Implementation of high-fidelity neutronics and thermal–hydraulic coupling calculations in HNET

To perform nuclear reactor simulations in a more realistic manner,the coupling scheme between neutronics and thermal-hydraulics was implemented in the HNET program for both steady-state and transient conditions.For simplicity,efficiency,and robustness,the matrixfree Newton/Krylov(MFNK)method was applied to the steady-state coupling calculation.In addition,the optimal perturbation size was adopted to further improve the convergence behavior of the MFNK.For the transient coupling simulation,the operator splitting method with a staggered time mesh was utilized to balance the computational cost and accuracy.Finally,VERA Problem 6 with power and boron perturbation and the NEACRP transient benchmark were simulated for analysis.The numerical results show that the MFNK method can outperform Picard iteration in terms of both efficiency and robustness for a wide range of problems.Furthermore,the reasonable agreement between the simulation results and the reference results for the NEACRP transient benchmark verifies the capability of predicting the behavior of the nuclear reactor.

Core and blanket thermal-hydraulic analysis of a molten salt fast reactor based on coupling of OpenMC and OpenFOAM

In the core of a molten salt fast reactor(MSFR),heavy metal fuel and fission products can be dissolved in a molten fluoride salt to form a eutectic mixture that acts as both fuel and coolant.Fission energy is released from the fuel salt and transferred to the second loop by fuel salt circulation.Therefore,the MSFR is characterized by strong interaction between the neutronics and the thermal hydraulics.Moreover,recirculation flow occurs,and nuclear heat is accumulated near the fertile blanket,which significantly affects both the flow and the temperature fields in the core.In this work,to further optimize the conceptual geometric design of the MSFR,three geometries of the core and fertile blanket are proposed,and the thermal-hydraulic characteristics,including the three-dimensional flow and temperature fields of the fuel and fertile salts,are simulated and analyzed using a coupling scheme between the open source codes OpenMC and OpenFOAM.The numerical results indicate that a flatter core temperature distribution can be obtained and the hot spot and flow stagnation zones that appear in the upper and lower parts of the core center near the reflector can be eliminated by curving both the top and bottom walls of the core.Moreover,eight cooling loops with a total flow rate of0.0555 m3 s-1 ensur an acceptable temperature distribusure an acceptable temperature distribution in the fertile blanket.

A set of new nucleon coupling constants and the proto neutron star matter

Using a new set of nucleon coupling constants CZll the properties of a proto neutron star are examined within the framework of the relativistic mean-field theory for the baryon octet system. It is found that the relative number density of A,≡ , and ≡0 for CZll are all smaller than those for GL97 and for both CZ11 and GL97, ∑-∑0 and ∑＋ do not appear. It is also found that the pressure and the maximum mass for CZll are all smaller than those for GL97. The maximum mass for CZ11 decreases by approximately 9 percent compared with that for GL97.

Effects of Tensor Couplings on Nucleonic Direct URCA Processes in Neutron Star Matter

The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter is investigated within the relativistic Hartree-Fock approximation. We particularly study the influences of the tensor couplings of vector mesons ω and ρ on the nucleonic direct URCA processes. It is found that the inclusion of the tensor couplings of vector mesons w and p can slightly increase the maximum mass of neutron stars. In addition, the results indicate that the tensor couplings of vector mesons ω and ρ lead to obvious enhancement of the total neutrino emissivity for the nucleonic direct URCA processes, which must accelerate the cooling rate of the non- superfluid neutron star matter. However, when considering only the tensor coupling of vector meson ρ, the neutrino emissivity for the nucleonic direct URCA processes slightly declines at low densities and significantly increases at high densities. That is, the tensor coupling of vector meson ρ leads to the slow cooling rate of a low-mass neutron star and rapid cooling rate of a massive neutron star.

