1. Neutron Capture Cross Section Measurement of Technetium-99 By Linac Time-of-Flight Method and the Resonance Analysis
   • K. Kobayashi, Samyol Lee, S. Yamamoto, T. Kawano
   • Nucl. Sci. Eng. (2003, in press).
2. Uncertainty Analyses in the Resolved Resonance Region of 235U, 238U, and 239Pu with the Reich-Moore R-Matrix Theory for JENDL-3.2
   • T. Kawano, K. Shibata
   • J. Nucl. Sci. Technol., 39, 807 (2002).
   • 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 derives 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 235U, 238U, and 239Pu resonance parameters in JENDL-3.2, with the Reich-Moore R-matrix formula.
3. Comparison of 235U Fission Cross Sections in JENDL-3.3 and ENDF/B-VI
   • T. Kawano, A.D. Carlson, H. Matsunobu, T. Nakagawa, K. Shibata, P. Talou, P.G. Young, and M.B. Chadwick
   • JAERI-Research 2001-058 (2002)
   • Comparisons of evaluated fission cross sections for 235U in JENDL-3.3 and ENDF/B-VI are carried out. The comparisons are made for both the differential and integral data. The fission cross sections as well as the fission ratios are compared with the experimental data in detail. Spectrum averaged cross sections are calculated and compared with the measurements. The employed spectra are, the 235U prompt fission neutron spectrum, the 252Cf spontaneous fission neutron spectrum, and the neutron spectrum produced by a 9Be(d,xn) reaction. For 235U prompt fission neutron spectrum, the ENDF/B-VI evaluation reproduces experimental averaged cross sections. For 252Cf and 9Be(d,xn) neutron spectra, the JENDL-3.3 evaluation gives better results than ENDF/B-VI.
4. Interference effect in the scattering amplitudes for nucleon-induced two-step direct process using the sudden approximation
   • T. Kawano and S. Yoshida
   • Phys. Rev., C, 64, 024603 (2001)
   • An implementation of calculation for two-step cross sections of the theory of Nishioka, Weidenmueller and Yoshida is described. Cross sections which excite a 2p-2h state are expressed in J-scheme, and a Yukawa interaction is assumed for the particle-hole pair creation. The Green's function which connects the one-step matrix element to the two-step one is represented in $r$-space. An interference effect among the amplitudes for the different intermediate states is examined by means of a spectroscopic amplitude. A strong interference appears for a certain configuration, and this is interpreted by a Boson approximation. Microscopically calculated two-step cross sections for 208Pb(p,p') reactions are averaged together with the true level density which is based on the random matrix theory to give a two-step cross section to the continuum energy region.
5. Effect of the preequilibrium process upon fast neutron fission spectra from 238U
   • T. Kawano, T. Ohsawa, M. Baba, and T. Nakagawa
   • Phys. Rev., C, 63, 034601 (2001)
   • A preequilibrium process for the prefission neutron which is emitted before scission is calculated with the model of Feshbach, Kerman, and Koonin. A forward-peaked angular distribution of the neutron emission from 238U bombarded by 14 and 18 MeV neutrons is expressed with the statistical multistep compound (MSC) process and the one-step direct process. The fission neutron energy spectra are calculated with the model of Madland and Nix, with some modifications by Ohsawa et al. The calculated total neutron emission spectra and their energy-angle distributions (double-differential cross sections) are compared with the experimental data, and a strength of the residual interaction V0 is estimated. The comparisons of the calculations with the experimental data show that the 14 MeV data are well reproduced but the 18 MeV data are underestimated. Anisotropy is seen in the angle-differential fission spectra, and this is due to an existence of the prefission neutron.
6. Calculation of the MSD Two-Step Process with the Sudden Approximation
   • T. Kawano and S. Yoshida
   • Proc. of the 9th Int. Conf. on Nuclear Reaction Mechanisms, 5--9 June, 2000, Villa Monastero, Varenna, Italy, Ed. E. Gadioli, Ricerca Scientifica ed Educazione Permanente Supplemento N.115, pp.181--189 (2000).
   • A method to calculate the two-step process is described according to the theory of Nishioka, Weidenmueller and Yoshida (NWY), in which the sudden approximation is used. The Green's function which connects the one-step matrix element to the two-step one is represented in r-space, and the Yukawa interaction is employed for a particle-hole pair creation. An effect of interference between the different intermediate states is investigated by means of a spectroscopic amplitude and a Boson approximation. Microscopically calculated two-step cross sections for 208Pb(p,p') reactions are averaged together with the true level density to give a two-step cross section to the continuum.
7. Calculation of the MSD Two-Step Process with the Sudden Approximation
   • S.Yoshida and T.Kawano
   • Proc. of the 1999 Symposium on Nuclear Data, Nov., 18-19, 1999, JAERI, TOKAI, JAERI-Conf 2000-005 pp.284-289 (2000).
   • A calculation of the two-step process with the sudden approximation is described. The Green's function which connects the one-step matrix element to the two-step one is represented in $r$-space to avoid the on-energy-shell approximation. Microscopically calculated two-step cross sections are averaged together with an appropriate level density to give a two-step cross section. The calculated cross sections are compared with the experimental data, however the calculation still contains several simplifications at this moment.
