CNP650压水堆不调硼负荷跟踪可行性研究

Investigations in Feasibility of load Follow with Constant Boron in CNP650 PWR

海南昌江核电厂等CNP650压水堆采用Mode-A控制模式,该模式采用黑体控制棒,有很好的基负荷运行能力,但负荷跟踪能力相对较差。而对一些具有小电网的国家或地区,负荷跟踪运行能力具有一定的市场需求。不调硼负荷跟踪通过棒控系统自动完成,大大减轻了操纵员负担;负荷跟踪过程基本不需要频繁地调硼操作,允许简化化学和容积控制系统设计,减少了废液处理成本。为此,在CNP650压水堆上进行了不调硼负荷跟踪研究。负荷跟踪过程主要有两个控制任务:一是反应性补偿;二是功率分布控制。根据不调硼负荷跟踪的控制任务,重新进行了控制棒的设计、分组和布置,设置两套独立控制的控制棒组(功率补偿棒组和轴向偏移控制棒组),分别用于堆芯反应性控制和轴向功率分布控制,以实现不调硼负荷跟踪。使用SCIENCE程序包进行典型的12h^3h^6h^3h、100%—50%—100%功率水平的日负荷循环计算来进行不调硼负荷跟踪分析。计算步骤为:进行三维堆芯模型计算;根据三维堆芯模型建立一维堆芯模型;在一维模型基础上,进行模拟计算。完成了海南昌江核电厂平衡循环寿期末典型的日负荷循环不调硼运行分析,模拟计算结果表明在CNP650压水堆上不调硼负荷跟踪运行模式是可行的。

The CNP650 PWR such as HNCJ NPP implements Mode-A strategy,which uses black control rods.The Mode-A strategy has fine capability of base load operation and bad capability of load follow operation.The capability of load follow operation is needed in some countries or regions with small grid.The automation of control is accomplished through manipulating control rod bank positions as opposed to frequently changing the core boron concentration of load follow in Mode-A,which eases operator burden.An additional purpose is to minimize and in many cases completely eliminate the need for soluble boron changes during load change transients,thus allowing a simplified Chemical and Volume Control System and minimizing waste water processing.A study of the load follow without boron adjustment was performed for CNP650 PWR.Two unique reactor control requirements that are reactivity control and power distribution control are needed to settle during load follow.On the base of control requirements,the control rods worth,sets and layout were redesigned.Two separate sets of control rods which are power compensation banks and axial offset control bank are dedicated to coolant temperature（reactivity）control and to control of axial offset to target value respectively in order to perform load follow with constant boron.The SCIENCE package is used to perform the analysis of load follow with constant boron referred to as 12h^3h^6h^3h（100%—50%—100%）load cycle.Three calculation steps which are setting the three-dimension core model,collapsing three-dimension core model into one-dimension core model,performing simulation on the base of one-dimension core model are carried out in sequence.At the burnup near the end of the 18-month refueling equilibrium cycle,the analysis of load follow with constant boron referred to typical daily load cycle are performed successfully.The calculation results confirm that load follow with constant boron in CNP650 PWR is feasible.