)

[en] A multinational team with the appropriate expertise participated in a work programme aimed at the development of systematics and nuclear models to assist in the evaluation of energy dependent fission yields for incident neutron energies of up to 150 MeV. New concepts for both systematics and theoretical models were developed, as described in later sections of this report. Various predictions of the fission product mass distributions were compared in a benchmark exercise that gave remarkably good results below 50 MeV. Reasons for the discrepancies at higher energies and some failures of the model predictions are discussed in Sections 5 and 6, pointing the way towards future investigations and fission yield evaluations. The problem of the disposal of nuclear waste is an important feature of the utilization of nuclear power. Thus, during the course of the 1980s and 1990s international efforts concentrated on new concepts of waste removal through transmutation. Several proposals were made, using classical thermal or fast reactors as incinerators, or accelerator driven systems. These highly technical proposals are being studied with regard to their feasibility, neutron economics and environmental safety, and nuclear data (including fission yields) are required for assessments and for the design and operational requirements of such facilities. While adequate nuclear data exist for thermal and fast reactor incineration, this satisfactory situation is not the case for accelerator driven systems. An international working group has studied the overall problem and recommended the assembly of the required nuclear data at intermediate incident neutron energies of up to at least 150 MeV. The staff at the IAEA have also assessed this situation in conjunction with appropriate external expertise and decided to contribute to this effort by the initiation of a coordinated research project (CRP) on fission yields up to 150 MeV. Evaluated fission yields as a function of incident neutron energy have to be presented in a way that any fission yield from any target nuclide can be obtained for any desired energy up to 150 MeV. Previous evaluations have focused on thermal, fast and 'high' (14-15 MeV) neutrons, as individual data sets. New concepts are required for the presentation of energy dependent fission yields, such as: (a) Functions for the description of energy dependent yields; (b) Yield sets at energy intervals with interpolation formulae; (c) Computer programs using systematics and/or theoretical models, with the desired fission yields as output. Any evaluation method will also require new procedures, and previous methods of analysis will not be feasible because experimental data are so scarce. Fission yield measurements are impossible for certain targets, while measurements at higher incident neutron energies are extremely difficult for other targets. Therefore, sufficient coverage of the desired neutron energy range by experimental data cannot be expected. Thus nuclear models and systematics need to be developed from the available experimental data to allow the calculation of fission yields and assist in future evaluations of energy dependent fission yields. The primary objectives of the CRP were to study all the problems involved in the development of nuclear models and systematics and to derive method for fission yield evaluation as a function of incident neutron energy. Hopefully such efforts will result in a new evaluation of the energy dependent neutron induced fission yields up to 150 MeV. However, this CRP entered an entirely new field of research, as usable models and systematics do not exist over such an energy range and the outcome of the work was deemed to be unpredictable. Therefore, the goals of the CRP were subsequently limited to the development of appropriate nuclear models and systematics for the prediction of fission yields as tools for the evaluation of energy dependent fission yields up to 150 MeV. (author)

[en] A method and code have been developed for mass resolution adjustment of mass distribution data measured by means of the kinetic energy method. Data were smoothed before adjustment with a second order function for 7 or 9 adjacent points, and the investigation shows that taking too few or too many data points in the smoothing procedure could lead to unreasonable results. The code was tested by folding the adjusted data with a Gaussian distribution and a resolution width the same as the one used in the adjustment procedure. Results were practically identical to the original unadjusted input data. The data uncertainties were also adjusted by the code. This code has subsequently been applied to re-define the mass distribution data measurements of Zoeller, Vives and Aystoe by the kinetic energy method. (author)

[en] Mass distribution data measured up to 200 MeV by the kinetic energy method by Zoeller were adjusted for mass resolution and used to study the systematics of the chain yield dependence on incident neutron energy. The energy dependence for each fission fragment mass number was represented by linear and quadric functions. Furthermore, the systematics of the whole mass distribution and representation by a 5 (or 3) Gaussian model as a function of the incident neutron energy was also investigated. A code was developed to deduce the model parameters by a non-linear least squares fit of the experimental data. The mass distributions calculated with these parameters were subsequently compared with the experimental data. However, comparisons with radiochemically measured yields revealed systematic differences between the data obtained by the two methods. The uncertainties and correlations in the systematics were also studied: uncertainties in the mass distributions can be reduced by 20-80% (about 50% on average) when calculated from the systematics, and greater reductions can be achieved when the initial uncertainty is higher. These studies have also shown that there is a strong but rather complicated correlation between the yields calculated from the systematics and the parameters of the systematics. (author)

[en] The mass distribution of ²⁵²Cf spontaneous fission was evaluated on the basis of seven sets of available experimental data. The measured data were modified on the basis of the authors' adopted standards and gray intensities by using our newly evaluated values, and the originally assigned uncertainties were adjusted. The evaluated experimental data were fitted with a spline function. In addition, a symmetric spline function fit of all experimental data was performed by symmetric reflection of the light mass peak into the heavy mass peak. These two sets of fitted data are recommended as reference for the mass distribution of ²⁵²Cf spontaneous fission. Uncertainties in the recommended data were considerably reduced compared to the measured values. The light and heavy mass peaks are not completely symmetric. Fine structure has been observed in experimental mass distributions around A = 109-112 and A = 136-139, which is probably real, but could not be reproduced in the evaluation due to inconsistencies in the measurement results. These phenomena and their physical background should be investigated further. (author)

[en] Experimental and analytical work has been performed to obtain information on the relative yields, mean values and variances of masses and kinetic energies of fragments from the fission of actinide nuclei through independent fission modes. Regularities in the behaviour of these characteristics with respect to their dependence on the nucleonic composition of the fissile actinides and incident particle (proton and neutron) kinetic energies have been used to develop new systematics for fragment mass yields from the fission of target nuclei from Th to Bk at incident particle energies between 5 and 200 MeV. (author)

[en] The statistical model for fission cross-section evaluations has been extended by including the concept of multi-modality of the fission process. The three most dominant fission modes, i.e. the two asymmetric standard I (S1) and standard II (S2) modes and the symmetric super long mode, are taken into account. Based on calculations of the nuclear surface within the multi-modal random neck rupture model, separate outer fission barriers are considered for each mode, while the inner barriers and isomeric wells are assumed to be the same. Deconvoluted fission cross-sections for the S1, S2 and super long modes of ^235,238U(n,f) and ²³⁷Np(n,f), based on experimental branching ratios, were calculated for the first time in the incident neutron energy range from 0.01 to 5.5 MeV, providing good agreement with the experimental fission cross-section data. In this way, branching ratios can also be deduced for incident neutron energies when no experimental data exist, and used for the prediction of the corresponding fragment mass yield distributions. (author)

[en] Systematics of fission product mass distribution with five Gaussian functions is proposed for application to minor actinide fission by neutrons and protons of energies above 100 MeV. This systematics is also applicable to fission by neutrons and protons of lower energy and to spontaneous fission. The mass distributions calculated using the systematics have been compared with various kinds of measured data, and good agreement was found. (author)