Phase Transitions in Neutron Stars Within Modified Quark-Meson Coupling Model

K-condensation and quark deconfinement phase transitions in neutron stars are investigated.We use themodified quark-meson coupling model for hadronic phase and the MIT bag model for quark phase.With the equationof state (EOS) solved self-consistently,we discuss the properties of neutron stars.We find that the EOS of pure hadronmatter with condensed K^- phase should be ruled out by the redshift for star EX00748-676,while EOS containingunpaired quark matter phase with B^(1/4) being about 180 MeV could be consistent with both this observation and thebest measured mass of star PSR 1913+16.But if the recent inferred massive star among Terzan 5 with M>1.68M_⊙is confirmed,all the present EOSes with condensed phase and decor,fined phase would be ruled out.

Development and validation of the code COUPLE3.0 for the coupled analysis of neutron transport and burnup in ADS

The analysis of the fuel depletion behavior is critical for maintaining the safety of accelerator-driven subcritical systems(ADSs). The code COUPLE2.0 coupling 3-D neutron transport and point burnup calculation was developed by Tsinghua University. A Monte Carlo method is used for the neutron transport analysis, and the burnup calculation is based on a deterministic method. The code can be used for the analysis of targets coupled with a reactor in ADSs. In response to additional ADS analysis requirements at the Institute of Modern Physics at the Chinese Academy of Sciences, the COUPLE3.0 version was developed to include the new functions of(1) a module for the calculation of proton irradiation for the analysis of cumulative behavior using the residual radionuclide operating history,(2) a fixed-flux radiation module for hazard assessment and analysis of the burnable poison, and(3) a module for multi-kernel parallel calculation, which improves the radionuclide replacement for the burnup analysis to balance the precision level and computational efficiency of the program. This paper introduces thevalidation of the COUPLE3.0 code using a fast reactor benchmark and ADS benchmark calculations. Moreover,the proton irradiation module was verified by a comparison with the analytic method of calculating the210 Po accumulation results. The results demonstrate that COUPLE3.0 is suitable for the analysis of neutron transport and the burnup of nuclides for ADSs.

Anti-noise performance of the pulse coupled neural network applied in discrimination of neutron and gamma-ray

In this study,the anti-noise performance of a pulse-coupled neural network(PCNN)was investigated in the neutron and gamma-ray(n-γ)discrimination field.The experiments were conducted in two groups.In the first group,radiation pulse signals were pre-processed using a Fourier filter to reduce the original noise in the signals,whereas in the second group,the original noise was left untouched to simulate an extremely high-noise scenario.For each part,artificial Gaussian noise with different intensity levels was added to the signals prior to the discrimination process.In the aforementioned conditions,the performance of the PCNN was evaluated and compared with five other commonly used methods of n-γdiscrimination:(1)zero crossing,(2)charge comparison,(3)vector projection,(4)falling edge percentage slope,and(5)frequency gradient analysis.The experimental results showed that the PCNN method significantly outperforms other methods with outstanding FoM-value at all noise levels.Furthermore,the fluctuations in FoM-value of PCNN were significantly better than those obtained via other methods at most noise levels and only slightly worse than those obtained via the charge comparison and zerocrossing methods under extreme noise conditions.Additionally,the changing patterns and fluctuations of the FoMvalue were evaluated under different noise conditions.Hence,based on the results,the parameter selection strategy of the PCNN was presented.In conclusion,the PCNN method is suitable for use in high-noise application scenarios for n-γdiscrimination because of its stability and remarkable discrimination performance.It does not rely on strict parameter settings and can realize satisfactory performance over a wide parameter range.

