Development of Reference Shunt for Short‐Time Alternating High Current Tests and Study of Measuring System

Short‐circuit tests for power circuit breakers and others require alternative short‐time current measurement, from a few kA to over several tens kA. However, the reference measurement system as a national standard or a specified secondary standard instrument to directly perform comparative test as a complete calibration test in high current class has not yet been established globally. The Japan Short‐Circuit Testing Committee (hereinafter referred to as “JSTC”) has therefore developed a shunt resistor that can be used as a standard instrument for high current measurement. Reference system using this shunt resistor is also considered by JSTC. The performance of the newly developed shunt resistor has been checked through several methods, such as resistance measurement, high power current test, high frequency current test, temperature rise test, and interference test. The results of the tests proved satisfactory performance. Resistance of the shunt resistor before and after the tests was invariant and stable. This makes the shunt resistor adequate for a reference in practical use. In addition, evaluation of uncertainty of the whole reference system including this shunt resistor satisfactorily fulfills the requirements of IEC 62475 edition 1.0, 2010.     

ESTIMATION OF DAILY INTAKE OF FOUR KINDS OF TRIHALOMETHANE BY JAPANESE HOUSEWIVES

Duplicate portions of the daily meals consumed by 30 housewives were collected for 3 consecutive days in the cities of Nagoya and Yokohama in Japan.
Meals were analyzed for chloroform, bromodichloromethane (BDCM), chlorodibromomethane (CDBM) and bromoform by using a purge-trap procedure. The average concentration (and the range) of these four kinds of trihalomethane in each of the 24 h duplicate meals were, chloroform 19.6±18.1 ppb(n.d.-106.8 ppb), BDCM 0.3±0.3 ppb(n.d.-1.7 ppb), CDBM 0.1±0.2 ppb(n.d.-0.6 ppb) and bromoform 0.5±1.3 ppb(n.d.-8.1 ppb).
The mean daily dietary intake of the four kinds of trihalomethane by housewives were, chloroform 40.0±25.4 μg, BDCM 0.6±0.5 μg, CDBM 0.3±0.3 μg and bromoform 0.9±1.3 μg.     

某轻混凝土γ屏蔽积累因子的计算

使用蒙特卡罗程序EGS4计算了光子能量范围0.015~15MeV、屏蔽厚度达40个平均自由程的某核电厂中使用的轻混凝土的γ照射量积累因子,程序计算中考虑了轫致辐射、荧光效应和相干（瑞利）散射对积累因子的影响。使用G-P近似拟合公式对γ屏蔽积累因子计算结果进行拟合计算,给出了相应的积累因子G-P拟合公式的拟合参数。利用此方法可得到此种轻混凝土的任意光子能量和屏蔽厚度的γ屏蔽积累因子。     

Mechanism of inactivation of heat-tolerant spores of Bacillus stearothermophilus IFO 12550 by Rapid Decompression

The effect of three rapid decompression methods to clear the mechanism of inactivation of heat tolerant spores of Bacillus stearothermophilus IFO 12550 was investigated. Pressurization of the spores at 200 MPa and 75°C for 60 min caused a kill of 10⁴ CFU/mL by the link-motion system but the nonrotational rod valve and E.G. seal methods gave a kill of about 10³ CFU/mL. Sterilization was due to the physical breakdown of spore coat, and was induced by its physical permeability of water at high pressure and temperature. Rapid decompression by the link-motion system at 200 MPa decreased the D-value of the spores from 3000 min (100°C, one atmosphere) to 6 min, 11 min, and 17 min at 95, 85, and 75°C, respectively.     

Formation Reaction of ZrO2 Scatterers in ZrF4-Based Fluoride Fibers

This paper clarifies the formation reaction of ZrO₂ crystals which appear as extrinsic scatterers in fluoride fibers. EPMA analysis indicates that BaO exists at grain boundaries of BaF₂ purified by sublimation. BaO reacts with ZrF₄ to form ZrO₂ at 600°C during a glass-melting process. The ZrO₂ formation reaction is influenced by H₂O. Ba(OH)₂, which is formed by the reaction between BaO and water vapor, melts at 370° to 420°C and reacts with ZrF₄ to form ZrO₂ at 450° to 520°C. When low-oxide-content BaF₂ is used for fiber preparation, scatterers significantly decrease.     

Improvement of the Half-embryo Test for Detection of Gamma-irradiated Grapefruit and Its Application to Irradiated Oranges and Lemons

The duration of the half-embryo test used for identification of gamma-irradiated grapefruit was shortened by increasing germination temperature to 35°C. Maximum shooting percentages were reached within 3 days. Gibberellin application reduced the required incubation time to 2 days. Half-embryos extracted from irradiated orange and lemon gave similar results to those of grapefruit. This half-embryo test is proposed as an identification method for irradiated citrus. Assessment can be made after 3 to 4 days when shooting percentage is greater than 50%.     

A Half-Embryo Test for Identification of Gamma-Irradiated Grapefruit

Whole grapefruit were exposed to 5, 15, 30, 50, and 100 krad doses of gamma-radiation. Seeds were removed and half-embryos, consisting of one cotyledon and embryo axis, dissected from the surrounding tissue. Nonirradiated half-embryos germinated faster than intact or partially dissected (outer seed coat removed) seeds. Shoot elongation was also quicker, occurring within 6 days. Irradiated half-embryos over 15 krad doses showed markedly reduced root growth and shoot elongation was almost totally retarded. Differences between irradiated and nonirradiated half-embryo were not affected when variety, harvest date, and fruit storage conditions were varied. This test could thus discriminate between irradiated and non irradiated grapefruit.     

Training and Research on Photovoltaic at HNCT

Translated from the Japanese