核电厂中间量程保护定值标定方法改进

基于目前中国改进型三环路压水堆（CPR1000）部分机组存在因中间量程电流饱和导致无法在48%额定功率（Pn）完成定值标定及核电厂大修经济性考虑，采用MCNP程序及核设计软件包SCIENCE，研究分析中间量程保护定值标定的新方法。分析结果表明，中间量程保护定值标定调整至30%Pn功率平台实施，采用改进方法标定的保护定值更接近于设计值。      

秦山核电厂核测系统的调试

本文介绍了秦山核电厂核测系统在装料前后、零功率和功率试验阶段的调试过程、方法和主要数据以及源量程、中间量程和功率量程之间的复盖情况。最后对将来核测系统的设计提出了几点建议。     

秦山第二核电厂中间量程保护设定值漂移和标定

商用核电厂中间量程探测器为反应堆提供升功率闭锁、低功率停堆以及非预期停堆3类保护控制信号。保护控制信号由中间量程测量的电流直接触发,然而在安全分析中是以反应堆的功率水平作为保护控制信号来进行分析的。中间量程电流与堆芯功率的对应关系受多种因素的影响可能发生变化,这种变化将导致中间量程功率保护设定值发生偏移。本文分析了保护设定值漂移的影响因素,提出了两种标定方法,给出了标定前后的相对偏差。     

宽量程中子监测装置信号处理算法研究

为适应宽量程中子监测装置处理反应堆功率及倍增周期信息的需要,本文结合裂变室探测器在坎贝尔工作模式下的信号特征,基于坎贝尔定理提出能够覆盖反应堆全量程范围的功率及倍增周期归一化信号处理算法,并利用FPGA技术完成了该算法的实现及验证。验证结果表明:利用归一化算法能够有效实现不同测量模式下不同量程间的"无缝"衔接,实现测量过程中功率及周期的准确及快速响应。     

启动前功率量程刻度系数的算法优化和应用

压水堆核电厂的设计中,RPN系统功率量程是监测核功率和轴向功率偏差△I的直接途径,功率量程刻度系数是保证监测结果准确性的重要参数。由于功率量程的核功率和轴向功率偏差示值直接参与反应堆的在线保护和控制,对启动前功率量程刻度系数的设定需要仔细地考虑。文章对常规刻度系数算法进行分析,指出算法中存在的不足之处及应用上的局限性,并应用修正方案对算法进行优化,经过实践验证,新的刻度系数计算方法能更好地满足机组现场需求,具有很好的推广意义。     

岭澳核电站2号机组一回路流量测量偏差分析及处理

针对岭澳核电站2号机组调试期间发生的二环路3台流量计指示全部超量程故障现象．从反应堆冷却剂流量测量原理入手．对一回路流量测量回路及现场实测数据进行了分析研究,并进行了多次现场试验及功率平台验证,指出二环路流量测量故障的根本原因是其对应弯管流量计的机械制造偏差．提出了对现有流量变送器的量程进行迁移并重新计算和整定相应测量回路参数作为临时解决措施．同时提出了在第一个换料大修期间更换适当量程的流量变送器作为永久解决方案。     

福清核电厂基于堆外核仪表系统中间量程测量的动态刻棒试验

通过分析堆外核仪表系统的功率量程和中间量程的性能，使用堆外核仪表中间量程的测量信号进行动态刻棒试验数据验证。验证结果表明，基于堆外核仪表系统中间量程的动态刻棒试验可作为传统动态刻棒试验的一种手段，其测量误差在验收准则允许范围内，且无需进行本底电流测量即可减少动态刻棒测量时间。      

基于运行数据的船用堆波动管热分层现象研究

基于运行数据将船用堆波动管热分层划分为升功率、降功率、变工况、小喷淋流量4类典型瞬态,对4类典型瞬态分别进行无量纲里查德森数（Ri）分析、瞬态工况数值模拟计算,得到波动管在4类典型瞬态下水平管段的热分层区间长度、持续时间和最大温差。结果表明,升功率和降功率瞬态热分层仅单次贯穿波动管,升功率瞬态的接头部位循环的热波动以及小喷淋流量瞬态水平段的长区间、长时间、大温差的热分层现象和变工况导致的热应力波动可能影响到波动管的安全。本文提出的基于运行数据的波动管热分层现象研究方法为后续热应力和热疲劳分析奠定了基础,同时可以为其他容积设备热分层研究提供参考。      

