同步辐射晶体单色器晶体热应变的模拟与实验结果的比较

报道了同步辐射装置光束线关键部件之一的晶体单色器晶体热应变的ANSYS有限元模拟结果,并与实验结果进行了比对,模拟结果在实验误差范围(约士15%)内与实验数据符合,证明了模拟结果的可靠性.     

中子应力谱仪常用聚焦单色器的模拟与比较

用蒙特卡罗中子射线追踪程序McStas对中子衍射应力谱仪单色器部件进行模拟优化:以Cu(220)比较了单色器起飞角和准直系统对样品处中子注量率、分辨率的影响;计算得到给定条件下单色器最佳单晶条数和镶嵌度;单晶条倾角精度建议好于0.1°;计算了Cu(222)、(220)和(002)在不同起飞角情况下获得的中子注量率;相同条件下,Cu和Ge常用晶体单色器中以Cu(220)获得的中子注量率最大,而Cu(222)获得的波长分辨率最佳。     

高放废液贮槽气镇器搅拌系统的数值模拟研究

以后处理厂高放废液贮槽气镇器搅拌系统为模拟对象,其中气相、液相和固相分别为空气、硝酸钠水溶液和球磨后的钛白粉,基于颗粒动力学理论,建立适用于高放废液贮槽气镇器搅拌系统的气、液、固三相流动的数学模型,用CFD商用计算软件对其进行计算,得到了高放废液贮槽气镇器搅拌过程中气、液和固三相的速度、压力和相含率等详细数据。研究结果表明,计算值与实验值吻合较好,验证了建立的数学模型的正确性和适用性,为高放废液贮槽气镇器搅拌系统进一步优化设计和放大提供参考。     

完美晶体双聚焦单色器与镶嵌晶体垂直聚焦单色器的模拟研究

为满足中子衍射应力分析谱仪高注量率和高分辨率的要求,采用蒙特卡罗模拟程序SIMRES对其单色器进行了模拟研究。分别从单色器衍射几何(对称、非对称和完全非对称)、聚焦条件(垂直和水平聚焦曲率)和晶体类型(完美晶体和镶嵌晶体)三个方面,以品质因子为量化指标,系统比较了与谱仪的注量率和分辨率的影响关系。研究结果表明:采用对称几何及完美晶体双聚焦方式可以获得最佳的谱仪性能。     

蒙特卡罗模拟机架和多叶准直器误差对旋转放疗剂量的影响

研究在常规直线加速器实施快速旋转调强放疗(IMAT)治疗过程中,内置多叶准直器(MLCs)和机架旋转误差对放疗剂量的影响。随机选择7例脑胶质瘤患者,并在常规直线加速器Varian 23EX上设计IMAT计划,对MLCs和机架分别引入不同大小误差。通过不一致指数和剂量体积直方图(DVH)评估引入误差对IMAT放疗临床剂量的影响。对于单侧MLCs随机误差,当MLCs随机误差达2 mm时计划靶体积平均剂量(PTV-D_mean)增加了约2.7%。当MLCs一侧外扩MLC-1 mm、MLC-2 mm、MLC-rnd时导致其PTV-D_mean平均偏差分别为1.12%、2.15%和1.15%,晶体的平均剂量偏差分别为5.25%、9.97%和5.49%。对于MLC两组叶片分别偏移±2 mm时导致PTV平均剂量的最大偏差为0.8%,晶体和脑干的最大剂量和平均剂量分别增加了11.4%、15.8%和1.99%、1.07%。引入机架角度误差,计划靶体积最小剂量(PTV-D_min)和PTV-D_mean最大剂量分别降低了2.7...     

用散射中子测量管道油垢厚度的实验与模拟

由~(241)Am-Be中子源、锂玻璃探测器和微机多道谱仪等组成的实验装置,测量了不同石蜡(模拟油垢)厚度的散射中子计数.同时用蒙特卡罗模拟,分别对~(241)Am-Be中子源、~(252)Cf中子源和14MeV中子源,计算得到了相似几何条件下,对应于不同石蜡(模拟油垢)厚度的散射中子计数.在模拟计算中,考虑了锂玻璃探测器的探测效率.对实验和模拟计算的结果进行了比较和讨论.     

