Earticle

The feedwater heaters are critical components in a nuclear power plant. As the operation years of heaters go by, the maintenance costs required for continuous operation increase. Integral drains cooler is the separate heat exchanger combined in the heater shell. The integral drains cooler must be isolated from the other zones. The integral drains cooler must be free from leakage and the entrance into the zone be sealed against the entrance of steam from the condensing zone. Cause of tubes leakage since tubes replacement is the same as the cause before tubes replacement. Therefore, feedwater refurbishment method was selected by heater internal structure condition.

A horizontal tube furnace with a wide uniform-temperature zone was developed using isothermal characteristics of a heat pipe. The heat pipe heating system consists of a concentric annular shaped stainless-steel container, sodium as a working fluid and a screen mesh wick structure. The performance test of the heat pipe revealed that temperature changes along seven consecutive positions of the heat pipe outer wall were less than${\pm}0.1^{\circ}C$, thereby ensuring the high isothermal property. The isothermal property of the heat pipe-adapted tube fumace was investigated and compared to a conventional non-heat pipe type tube furnace. The temperature distribution measurement showed that the uniform temperature zone, in which temperature change is less than${\pm}$1$^{\circ}$C, of the heat pipe employed tube furnace system was about three times longer compared to the conventional tube furnace system.