A new navigation strategy for underwater robot in reactor pool combined propeller speed detection and dynamics analysis with sonar data correction

The navigation reliability of remote-operated vehicle (ROV) in nuclear power plant is very important. It is necessary to carry out redundant navigation design using components with stronger anti-radiation performance compared with traditional navigation devices, to ensure relatively high precision navigation in the case of failure of traditional navigation equipment. The paper proposes a new navigation algorithm for ROV working in the reactor pool combined propellers’ rotating speed detection with hydrodynamics analysis and sonar data correction without using other sensors, just as a redundant navigation strategy. The designed ROV can work at any water depth thanks to the high-precision depth control algorithm. At first, the hydrodynamics analysis of ROV is completed. After that, the dead reckoning (DR) is implemented combined with rotating speed detection of high-performance propellers with dynamics analysis of ROV. Then, the error of DR is analyzed and compensated through repeated field experiments. At last, the sonar data are added to correct the deduced position of ROV when it stops. Field experiment verifies that the precision of the proposed algorithm is high enough to be used as a redundant navigation strategy for ROV working in the reactor pool of the nuclear power plant.     

Development of localization system using ultrasonic sensor for an underwater robot to survey narrow environment

This paper describes a localization system for a swimming robot to survey underwater narrow environments. In that environment, external sensors cannot be set up to localize the robot position, as there are many structures and the robot moves three-dimensionally. Therefore, the position needs to be calculated only by internal sensors. In this work, a new localization method based on map-matching is proposed, referring to cross-sectional shape data cut from a three-dimensional computer-aided design (CAD) data as an environmental map and structural shapes measured by a range sensor. As a range sensor, an ultrasonic sensor which is two-dimensional scanning-type was developed. The reflected signals of the ultrasonic sensor have some noise. Only structural shape data are extracted from the reflected signals. The image correlation is used as the matching method. Experiments to evaluate the performance of the proposed system were implemented at a mock-up environment. As a result, it was confirmed that the position was detected with an accuracy of 100 mm. The error is mainly caused by measurement error of the ultrasonic sensor that is used to calculate structural shapes. We concluded to improve the measurement accuracy of the ultrasonic sensor to reduce localization error.     

Implementation of remotely operated vehicle for direct inspection of reactor pressure vessel and other water-filled infrastructure

To reduce the irradiation exposure time of inspection personnel inspecting the reactor pressure vessel and other water-filled infrastructure during overhaul period, a remotely operated vehicle (ROV) is developed to help monitor the underwater environment and salvage small parts like bolts and nuts in the reactor pool and other water-filled infrastructure of the nuclear power plants. It is designed to be compact, light and radiation resistant. The depth control strategy based on fuzzy proportion integration differentiation is proposed for the ROV to suspend at any depth of the reactor pool. And the integrated navigation algorithm based on the Kalman filter fuses data from sensors, including sonar, depth gauge, three-axis accelerometer, three-axis gyroscope and three-axis magnetometer. Radiation testing has been conducted to verify ROV's ability to work in the reactor pool and other water-filled infrastructure under the environment of high irradiation. Eventually, field experiment was conducted in the reactor simulation pool of the Daya Bay Nuclear Power Plant, and the result verifies the effectiveness of the depth control algorithm, the integrated navigation algorithm and also the leak tightness of the ROV.     

Development of Position Sensitive Helium-3 Proportional Counter for Thermal Neutrons with Novel Signal Readout

A position sensitive ³He proportional counter for thermal neutrons with a novel signal read- out method which has two pre-amplifiers at only one end of the counter body has been developed. It has an advantage for usage in a special environment, such as in a subcritical facility or in water, or for insertion into a narrow space. The characteristics of the counter were evaluated with thermal neutrons. The position resolution was 7 mm with an effective length of 1,200 mm. The integral non-linearity of position signal was less than 0.5%.     

