K. Kosako

JENDL-3.2 Covariance File

Covariances of neutron nuclear data have been estimated for 16 nuclides contained in JENDL-3.2. The physical quantities for which covariances are deduced are cross sections, resolved and unresolved resonance parameters, the first order Legendre-polynomial coefficients for the angular distribution of elastically scattered neutrons, and fission neutron spectra. As for 233,235,238U and 239,241Pu, covariances were obtained also for the average number of neutrons emitted in fission. Least-squares methods were applied to obtain the covariances of those cross sections which were based on experimental data. A simultaneous evaluation method yielded uncertainties in the fission cross sections of 235U, 238U, 239Pu, 240Pu and 241Pu. Covariances of nuclear model calculations were determined from uncertainties in model parameters. The covariance file thus obtained is processed by a system which has been developed, and used for the adjustment of group cross sections.

Analyses and Intercomparison for Phase I Fusion Integral Experiments at the FNS Facility

Phase I integral experiments of U.S./JAERI Collaborative Program on Fusion Breeder Neutronics which are carried out at the Fusion Neutronics Source (FNS) facility at JAERI ranged from D-T neutron source characterization experiments, tritium production rate (TPR) measurements in a reference Li/sub 2/0 assembly, first wall experiments with and without coolant simulation and beryllium neutron multiplier experiments in various configurations. Both U.S. and Japan have independently analyzed these experiments using their own data base and codes. Analytical predictions obtained by both countries are compared to measured values. Results of this intercomparison is presented in this paper.

Analysis of neutronics parameters measured in Phase-II experiments of the JAERI/US collaborative program on fusion blanket neutronics. Part I: Source characteristics and reaction rate distributions

Fusion blanket neutronics parameters measured in the Phase II assembly have been analyzed at both JAERI and the US. Both parties have analyzed the experiments independently by using different nuclear data and calculational methods based on 3-D Monte Carlo and 2-D Sn codes. This part includes the results of the analysis on the source characteristics in the assembly and the reaction rate distributions in the test zone consisting of Li2O with and without a beryllium multiplier. The source characterization has been made by measuring the neutron spectrum and various reaction rates. These reactions include 58Ni(n,2n), 58Ni(n,p), 27Al(n,α), 93Nb(n,2n), 197Au(n,2n), and 197Au(n,γ). The ratios of calculated to measured values are compared among both countries and the different nuclear data used. Considerable discrepancies have been observed for the 58Ni(n,2n), 58Ni(n,p) and 93Nb(n,2n) reactions depending on which nuclear data was used, while good agreement is seen for the reactions 197Au(n,2n) and 27Al(n,α). The distributions of these reaction rates in the test zone have also been analyzed to examine the prediction accuracy of neutronics parameters in a breeder zone. Using the recently measured cross sections at the FNS resulted in a significant reduction in the discrepancies for most reaction rates.

Phase III experimental results of JAERI/USDOE collaborative program on fusion neutronics

Abstract A pseudo-line D–T neutron source has been developed with new experimental techniques. This line source was applied in sophisticated neutronics experiments for an annular blanket arrangement simulating the tokamak geometry, as a new series in the JAERI/USDOE collaborative experimental program on fusion neutronics. The source characteristics of the present line source and the measurements for an annular assembly are described. The discussion on the experimental results focuses on the tritium production rate measured in an annular blanket and comparisons were made with the previous point source experiment, and also between the annular blankets with and without an armor reflector of graphite.

A Line D-T Neutron Source Facility for Annular Blanket Experiment: Phase III of the JAERI/USDOE Collaborative Program on Fusion Neutronics

AbstractA new experimental arrangement using pseudo-line D-T neutron source has been developed to investigate the neutronics performance in the fusion blanket and related components. The arrangement is simple in construction and gives well-simulated fusion reactor environment combined with the flexibility in testing various factors. In examining the deficiencies in nuclear data, calculation methods or modeling, it provides a powerful means either for basic benchmark experiments in clear geometry or design-supporting experiments with complexity of the recent blanket design. The features of the line source facility and the experimental scope are described.

JENDL Photonuclear Data File

JENDL Photonuclear Data File 2004 was released in March 2004 and contains the photonuclear data for 68 nuclides from 2H to 237Np. We were proceeding on the evaluation work with the help of theoretical calculations based on statistical nuclear reaction models. The photonuclear cross sections that are to be contained in the file are as follows: photoabsorption cross sections, yield cross sections, and double‐differential cross sections for photoneutrons, photoprotons, photodeuterons, phototritons, photo‐3He‐particles and photoalpha‐particles, and isotope production cross sections. For the actinide nuclides, physical quantities related to photofission reactions are also included. The maximum energy of incident photons is 140 MeV, which is the energy at which the pion production channel opens.