百千瓦级空间核反应堆屏蔽优化研究

屏蔽体尺寸和重量对空间核反应堆和核动力航天器性能有着重要影响,因而屏蔽设计优化是空间核动力系统设计的关键。本文以JIMO项目反应堆为对象,在铍-碳化硼-钨-氢化锂分层组合屏蔽方案的基础上,考虑到辐照剂量的径向分布,采用蒙特卡罗方法计算了负载处辐照剂量和氢化锂中子剂量,分析了屏蔽设计原理,并提出了分步优化方法以实现屏蔽优化。根据结果分析,调整了铍和碳化硼的厚度比例、钨半径及布置位置,获得了优化的屏蔽方案,在满足屏蔽要求的基础上质量减少了98.41 kg。提出的屏蔽方案及设计流程可为空间核电源屏蔽设计优化提供参考。

小角中子散射原位热力耦合加载装置

热力耦合近工况条件下材料微观结构的原位实验研究,对于深入理解材料服役性能演化机制十分重要,可给出样品微观上的纳米结构尺度分布。为充分发挥小角中子散射统计性好、取样体积大可开展原位实验等优势,本文基于中国先进研究堆小角中子散射谱仪,设计并研制了一台高温和拉力同时加载的原位实验装置,并实现了高温高压下原位测量材料的纳米尺度形貌变化。实验测试结果表明,装置最大载荷可达20 kN,最高温度800℃,控温精度优于±1℃。利用该装置对镍基单晶高温合金样品进行了原位小角中子散射测试,发现温度拉力条件下样品内部纳米结构的明显变化,表明基于该装置可开展热力耦合加载下的原位小角中子散射实验。该装置及其相应实验方法,可用于核电不锈钢等多种高温结构材料的原位加载实验研究,提供微观结构演化数据。

KRUSTY-HEU热管空间堆体积优化及热力耦合特性研究

空间热管堆具有小型化、长寿期、环境适应性强等优点,在航天领域中有广阔的应用前景。本文针对由洛斯阿拉莫斯国家实验室提出的高富集度热管空间堆高浓缩铀方案KRUSTY-HEU,在保持反应性不变的前提下,通过添加慢化剂材料的方法进行体积优化,减小控制棒的体积并降低反射层厚度,用以降低航天器的发射成本和发射载荷。在慢化剂布置方面,本文提出了芯块内层添加慢化剂、芯块内部中间层添加慢化剂和慢化剂与燃料弥散3种方案,并对反应性和安全性进行对比。结果表明,芯块内层添加慢化剂方案优于其他两种方案,最低的反射层厚度为8.69 cm,较之前降低了3.11 cm,体积降低了约30%。针对优化后的方案进行了中子学和热力学分析,结果表明温度对反应性影响较小且移动反射层能够很好地控制反应性,同时燃耗引起的反应性损失较小。在正常运行时,堆芯温度和热位移与之前相差不大,热应力最大处为慢化剂和芯块的交界面,超过了堆芯材料屈服极限。通过在慢化剂和芯块间添加间隙,在材料屈服极限内有效地降低了热应力。单管失效分析表明堆芯温度、位移和热应力发生变化,但未影响其安全性。综上所述,本文提出的芯块内层添加慢化剂方案可有效降低KRUSTY-HEU的体积,热力耦合特性表明优化后的堆芯仍具有较高的安全性和稳定性。

Flow field effect of delayed neutron precursors in liquid-fueled molten salt reactors

In molten salt reactors(MSRs),the liquid fuel salt circulates through the primary loop and a part of the delayed neutron precursors(DNPs)decays outside the reactor core.To model and analyze the flow field effect of DNPs in channel-type liquid-fueled MSRs,a three-dimensional space-time dynamics code,named ThorCORE3D,that couples neutronics,core thermalhydraulics,and a molten salt loop system was developed and validated with the Molten Salt Reactor Experiment(MSRE)benchmarks.The effects of external loop recirculation time,fuel flow rate,and core flow field distribution on the delayed neutron fraction loss of MSRE at steadystate were modeled and simulated using the ThorCORE3D code.Then,the flow field effect of the DNPs on the system responses of the MSRE in the reactivity insertion transient under different initial conditions was analyzed systematically for the channel-type liquid-fueled MSRs.The results indicate that the flow field condition has a significant effect on the steady-state delayed neutron fractions and will further affect the transient power and temperature responses of the reactor system.The analysis results for the effect of the DNP flow field can provide important references for the design optimization and safety analysis of liquid-fueled MSRs.