8. Revision of Heavy Nuclei Data in JENDL-3.2
   • T.Kawano and Heavy Nuclear Data Evaluation Working Group
   • Proc. of the 1999 Symposium on Nuclear Data, Nov., 18-19, 1999, JAERI, TOKAI, JAERI-Conf 2000-005 pp.104-109 (2000).
   • In order to deal with problems concerning the data of heavy nuclides in JENDL-3.2, a working group was organized to update the evaluated nuclear data of Uranium, Plutonium, and Thorium isotopes. The current status of the working group is reviewed, and some results about resonance parameters, secondary neutron energy spectra, fission cross sections, and direct/semidirect capture process are shown.
9. Simultaneous Evaluation of Fission Cross Sections of Uranium and Plutonium Isotopes for JENDL-3.3
   • T.Kawano, H.Matsunobu, T.Murata, A.Zukeran, Y.Nakajima, M.Kawai, O.Iwamoto, K.Shibata, T.Nakagawa, T.Ohsawa, M.Baba, and T.Yoshida
   • J. Nucl. Sci. Technol., 37, 327 (2000)
   • A simultaneous evaluation of the fission cross sections of U233U, U235, U238, Pu239, Pu240Pu and Pu241 was carried out for the evaluated nuclear data library JENDL-3.3. A least-squares method was applied to selected absolute and relative measurements on the fission cross sections. Covariance matrices of the experimental data were constructed from the uncertainty information reported in the references. The fission cross sections obtained were compared with the JENDL-3.2 and ENDF/B-VI evaluations.
10. Evaluation of Fission Cross Sections and Covariances for U233, U235, U238, Pu239, Pu240, and Pu241
    • T.Kawano, H.Matsunobu, T.Murata, A.Zukeran, Y.Nakajima, M.Kawai, O.Iwamoto, K.Shibata, T.Nakagawa, T.Ohsawa, M.Baba, and T.Yoshida
    • JAERI-Research 2000-004
    • A simultaneous evaluation code SOK (Simultaneous evaluation on KALMAN) has been developed, which is a least-squares fitting program to absolute and relative measurements. The SOK code was employed to evaluate the fission cross sections of U233, U235, U238, Pu239, Pu240 and Pu241 for the evaluated nuclear data library JENDL-3.3. Procedures of the simultaneous evaluation and the experimental database of the fission cross sections are described. The fission cross sections obtained were compared with evaluated values given in JENDL-3.2 and ENDF/B-VI.
11. Covariance Evaluation with the KALMAN System
    • T.Kawano and K.Shibata
    • Proc. of the Covariance Matrices: Generation, Formats and Applications in Nuclear Energy Technologies, 22--23 April, 1999, BNL, Upton, New York, U.S.A. (to be published)
    • The KALMAN system has been developed to evaluate covariances of the evaluated nuclear data libraries. Calculation codes of an optical model, a Hauser-Feshbach model, an improved Madland-Nix model, and Reich-Moore R-matrix theory were incorporated into the system to generate the covariances of various quantities. The system is applied to some simple examples to show how the system works and how to estimate covariances in case few experimental data are available.
12. Evaluation of Covariance for Fission Neutron Spectra
    • T.Kawano, T.Ohsawa, K. Shibata, H.Nakashima
    • JAERI-Research 99-009, pp.1--43 (1999)
    • A covariance evaluation system for the evaluated nuclear data library JENDL-3.2 was established, and the covariance data for fission spectra of 233U, 235U, 238U, 239Pu were evaluated. Two methods were employed to evaluate the covariance. The first one is based on the experimental data, and the second one is based on a model calculation including some kinds of renormalizations. The later technique was adopted for the covariance evaluation for the evaluated fission spectra in JENDL-3.2. We performed an adjustment of the evaluated fission spectrum of 235U using the spectrum averaged cross section of 27Al(n,p), 46,47,48Ti(n,p), 54,56Fe(n,p), 58Ni(n,p), 90Zr(n,2n) reaction. It was demonstrated that the adjusted sperctrum is normalized to unity.
13. 1 Microscopic Calculation of the Multistep Compound Process
    • T.Kawano
    • Phys. Rev., C, 59, 865 (1999)
    • The Feshbach, Kerman, and Koonin model of statistical multistep compound (MSC) process is calculated microscopically, and comparisons of the microscopically calculated MSC process with a phenomenological phase space model are made. The microscopic model gives small particle emission probability in comparison with the constant wave function approximation, and a simple way to get rid of the difference is proposed. A 2p-1h doorway state formation cross section is calculated with the spherical Nilsson model, and a strength of the residual interaction V0 is estimated from the doorway state formation cross section. The obtained V0 is in the same magnitude as those derived in the previous MSD analyses. Comparisons of the microscopic MSC calculations with the experimental data show that the calculated particle emission spectra reproduce the measurements at backward angles.