基于Apros的套管式蒸汽发生器给水控制优化研究

针对套管式蒸汽发生器强耦合性造成的给水控制问题，以采用套管式蒸汽发生器的商用模块化小型反应堆汽水循环系统为研究对象，基于APROS软件建立汽水循环系统仿真模型。稳态仿真结果表明，仿真模型具有较高的仿真精度，满足仿真分析需求。通过升降负荷瞬态仿真试验，研究了套管式蒸汽发生器瞬态运行特性，研究结果表明，采用传统控制方案时，蒸汽流量和给水流量负荷跟随性较好，但蒸汽压力存在较大波动，且在功率由80%FP(FP为满功率)降至50%FP时会触发蒸汽排放。针对该问题提出了给水控制优化方案，仿真试验结果表明，优化后蒸汽压力波动范围明显降低，未触发蒸汽排放动作，系统安全性和稳定性得到了有效提升。     

DL123型六节中子电离室研制

本文介绍了核电堆功率量程用DL123型六节中子电离室的结构设计和关键性能试验测试.     

Estimating Time Dependence of Edge Plasma Turbulence in IR-T1 Tokamak

Time dependence of edge plasma turbulence was investigated in the IR-T1 tokamak. Time dependence of fluctuation level and spectra were measured using Langmuir probe in the region r/a = 0.8–1. In all times of typical shot, the edge plasma was turbulently unstable, with a broad band fluctuation spectrum in the range of frequencies f = 10–1000 kHz. The relative fluctuation level as monitored by the ion saturation current J⁺ was very high, in the range ?0.1–0.6 all over the time, while the fluctuation power spectra were roughly invariant in shape.     

Thermal power estimation by fouling phenomena compensation using wavelet and principal component analysis

A small percentage of reactor thermal power can be overestimated because of fouling phenomena in a secondary feedwater flowmeter. This study proposes a signal processing technique for the compensation of a degraded flowmeter such a secondary feedwater flowmeter in nuclear power plants. The technique proposed is mainly focused on noise classification and step-by-step noise reduction. The noises focused are classified into the rapid distortion caused by environmental interference, the flow fluctuation according to plant state transition and the degradation by fouling phenomena qualitatively. The multi-step de-noising technique reduces each noise by three techniques step-by-step. The wavelet analysis as a low frequency pass filter to remove the rapid distortion, the linear principal component analysis (PCA) to predict a steady-state value from the fluctuation, and the non-linear PCA implemented as an autoassociative neural network (AANN) to predict an original value from the signal including fouling phenomena are developed. The main purpose of this approach is to make an AANN concentrate on compensating the degradation by fouling phenomena itself. For the demonstration the signals from a simulator and signal modeling were used so that the role and the performance of each noise removal step was represented. In addition a thermal power deviation estimator is proposed to recognize the degradation effect of each operating parameter for reactor thermal power calculation.     

Monte Carlo criticality analysis of random media under bounded fluctuation driven by normal noise

In Monte Carlo criticality analysis under material distribution uncertainty, it is necessary to evaluate the response of neutron effective multiplication factor (k_eff) to the space-dependent random fluctuation of volume fractions within a prescribed bounded range. Normal random variables, however, cannot be used in a straightforward manner since the normal distribution has infinite tails. To overcome this issue, a methodology has been developed via forward–backward-superposed reflection Brownian motion (FBSRBM). Here, the forward–backward superposition makes the variance of fluctuation spatially constant and the reflection Brownian motion confines the fluctuation driven by normal noise in a bounded range. In addition, the power spectrum of FBSRBM remains the same as that of Brownian motion. FBSRBM was implemented using Karhunen–Loève expansion (KLE) and applied to the fluctuation of volume fractions in a model of UO₂–concrete media with stainless steel. Numerical results indicate that the non-negligible and significant fluctuation of k_eff arises due to the uncertainty of media formation and just a few number of terms in KLE are enough to ensure the reliability of criticality calculation.     

