一种抑制高压加速管电子负载效应的新方法

电子负载效应在高压加速管中是需要避免的,因为电子负载效应往往会造成加速管中出现大量的电子流,使得高压难以继续升高,而电子负载效应与加速管中的杂散粒子倍增有关。本文介绍了如何利用透镜电场抑制电子负载效应。通过不等梯度电位形成透镜电场,透镜电场对中心轴上加速的粒子不造成影响,而对远离主轴的杂散粒子起到消散的作用,可以有效地阻止这些杂散粒子长距离飞越,减弱杂散粒子的倍增能力。可见透镜电场能够对电子负载效应起到抑制的作用。     

泵吸式土壤测氡仪气压校正方法的初步研究

泵吸采样过程中,当土壤透气性差时,实际采样到的土壤气进气量将不同程度偏小,引起收集室内气体被扩张,气压降低,影响氡浓度测量结果.根据密闭容积气体特性,可以推导出气压校正系数,校准泵吸式测氡仪进气量难以预计引起的测量误差.为验证校正效果,设计制作了带气压校正器的便携瞬时土壤测氡仪,已获国家专利.两条剖面实验数据表明,校正后氡浓度测量结果更接近理论值,且由进气量原因引起的平均相对偏差高达60%,可用该项校正技术解决.     

能探测伴随粒子的测井中子管

报道一种带有环形α粒子探测器的新型测井中子管，它能够给出发射中子飞出方向和产生时刻的指示，测井时利用它给出的中子飞出方向和产生时刻的指示信号可以去除测量中的本底。     

A new method for uranium enrichment

A new method for uranium enrichment is presented. This method is based on exciting ²³⁸U to its isomeric levels at 2557.6 and 2557.6 + x keV. These isomeric levels have SF decay modes. Enrichment is thus obtained by fissioning only the ²³⁸U isotopes. Three ways for exciting ²³⁸U to ^238mU are discussed.     

一种新的GM计数管Time-To-Count 测量方法

主要介绍了目前最新的GM计数管Time-To-Count测量方法的基本原理及其工作模型，对测量方法的基本特点进行了探讨，通过方案设计加工加以实现并给出了试验结果。     

A new correlation method for transit-time estimation

A new correlation method for transit-time estimation is proposed. The transit-time of a propagating quantity between two points along the propagation path could be measured by noise analysis technique when this quantity conveys some measurable stochastic signal with it. This is usually performed by observing directly the peak in the cross-correlation function of the stochastic signal measured at two points in the propagation path, or indirectly by reading the slope of the phase-angular frequency curve. The proposed method presents the transit-time information directly in the same way as in the ordinary cross-correlation technique, but with a better resolution when the conveyed noise signal is band-limited. It also rejects extraneous noise contamination when such noise appears in a narrow frequency band. The usefulness of this method was tested in an air-water two-phase flow channel to estimate the transit-time of the bubbles.     

A new method for improving critical extrapolation

The divergent phenomenon of critical extrapolation and ρ–1/N extrapolation curve is analyzed during the physical startup of a reactor. Aiming at the deficiency of the existing improving method—constant neutron source elimination (CNSE) method, a new method—variable neutron source elimination (VNSE) is proposed. This new method aims at getting accurate neutron count rate for extrapolation, and considers all the errors caused by the neutron source leakage, reactor spatial effect and neutron detector positions as a whole. Applied to a small reactor, this VNSE method can remove all errors and eliminate the divergence of extrapolation so that the accurate ρ–1/N extrapolation curve is got. The VNSE method is efficient and accurate for the critical extrapolation.     

一种QAC实现方法与电路设计

介绍了一种新的QAC的方法和电路,该电路主要由电流转换电路、恒流源电路、积分电路、模拟开关电路等组成,其突出特点是转换速度快、电路简单、输入信号范围大（≤600pC）,适合构成多路QDC或多路QAC,在大型探测器阵列前端电子学系统中有着广泛的应用前景。     

A simple derivative spectrophotometric method for simultaneously detecting nitrate and nitrite in plasma treated water

A spectrophotometric technique is developed to simultaneously quantify nitrate and nitrite in plasma treated water. The measurement is based on examining the inflection points (wavelengths) in the derivative absorbance of the nitrate or nitrite solution. At the inflection points of the pure nitrate solution, the derivative absorbance is zero and independent of the nitrate's concentration, and thus the nitrite's concentration in a mixed nitrate and nitrite solution can be obtained by using the Beer's law at these points. The nitrate's concentration can also be achieved from the inflection points of nitrite in the same manner. The relation between the tested substance's (nitrate or nitrite) concentration and the second- or the third-order absorbances is obtained at these inflection points. Test measurements for mixed aqueous solutions of nitrate and nitrite with or without hydrogen peroxide confirm the reliability of this technique. We applied this technique to quantify the nitrate and nitrite generated in air plasma treated aqueous solutions. The results indicate that both nitrate and nitrite concentrations increase with the plasma treatment time, and the nitrite species is found to be generated prior to the nitrate species in the air plasma treated aqueous solution. Moreover, the production rate of total nitrogen species is independent of the solutions' pH value. These results are relevant to diverse applications of plasma activated solutions in materials processing, biotechnology, medicine and other fields.     

