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Research Papers: Nuclear Power

Recent Moisture Separator Reheater Design Technologies

[+] Author and Article Information
Jun Manabe, Jiro Kasahara, Issaku Fujita

 Mitsubishi Heavy Industries, Ltd., 1-1-2 Arai-cho, Takasago 676-8686, Japan

Toshiki Kojima

 Mitsubishi Heavy Industries, Ltd., 1-1-1 Wadamisaki-cho, Kobe 652-8585, Japan

J. Eng. Gas Turbines Power 132(10), 102905 (Jul 02, 2010) (10 pages) doi:10.1115/1.4000612 History: Received July 21, 2009; Revised October 09, 2009; Published July 02, 2010; Online July 02, 2010

The moisture separator reheater (MSR) is a key piece of equipment in reheat systems in nuclear steam turbines that use saturated main steam, where it helps improve turbine efficiency and suppress flow-accelerated corrosion. Fundamental to achieving a compact, reliable MSR design are methods for predicting mist separator vane performance and suppressing tube drainage instability. First, we devised a method for predicting separator performance based on the observation of mist separation behavior under an air-water test. We then developed a method for predicting performance under steam conditions from air-water test data and verified it by means of a comparison with the actual results of a steam condition test. The instability of tube drainage associated with both subcooling and temperature oscillation at turbine partial load, which might adversely affect the seal welding of the tubes to the tube sheet due to thermal fatigue, was measured on an existing unit to clarify the behavior. We then developed a technique for increasing venting steam, which had been operating at a constant flow rate, to suppress instability and verified its effectiveness. Both methods were applied to current MSR models, which were adopted for nuclear power plant turbines commercially placed in service from 1984 to 2009, and the effectiveness of the methods was demonstrated. The separator vane mist carryover rate was less than 0.1%, and tube drainage instability was suppressed, demonstrating the effectiveness of the simple design concept of a two-flow U-tube instead of the prevailing four-flow U-tube design. We put forth a new concept in the design of MSRs for 1700 MW class advanced pressurized water reactor (APWR) units based on associated technologies, along with advanced technology for the compact design of pressure vessels and multidisciplinary optimum design for evaluating heat exchanger tube bundles.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Turbine expansion diagram

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Figure 2

Velocity triangles for the turbine blades

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Figure 3

Structure of the current MSR models

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Figure 4

An estimate of one state inside a tube

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Figure 5

Test facility flow diagram for air-water test

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Figure 6

Conventional (left) and advanced (right) vanes

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Figure 7

Re-entrainment of the accumulated drain

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Figure 8

Separator performance during air-water model testing

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Figure 9

Blow-by inhibiting partition plate

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Figure 10

Steam model test facility flow

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Figure 11

Actual steam condition test results and predictions from air-water

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Figure 12

Air-water test results with blow-by inhibiting partition plate

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Figure 13

Tube drainage and ventilation steam

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Figure 14

Heat transfer load distribution

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Figure 15

Measured items for tube drainage: (a) side view of the measured items and (b) two-phase flow temperature of heat transfer tube internal outlet

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Figure 16

Thermocouples at the tube internal outlet (left) and tube outer surface (right)

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Figure 17

Tube drain instability with and without increase in excess steam under 50% turbine load

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Figure 18

Tube drain instability under 100% turbine load

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Figure 19

Mechanism of drainage instability

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Figure 20

New moisture separator reheater design for 1700 MW class units

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Figure 21

Cycle steam flow pattern CFD

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Figure 22

Velocity vector around the separator vane

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Figure 23

Separator vane face velocity contours

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Figure 24

Selection of TTDs

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Figure 25

Optimum TTD and vessel diameter

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