WWER机组堆内仪表系统DNBR异常分析及对策研究

为分析国内某水冷却水慢化动力堆（WWER）机组在首次热试升功率期间出现堆内仪表系统（ICIS）上、下层软件指示的偏离泡核沸腾比（DNBR）不一致的原因，通过研究WWER机组热工水力设计和事故分析程序采用的临界热流密度（CHF）关系式，并采用WWER机组事故分析程序DINAMIKA-97模拟50%、75%和90%功率平台工况，计算其DNBR并与热工水力测量试验的测量值进行比较，判断差异产生原因为ICIS上、下层软件采用了不同的CHF关系式；对100%功率平台的DNBR进行预测，与后续下层软件热工水力测量试验测量值符合得良好，进一步证实了以上判断。因此，建议对ICIS上、下层软件采用的CHF关系式进行修改，统一采用保守的CHF关系式，以取得保守的DNBR。 

Analysis and Solution to Abnormity of DNBR Indicated by ICIS of a WWER Unit

To analyze the reason of difference between the departure from nucleate boling ratio (DNBR) indicated by the upper-level software and lower-level software of the in-core instrumentation system (ICIS) at a certain water-cooled water-moderated power reactor (WWER) unit under its first thermal test during raising power, an investigation was made on the critical heat flux (CHF) correlations adopted in the reactor thermal and hydraulic design and accident analysis of WWER unit. On the above basis, the reason behind the difference was found to be the use of different CHF correlations by the upper-level software and the lower-level software of ICIS through the simulation of thermal tests under 50%, 75% and 90% power level using WWER accident analysis code DINAMIKA-97, calculation of DNBRs and comparison with the ones measured in thermal-hydraulic tests. DNBR under 100% power level was predicted, which coincided with the measured DNBR very well and proved the correctness of the guess further. It is suggested that the CHF correlations adopted by the upper-level software and the lower-level software shall be modified to the same conservative CHF correlation to get a conservative DNBR.