「人に優しい原子力」へのアプローチとして,人間中心に再構成した,システムの設計解析・運用 管理・教育訓練のためのヒューマンインタフェース開発の現状と,次世紀のヒューマンインタ フェースへの夢と課題を解説する。

抄録全体を表示

The effective delayed neutron fraction β_eff is an important reactor physics parameter, because it plays a role of a conversion factor between the calculated reactivity in Δk/k unit and the measured one in dollar unit. In 1970's, central-sample-worth measurements were done to accumulate the basic data for fast reactor design. Calculated values to these measurements were 30% overestimate. It was pointed out that the 10% of this discrepancy was due to the β_eff. Recently, as an origin of systematic discrepancy between the calculated and measured reactivity is due to the β_eff, needs for experimental method obtaining the β_eff with 1-2% accuracy have been stressed in order to re-examine delayed neutron data and calculational method.
In this report, we describe the β_eff measurements by using the method proposed by E.F. Bennett at the Kyoto University Critical Assembly (KUCA) of the Kyoto University Research Reactor Institute. This method is based on the measurements of covariance between neutron counts and the absolute fission rate. Measurements were performed with the 3/8″ P36EU thermal neutron system which was composed of 93.3% enriched uranium plates of 1/16″ thickness and 3/8″ polyethylene moderator plates, and the 1/8″ P80EU system which was composed of 1/8″ polyethylene plates and had slightly hard neutron spectrum.
As the results of several measurements, the β_eff of the 3/8″ P36EU system ranged from 7.60 ±0.18 to 7.96±0.19, and from 8.07±0.18 to 8.14±0.18 for the 1/8″ P80EU system. The latter is slightly large because of hard neutron spectrum. The experimental accuracy is ±2.2%- ±2.9% which did not clear the target accuracy of 1-2%. But this may be improved by means of an improvement of fission rate measurement. Comparing with these measurements and the calculated values based on the JENDL-2 nuclear data file, they agreed within the range form -4% to 1.5%. Then we concluded that the covariance method was usable to evaluate the β_eff value of thermal neutron system.

抄録全体を表示

Crevice corrosion characteristics of 13% chromium martensitic stainless steel bearing 3.5% nickel and zirconium alloy containing 2.5% niobium (Zr-2.5wt%Nb) were investigated in high temperature pure water. Corrosion of the stainless steel occurred in the crevice, while corrosion of the Zr-2.5wt%Nb was inhibited. Corrosion pits were formed on the stainless steel in the early period of the corrosion test. However, these pits were repassivated in the subsequent corrosion test and the pits did not propagate. The Zr-2.5wt%Nb allo absorbs the subsequent corrosion test and the pits did not propagate. The Zr-2.5wt%Nb allo absorbs the correlated with the corrosion of the stainless steel.

抄録全体を表示

Detailed gas-liquid two-phase flow prediction is required for development of high performance components of nuclear reactors and oil power generation plants, while performance components of nuclear reactors and oil power generation plants, while accelerated calculation method was developed by combining gas and liquid velocity accelerated calculation method was developed by combining gas and liquid velocity unified volumetric velocity of two-phase mixture was calculated instead of individual phase velocities and the calculation process became simpler. Velocity calculation error for a phase of small fraction could be reduced in convergence criteria of mass conservation because acceleration slip was obtained exactly from the momentum balance equations. Calculation time for two-phase flow in a chimney of a natural circulation reactor was about a half of the previous calculation method.

抄録全体を表示