Liqin Hu

Design and R&D Progress of China Lead-Based Reactor

Liquid lead or lead-based alloy is a potential candidate coolant for fast reactors and ADS subcritical reactors because of its many unique nuclear, thermal-physical and chemical attributes. Chinese Academy of Sciences (CAS) had launched an engineering project to develop ADS system and lead-based reactors. Series CLEAR reactor conceptual designs were finished, and the preliminary engineering design for the China Lead-based research reactor (CLEAR-I) was underway. The key components prototypes for engineering validation including the control rod drive system, refueling system, fuel assembly have been constructed, the validation experiment are carrying out. KYLIN series PbBi experimental loops has already been built to perform structure material corrosion experiment, thermal-hydraulics experiment and safety experiment for CLEAR series reactors. The highly intensified neutron generator HINEG will be constructed to take the benchmark experiment of neutronics simulation codes. In this paper, the design and R&D progress are presented.Copyright

Preliminary safety analysis for the Chinese ITER Dual Functional Lithium–Lead Test Blanket Module

Safety analysis is part of the ITER Test Blanket Module (TBM) design process ensuring that the TBM does not adversely affect the safety of ITER. To get the licence for TBM as a whole with ITER, relevant safety analysis is required for each TBM system proposed by each party. The safety analysis for the Chinese Dual Functional Lithium–Lead Test Blanket Module (DFLL-TBM) has been performed based on the latest DFLL-TBM design. In this paper, the following safety considerations, such as source terms, operational releases, accident sequence analyses and waste assessment, were analysed. Both the deterministic approach and the complementary systematic approach starting with failure mode and effects analysis studies were adopted in the accidental analysis. The preliminary results showed that the DFLL-TBM system at normal operating conditions and under accident scenarios did not add additional safety hazards to the ITER machine and could meet the ITER safety requirements and additional safety requirements for the TBM system.

Development of Chinese Female Computational Phantom Rad-Human and Its Application in Radiation Dosimetry Assessment

Abstract Dose conversion coefficients are important physical quantities in radiation dosimetry assessment and can be derived from Monte Carlo simulation based on human computational phantoms. In order to accurately evaluate the dose to a human body especially for a Chinese female, a precise whole-body Chinese female computational phantom named Rad-Human was constructed based on high-resolution digital color slice images of an adult female body. Rad-Human includes 46 tissues and organs with a minimum voxel size of 0.15 × 0.15 × 0.25 mm for head and neck and 0.15 × 0.15 × 0.5 mm for other regions, and it contains more than 28.8 billion voxels. Conversion coefficients and effective doses of external radiation, specific absorbed fractions, and S values of internal radiation for different energies for Rad-Human were calculated. The calculated dose conversion coefficients were reasonable comparing and analyzing the relationship between dose and organ characteristics with those values of the International Commission on Radiological Protection (ICRP) reference phantom. Based on the information and simulation results of Rad-Human, a set of more complete data of dose conversion coefficients in the radiation field was constructed for a Chinese adult female. Dose discrepancies that were observed were due to differences of body structures between the two phantoms. The differences of dose conversion coefficients between Rad-Human and the ICRP reference phantom demonstrate that Rad-Human can more accurately assess the exposure dose especially for a Chinese female.

Development and Application of a Risk Monitor for Nuclear Power Plant

Risk monitor, which has been widely used in the progress of RID (Risk Informed Decision) in a NPP (Nuclear Power Plant), is a plant specific real-time analysis tool to determine the instantaneous risk based on actual plant configuration. Based on wide investigation of challenges and technical issues during the development of a risk monitor, a prototype named Risk Angel has been designed by FDS Team in collaboration with several institutes and universities. An overview of the architecture and main functions of Risk Angel were introduced in this paper, as well as the quantitative approach, the calculating engine and the model development. Risk Angel has been applied in a nuclear power plant in P.R. China.Copyright

A new decomposition algorithm for complex voting gates processing in qualitative fault tree analysis

Fault tree analysis technique is one of the main methods of reliability analysis. In a fault tree, voting gate, namely k out of n (k/n) gate, is one of the standard Boolean logic constructs which can represent AND, OR and NOT gates. It is traditionally expanded into a combination of AND and OR gates, but such expansion results in combinatorial explosion problem in determining minimal cut sets of the fault tree for even a not very big n, especially when the voting gate inputs are complex sub-trees rather than basic events. In this article, a new decomposition algorithm based on expanded combination formula which can decompose the voting gates more quickly while the space and time complexity is lower than the traditional expansion was proposed. The results of experiments on fault trees with voting gates showed that this algorithm was more efficient than the traditional expansion method and the recursive decomposition method.

Deformable image registration of CT images for automatic contour propagation in radiation therapy

Radiotherapy treatment plan may be replanned due the changes of tumors and organs at risk (OARs) during the treatment. Deformable image registration (DIR) based Computed Tomography (CT) contour propagation in the routine clinical setting is expected to reduce time needed for necessary manual tumors and OARs delineations and increase the efficiency of replanning. In this study, a DIR method was developed for CT contour propagation. Prior structure delineations were incorporated into Demons DIR, which was represented by adding an intensity matching term of the delineated tissues pairs to the energy function of Demons. The performance of our DIR was evaluated with five clinical head-and-neck and five lung cancer cases. The experimental results verified the improved accuracy of the proposed registration method compared with conventional registration and Demons DIR.