轴向非均匀加热对并联通道流动不稳定性的影响

基于均相流模型建立并联通道系统的控制方程,采用交错网格技术和半隐式差分离散控制方程,并使用追赶法求解来模拟并联通道的两相流动特征。采用轴向余弦功率加热模拟轴向非均匀功率加热。运用小扰动法,获得了不同压力、入口过冷度和轴向功率加热方式下的稳定性边界（MSB）和三维不稳定性空间。对于余弦和均匀功率加热,系统稳定性均随系统压力的增大而增强。余弦功率加热在高过冷度区降低并联通道系统稳定性,而在低过冷度区增强系统稳定性。随进口阻力系数的增加,处于余弦功率加热的并联通道系统稳定性增强,MSB的拐点逐渐向高过冷度区移动。     

Real-time mirror steering for improved closed loop neoclassical tearing mode suppression by electron cyclotron current drive in DIII-D

The development and operation of the neoclassical tearing mode (NTM) avoidance and control system for DIII-D, which uses six sets of real-time steerable mirrors in order to move the electron cyclotron current drive (ECCD) deposition location in plasma, is described. The real-time DIII-D NTM control algorithm residing in the Plasma Control System (PCS) automatically detects an NTM by analysis of the Mirnov diagnostics, employs motional Stark effect (MSE) EFIT MHD equilibrium reconstruction to locate the rational q-surface where the NTM island can be found, then calculates the appropriate mirror position for alignment of the ECCD with the island using ray tracing. The control commands from PCS are sent to the electron cyclotron system to switch on and off or modulate the gyrotrons and to the steerable mirror system to move the steerable mirrors to the requested positions. Successful NTM suppression has been achieved in DIII-D using this control system to rapidly align the NTM island and the ECCD deposition location, and to actively maintain the alignment as plasma conditions change.     

Development of automatic algorithm for localizing loose parts with a steam generator

In this paper, an automatic localization algorithm for estimating the impact location by loose parts in a Steam Generator using modified triangular method is proposed and applied to the impact test data of YongGwang Nuclear Power Plant Unit 3 Steam Generator. The algorithm, at first, was developed at the Mock-up system and modified to apply for the real plant. The Steam Generator is modeled as a cylinder shape and the modified method is used to find out the impact point of a loose part on the model. The result of estimated impact point applying to the developed algorithm has below about 5% average error. If the algorithm will be installed in the existing plant or next generation plant, the safety and reliability of Nuclear Power Plant will be improved.     

A drift tube accelerating structure for CRYRING

A conceptual design has been developed for a driven (non-resonant) drift-tube (DD-T) accelerating structure for CRYRING. Because the ring is small and accelerating voltage requirements not too large, it is possible to use a DD-T to cover the broad frequency range required at modest cost. The control of the system requires only a frequency signal from a beam position pick up and a voltage level signal. With the DD-T can be provided nonsinusoidal wave forms for bunch shaping to improve the space charge limit. A full scale low power model was used to verify the essential features of the design.     

Reactor core isolation cooling system analysis of the Fukushima Daiichi Unit 2 accident with RELAP/ScdapSIM

The reactor core isolation cooling (RCIC) system is an auxiliary system of a boiling water reactor (BWR) that provides makeup water in the case of a severe accident. During the Fukushima accident, the extended operation of the RCIC had a large influence on the accident progression and delayed the core meltdown by almost 70 h. During the Fukushima accident, the water level in the reactor pressure vessel (RPV) was assumed to rise enough to flood the main steam line (MSL), which caused the water to move through the RCIC steam turbine and reduce the overall system water injection capability. A RELAP/ScdapSIM analysis was carried out by using RCIC nodalization to reproduce the Fukushima accident and evaluate the impact of the RCIC system on the accident progression. A coefficient based on the critical flow model was included in the RELAP/ScdapSIM source code to reproduce the degradation suffered by the turbine due to the presence of water. Although highly simplified, the analysis demonstrated the RCIC system's feedback capability, which allows the RCIC to control the plant conditions for a long period of time without any human interaction.     

