Superheated steam channels

SHS-3—superheated-steam channel with 3% uranium enrichment and SHS-2—superheated-steam channel with 2% uranium enrichment. 

Distribution deformation near the end of operating period was explained by the nonuniform fuel bumup. The results proved a possibility of elementary diffusion theory application for determining neutron density distributions and showed the impact of the arrangement of the superheated steam channels on power distribution. 

Figure A5.7 Principal design scheme of boiling-water and superheated steam channels ...

Table A5.5 Average parameters of BNPP Unit 1 before and after installation of superheated steam channels (Dollezhal et al., 1969)...

To complete the broad picture of what is meant by burn-out, it is useful to consider further the particular burn-out condition which produces tolerable wall temperatures. Such a condition must occur, for example, in any practical, once-through boiler system, where a change from, for example, liquid water at inlet to superheated steam at outlet takes place in a single heated channel. Normal operation of nuclear reactors beyond burn-out has also been contemplated, and Collier et al. (C5) have described successful experiments with irradiated Zircaloy-clad rods operating continuously beyond burn-out... 

The steam enters through the top of the channel head of the reboiler. Any superheat in the steam is quickly lost to the tubes. Superheated steam does very little in increasing heat-transfer rates in a reboiler. Actually, when considering the temperature difference between the steam and the process fluid, it is best to use the saturated steam temperature, as the real temperature at which all the heat in the steam, is available. For example, assume the following steam flow to a reboiler ... 

Power split between superheated steam and boiling water and channels... 

Water circulates in the closed loop consisting of a reactor, steam separator, preheater, and a circulation pump. Partial evaporation is achieved in the first group of channels. Steam exiting the steam separator is directed to the boiling section of the SG and condenses there. Condensate from the boiler is mixed with water from the separator. The cooled water is fed to a preheater and then directed to circulation pumps. The generated steam on the secondary side is superheated in the second group of channels and then directed to the turbine. 

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