世の中に初めて出てくるリスクや巨大リスクは常に保険として成り立つかどうかという選択にさらされる。保険として成り立つかどうかは,そのリスクが定性化でき,定量化でき,そして突発性と不測性があるかどうかでほぼ決まる。リスクの定性化の過程は危機管理におけるリスクの洗出し過程とよく似ている。
原子力リスクにつき保険になるかどうかはいろいろ議論があり,英国で原子力保険プールという特殊な方法で保険化されたが,十分ではないことがスリーマイルアイランド(TMI)の事故ではっきりした。TMIの分析に東海村の事故を重ね合わせ,行政に責任が大きいことを指摘した。最後に,原子力保険について少し説明をした。

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High Temperature Engineering Test Reactor (HTTR) is a graphite-moderated, helium-cooled reactor which has 30MW of thermal power amd 950°C of outlet coolant-gas temperature.
The fuel loading of the HTTR was started on July 1, 1998. from the core periphery. The first criticality was attained in annular type core of 19 columns on Nov. 10, 1998.
The startup core physics tests consisted mainly of tests for licensing and tests for establishing the technology bases necessary for HTGRs. It was confirmed in the former tests that all fuel blocks are loaded in certain positions and the excess reactivity is less than the limit. Experimental data for the annular core are obtained in the latter tests. Also, it was confirmed that the inverse kinetics method and delayed integral counting method are useful for the measurement of scram reactivity even if it takes about 10s for rod insertions. Furthermere, control rod worth curve, axial neutron flux distribution, etc. were measured to grasp the core performance.
All tests planned in the startup core physics tests had been successfully performed and were completed on Jan. 21, 1999. It was confirmed from the tests that the HTTR was capable to step up to the power ascension tests.

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In a Level Set Method, it is essential that interface tracking and mass conservation are extremely precise. In addition, taking account of surface tension is also required in order to analyze fluid dynamics in two-phase flows which is a basic flow in nuclear engineering. Therefore, we must investigate the precision of surface tension that is included as a body force in Navier-Stokes equation for the purpose of accurate analysis of surface tension dominated flow. Accordingly, first, the precision of surface tension is examined by a static spherical drop problem. Next, analysis of a drop oscillation in zero gravity environment is performed. Consequently, it is indicated that an error norm of pressure induced by surface tension is large when density ratios between a drop and the surrounding fluid are large and the thickness of interface is small. In the analysis of a drop oscillation, it was also obtained reasonable results qualitatively, although the period of a drop oscillation varied according to the thickness of interface.

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For the future autonomous plant, automatic control and diagnostics are being incorporated and operators are mainly engaged in the high levels of diagnosis and decision-making in emergencies. Therefore these matters will be performed through the Man-Machine Interface (MMI). Ship Research Institute has been carrying out the research on the MMI system for autonomous power plants. The automatic classification system of plant states is one of the functions of this MMI and the system utilizes COBWEB, which is known as a way of clustering data to acquire concepts. In this paper, many plant states produced by a plant simulator we examined in order to confirm the effectiveness of this system. The system has well classified plant states produced by a plant simulator.

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