核仪表系统源量程通道投入滞后问题分析

Analysis and Solution of Operation Lag of Source Range Channel for Nuclear Instrumentation System

方家山核电1号机组104大修停堆过程中,当反应堆功率下降至热停堆状态后,由于中间量程通道电流较大,在进行硼化干预后共用了10小时40分钟P6信号才消失。相比以往核电站大修,P6信号消失滞后,导致源量程通道投入滞后。对反应堆运行而言,在低功率状态下,源量程通道计数率更能准确地反映核反应堆的状态,源量程通道投入滞后对监视反应堆状态是不利的。通过分析反应堆停堆及启堆前期堆芯物理状态变化、泄漏中子和γ变化、中间量程通道电流变化、P6信号出现或者消失时机变化以及引起源量程切除或者投入时机变化,最终得出中间量程补偿电压的不合理设置是导致源量程投入滞后问题的根本原因,并给出了两种调整中间量程探测器补偿电压的实施方案。

During 104 overhaul shutdown of FJS NPP unit 1,the P6 signal disappear takes 10 hours and 40 minutes with boronation measure,because of the larger current value of intermediate range channel when the reactor power reaches hot shutdown condition.Comparation with other NPP overhauls,the P6 signal disappearance lag causes the operation lag of source range channel.It is not good for monitoring the state of reactor,because counting rate of source range can reflect the state of reactor more accurately at low power level.After analyzing the changes of core physical state during reactor shutdown and start-up,the changes of leakage neutron and γ,the changes of intermediate range current,the time changes of the P6 signal generation or disappearance and the changes of time to cut off or drop into source range channel,the root cause was fixed on the unreasonable setting of compensated voltage of intermediate range channel.Two implementation schemes of adjusting the compensated voltage of intermediate range detector are given.