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To improve the efficiency of the Japanese nuclear power plants the National Metrology Institute of Japan (NMIJ) has put a research and testfacility into operation for the measurement of ultra-large flows. Theheart of this facility includes four Altosonic V ultrasonic flowmetersarranged in series with electromagnetic Optiflux flowmeter from Krohne.
The energy demand growing globally and the discussion aboutclimatic change have placed the power engineering sector increasinglyin the focus of public interest. New technologies are in demand in order to use resources more effectively and with less harm for the environment. A new research facility in Japan now shows that with the help of ultramodern measuring technology one has come quite a bit closer tothis goal. The research results of this project was called into beingfor the Japanese nuclear power industry but can also be transferred toconventional power plants operating on the basis of fossil energy sources.
Apart from the energy source used, the basic circuit in nuclear power plants and conventional coal-fired power plants is the same. In a reactor or boiler water is, by being heated up, converted into water vapour/steam which is under high pressure and at a high temperature.
The steam is passed through a turbine which in turn drives the generator producing steam. To produce the necessary pressure difference there is a condenser located downstream of the turbine, in which the steam is cooled down sharply. In the next step, the water ispassed to a feedwater tank, from where it is conveyed by means of thefeedwater pump back into the reactor or boiler for renewed heating-up.
Downstream of the feedwater tank and the feedwater pump a flowmeter is arranged which is referred to as the 'feedwater flowmeter'.It is of particular importance for control of the process, as with theflow rate measured here in conjunction with a temperature measuring system the output of the reactor or boiler is determined and the meeting of the maximum degree of capacity utilisation is monitored. This flow measurement is where NMIJ's research facility starts from.
The inaccuracy of this flow and temperature measurement so far amountsto a total of 2 to 3 percent, about 90 percent of the inaccuracy originating from the flowmeter. For safety reasons the whole circuit is naturally controlled in such a way that the measuring accuracy is taken into account and the maximum utilisation of the plant is reduced by 2 to 3 percent. The undesirable effect of this way of proceeding is hencea reduction of the plant efficiency by a total of 2 to 3 percent dueto the uncertainty of the measurement.
It is now the aim of the NMIJ project to reduce the inaccuracy if this measurement to 1 percent and to increase the efficiency accordingly. For this purpose, the test facility was built in which flow rates are generated correspondingto those in a nuclear power plant. For the entire project, the NMIJ has estimated a period from 2004 to 2008 and a capital expenditure volume of approximately 3 billion yen, i.e. about 18 million euros. Ultimately the gain will be enormous. With the insights gained, not only theeffectiveness of all nuclear power plants, but of all thermal power plants worldwide can be improved by 1 to 2 percent. The NMIJ translatesthe gain in effectiveness for the 55 Japanese nuclear power plants into a saving of new fossil fuel-fired power plants and hence into a saving of 200,000 tonnes of CO2 emissions per annum.
Announcements of interest in the Japanese project have already been received fromdifferent countries. In Japan starting from the local conditions the main focus so far has been on the utilisation of the research results for nuclear power plants. However, it seems in principle that a transfer to other power plant types is possible.
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