14. Analysis of 58Ni(n,alpha) Reaction Cross Sections with the Hauser-Feshbach Statistical Theory and the Bayesian Parameter Estimation Method
    • T.Kawano, T.Sanami, M.Baba, and H. Nakashima
    • J. Nucl. Sci. Technol., 36, 256 (1999)
    • Experimental data of 58Ni(n,alpha) reaction cross sections are analyzed with the Hauser-Feshbach statistical model with the width fluctuation correction by Moldauer. A neutron optical potential which was derived from neutron induced reaction data is used for an entrance channel in order to fix the total reaction cross sections at reliable values. Global optical potentials are used for the proton and alpha-particle emission channels, and level density parameters of the residual nuclei are determined from the cumulative plot of discrete levels. These parameters are adjusted to the experimental data of 58Ni(n,alpha) and (n,p) reaction cross sections, including the angular distribution of the emitted alpha-particles. The obtained parameters yield a good fit to the experimental cross sections of those reactions up to 8 MeV.
15. Estimation of Energy Dependence of the Optical Potential Parameters for 209Bi
    • T.Kawano
    • Nucl. Sci. Eng., 131 , 107 (1999)
    • A parameter estimation method based on a Bayes' theorem is applied to the parameters of the neutron optical potential for 209Bi. The potential parameters at a certain energy are determined according to an assumption that parameters vary gradually with the incident neutron energies, and it is demonstrated that the method can be used as an efficient tool for investigating the energy dependence of the optical potential parameters. The derived potential parameters are expressed by both a polynomial function and a Brown-Rho parameterization, and the energy dependencies are interpreted by a dispersion relation theory. Both expressions of the energy dependent parameters give a good description of the experimental elastic scattering cross section and the total cross section.
16. Validity of DWBA Calculations for Neutron Inelastic Scattering from Molybdenum Isotopes
    • T.Kawano, Y. Watanabe, and M. Kawai
    • J. Nucl. Sci. Technol., 35, 519 (1998)
    • Neutron inelastic scattering cross sections for molybdenum isotopes are calculated with the DWBA and the coupled-channels methods. Anomalous enhancement of the DWBA cross sections near the threshold energy appears when the adopted optical potential has a shallow imaginary part. Calculations with some simplified optical potentials indicate that the enhancement can be related with the p-wave strength, and it is found that the problem comes from the optical potential used. When an adopted optical potential to the DWBA calculation is physically reasonable, differences between the calculated cross sections with the DWBA and those with the coupled-channels theory are small. Experimental data of 92Mo, 98Mo and 100Mo are well reproduced by the calculated cross sections with the DWBA and the Hauser-Feshbach-Moldauer statistical model, and it is concluded that the DWBA is an appropriate method to evaluate cross sections of inelastic scattering from the molybdenum isotopes.
17. Development of the Multistep Compound Process Calculation Code
    • T.Kawano,
    • Proc. of the 1997 Symposium on Nuclear Data, Nov., 27-28, 1997, JAERI, TOKAI, JAERI-Conf 98-003, p.312 (1998).
    • A program "cmc" has been developed to calculate the multistep compound (MSC) process by Feshbach-Kerman-Koonin. A radial overlap integral in the transition matrix element is calculated microscopically, and comparisons are made for neutron induced 93Nb reactions. Strengths of the two-body interaction V0 are estimated from the total MSC cross sections.
18. Master equation approach to statistical multistep compound reactions
    • T.Kawano, M.Nakamura, and Y.Watanabe
    • Phys. Rev. C, 57, 978 (1998).
    • A master equation is incorporated in Feshbach, Kerman, and Koonin model calculations of statistical multistep compound (MSC) emission. Damping X and Y functions which describe the particle-hole annihilation process are derived. The MSC cross sections are calculated with the master equation. The effect was found to be large at lower energies for light nuclei, but not significant when the incident energy is above 20 MeV. The difference between a closed form solution and the master equation result is masked by the large multistep direct and evaporation components.
19. Covariance Evaluation System
    • T.Kawano and K.Shibata(JAERI)
    • JAERI-Data/Code 97-037 (in Japanese)
    • A covariance evaluation system for the evaluated nuclear data library was established. The parameter estimation method and the least squares method with a spline function are used to generate the covariance data. Uncertainties of nuclear reaction model parameters are estimated from experimental data uncertainties, then the covariance of the evaluated cross sections is calculated by means of error propagation. Computer programs ELIESE-3, EGNASH4, ECIS, and CASTHY are used. Covariances of 238U reaction cross sections were calculated with this system.
20. Partial-wave analysis with the optical model for the resolved and unresolved resonance region of 56Fe
    • T.Kawano and F.H.Froehner(FZK,INR)
    • Nucl.Sci. Eng., 127, 130 (1997)
    • We have studied optical model fits to total neutron cross sections of 56Fe using the accurate data base existing in the resolved and unresolved resonance region. Averages over resolved resonances were calculated from resonance parameters in Reich-Moore (reduced R matrix) approximation with Lorentzian weighting. Optical potential parameters were obtained for the s-, p-, and d-waves that reproduce the smoothed cross sections in the resolved resonance region. The p-wave optical potential was found to differ from the S-wave potential. When the appropriate higher angular momentum contributions are added, the average total cross sections can be fitted quite well, from the resolved resonance region all the way up to 20 MeV.

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