Design and Development of Virtual Assembly Prototype System for CLEAR-I

China LEAd-based research Reactor (CLEAR-I), which is one part of Accelerator Driven subcritical System (ADS) proposed by Chinese Academy of Sciences. Assembly scenario simulation is part of the CLEAR-I RD 2) immersive experience in virtual environment; 3) interactive virtual assembly simulation of complex components. The paper describes the system architecture, main methods and its preliminary application to CLEAR-I.Copyright

A Variable Ordering Heuristic Based on Zero-Suppressed Binary Decision Diagrams

Two approaches have been proposed to solve the large-scale fault trees or event trees for Probabilistic Safety Assessment in a nuclear power plant. The first one consists in MCS/ZBDD, which uses ZBDDs (Zero-suppressed Binary Decision Diagrams) to implement classical MCS (Minimal Cut Sets) algorithm. The second consists in designing heuristics and strategies to reduce the complexity of the BDDs (Binary Decision Diagrams) construction. This paper was motivated to combine the MCS/ZBDD and designing heuristics for ZBDDs together. A heuristic, which took the failure rate of basic event into account and utilized that truncation could be implemented on ZBDDs during the calculating process, was proposed. This heuristic accelerated the analysis progress by bringing forward the truncation and reducing the complexity of the intermediate ZBDDs. RiskA, a Zero-suppressed Binary Decision Diagram package extended to safety and reliability analysis, has adopted this heuristic. RiskA’s truncation strategies, which had some relations with the ordering scheme, were also introduced. The correctness and efficiency of this new heuristic were verified by some practical models’ analyses.Copyright

Impacts of lung and tumor volumes on lung dosimetry for nonsmall cell lung cancer

Abstract The purpose of this study was to determine the impacts of lung and tumor volumes on normal lung dosimetry in three‐dimensional conformal radiotherapy (3DCRT), step‐and‐shoot intensity‐modulated radiotherapy (ssIMRT), and single full‐arc volumetric‐modulated arc therapy (VMAT) in treatment of nonsmall cell lung cancers (NSCLC). All plans were designed to deliver a total dose of 66 Gy in 33 fractions to PTV for the 32 NSCLC patients with various total (bilateral) lung volumes, planning target volumes (PTVs), and PTV locations. The ratio of the lung volume (total lung volume excluding the PTV volume) to the PTV volume (LTR) was evaluated to represent the impacts in three steps. (a) The least squares method was used to fit mean lung doses (MLDs) to PTVs or LTRs with power‐law function in the population cohort (N = 32). (b) The population cohort was divided into three groups by LTRs based on first step and then by PTVs, respectively. The MLDs were compared among the three techniques in each LTR group (LG) and each PTV group (PG). (c) The power‐law correlation was tested by using the adaptive radiation therapy (ART) planning data of individual patients in the individual cohort (N = 4). Different curves of power‐law function with high R2 values were observed between averaged LTRs and averaged MLDs for 3DCRT, ssIMRT, and VMAT, respectively. In the individual cohort, high R2 values of fitting curves were also observed in individual patients in ART, although the trend was highly patient‐specific. There was a more obvious correlation between LTR and MLD than that between PTV and MLD.

SU‐E‐I‐07: Response Characteristics and Signal Conversion Modeling of KV Flat‐Panel Detector in Cone Beam CT System

Purpose: The flat-panel detector response characteristics are investigated to optimize the scanning parameter considering the image quality and less radiation dose. The signal conversion model is also established to predict the tumor shape and physical thickness changes. Methods: With the ELEKTA XVI system, the planar images of 10cm water phantom were obtained under different image acquisition conditions, including tube voltage, electric current, exposure time and frames. The averaged responses of square area in center were analyzed using Origin8.0. The response characteristics for each scanning parameter were depicted by different fitting types. The transmission measured for 10cm water was compared to Monte Carlo simulation. Using the quadratic calibration method, a series of variable-thickness water phantoms images were acquired to derive the signal conversion model. A 20cm wedge water phantom with 2cm step thickness was used to verify the model. At last, the stability and reproducibility of the model were explored during a four week period. Results: The gray values of image center all decreased with the increase of different image acquisition parameter presets. The fitting types adopted were linear fitting, quadratic polynomial fitting, Gauss fitting and logarithmic fitting with the fitting R-Square 0.992, 0.995, 0.997 and 0.996 respectively. For 10cm water phantom, the transmission measured showed better uniformity than Monte Carlo simulation. The wedge phantom experiment show that the radiological thickness changes prediction error was in the range of (-4mm, 5mm). The signal conversion model remained consistent over a period of four weeks. Conclusion: The flat-panel response decrease with the increase of different scanning parameters. The preferred scanning parameter combination was 100kV, 10mA, 10ms, 15frames. It is suggested that the signal conversion model could effectively be used for tumor shape change and radiological thickness prediction. Supported by National Natural Science Foundation of China (81101132, 11305203) and Natural Science Foundation of Anhui Province (11040606Q55, 1308085QH138)