快中子堆主壳顶盖环形空间自然对流的实验研究与数值模拟

快堆顶盖存在一些大小不同的环形空间,这些空间是由穿过顶盖结构的一次泵及热交换器构成的,并使环形空间内的氩气产生自然对流。用有机玻璃建造的实验台,模拟快中子堆主壳顶盖竖直环形空间,进行自然对流实验研究。同时,采用LVEL零方程湍流模型对自然对流进行了数值模拟,所获结果与实验数据基本吻合,表明该模型比常用的kε模型所得出的流型与文献中的和该实验的观测结果更加相符,也能够更加准确地预测环形空间内的温度场与速度场。     

基于实验与模拟相结合的气体样品(n,α)反应截面测量方法研究

建立了一套利用屏栅电离室测量快中子诱发气体样品(n,α)反应截面的方法。针对气体样品测量中存在的样品核数确定、中子注量测量、待测事件挑选等问题,本方法首先利用模拟计算结果选择合适的气体样品有效区域,使得事件区尽量无本底覆盖且易于统计;再利用中子准直器和阴极、阳极信号时间信息,分离并统计样品有效区域产生的事件数;最后利用实验测量的238U(n,f)裂变计数和SuperMC模拟结果,得到有效区域内的中子注量。利用该方法在中子能量为471、487、500、512、529和545 MeV的能点系统地测量了14N(n,α0)反应的相对截面,结果与ENDF/B Ⅷ0符合良好。     

不同来源腐殖酸与U(Ⅵ)结合特性差异的实验与分子动力学模拟北大核心CSCD

采用元素分析、化学滴定、光谱分析等方法对三种不同来源腐殖酸(AHA、YHA和EHA)进行了分析表征和官能团测定,系统地研究了不同pH、时间、温度和离子强度下它们与U(Ⅵ)的配位行为,并借助分子动力学模拟方法研究了不同腐殖酸模型与U(Ⅵ)相互作用的溶液动力学,探究了动力学过程、配位结构和作用机理。实验结果表明:三种不同来源腐殖酸的元素组成和官能团类型基本相似,均具有较强的芳香性和共轭双键,但也略有差异。YHA的低H/C原子比、高酸度和高官能团含量表明其腐殖化程度较高,存在高的共轭性或芳香族成分,具有较强的金属配位能力。不同来源腐殖酸与U(Ⅵ)的配位行为存在显著差异,且受pH、时间、温度和离子强度的明显影响。分子动力学模拟表明:单个腐殖酸分子与U(Ⅵ)的配位在很短时间内完成,主要的结合位点为羧基,在水溶液中可自发形成具有显著差异的HA-U(Ⅵ)配位结构,其主要驱动力为静电相互作用。上述研究结果不仅有助于进一步理解腐殖酸存在下铀在环境中的化学行为,对放射性废物的地质处置及安全性评价也具有参考价值。     

CsI (T1)晶体量能器探测单元宇宙射线实验的建立与调试

建立一套CsI (T1)晶体量能器探测单元的宇宙射线测量系统,用于探测器单元的质量检测,以及发光强度与均匀性测量.本文针对于此实验装置的径迹与定位系统、电子学系统的研究作了较为详尽的说明,并对前期的Monte Carlo研究作了简要介绍.     

Feedforward compensation of the insertion devices effects in the SSRF storage ring

The lattice of the Shanghai Synchrotron Radiation Facility(SSRF) storage ring was upgraded in the Phase-II beamline project, and thus far, 18 insertion devices(IDs) have been installed. The IDs cause closed-orbit distortions, tune drift, and coupling distortions in the SSRF storage ring, all of which are significant issues that require solutions. In this study, an ID orbit feedforward compensation system based on a response matrix using corrector coils was developed, and it was applied to all co...     

上海光源储存环光子吸收器布局设计

电子束经过储存环弯转磁铁发生偏转时,产生总功率-435 kW的同步辐射光,其中仅有一小部分被引入光束线、实验站,其余须在储存环中被光子吸收器吸收处理,并准直引出光束.本文对上海光源(SSRF0储存环同步辐射光的处理方法进行了讨论,并介绍了光子吸收器的布局、结构、性能及运行状况.     

NSRL前端活动水冷光屏的结构及热分析

活动水冷光屏是光束线前端的重要部件，主要用来吸收高强度的同步辐射功率、承受和释放热负载，保护其下游位置仪器设备免遭热载破坏。介绍中国科学技术大学国家同步辐射实验室(NSRL)的合肥同步辐射光源(HLS)光束线前端活动水冷光屏的结构，利用有限元分析程序ANSYS5．5进行热力学分析，确认其合理性。     

Internal elemental imaging by scanning X-ray fluorescence microtomography at the hard X-ray microprobe beamline of the SSRF: Preliminary experimental results

