Yukinori Kanda

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.

Second Version of Japanese Evaluated Nuclear Data Library (JENDL-2)

Compilation of the second version of Japanese Evaluated Nuclear Data Library (JENDL-2) has been completed. The aim of JENDL-2 is the applications to fast, thermal and fusion reactors, and shielding problems. The evaluated data for 181 nuclides were stored in the ENDF/B-IV format. Various benchmark tests have been performed, and applicability of JENDL-2 was confirmed for the fast and thermal reactor calculations and for the shielding problems. In this review, evaluation work for JENDL-2 is briefly described, and the results of the benchmark tests are summarized.

Burn characteristics of D-T ignited D-D and D-3He fuel pellets for inertial confinement fusion reactors

The burn characteristics are examined of an inertially confined advanced fuel pellet ignited by D-T burn, i.e. a D-T ignitor/D-D fuel and a D-T ignitor/D-3He fuel pellet. With the help of numerical simulations of a bare target model, conditions are derived for the pellet compression needed in an advanced fuel fusion reactor. It is found that a D-T/D-D pellet having a total ρR value of ~ 13 gcm−2 and an ignitor with a ρR of ~ 5 gcm−2 is required for a reactor operating without tritium breeding blanket. A scaling chart of the fuel burnup and the internal tritium breeding ratio is given, and a condition to be imposed on the ignitor for efficient burn is discussed.

Effect of neutron heating on the burn dynamics of DT ignitor/DD fuel pellets

Bum simulations have been carried out for the DT ignitor/DD fuel pellet model by using a hydrodynamic code including neutron transport. The results showed that neutron heating has large effects on the bum performance, for instance the fusion yield and the internal tritium breeding ratio. The DD burning could be sustained by neutron heating and thus sufficient tritium could be bred by using one of the branches of the DD reaction, D + D → p + T. Furthermore, several treatments for neutron transport were compared. It was found that the treatment of the anisotropy of neutron scattering has a larger influence on the bum performance than the treatment of the time dependence of neutron transport. Finally a compressed state of the pellet was proposed as a candidate for the advanced fuel ICF reactor TAKANAWA-I.

Helium trapping in aluminium near the critical dose on blister formation

Blistering and flaking caused by energetic He ions emitted from the plasma in fusion reactors possibly contribute to first-wall erosion. In order to study their characteristics, the numbers of He atoms trapped in He-ion-irradiated Al samples have been measured by a He atom measurement system and every sample has been observed by a scanning electron microscope. The samples have been prepared from a polycrystalline plate and irradiated with 20 keV He ions at room temperature. The saw-tooth like variation of the trapped He atoms with the dose has three edges corresponding to the blistering, flaking and double flaking, respectively. The critical doses for the three events are found to be 4 × 1021, 7 × 1021, 12 × 1021 He atoms m−2, respectively. The average number of He atoms included in an event is 5.4 × 1010 He atoms in the case of the blistering and 2.1 × 1011 He atoms in the case of flaking.

Characteristics of σ-transitions in an atomic-beam polarized deuteron source

Abstract Quantum mechanical calculations of the degree of polarization after inducing σ -transitions in an atomic-beam polarized deuteron source have been done. Four parameters are found to be important for characterizing the performance of rf transitions. These are the strength of the rf oscillating magnetic field, the field gradient of the static magnetic field, the separation efficiency of atomic states and the temperature of atomic gas. It is shown that the degree of polarization can conveniently be evaluated by an “adiabatic field factor” which is defined by the first two of these four parameters irrespective of the kind of σ -transition. Some applications of the present results are also discussed.

Simultaneous evaluation of fission and capture cross sections and their covariances for heavy nuclei

Abstract The fission cross sections of 235U, 238U, 239Pu, 240Pu, and 241Pu, and the capture cross sections of 197Au and 238U have been simultaneously evaluated for JENDL-3 in the energy range from 50 keV to 20 MeV. A generalized least squares method has been applied to estimate their cross sections and associated covariances from experimental data of absolute and ratio measurements. The experimental covariances were estimated from the partial errors for each measurement. The partial errors were categorized to a few groups which have specific correlation factors. The correlation only in neutron energies was taken into account. The presently evaluated fission cross sections of 235U and 239Pu are a few percent lower than those of JENDL-2 below 1 MeV.

Material testing capability of the fusion engineering facility, FEF

Abstract A neutronics analysis is performed for FEF to examine the materials testing capability and radiation damage rates in the components. It is found that an average atomic displacement rate of ~ 60 dpa could be obtained in the first 24 l of the test module volume within 10 y. Neutron streaming through ducts for the neutral beam injector and radiofrequency heating as well as through the end plug region seriously affects the system performance of FEF.

Helium trapping and surface deformation of helium-ion-implanted aluminium

Abstract Helium ions accelerated to 20 keV were implanted into Al samples at room temperature. The formation of blisters and flakes at the surface was observed as a function of He + irradiation fluence by scanning electron microscopy and the number of He trapped in the Al was also determined. To examine the influence of microstructure studies were carried out for 400°C, 2 h (well-annealed) samples, 300°C, 0.5 h (moderately-annealed) samples, and compared to previous results for as-received (cold-rolled) Al. The number of trapped He varies in a saw-toothed form with He ion fluence for the samples with flakes and the surface deformation is predominantly by flaking for the well-annealed samples. The moderately-annealed samples undergo blistering and flaking. Results are discussed from the viewpoint of a correlation between the predominant surface deformation mode and the near-surface microstructural condition.

Neutronic optimization for a blanket of the laser fusion reactor, SENRI-I

Neutronic calculations were performed to optimize the SENRI blanket in terms of energy multiplication as well as tritium breeding ratio. The blanket employs a thick (∼ 64-cm) Li layer as breeder/coolant. Three approaches were taken here to achieve the goal: (1) reduction of6Li in the lithium, (ii) replacement of the Li layer by a molten-salt (flibe) layer, and (iii) shipment of excess tritium to a nonbreeding blanket. It was found that the excess tritium produced in the SENRI blanket could be used effectively to obtain additional power by fueling a nonbreeding D-T reactor.