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General Articles |
Vol.1, No.1 (May, 2009), GA3 |
Virtual Plant and Maintenance Revolution |
Kenzo MIYA, President of Japan Society of Maintenology |
1. Introduction Maintenance work at a nuclear power plant is enormous in many divergences. The role of maintenance business we expect is first to prevent an accident and secondly to increase economic efficiency which is normally accomplished by raising the rate of operation availability. Consequently, that is to bring useful products and services in our society. In the meantime, there is one of growing concerns of social issues that a vast amount of industrial waste is built up if we fail to extend equipment lifetime by renewing the facility. Eventually the burden gets exceedingly on top of our society. Conversely if we can extend 50 years of the lifetime to 100 years or what more, 100 years to 150 years, the effectiveness should immeasurably be high. The recent roles and importance of maintenance exists in this perception.? 2. Recovery from Deterioration of Equipment and Facility, and Maintaining a Safety LevelAt a nuclear power plant facility, it is possible for example to maintain the existing nuclear reactor at the same level of the newly-built plant by properly replacing the large facility that refers to safety every 10 years. Why is it possible? Its rationality is laid on the following contexts:(1) In a case of a nuclear power plant, it is imperative to prevent a radioactive accident in where there is a group of equipment directly involved (safety equipment) and another group of many of equipment not involved or not directly related to safety (ordinary equipment). A conventional maintenance is designed to not only keep functions of the equipment in good condition but also to satisfy the technical standard. (2) In cope with an age-related deterioration of the facility at a nuclear power plant, it should be achieved to keep the safety level at the same level of newly-built facility by replacing the safekeeping equipment in proper time intervals, or taking deterioration recovery measures. This is performed based on the long-term maintenance plan that is formulated in “periodical safety review”. As for non-safekeeping equipment, the industry has always made the effort to minimize breakdown. In addition, safety inspection by the regulatory authority is an integral part of effective prevention measure. (3) Not to mention, a safety level of the existing reactor cannot be the same level as a newly-built reactor.? Separating a safety level from a maintenance level, it is conceivable that both safety level of old and new reactors is same when reliability of the existing one can be maintained at the level of the new reactor. In brief, that is an essential key to effectiveness of maintenance to maintain an old equipment in the same condition as a new one by taking deterioration recovery measure to safety equipment. The industry is normally responsible for a trouble is not related to safety. Even though the trouble just occurs, it should be bearable as far as their effort toward minimizing accidents continues. It is also socially a common notion that a minor accident is an industry issue. Safety standard referred by this paper is not on a term of “absolute safety” but on socially common idea.?In approaching to materialization of this idea, a plant safety needs to be quantitatively measured. How we can achieve this is an issue. To clear this, a“virtual plant” is proposed. A virtual plant has potential to drastically help bring about how maintenance should be carried out, which facilitates quantifying the data for safety. Therefore when this idea is materialized, it would be affirmed that “maintenance revolution” is literally realized. 3. What Can a Virtual Plant DoBriefly speaking, a virtual plant is a copy of actual plant. A static virtual plant can be built in a capacity of a computer. As an example of what it is, CAD (Computer Aided Design) seems to be a kind of a virtual plant but it is not, because its functions are limited in it. CAD provides only part of functions for the virtual plant and does not include a concept of time, i.e. the point at which an event occurs. For the reason, CAD cannot be equal to that of an actual reactor. How can we adapt the concept of time to the system? The way to do is to measure deterioration data changing every moment in the actual reactor and to link the data properly to each component concerned in the virtual plant. In this way, a chronological pole is ideally set in the virtual plant. Considering the fact that an equipment lifetime is just a few decades in case of a nuclear plant, it would be reliably enough to measure and update the data annually. The more the actual data is linked to the virtual plant, the closer the virtual plant comes to the actual reactor. This is a considerable advantage. Details of what a virtual plant can do is specifically outlined as follows: (1) Grasp of Tendency of Deterioration (2) Assessment and Projection of Deterioration (3) Likelihood of Weak Components (4) Implementation of a Virtual Maintenance (5) Determination of Maintenance Plan (6) Assessment of Safety Level and Maintenance Level (7) Human Factor and Virtual Maintenance As explained in the above a concept of a virtual plant and its effectives, it would drastically changes the way of maintenance. The new way of maintenance will bring benefits such as ability to detect weakness of equipment/facility in advance, and so forth. We can remark that there appears the proper situation where maintenance revolution will be taken up as we perceive the concept of a virtual plant that would be adapted to the actual plant maintenance. |