Hideshi Yasuda

Experimental and Theoretical Study of the Residual Product Nuclide Yields in 100-2600 MeV Proton-Irradiated Thin Targets

The work is aimed at experimental determining and computer simulating the independent and cumulative yields of residual product nuclei in the target and structure materials of the transmutation facilities driven by high-current accelerators. The ITEP U-10 accelerator was used in 48 experiments to obtain more than 4000 values of the yields of radioactive residual product nuclei in 0.1-2.6 GeV proton-irradiated thin 182, 183, 184, 186W, natW, 56Fe, 58Ni, 93Nb, 232Th, 232Th, natU, 99Tc, 59Co, 63, 65Cu, natHg, 208Pb, and 27Al targets. The results of verifying the LAHET, CEM95, CEM2k, CASCADE, CASCADE/INPE, YIELDX, HETC, INUCL, and other simulation codes are presented.

Measurement of Activation Reaction Rate Distributions in a Lead Assembly Bombarded with 500-MeV Protons

Abstract Reaction rate distributions of various activation detectors such as the natNi(n,x)58Co, 197Au(n,2n)196Au, and 197Au(n,4n)194Au reactions were measured to study the production and the transport of spallation neutrons in a lead assembly bombarded with protons of 500 MeV. The measured data were analyzed with the nucleon-meson transport code NMTC/JAERI combined with the MCNP4A code using the nuclide production cross sections based on the JENDL Dosimetry File and those calculated with the ALICE-F code. It was found that the NMTC/JAERI-MCNP4A calculations agreed well with the experiments for the low-energy-threshold reaction of natNi(n,x)58Co. With the increase of threshold energy, however, the calculation underestimated the experiments, especially above 20 MeV. The reason for the disagreement can be attributed to the underestimation of the neutron yield in the tens of mega-electron-volt regions by the NMTC/JAERI code.

Conditional Polarity Correlation Method for Improved Reactor Noise Analysis

A correlation function for reactor noise is determined through a conditional polarity-correlation technique in which the polarity of neutron-counting fluctuations is analyzed with the start condition that the counting rate reaches a preset level. This technique, evidently, is an example of flash-start technique, developed for the purpose of improving the efficacy of reactor noise analysis. In the present case, the conditional polarity-correlation function is described mathematically assuming that the counting fluctuations of the detector conform with a Gaussian distribution. The expression thus derived reveals that this function is approximately proportional to a cross-correlation function and is a differential type of polarity-correlation function. In order to examine the validity of the obtained expression, an experiment was performed in a graphite-moderated reactor at slightly subcriticai state to measure the conditional polarity-correlation function. A novel contrivance was adopted in the experiment t...

THRESHOLD REACTION RATES AND ENERGY SPECTRA OF NEUTRONS IN THE 0.8 - 1.6 GeV PROTON-IRRADIATED W, Na TARGETS

Considering the prospects of using the W-Na target assemblies in ADS facilities, the experiments were made to study the nuclear-physics characteristics of W and Na, and the composite structures thereof in their interactions with 0.8-GeV and 1.6-GeV protons. The neutron and proton-induced reaction rates were measured inside, and on the surface of, a cylinder-shaped heterogeneous W-Na assembly together with the double-differential spectra of secondary neutrons emitted from different-depth W and Na discs. The measurement results were simulated by the LAHET, CEM2k, and KASKAD-S codes in terms of the latest versions of nuclear databases.

Thermal Neutron Capture Cross Section of 232Pa

There are measured radiation capture cross-sections of neutrons σn,γ(232Pa) caused by a short-lived (T1/2=31.44 hour) nucleus of 232Pa near the thermal point. The samples of 231Pa weighing ~50 μg were irradiated in a flux of neutrons of IRT reactor (MEPI, Moscow). σnγ was calculated as related to the amount of built up in the course of irradiation atoms of 232Pa and 233Pa (T1/2=27 day). The build-up of 232Pa and 233Pa was defined by the results of irradiated samples γ-spectrometry performed with the use of radiometric measurement complex belonging to MEPI. The contribution of epicadmium neutrons was taken into account as to 233Pa build-up in the samples of 231Pa irradiated in cadmium cases. Thermal neutron capture cross section of 232Pa constituted σth=(655±69) bam.

Investigations of Neutron Characteristics for Salt Blanket Models; Integral Fission Cross Section Measurements of Neptunium, Plutonium, Americium and Curium Isotopes

Neutron characteristics of salt blanket micromodels containing eutectic mixtures of sodium, zirconium, and uranium fluorides were measured on FKBN-2M, BIGR and MAKET facilities. The effective fission cross sections of neptunium, plutonium, americium, and curium isotopes were measured on the neutron spectra formed by micromodels.