用于校准192Ir医用源的阱型电离室

研制了一种用于校准医用¹⁹²Ir源的阱型电离室。该电离室的灵敏体积约为271cm³，在极化电压约为300V时，电离室的离子收集效率约为99.96%，总位置灵敏度变化小于0.3%。该阱型电离室对¹⁹²Ir的响应因子为0.230nA/GBq，其相对合成不确定度为1.5%，与IAEA校准过的阱型电离室比对，在不确定度范围内一致。     

空间质子辐射有效剂量测量的闪烁探测器理论设计

有效剂量可解决航天员在空间飞行中所受质子辐射的危害比较与评价问题,在空间辐射危害评价中具有重要应用。为实现空间质子辐射有效剂量监测,针对空间各向同性质子辐射,利用蒙特卡罗程序设计了一种闪烁探测器。通过对探测器结构的特殊设计,在20-400 Me V能量范围内,各向同性质子在该探测器内沉积的能量与国际辐射防护委员会(International Commission on Radiological Protection,ICRP)116号报告提供的质子有效剂量基本成正比。通过探测质子沉积能量来监测质子辐射有效剂量,克服了直接测量有效剂量所存在的困难。对AP8MIN模型地球俘获带质子能谱与随机抽样质子辐射能谱,经数值计算,探测器给出的有效剂量与ICRP116号报告给出的有效剂量的相对偏差均小于±8%。     

Space-time Resolved Spectroscopic System Based on a Rotating Hexahedral Mirror for Measurement of Visible and Ultraviolet Spectral Line Emissions

By using a rotating hexahedral mirror placed in front of the objective lens and two sets of visible and ultraviolet monochromators coupled with a branchy quartz fiber bundle, a space-time resolved spectroscopic system has been developed on the HT-7 superconducting tokamak. A center monitoring system has been used including a Helium-Neon laser and a photodiode detector to indicate the absolute position of the measurement in order to reduce the error caused by the uncertain emissive position of the plasma. By using the asymmetric Abel inversion, the space-time resolved local emission coefficients of the spectroscopic line emissions have been obtained. Presented in this article are simultaneous measurements of two spectral line emissions such as CV-227.1 nm and OV-278.1 nm during a single plasma discharge on the HT-7. Experimental results indicate that the time resolution is better than 3 ms, the space resolution is better than 1.5cm, the ratio of signal to background is better than 10：1, and the relative error of chord-integrated emission profile is less than 10%. Compared to traditional multichannel detecting systems, this system has considerably improved measurement efficiency, reduced uncertainty, and is therefore suitable for transport studies of global particles and impurities.     

Control rod position measurement by two-electrode capacitance sensor in nuclear heating reactor

ABSTRACT

This study employed a new method for measuring the ungrounded/grounded control rod position. In this connection, a sensor system based on the two-electrode capacitance is applied to measure the rod position in NHR. The application of the capacitance sensor is extensively developed with measuring insulating objects. However, the capacitance sensors measuring for ungrounded/grounded control rod position are seldom studied earlier. In addition, the proposed model was set up with ungrounded/grounded control rod for the two-electrode sensor. According to the different electric properties of ungrounded and grounded control rod, this apparatus determines the control rod position using an interface electronics method and two-electrode capacitance sensor. The subsequent experiment and calibration analyses on the data indicate the high reliability and accuracy of the apparatus for monitoring rod position. It is demonstrated that such a system can be applied to automatic real-time monitoring of control rod positon in nuclear heating reactor.     

Design and construction of accelerator signal electrodes

A method is given for making a design calculation of signal electrodes for fixed burst parameters and fixed overall dimensions of the field-free space in the accelerator vacuum chamber. Also the sensitivity may be determined when measuring either the intensity or the position of the center of gravity of the beam. A method is given for finding the engineering limitations placed on the construction of measuring apparatus. The results of the calculation made by this method are in good agreement with experiment.     

A new assessment method for demonstrating the sufficiency of the safety assessment and the safety margins of the geological disposal system

A new method for demonstrating the sufficiency of the safety assessment and safety margins of the geological disposal system has been developed. The method is based on an existing comprehensive sensitivity analysis method and can systematically identify the successful conditions, under which the dose rate does not exceed specified safety criteria, using analytical solutions for nuclide migration and the results of a statistical analysis. The successful conditions were identified using three major variables. Furthermore, the successful conditions at the level of factors or parameters were obtained using relational equations between the variables and the factors or parameters making up these variables. In this study, the method was applied to the safety assessment of the geological disposal of transuranic waste in Japan. Based on the system response characteristics obtained from analytical solutions and on the successful conditions, the classification of the analytical conditions, the sufficiency of the safety assessment and the safety margins of the disposal system were then demonstrated. A new assessment procedure incorporating this method into the existing safety assessment approach is proposed in this study. Using this procedure, it is possible to conduct a series of safety assessment activities in a logical manner.     

