Internet Thermoflow

Products > Conventional Steam Plant > THERMOFLEX > Sample 3

Nuclear Steam Cycle

This model is included in the samples directory of the demonstration CD as (S1-08)Nucl_Cycle.tfx. It is the steam cycle in a nuclear plant with six feedwater heaters, and steam reheat.

Nuclear steam generation is modeled here using a ‘package boiler’ icon set to generate a known amount of steam at specified pressure and temperature. This saturated steam expands into the wet zone in the HPT and exits at approximately 87% quality. The moisture separator collects much of the wetness and the exit steam is reheated in two stages. The two reheaters in the orange region condense steam bled from the HPT to reheat steam exiting the HPT. Condensate returns to the feedwater train and reheated steam expands in the LPT. Four LPT groups are shown in the green region. Steam bled from the low pressure turbine heats feedwater before the feedpump.

The Mollier chart for this cycle is shown here. Note that in contrast to fossil fired cycles which generate high pressure, high temperature superheated steam; in nuclear cycles the HPT inlet steam is saturated at modest pressure. HPT expansion is entirely in the saturation zone, exiting the HPT at approximately 87% quality. The reheated steam entering the LPT is superheated and expands into the wet zone with an exit quality of approximately 87%.