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Development of Simplified Feed-water Heating System using Multi-stage Steam Injectors for Nuclear and Thermal Power Plant

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Fig.1 

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Fig.2 

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Fig.3 

1. Summary

A steam injector (SI) is a passive jet pump with no movable parts, able to drive water by supersonic steam jet, reaching a discharge pressure even higher than the supply steam pressure. Moreover the SI works as a direct contact heat exchanger between steam and water. We developed multi-stage SIs by using steam directly extracted from the turbine, which has high performance in wide operation range and can be used in parallel-operation to simplify feed-water heating system of nuclear and thermal-power plant.

2. Details of the Technique

The “simplified feed-water heating system using multi-stage SIs” has been developed for the feed-water system of the current ABWR (Advanced Boiling Water Reactor). Fig.1 shows the current low-pressure feed-water heating system, in which the heaters are set up above the condenser as necked heaters. We have developed the multi-stage SIs system as shown in Fig.2, composed of in-line four SIs and a jet deaerater. The feed-water heating system can be greatly simplified by replacing the current low-pressure heaters with the compact multi-stage SIs as shown in Fig.3. Moreover, the multi-stage SIs system can be applied to the feed-water heating system of thermal power plants.

The multi-stage SIs system makes it possible to reduce the volume and weight of the low-pressure feed-water heating system by around one third of that of ABWR and the height of the turbine building by around 3.5m, it would be possible to cut down construction cost consequently. Moreover, the maintenance cost and the loss of electricity generation can be reduced since it becomes unnecessary to replace the feed-water heaters two times with 6 months in the plant life cycle. We are planning to make the system wide use in the small-sized system before applying to the large-sized system.

3. Endurance Test

We carried out endurance tests by continuous operation using steam from the thermal-power station at SIET in Italy and confirmed that there was no performance degradation and erosion damage under more severe conditions than those for normal feed-water heater.


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