（e,2e）实验的符合测量系统

研制成功的（ｅ，２ｅ）实验的符合测量系统由快时间道和慢位置道组成。以该系统四个慢符合道的位置信息电荷脉冲信号和快符合道中的时间信息作为五个参数，测得了电子碰撞Ｈｅｌｓ的符合时间谱和电离能谱。     

PSD位置测量系统在波荡器磁场测量中的应用

位置敏感探测器(Position Sensitive Detector,PSD)是一种基于横向光电效应(x和y方向)的光电位置敏感器件,可直接探测到入射光斑的能量中心位置,在波荡器磁测中可用于获得霍尔探头测量过程中的横向位置变化。为了在狭小或封闭空间内实现对波荡器(尤其是真空内波荡器)磁场进行高精度的测量,我们设计并搭建了测试系统,对导轨直线度(x和y方向)进行了测量。实验结果表明,该位置测量系统具有5μm的测量精度,可以满足霍尔探头在波荡器磁测过程中的位置精度要求。     

Study of capsule position monitoring methods for ITER neutron activation system

The reliable monitoring of the position of an encapsulated activation sample is essential to ensure the diagnostic accuracy and the maintenance of the ITER neutron activation system (NAS). Conventional methods using optical or electrical detectors to determine the capsule position is difficult to be used in the ITER NAS because of limited space as well as extremely high electromagnetic and radiation environment. In this study, new methods using the flow rate change inside a transfer tube assembly and the propagation characteristics of sound wave are investigated for the reliable determination of the capsule position. Experimental results confirm that the abrupt reduction of flow rate in the transfer tube assembly provides information for the final position of the capsule with a high spatial resolution less than 1 mm. The variation of flow rate is also found to indicate the operational status of the pneumatic transfer system. In the case of capsule lost accident, a laboratory scale test has demonstrated that the exact position of the lost capsule can be determined by the sound wave method in which the time delay between an incident sound signal and a reflected one by the capsule is measured so as to provide the position of the capsule with a spatial resolution of 0.2 m. These two capsule position monitoring methods are expected to improve the accuracy, operational stability, and the ability to handle the accident in the ITER NAS.     

Floating Ring Stabilization System

The necessity of magnetically levitating a superconducting, current carrying ring without mechanical supports requires an electrical stabilizing system. The ring, when supported, has only one equilibrium position and this position is one of unstable equilibrium. The ring is free to move with up to six degrees of freedom. Two degrees are dictated by the ability of the ring to move in any direction in the plane of the ring. Additionally, the ring can be tilted requiring three more reference points to determine a new plane. The sixth degree of freedom is the ability of the ring to rotate upon its own axis, but because external forces tending to cause this rotation can, in principal, be eliminated, a restoring supply is not provided. Each of the five identical stabilizing supplies in this system has a feedback loop composed of the following segments. The position detector element is an optical head which sends a light beam across an optical edge on the ring, the reflection of which is sensed on a photo diode. This diode voltage signal, proportional to the ring position, is the input to an amplifier whose output is a signal proportional to position, velocity and ring acceleration. A 50 volt, 100 ampere, bidirectional dc transistor power supply is activated from this signal which in turn powers the appropriate stabilizing coil located near the floating current carrying ring.     

一体化总中子探测仪的研制

研制的一体化总中子探测仪将电子学部件小型化并集成于探测器顶部,与探测器组成一体,达到了体积小、移动方便的目的;用能转动方向的LED实时显示测量结果,通过计算机进行数据处理和报警显示;探头部分设计为具有一定的探测方向性。该探测仪可用于核视察及在车间、仓库进行长期监测,也可用于寻找在设备或核废物中能发射中子的核材料。仪器对前方相距10cm处的252Cf中子源的探测效率为0.92%。经过长期试用考验,总中子探测仪稳定可靠。