Synchrotron-based X-ray micro-fluorescence (μ-SXRF) is a non-destructive analytical technique and has been widely used to detect and quantify the elemental composition of samples in their natural state. To determine the internal elemental distributions within samples, X-ray fluorescence microtomography has been developed based on the hard X-ray microprobe at beamline BL15U1 of the Shanghai Synchrotron Radiation Facility (SSRF) in Shanghai, China. This technique was applied to image the cross-sectional distributions of multiple elements within a single human hair, and its validity was evaluated by comparing the results with the elemental maps of a thin hair section obtained using the well-established μ-SXRF mapping method. Elemental images of S, Ca, Mn, Fe, Cu, and Zn within a virtual slice of the hair were reconstructed after the tomographic measurements. The tomographic images of heavy elements like Fe, Cu, and Zn were found to be in good agreement with the corresponding μ-SXRF maps. Light elements, such as S, however, represented different patterns due to non-negligible self-absorption in the sample, and sophisticated correction algorithms accounting for such effects are required for obtaining qualitatively and quantitatively more accurate images. Compared to μ-SXRF mapping, X-ray fluorescence microtomography reduces the sample preparation requirements and has been demonstrated in this work as being a more ideal and effective imaging modality to non-destructively mapping out the internal distribution of heavy elements within samples at the micrometer scale at the SSRF.     

A simulation of the temperature distribution in the SPIRAL target

We developed a model and a computer program to calculate the temperature distribution in the target which will be used in the SPIRAL project a GANIL. The results of the numerical simulation are compared with measurements performed with several types of targets.     

On the analysis of neonatal hamster tooth germs with the photon microprobe at Daresbury, UK

Complementary to the micro-PIXE experiments performed on hamster tooth germs to elucidate the role of fluoride during the growth, the photon microprobe at Daresbury was used to obtain information on the distribution of Zn. The germs of fluoride-administered hamsters, together with a control group, were analyzed with the micro-synchrotron radiation fluorescence method (micro-SXRF).     

Primary yields and reaction sets with corresponding rate constants for computer simulation of water radiolysis at elevated temperature

The chemical conditions of coolant water in light water reactors are important factors affecting the corrosive environment and the integrity of the structural materials. Computer simulations have commonly been used to predict chemical environment changes due to water radiolysis under extreme conditions. Initial parameters, including the chemical reactions, rate constants, and primary yields of water decomposition by radiolysis, have been reported by several groups in the past few decades. Using a FACSIMILE simulation, the variations caused by utilizing different sets of primary yields of water radiolysis, including γ-rays and fast neutrons, along with the chemical reactions and rate constants at 285 °C were evaluated in this study. The rate constant of the reverse reaction of OH + H₂ → H + H₂O was found to be the main factor controlling the variation between the different sets of chemical reactions and rate constants.     

电子加速器扫描盒前端法兰传热的数值模拟

加速器内电子束团在传输过程中因束流传输截面发散或偏离中心,会超出尺寸一定的传输器件.为防止因此导致扫描盒前端法兰盘局部温升过高,在法兰的外侧安装温度传感器以实时监测受照点的温度,从而及时调整系统的电流、电压、聚焦等有关参数.建立了法兰盘两侧热传导的数学模型,用数值模拟的方法计算得出了放置温度传感器的测量点B和受照点A的温度关系.计算结果与实验值符合,证明了数学模型的正确性,并为加速器的调试、运行提供了一种重要的检测手段.     

Comparison of 3D reaction rate distributions measured in an Optima2 BWR assembly with MCNPX predictions

As part of a joint research programme between the Paul Scherrer Institute (PSI) and swissnuclear, with the co-operation of the Leibstadt nuclear power plant in Switzerland and fuel suppliers Westinghouse Sweden, measurements and calculations have been made of the axial and radial distributions of fission and ²³⁸U capture rates in the fuel rods of a Westinghouse SVEA-96 Optima2 boiling water reactor assembly. The measurements, made in the zero-energy research reactor PROTEUS at PSI, have been compared with calculations carried out using the Monte Carlo code MCNPX. The results reported are for the regions near the ends of the part-length fuel rods, which are a feature of SVEA-96 Optima2 assemblies. The sudden increase in moderation above the ends of the part-length rods leads to power peaking in the adjacent rods. Careful attention needs to be given to this phenomenon in the deployment of such fuel, the present paper providing experimental evidence for the ability of a stochastic code to predict such effects.     

Improvement in estimation of first peak power based on non-linear temperature feedback reactivity in criticality accident with instantaneous reactivity insertion

A simple equation for the first peak power in a criticality accident due to instantaneous reactivity insertion into nuclear fuel solution system has been developed to improve the accuracy in the estimation of the first peak power keeping the easiness of calculation.

The equation is based on the assumption that temperature feedback reactivity is a second-order function of an increase in fuel temperature. Peak power estimated using the equation was in a range between about a half and twice of experimental value. Its applicability to a wide range of initial reactivity and accuracy of estimation have been confirmed in the comparison to one-point kinetics numerical calculation.

The expression suggests the first peak power increases with the square of small initial reactivity and three-halves power of large initial reactivity.