加速器驱动次临界系统束流瞬态分析模型的开发

Development and Validation of Simulation Model for ADS Beam Interruption Transient

加速器驱动次临界系统利用散裂反应产生外源中子驱动次临界堆运行,具有次临界固有安全性,同时具备能谱硬、嬗变能力强等特点,被国际公认为核废料处理的最有效手段。ADS系统中外中子源由质子束流轰击散裂靶产生,束流的瞬态变化将直接引起次临界堆堆芯功率的波动,从而影响整个ADS系统的安全运行。本文在调研分析国际现有的ADS束流瞬态分析模型的基础上,提出一种新型的ADS束流瞬态分析模型。基于通用CFD程序FLUENT,通过用户自定义功能(UDF)将中子动力学模型(PKM)和燃料棒瞬态热分析模型(PTM)集成进入FLUENT软件中,完成FLUENT-ADS束流瞬态分析模型开发。采用OECD/NEA发布的ADS失束事故国际基准例题进行模型验证,关键校验参数与发布结果吻合较好,最大计算误差为5. 2%,与国际同类功能的计算程序相当,模型具有一定的可信度,可满足ADS束流瞬态特性初步分析研究要求。

Accelerator Driven Sub-critical System （ADS） applies the spallation neutrons as the external neutron source to drive the sub-critical reactors. It has the sub-critical inherent safety feature and the large flux and powerful transmutation ability for long-lived radiation nucleus, and it has been universally regar- ded as the most promising approach to dispose the long-lived nuclear wastes. In the ADS system, the ex- ternal neutron source is generated by the proton beam bombarding of the spaUation targets. The beam in- terruption transients will directly cause the power fluctuation of the subcritical reactor core, and then affect the safety of the whole ADS system. In this paper, a new ADS beam interruption transient model is pro- moted by researching the existed ADS model and methods worldwide. Based on the universal CFD programme FLUENT, the new model FLUENT -ADS is developed by integrating Point Kinetic Model （PKM） and Pin Thermal Model （PTM） with the assistance of User Defmed Functions （UDF） tools. Validated by the international benchmark published by OECD/NEA, the key validating parameters could meet the results in this paper with a maximum calculation error of 5.2% which is equivalent to other international calculation programmes with similar functions. The results demonstrate that the new model has certain credibility, and it could meet the preliminary requirements of the research and analysis of ADS beam interruption transient.