Impact of photoneutrons on reactivity measurements for TMSR-SF1

The solid-fueled thorium molten salt reactor(TMSR-SF1) is a 10 MW_(th) test reactor design to be deployed in 5-10 years by the TMSR group.Its design combines coated particle fuel and molten FLiBe coolant for great intrinsic safety features and economic advantages.Due to a large amount of beryllium in the coolant salt,photoneutrons are produced by(y,n) reaction,hence the increasing fraction of effective delayed neutrons in the core by the photoneutrons originating from the long-lived fission products.Some of the delayed photoneutron groups are of long lifetime,so a direct effect is resulted in the transient process and reactivity measurement.To study the impact of photoneutrons for TMSR-SF1,the effective photoneutron fraction is estimated using k-ratio method and performed by the Monte Carlo code(MCNP5) with ENDF/B-Ⅶ cross sections.Based on the coupled neutronphoton point kinetics equations,influence of the photoneutrons is analyzed.The results show that the impact of photoneutrons is not negligible in reactivity measurement.Without considering photoneutrons in on-line reactivity measurement based on inverse point kinetics can result in overestimation of the positive reactivity and underestimation of the negative reactivity.The photoneutrons also lead to more waiting time for the doubling time measurement.Since the photoneutron precursors take extremely long time to achieve equilibrium,a "steady" power operation may not directly imply a "real" criticality.

From the Dark Neutron to the Neutron Decay Anomaly and Lithium Cosmologic Problem

In the context of the geometric model of particles (PGM), we show two different forms of the structure of the quark positions making up the neutron: first, an ordinary form, while the second is a “dark” form (difficult to detect). By the “dark” form we attempt of explaining the anomaly of the neutron lifetime (τ) in its decay observed in two different experiments as that in “bottle” and “in beam” and expressed by discrepancy between the two lifetimes (τbottle ≠ τbeam). Using the structure equation of the dark neutron, we calculate its mass. In this framework, two problems can be resolved: the asymmetry between matter and antimatter and the abundance into universe of Lithium 7Li than the 6Li.

Influence of Interactions on Populations for Hyperons in Neutron Stars

The numerical results of the populations for the baryon octet in neutron star matter have been presented by solving a set transcendental equations in the framework of the relativistic mean field approximation. The influence of the hyperon interactions on hyperon populations in neutron star matter is discussed. The results manifest that when the ratio of the hyperon-to-nucleon couplings increases, all hyperons appear towards low baryon density direction.

CorTAF2.0核热耦合及杂质沉积模块开发及初步应用

核反应堆堆芯中存在复杂的多物理场耦合作用机制。传统核反应堆堆芯分析方法无法满足高保真、多模型计算需求,而跨平台计算存在数据传递失真、计算效率低下、分析尺度不兼容等问题。本文基于压水堆全堆芯通道级热工水力程序CorTAF,针对堆芯核热耦合与杂质沉积现象,分别构建并植入中子扩散方程和杂质沉积及热阻模型,形成具有核热耦合和杂质沉积模块的CorTAF2.0程序。结合标准题和实验数据开展模型验证。基于该程序分别进行压水堆全堆芯核热耦合及杂质沉积模拟,获得了中子通量分布、功率分布和包壳杂质沉积结垢量分布,拓展了CorTAF程序对中子物理和长期运行条件下杂质沉积的分析能力。本文工作对压水堆全堆芯多物理场耦合分析具有借鉴和参考意义。