A Precise Cyclic CMOS Time-to-Digital Converter With Low Thermal Sensitivity

In this paper, a precise cyclic CMOS time-to-digital converter (TDC) with low thermal sensitivity is proposed. Through compensation, the thermal sensitivity of the new cyclic time-to-digital converter is reduced dramatically. The proposed TDC not only possesses reduced thermal sensitivity but also has a small chip size. The circuit was fabricated with TSMC 0.35$mu$m CMOS technology. The size of the circuit is only 0.40 mm by 0.30 mm. The experimental results show that a$pm$6% resolution variation of the new TDC was achieved over 0$,^circhboxC$to 100$,^circhboxC$temperature range which is much better than the$pm$25% resolution variation of the original uncompensated version. The effective resolution is as fine as 57.3ps/LSB at room temperature with a fluctuation of$pm$3.5 ps over 0$,^circhboxC$to 100$,^circhboxC$temperature range, and the corresponding integral nonlinearities are all within$pm$0.8 LSB. The minimum measurement rate is 33 kHz. The measured power consumption is about 3.5 uW.     

Effect of Various Parameters on Edge Plasma Stability in IR-T1 Tokamak

Edge plasma turbulence was investigated over a wide range of plasma and field parameters in the IR-T1 tokamak for the first time. Fluctuation levels and spectra were measured using two arrays of Langmuir probe in the region r/a = 0.75–1.2. Under almost all conditions the edge plasma was turbulently unstable, with a broadband fluctuation spectrum in the drift wave range of frequencies f = 10–1000 kHz. A stable state was observed only in the very cold, low-current discharge formed at unusually high neutral filling pressure. Otherwise, the relative fluctuation level as monitored by the ion saturation current was very high, in the range $ {{\tilde{\rm J}^{ + } } \mathord{\left/ {\vphantom {{\tilde{\rm J}^{ + } } {\bar{\rm J}^{ + } }}} \right. \kern-0pt} {\bar{\rm J}^{ + } }} \cong 0.2{-}0.8 $ , while the fluctuation power spectra were roughly invariant in shape. The relative fluctuation level was always highest near the wall and decreased monotonically toward the plasma centre.     

某核电厂控制棒测量棒位跳变问题分析与处理

控制棒提供堆芯反应性控制与停堆裕量,其真实物理棒位由棒位测量系统监测。某核电厂棒控与棒位测量系统设备换型后,在系统调试阶段出现了真实棒位不变测量棒位频繁跳变的问题。本文通过棒位测量原理及后处理电路特性研究,结合已有数据分析,确定了棒位频繁跳变根本原因是探测器初级线圈供电不同频同相,并给出了棒位探测器参数设定方法。通过现场采集数据,开发棒位探测器校准数据处理软件解决了该核电厂棒位跳变问题,同时针对测量棒位跳变问题的根本原因提出了硬件层面的优化建议。      

加速器驱动次临界反应堆次临界度测量方法研究

以IAEA ADS基准题和日本京都大学KUCA实验装置为对象,对作者提出的次临界度测量方法[1]进行了更广泛的可行性验证。结果表明:对于局部区域功率变化引起的小扰动,通过改进表征中子注量率空间分布的特征参数,该方法仍然具有高的精度;而对于控制棒插入引起的大扰动,通过引入修正因子的方法,也仍然能准确测量次临界度。     

铀浓缩产品丰度控制分析

从离心级联实际生产运行出发,基于价值函数公式,推算出因丰度波动在精料收料容器中造成的分离功损失的表达式。公式显示,丰度波动会导致精料容器内发生分离功损失,且与收料质量呈线性关系,与丰度波动大小呈二次函数关系。分析引起级联精料丰度波动的各种因素变化是否会造成级联内部分离功损失的变化。结果表明,每一种影响因素的参数变化时,级联内部机组压力、流量都会重新调整并进入新的稳态,导致级联偏离理想工况,分离能力下降且级联混合分离功损失相应增加。因此,对精料流产品丰度控制提出优化策略,在实际运行中,应尽可能减少影响产品丰度的参数变化,以减小分离功的损失。     

摇摆运动下单相自然循环核热耦合特性研究

采用考虑6组缓发中子的点堆中子动力学模型,开发了核反馈模拟模块,并将之与摇摆条件下单相自然循环热工水力计算模型进行合并,基于Matlab软件编制了相应的计算程序,实现了摇摆条件下单相自然循环核热耦合的模拟计算。计算结果表明：摇摆条件下,与不考虑核反馈相比,考虑核反馈后核热耦合效应使系统流量降低,系统功率产生波动;系统功率的平均值随摇摆频率及振幅的增大而降低,而系统功率的振幅则随摇摆周期及振幅的增大而增大。核热耦合效应使燃料元件温度的波动振幅减小,起到了抑制燃料温度波动的作用。