A new method for lengthening SR pulses periodicity in HLS

1IntroductionSynclirotronradiation(SR)isapowerfultoolfOrresearchinphysics,chedristryandbio1ogy.SReAnttedfromdipolemagnetisaseriesofpulseswithastrict"timestructure."ItsperiodisdeterndnedbythefrequencyofRFcavityandtheililingmodeofelectronbu-nches,sowecanadjusttheperiodofSRpulsebychangingthenUInberofelectronbunchesinstoragering.SincethestorageringofHLSisouly66mlong,thecycllcalperiodofelectron,Tc,is22ons,thatis,evenifinsinglebunchoperationmodethemakimumperiodoftheSRpulseis22Ons.However,som…     

A new method for photon transport in Monte Carlo simulation

Monte Carlo methods are used to evaluate data methods such as scatter and attenuation compensation in single photon emission CT (SPECT), treatment planning in radiation therapy, and in many industrial applications. In Monte Carlo simulation, photon transport requires calculating the distance from the location of the emitted photon to the nearest boundary of each uniform attenuating medium along its path of travel, and comparing this distance with the length of its path generated at emission. Here, the authors propose a new method that omits the calculation of the location of the exit point of the photon from each voxel and of the distance between the exit point and the original position. The method only checks the medium of each voxel along the photon's path. If the medium differs from that in the voxel from which the photon was emitted, the authors calculate the location of the entry point in the voxel, and the length of the path is compared with the mean free path length generated by a random number. Simulations using the MCAT phantom show that the ratios of the calculation time were 1.0 for the voxel-based method, and 0.51 for the proposed method with a 256×256×256 matrix image, thereby confirming the effectiveness of the algorithm     

A statistical approach to the prediction of pressure tube fracture toughness

The fracture toughness of the zirconium alloy (Zr-2.5Nb) is an important parameter in determining the flaw tolerance for operation of pressure tubes in a nuclear reactor. Fracture toughness data have been generated by performing rising pressure burst tests on sections of pressure tubes removed from operating reactors. The test data were used to generate a lower-bound fracture toughness curve, which is used in defining the operational limits of pressure tubes. The paper presents a comprehensive statistical analysis of burst test data and develops a multivariate statistical model to relate toughness with material chemistry, mechanical properties, and operational history. The proposed model can be useful in predicting fracture toughness of specific in-service pressure tubes, thereby minimizing conservatism associated with a generic lower-bound approach.     

一种基于PC/104的便携式建材放射性检测仪

介绍了一种新型的便携式建材放射性检测仪。给出了仪器总提框图,讨论了其工作原理、具体的电路实现和仪器下位机软件框图。仪器以PC／104为核心,结合A／D采集卡和PKD-01等集成芯片．具有电路结构简单．可靠性和稳定性高的特点。     

Senhor-II — A computer code for loss-of-coolant accidents of pressure tube type reactors

An ATR LOCA analysis code, SENHOR-II, was developed which evaluates the loss-of-coolant accident in a reactor primary loop composed of parallel pressure tubes and downcomers connecting a steam drum to a lower header. The reactor system is divided into reservoirs and channels. The reservoirs are assumed to be saturated and equilibrated. The channels are treated one-dimensionally and their flows are assumed quasi-steady. The reservoir effect of piping, the heating up of fuel rods, the thermal capacity of structures, and the effects of steam separators and water level in the steam drum are considered. Calculated results are compared with the experimental results of the blowdown test performed with the mock-up test loop in -arai Engineering Center of PNC, and the adequacy of the calculation model and formulae is confirmed.     

Sensitivity analysis of input parameters for pressure tube integrity evaluation

Pressure tubes in CANDU reactor are the most important components that contain fuel. The operating experiences show leaks and burst in pressure tubes over the past two decades. The integrity of pressure tubes is, therefore, key concern in CANDU reactor. Once a CANDU reactor put into operation, their integrity could be checked by in-service-inspection. However, comparing to the total number of pressure tubes in a CANDU reactor, only a small number of pressure tubes are selected for inspection, since there is no weld. The inspection scope and results have been treated so far using a deterministic approach. Taking into account the difficulty in inspection sampling and in extrapolating the results to the entire core, a probabilistic approach is necessary. In this study, probabilistic integrity assessments are carried out considering key factors, such as initial hydrogen concentration, defect shape, delayed hydride cracking (DHC) velocity and fracture toughness. The leak and failure probabilities are calculated as a function of time by applying Monte Carlo simulation.     

Advanced fuel elements for passive pressure tube light water reactors

This paper focuses on the development of advanced fuel elements for innovative pressure tube light water reactors. Considerations and constraints that affect the design process and various possible options are discussed. The two most promising fuel designs, which can survive a loss-of-coolant accident without primary coolant replenishment, while having sufficient margins to fuel design limits, are proposed, described and evaluated. It is demonstrated that this key objective can be achieved, provided that reliable SiC cladding or coating, which can withstand operating and accident conditions without failure, can be manufactured. Recent advances in ceramic coating technologies and experimental tests of coated specimens indicate that the attainment of this goal is feasible.     

On the thermal analysis of pressure tube/calandria tube contact in CANDU reactors

Under abnormal conditions contact between a pressure tube and the surrounding calandria tube in the core of a CANDU reactor may take place. The resulting temperature field may adversely affect the hydrogen diffusion characteristics in the pressure tube material. This paper is concerned with the thermal aspects of contacting pressure and calandria tubes. A critical review of existing thermal interfacial conductance correlations and their applicability to this problem was carried out. Experiments were also carried out to obtain detailed temperature distribution in the walls of typical pressure and calandria tubes in contact under simulated operating conditions. The thermal fields in both tubes were obtained as functions of the contact pressure and system temperatures. The results showed that the heat flow within the contact area is essentially one-dimensional. The data was used to calculate the interfacial thermal conductance as a function of contact pressure. The results were compared with available interfacial conductance correlations and an assessment of their applicability was accordingly made.     

改进电子直线加速器束流品质的新方法

简单介绍了自适应前馈控制的工作原理、具体实现及其在速调管、微波枪和加速管上的应用,并对实现热阴极微波枪这种时变、非线性、大迟滞系统的控制作了重点介绍。