Measurement and Calculations of Angular Neutron Flux Spectra from Iron Slabs Bombarded with 14.8-MeV Neutrons

In a next step experimental deuterium-tritium (D-T) burning fusion reactor such as the International Thermonuclear Experimental Reactor (ITER), iron is a key material in the shielding component for protecting the superconducting magnet from radiation heating. In this paper, angular neutron flux spectra leaking from iron slabs with various thicknesses up to 600 mm have been measured by the time-of-flight technique. The results are compared with calculations by the MCNP Monte Carlo code and the DOT3.5 two-dimensional discrete ordinates code with the JENDL-3 nuclear data file and wit ENDF/B-IV. In the DOT3.5 calculations, a cross-section set with a self-shielding correction factor is also applied to examine its effect. The results show that the MCNP calculations based on both files agree very well for the main part of the deeply penetrating neutron spectrum, but the DOT3.5 code without a self-shielding correction underestimates the high-energy flux and the flux in the resonance energy range with increasing slab thickness. The self-shielding correction factor improves the underestimation, but the calculated flux is still smaller than the MCNP calculation.

Measurement and Analysis of Nuclear Heat Depositions in Structural Materials Induced by D-T Neutrons

AbstractNuclear heat deposition rates in ten different materials, Li2CO3, Graphite, Ti, Ni, Zr, Nb, Mo, Sn, Pb and W, subjected in D-T neutrons have been measured by a microcalorimetric technique in the frame work of JAERI/USDOE collaborative program on fusion neutronics. A great improvement in accuracy of experimental data was achieved by introducing a high sensitivity voltmeter and applying constant current on the thermal sensors. The measured heating rates were compared with calculations to verify the adequacy of the currently available data base relevant to the nuclear heating process. In general, calculations with data of JENDL-3 and ENDL-85 libraries gave excellent agreements with experiments for all materials except Zr. The calculation with the MBCCS suffered large discrepancy from measurement.

Analysis of neutronics parameters measured in Phase II experiments of the JAERI/US collaborative program on fusion blanket neutronics. Part II: Tritium production and in-system spectrum

Tritium Production Rate (TPR) and in-system spectrum measurements were performed on a Li2O test assembly (with and without beryllium multiplier) at the FNS facility at JAERI in addition to other neutronics parameters that include source neutron characterization and in-system reaction rates discussed in a companion paper. These activities are part of an on-going collaborative program between JAERI and the US. Calculations for the neutronic parameters were performed independently by both parties based on various 3-D Monte Carlo and 2-D discrete ordinales codes and data libraries. Local and zonal TPRs were measured by various techniques and comparisons were made to predictions. The calculated to measured values, C/E, for integrated zonal TPR from natural lithium are typically C/E = 0.97–1.07 but local TPR has larger uncertainties (C/E = 0.85–1.13). Predicted enhancement in tritium breeding upon including the Be multiplier is in the order of 7–8% while measurements indicate an approximately 10% increase in integrated TPR. The in-system spectra are well-predicted at En > 10 MeV by various codes as compared to NE213 measurements, although calculation tends to overpredict the 14.1 MeV peak. Large discrepancies, however, were observed in the energy range 1.01 MeV

JENDL Fusion File 99

The double-differential cross sections (DDXs) of secondary neutrons have been evaluated for 79 isotopes and 13 natural elements ranging from H to Bi to improve the accuracy of predictions for the neutronics calculations in the D-T thermonuclear fusion applications. The data given in JENDL-3.1, which was the newest version of JENDL general purpose file when this project was initiated, was combined with new calculations based on the optical model, DWBA, pre-equilibrium and multi-step statistical models, and the DDX data were generated based on various kinds of systematics for medium-mass nuclei. Different methods were employed for light nuclei to which the above method could not be applied. In addition, the DDXs for emission of charged particles (p, d, t, 3He and α-particle) were given for 2H, 9Be and elements heavier or equal to F. The present results give an overall good description of the measured DDX data of both the neutron and charged particles emission channels. The data were compiled in ENDF-6 format, and released in 1999 as a special purpose file of JENDL family, namely, JENDL Fusion File 99.