Verification of a self-developed CFD-based multi-physics coupled code MPC-LBE for LBE-cooled reactor

To perform an integral simulation of a pool-type reactor using CFD code,a multi-physics coupled code MPC-LBE for an LBE-cooled reactor was proposed by integrating a point kinetics model and a fuel pin heat transfer model into self-developed CFD code.For code verification,a code-to-code comparison was employed to validate the CFD code.Furthermore,a typical BT transient benchmark on the LBE-cooled XADS reactor was selected for verification in terms of the integral or system performance.Based on the verification results,it was demonstrated that the MPC-LBE coupled code can perform thermal-hydraulics or safety analyses for analysis for processes involved in LBE-cooled pool-type reactors.

Transient Flow Simulation for VVER-1000 Using MCNP6/ANSYS Codes

Investigating the time-dependent behavior of nuclear reactors during loss of flow accidents is necessary for safety assessment.Coupled neutronic/thermal-hydraulic codes are used to simulate a full three-dimensional model and predict the essential safety parameters.MCNP6/ANSYS-FLUENT17.2 coupled scheme is used in the present study to simulate a three-dimensional model for VVER-1000 assembly and analyze its behavior during a LOFA(loss of flow accident).Three LOFA scenarios are proposed to represent the failure of one,two or three of the coolant pumps.The influence of the accident on the reactivity and axial power distribution of the assembly is determined considering thermal-hydraulic feedbacks.Then the data obtained are provided to the thermal-hydraulic code to calculate the actual temperature values.The results of the study showed that the developed coupling scheme granted an actual and precise description of the axial behavior of the assembly during LOFA.The output data obtained from both neutronic and thermal-hydraulic calculations have a strong feedback effect;this demonstrated the effect of data exchange between codes to predict accurate values for the main safety parameters.Moreover,it revealed the importance of studying the detailed axial distribution of the safety parameters for the reactor assessment during accidents rather than taking average values in calculations.

Low-Density Parity-Check Codes: Research Status and Development Direction

In this paper, we conclude five kinds of methods for construction of the regular low-density parity matrix H and three kinds of methods for the construction of irregular low-density parity-check matrix H. Through the analysis of the code rate and parameters of these eight kinds of structures, we find that the construction of low-density parity-check matrix tends to be more flexible and the parameter variability is enhanced. We propose that the current development cost should be lower with the progress of electronic technology and we need research on more practical Low-Density Parity-Check Codes (LDPC). Combined with the application of the quantum distribution key, we urgently need to explore the research direction of relevant theories and technologies of LDPC codes in other fields of quantum information in the future.

A novel chaotic stream cipher and its application to palmprint template protection

Based on a coupled nonlinear dynamic filter （NDF）, a novel chaotic stream cipher is presented in this paper and employed to protect palmprint templates. The chaotic pseudorandom bit generator （PRBG） based on a coupled NDF, which is constructed in an inverse flow, can generate multiple bits at one iteration and satisfy the security requirement of cipher design. Then, the stream cipher is employed to generate cancelable competitive code palmprint biometrics for template protection. The proposed cancelable palmprint authentication system depends on two factors： the palmprint biometric and the password/token. Therefore, the system provides high-confidence and also protects the user＇s privacy. The experimental results of verification on the Hong Kong PolyU Palmprint Database show that the proposed approach has a large template re-issuance ability and the equal error rate can achieve 0.02%. The performance of the palmprint template protection scheme proves the good practicability and security of the proposed stream cipher.

Simulations of THM processes in buffer-rock barriers of high-level waste disposal in an argillaceous formation

The main objective of this paper is to investigate and analyse the thermo-hydro-mechanical（THM） coupling phenomena and their influences on the repository safety.In this paper,the high-level waste（HLW） disposal concept in drifts in clay formation with backfilled bentonite buffer is represented numerically using the CODE BRIGHT developed by the Technical University of Catalonia in Barcelona.The parameters of clay and bentonite used in the simulation are determined by laboratory and in situ experiments.The calculation results are presented to show the hydro-mechanical（HM） processes during the operation phase and the THM processes in the after-closure phase.According to the simulation results,the most probable critical processes for the disposal project have been represented and analyzed.The work also provides an input for additional development regarding the design,assessment and validation of the HLW disposal concept.

Semi-LDPC Convolutional Codes:Construction and Low-Latency Windowed List Decoding

This paper presents a new coding scheme called semi-low-density parity-check convolutional code(semi-LDPC-CC),whose parity-check matrix consists of both sparse and dense sub-matrices,a feature distinguished from the conventional LDPC-CCs.We propose sliding-window list(SWL)decoding algorithms with a fixed window size of two,resulting in a low decoding latency but a competitive error-correcting performance.The performance can be predicted by upper bounds derived from the first event error probability and by genie-aided(GA)lower bounds estimated from the underlying LDPC block codes(LDPC-BCs),while the complexity can be reduced by truncating the list with a threshold on the difference between the soft metrics in the serial decoding implementation.Numerical results are presented to validate our analysis and demonstrate the performance advantage of the semi-LDPC-CCs over the conventional LDPC-CCs.