The test facility of the prototype sodium heated once-through steam generator (OTSG) is used to verify the accuracy and reliability of the design for the sodium heated OTSG. Besides, according to the test data, the structure and parameters of steam generator can be improved. In this paper, the start-up mode of the test facility of the prototype sodium heated OTSG was pre-analyzed by using the modified RELAP5 MOD4.0. Two kinds of modes to reach the steady state, one is step change mode the other is linear change mode. These two modes are adopted respectively to analyze the thermal hydraulic characteristics of prototype sodium heated OTSG under different conditions. The results show that the step change mode can be used to reduce the time of reaching steady state in low power starting. When the loop is running under high power condition, step change mode can reduce the temperature raise rate and increase the safety of the system.

钠加热直流蒸汽发生器（OTSG）的原型测试设施用于验证钠加热OTSG设计的准确性和可靠性。此外，根据测试数据，可以改善蒸汽发生器的结构和参数。在本文中，使用改良的RELAP5 MOD4.0对原型钠加热的OTSG的测试设备的启动模式进行了预分析。达到稳态的两种模式，一种是步进变化模式，另一种是线性变化模式。分别采用这两种模式分析了在不同条件下原型钠加热的OTSG的热工水力特性。结果表明，阶跃变化模式可用于减少低功率启动时达到稳态的时间。当环路在高功率条件下运行时，