WWER反应堆压力容器热-力耦合行为

目的研究纯Fe、Fe-Cr和Fe-Ni二元体系合金及Fe-Cr-Ni三元体系合金材料压力容器在辐照条件下的热-力耦合行为。方法选用纯Fe、Fe-36Ni和16MND5二元体系合金以及SA508-3三元体系合金材料为研究对象,采用ABAQUS有限元软件建立压力容器模型,基于UMAT功能将Zr-4包壳材料热源的热膨胀系数模型导入有限元软件中,模拟不同合金材料的压力容器在中子辐照和高温、高压作用下的热-力耦合行为,分别分析压力容器温度场、位移场和应力场的分布情况及随辐照时间的变化情况。结果包壳温度由内壁向外壁依次降低,包壳内壁温度为353℃,最大温差为20℃。Fe-36Ni合金受到的最大应力为3.45 MPa,而纯铁受到的最大应力只有1.2 MPa。在中子辐照作用下温度和应力主要集中在压力容器的中心部位,而在压力容器的上下两端容易产生位移集中。结论合金体系的不同不影响辐照作用下压力容器的温度场、位移场和应力场的分布规律。温度、位移和应力值的大小随着合金体系的改变而改变,温度场和应力场对合金体系更为敏感,即辐照作用下燃料元件的宏观力学性能对合金元素具有敏感性。

Neutron star cooling in various sets of nucleon coupling constants

The influences of nucleon coupling constants on the neutrino scatting and cooling properties of neutron stars are investigated. The results in the GM1, GPS250 and NL-SH parameter sets show that the magnitude of the neutrino emissivity and density ranges where the dUrca process of nucleons is allowed differ obviously between the three parameter sets in nucleon-only and hyperonic matter. Furthermore, the neutron stars in the CPS250 set cool very quickly, whereas those in the NL-SH set cool slowly. The cooling rate of the former can be almost three times more that of the latter. It can be concluded that the stiffer the equation of state, the slower the corresponding neutron stars cool. The hyperon A makes neutrino emissivity due to the direct Urca process of nucleons lower compared with nucleon-only matter, and postpones the dUrca process with muons. However, these A effects are relatively weaker in the GPS250 set than in the GM1 set.

反应堆核热耦合松耦合数值仿真研究综述

在反应堆运行过程中,包含多个性质不同却相互联系的物理现象,涉及反应堆物理、热工水力、材料、系统控制等专业。本文主要探讨堆芯反应堆物理与热工水力间的相互作用,且主要关注对反应堆安全运行具有重要意义的耦合现象,对核热耦合的松耦合数值仿真研究进展进行广泛综述。本文先简要介绍核热耦合的原理方法和主流数值仿真程序,随后依据仿真程序自身特点进行科学分类,最后着重研究四类松耦合数值仿真方法现阶段的实际应用情况,给出了典型算例,并分析其计算效果及实用价值。

基于Fluent的铍钯铜复合材料中子靶系统热固耦合分析

电子器件领域中高热流密度电子器件的散热问题已经成为制约高新技术发展的重要因素,简单结构的中子靶系统已无法满足某类电子器件的散热需求.为此,设计和开发了新型高效的微通道铍钯铜复合材料中子靶系统,利用液体冷却技术解决了铍钯铜复合材料的散热问题.运用ANSYS Fluent和Static Structural仿真软件中湍流模型和有限元分析方法,对比分析了不同结构的铍钯铜复合材料中子靶系统的流场及其热应力分布,优化设计出结构紧凑、换热性能好的微通道铍钯铜复合材料中子靶系统.

Neutron star cooling and GW170817 constraint within quark-meson coupling models

In the present work,we used five different versions of the quark-meson coupling(QMC)model to compute astrophysical quantities related to the GW170817 event and the neutron star cooling process.Two of the models are based on the original bag potential structure and three versions consider a harmonic oscillator potential to confine quarks.The bag-like models also incorporate the pasta phase used to describe the inner crust of neutron stars.With a simple method studied in the present work,we show that the pasta phase does not play a significant role.Moreover,the QMC model that satisfies the GW170817 constraints with the lowest slope of the symmetry energy exhibits a cooling profile compatible with observational data.