非能动余热排出系统数学模型研究与运行特性分析

利用某型核动力装置非能动余热排出系统1:10原理性试验的8个稳态工况、6个启动工况的试验数据,验证RELAP5/MOD3.2程序对本类型非能动余热排出系统的适用性。结果表明:垂直管内蒸汽凝结换热系数对两相流自然循环的流动与传热影响大;RELAP5/MOD3.2程序过低估算了垂直管内蒸汽流速对蒸汽凝结换热系数的影响,计算结果与试验结果偏差大。对RELAP5/MOD3.2程序垂直管内的蒸汽凝结换热模型进行修正,修正后的计算结果与试验值基本吻合;采用RELAP5程序对垂直管内两相流自然循环传热进行计算,须选择热前沿跟踪模型。对非能动余热排出系统的稳态与瞬态运行特性进行分析,理论计算与试验结果均表明:稳态工况下,系统可以实现稳定的两相流自然循环,系统排热能力受蒸汽发生器水位的影响大,冷却水入口温度与系统压力的影响相对较小;系统的启动特性良好,可快速地建立环路的自然循环,带走反应堆的衰变热。

Mathematic model research and operating characteristic analysis of passive residual heat removal system

The experiment data of eight steady-state conditions and six startup conditions,which are obtained from the principle experimental platform of the passive residual heat removal system(PRHRS) that is one tenth of its actual size in one type of nuclear power plant,are used to evaluate the application of RELAP5/MOD3.2 Code to PRHRS.The results show that the effect of steam condensation heat transfer coefficient of the vertical pipe is strong on the flow and heat transfer of natural circulation for two-phase flow,and that the effect of the steam velocity on the steam condensation heat transfer coefficient in RELAP5/MOD3.2 Code is underestimated so that the differences of computing results and experiment results are large.Therefore,the condensation heat transfer model in the vertical pipe was modified and the computing results were consistent to the experiment results.And the thermal front tracking model in RELAP5 Code should be chosen to compute heat transfer of natural circulation for two-phase flow in vertical pipe.Then the steady and transient state operating characteristics for PRHRS are analyzed.Both the calculation and the experiment indicate that the steady natural circulation for two-phase flow can be realized in the steady-state condition,and the level of steam generator influences the system ability to remove heat greatly,however,the inlet temperature of the coolant and the pressure do little,and the system startup performance is good,so natural circulation can be established quickly to remove the decay heat.