Validation of 1-D Code Developed to Analyze Passive Decay Heat Removal System Using Thermosyphon for Low Temperature and Low Pressure Pool-type LWR

摘要

Low temperature and low pressure pool-type LWR is being developed in KAIST. This reactor has high safety due to large thermal inertia of reactor coolant and low operation pressure. This reactor is designed dedicated for seawater desalination without electric generation. To enhance safety, passive decay heat removal (PDHR) system using thermosyphon is designed for the pool-type reactor. Thermosyphon, vertical and wickless heat pipe, transfers heat from heat source to heat sink effectively by evaporation and condensation of working fluid. After Fukushima accident, PDHR system has been interested as management of station black out (SBO). Thermosyphon is able to remove decay heat during SBO because it is fully passive device using gravity and buoyancy as driving force of working fluid. The PDHR system is consist of thermosyphons which evaporator is submerged in hot pool of reactor and condenser is exposed to heat sink. Working fluid of thermosyphon is heated in hot pool and cooled in heat sink simultaneously. To reduce heat loss during normal operation, the heat sink is filled with air and auxiliary water tank provides water to heat sink in accident. To design diameter and length of thermosyphon of PDHR system, heat transfer in thermosyphon is analyzed by 1-D code. For validation of the 1-D code, experiments are performed for single thermosyphon. The experimental thermosyphon having 4.12cm and length of 160cm is made by copper and investigated under the condition similar with designed thermosyphon for PDHR system. In experiment, electric heater gives heat flux on the evaporator and water heat sink removes heat on the condenser at the saturation temperature. In this study, experimental data about condensation and evaporation of working fluid are reported.