Yong-kuo Liu

Q-switched Ho:YAlO3 laser pumped by Tm:YLF laser at room temperature

A Q-switched high efficient Ho:YAlO3 (Ho:YAP) laser pumped by a diode-pumped Tm:YLF laser at room-temperature is realized. The maximum output energy reaches 1.58 mJ under the repetition frequency of 5 kHz, when the incident pump power is 15.6 W. The pulse width is 22 ns. The wavelength is 2118 nm when the transmission of output coupler is 30%. The beam quality factor is M2 ∼ 1.39 measured by the traveling knife-edge method.

Condition Monitoring of Sensors in a NPP Using Optimized PCA

An optimized principal component analysis (PCA) framework is proposed to implement condition monitoring for sensors in a nuclear power plant (NPP) in this paper. Compared with the common PCA method in previous research, the PCA method in this paper is optimized at different modeling procedures, including data preprocessing stage, modeling parameter selection stage, and fault detection and isolation stage. Then, the model’s performance is greatly improved through these optimizations. Finally, sensor measurements from a real NPP are used to train the optimized PCA model in order to guarantee the credibility and reliability of the simulation results. Meanwhile, artificial faults are sequentially imposed to sensor measurements to estimate the fault detection and isolation ability of the proposed PCA model. Simulation results show that the optimized PCA model is capable of detecting and isolating the sensors regardless of whether they exhibit major or small failures. Meanwhile, the quantitative evaluation results also indicate that better performance can be obtained in the optimized PCA method compared with the common PCA method.

Research of Nuclear Power Plants Diagnosis Method Based on Data Fusion

Data fusion is a method which suits for complex system fault diagnosis such as nuclear power plants, and is multi-source information processing technology. In this paper, the data fusion information hierarchical thinking used and the nuclear power plants fault diagnosis divided into three levels. In data level data mining method adopted to handle data and reduction attributes. In feature level three parallel neural networks used to deal with attributes reduction of data level and the outputs of three networks are as the basic probability assignment of Dempster-Shafer (D-S) evidence theory. The improved D-S evidence theory synthesizes the outputs of neural networks in decision level, which conquers the traditional D-S evidence theory limitation that cannot dispose conflict information. The diagnosis method is tested through using correlation data of document. The test results indicate that the data fusion diagnosis system can diagnose nuclear power plants faults accurately and the method which has a certain applicable value in use.Copyright

Virtual reality-based adaptive dose assessment method for arbitrary geometries in nuclear facility decommissioning

This paper presents an improved and efficient virtual reality-based adaptive dose assessment method (VRBAM) applicable to the cutting and dismantling tasks in nuclear facility decommissioning. The method combines the modeling strength of virtual reality with the flexibility of adaptive technology. The initial geometry is designed using three-dimensional computer-aided design tools, and a hybrid model composed of cuboids and a point-cloud is generated automatically according to the virtual model of the object. In order to improve the efficiency of dose calculation while retaining accuracy, the hybrid model is converted to a weighted point-cloud model, and the point kernels are generated by adaptively simplifying the weighted point-cloud model according to the detector position, an approach that is suitable for arbitrary geometries. The dose rates are calculated using the point kernel method. To account for radiation scattering effects, buildup factors are calculated using the geometric progression formula in the fitting function. The geometric modeling capability of VRBAM was verified by simulating basic geometries, which included a convex surface, a concave surface, a flat surface and their combination. The simulation results show that the VRBAM is more flexible and superior to other approaches in modeling complex geometries. In this paper, the computation time and dose rate results obtained from the proposed method were also compared with those obtained using the MCNP code and an earlier virtual reality-based method developed by the same authors.

A fast simulation method for radiation maps using interpolation in a virtual environment

In nuclear decommissioning, virtual simulation technology is a useful tool to achieve an effective work process by using virtual environments to represent the physical and logical scheme of a real decommissioning project. This technology is cost-saving and time-saving, with the capacity to develop various decommissioning scenarios and reduce the risk of retrofitting. The method utilises a radiation map in a virtual simulation as the basis for the assessment of exposure to a virtual human. In this paper, we propose a fast simulation method using a known radiation source. The method has a unique advantage over point kernel and Monte Carlo methods because it generates the radiation map using interpolation in a virtual environment. The simulation of the radiation map including the calculation and the visualisation were realised using UNITY and MATLAB. The feasibility of the proposed method was tested on a hypothetical case and the results obtained are discussed in this paper.

30.6 W CW Tm3+ fiber laser of seed amplification

We use all fiber single-mode lasers as seed source, all fiber amplifiers and pump laser coupling amplifier has been experimentally investigated, respectively. The max output power of all fiber amplifier is 30.6 W, corresponding slope efficiency is 39.1%. The two setups, amplifier output laser spectrum finely holds the property of seed laser spectrum, the wavelength of output laser are both 1947.6 nm, the spectrum width is less than 2 nm as same as the wavelength of seed laser. We estimate the beam quality to be M2 = 2.42, clearly indicating nearly diffraction-limited beam propagation.

Q-switched Ho:YAP laser with a volume bragg grating pumped by a Tm-doped silicon fiber laser

We reported the Q-switched Ho:YAlO3 laser with a volume Bragg grating pumped by the Tm doped fiber laser. The Ho:YAP laser maximum output energy was 1.04 mJ under the repetition frequency of 5 kHz when the incident power was 12.49 W with the threshold of 2.38 W. The Ho:YAP output wavelength was centered at 2117.9 nm with bandwidth of about 0.3 nm. The pulse width is 23.9 ns.

Application Research of Two Real-Time Fault Diagnostic Methods in the Nuclear Power Plants

In order to guarantee the safety of nuclear power plants (NPP), we built two real-time fault diagnosis systems adopting VISUAL BAS6.0 programming language, which apply neural network technology and data fusion technology respectively. The fault diagnosis systems interchange data with the simulator timely utilizing communication interface. We insert faults on simulator to test the two systems on line. The advantages and disadvantages are illuminated and contrasted through analyzing the faults diagnostic results off- line, which establish the foundation for the further research and application to the fault diagnosis system of the nuclear power plants. (authors)