Almost all residential air conditioners in Japan are inverter air conditioners in which a permanent magnet synchronous motor (PMSM) is driven by a PWM inverter. The inverter technology can reduce the energy consumption to less than half that of air conditioners driven by a constant-speed induction motor (IM). This paper reviews the trends and the latest energy-efficient technologies for the motor and the power converter that achieve considerable energy saving.
Japan Atomic Energy Agency (JAEA) has carried out research and development to establish the technical basis of High Temperature Gas-cooled Reactor (HTGR) by using High Temperature engineering Test Reactor (HTTR). On March 11th, 2011, the Great East Japan Earthquake of magnitude 9.0 occurred. When the great earthquake occurred, the HTTR had been stopped under the periodic inspection and maintenance of equipment and instrument. In the great earthquake, the maximum seismic acceleration observed at the HTTR exceeded the maximum value in seismic design. The visual inspection of HTTR facility was carried out for the seismic integrity conformation of HTTR. The seismic analysis was also carried out using the observed earthquake motion at HTTR site to confirm the integrity of HTTR. The concept of comprehensive integrity evaluation for the HTTR facility is divided into two parts. One is the “inspection of equipment and instrument”. The other is the “seismic response analysis” for the building structure, equipment and instrument using the observed earthquake. For the basic inspections of equipment and instrument were performed for all them related to the operation of reactor. The integrity of the facilities is confirmed by comparing the inspection results or the numerical results with their evaluation criteria. As the result of inspection of equipment and instrument and seismic response analysis, it was judged that there was no problem to operate the reactor, because there was no damage and performance deterioration, which affects the reactor operation. The integrity of HTTR was also supported by the several operations without reactor power in cold conditions of HTTR in 2011, 2013 and 2015.
On Mar. 11, 2011, the 2011 off the Pacific coast of Tohoku Earthquake of magnitude 9.0 occurred. When the great earthquake occurred, the high temperature engineering test reactor (HTTR) had been stopped under the periodic inspection and maintenance of equipment and instruments. A comprehensive integrity evaluation was carried out for the HTTR facility because the maximum seismic acceleration observed at the HTTR exceeded the maximum value of design basis earthquake. The concept of comprehensive integrity evaluation is divided into two parts. One is the “visual inspection of equipment and instruments.” The other is the “seismic response analysis” for the building structure, equipment and instruments using the observed earthquake. All equipment and instruments related to operation were inspected in the basic inspection. The integrity of the facilities was confirmed by comparing the inspection results or the numerical results with their evaluation criteria. As the results of inspection of equipment and instruments associated with the seismic response analysis, it was judged that there was no problem for operation of the reactor, because there was no damage and performance deterioration. The integrity of HTTR was also supported by the several operations without reactor power in cold conditions of HTTR in 2011, 2013, and 2015. Additionally, the integrity of control rod guide blocks was also confirmed visually when three control rod guide blocks and six replaceable reflector blocks were taken out from reactor core in order to change neutron startup sources in 2015.
There is no standard method for evaluating shielding effect of magnetically shielded room (MSR) for alternating magnetic noises at the frequency of less than several hundred Hz. Usually, the magnetic noise is intentionally applied by using a single exciting coil or a pair of coils set up outside the MSR, and then a reduction of magnetic noise due to the MSR is evaluated. In this paper, in order to establish the standard evaluation method, size and configuration of the noise generation coil is investigated by the finite element analysis and by experiments using a model MSR. In these studies, 3-D magnetic fields and eddy currents are taken into account. The MSR is a brick type and has a door as the same as the actual MSR to take account of complicated eddy current distribution due to the door. First, in order to find conditions for applying the uniform magnetic noise, the effect of the size of a pair of exciting coils on the shielding effect is discussed by setting up the coils just close to the MSR, and the effect of the distance between the coil and MSR is also discussed by using a pair of coils of small size. Second, the effect of the non-uniform noise is discussed by using the small coils which simulate near noise sources such as an electric wire, measuring equipment and so on. The following results are obtained: (1) The shielding effect for the uniform magnetic noise can be evaluated by using a pair of exciting coils larger than the size of a MSR set close to the MSR, and a pair of small coils yield the excessive shielding effect compared with the case using large coils, (2) In the case when a pair of small coils are set up sufficiently far from the MSR, the shielding effect is nearly the same as that for the uniform magnetic noise especially at several ten Hz, (3) The frequency dependence of the shielding effect for non-uniform magnetic noise is different from that for the uniform noise. Especially when a single small coil is set in front of the door for applying the noise in the vertical direction at the center point of the MSR, the shielding effect does not change at the frequency of less than about 20Hz and then diminishes gradually because of eddy currents. This tendency is different from that for a pair of large coils for the uniform noise. Therefore, it is required to evaluate the shielding effect for both uniform and non-uniform magnetic noises.
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