Tokyo University of Mercantile Marine (TUMM) completed a study of flashing and condensation of high-pressure saturated water within the water-filled containment, as generated in a small loss-of-coolant accident of the DRX and SCR (joint study with SRI), and a study of the flashing hammer phenomenon caused when high-pressure saturated water contacts cold water (joint study with JAERI)4). Kobe University of Mercantile Marine (KUMM) successively completed studies on the "thermal now" phenomenon of the passive safety system of a marine reactor (joint study with Kyoto University), and on dynamic characteristics and control of a marine reactor5).
References
1) Materials provided by Dr. Toshihisa Ishida (JAERI).
2) Materials provided by Dr. Akio Yamaji (SRI).
3) Materials provided by Dr. Akira Otsubo (JNC).
4) A. Saito et al., Proceedings of Heat Transfer Symposium of Japan, vol., 1999.
5) Materials provided by Prof. Tomoo Otsuji (KUMM).
[Tomoji TAKAMASA]
11. Automatic Control
The year 1999 started to cope with the Y2K problem before a new millennium. In particular, the field of the automatic control includes many systems using the computer technology, and felt anxious. Fortunately enough, thanks to the efforts of operators and manufacturers, no serious problems or accidents occurred reportedly. In making use of the computer technology in the automatic control, the improvement of its reliability and the independence and redundancy of the system have been discussed, but it was again recognized this year that newly suspicious problems are present.
The field related to the automatic control in 1999 includes applications of the current computer technology and the modern control theory as illustrated in the following examples.
11.1 Autonomous Underwater Vehicle (AUV)
Underwater vehicles used in the underwater examination and observation are classified into the manned submersibles represented by "SHINKAI 6500", and the unmanned submersibles. The unmanned submersibles are further classified into the cabled unmanned submersibles represented by "KAIKO" and the cable-less unmanned submersibles, and the cableless submersibles are generally referred to as "Autonomous Underwater Vehicle; AUV".
The AUV has no cables to transmit/receive the power and control signals, and is provided with the power sources and sensors, and the computers to control the vehicle motion, the equipment operation and the judgment of the operation, enabling the autonomous motions. The AUV navigates in water to achieve the examination and observation without any supports above the water.
KDD Institute and MES reported that the final field tests were carried out on the new cable-less underwater robot for extensive oceanographic examination (which is regarded to be equivalent to AUV, and introduced in this section), and excellent results were obtained. This robot is introduced as the autonomous underwater robot incorporating the fuzzy control as its characteristic. The optimum solution for the operation of the robot is obtained by constructing the robot motion model and the control system model on the computer, and simulating them.
Japan Marine Science & Technology Center (JAMSTEC) introduced the construction of the Autonomous Underwater Vehicle (AUV). The vehicle is provided with fuel cells for underwater equipment and employs the novel power source in place of the conventional batteries, enabling more extensive operations. It employs the hybrid navigation system combining the light ring gyroscope with the Doppler current meter for the inertial navigation system forming the main body of the autonomous navigation, and moves between the sea level and the arbitrary water depth following the designated program for the navigation on the designated route.
