18F标记多肽方法研究进展

随着正电子发射断层(Positron Emission Tomography,PET)显像技术在检测肿瘤、神经精神疾病和心脏疾病等方面的广泛应用,正电子核素18 F标记多肽作为PET示踪剂,近年来得到了快速发展,目前已有多种18F标记多肽的方法。本文以标记反应的特点,总结了以下七种18 F标记多肽的方法:1)18 F标记辅基法;2)固相标记法;3)18F-AlF络合标记法;4)点击化学法;5)18F-19F同位素交换法;6)芳香环亲电、亲核氟标法;7)其他标记法。并对各种方法的优缺点进行了比较。     

液闪探测器的几种n/γ甄别方法研究

利用液闪探测器研究了几种数字化波形甄别方法的n/γ甄别能力。以Am-Be源作为混合场源,用示波器对EJ-301和BC501A两种液闪探测器信号进行数字化采集,分别用上升时间法、电荷比较法、脉冲梯度分析和频率梯度分析等数字化波形甄别方法对采集的信号进行了n/γ离线甄别分析,比较了4种方法的甄别效果,并用MPD-4甄别单元从实验上验证了各方法的可靠性。结果表明：对于液闪探测器,4种数字化方法具有较好的甄别一致性和准确性,上升时间法的甄别效果最好,是实时甄别系统甄别算法的理想选择。     

CLYC探测器n/γ聚类甄别方法研究

为了高性能分辨探测中子与γ射线,搭建了一套基于Cs₂LiYCl₆:Ce³⁺(CLYC)探测器和数字示波器的数字化核脉冲采集系统。通过Matlab编程,研究了系统聚类法和K-means聚类法两种n/γ脉冲波形甄别方法,并与传统的电荷比较法进行了对比。结果表明,两种聚类法均可准确分辨脉冲类别,K-means聚类法在计算时间和内存占用方面更具优势,有利于实时脉冲处理。该研究为研制基于CLYC探测器的n/γ双模式探测谱仪提供了一种有用的脉冲波形甄别技术解决方案。     

A NRC-BNL benchmark evaluation of seismic analysis methods for non-classically damped coupled systems

Under the auspices of the U.S. Nuclear Regulatory Commission (NRC), Brookhaven National Laboratory (BNL) developed a comprehensive program to evaluate state-of-the-art methods and computer programs for seismic analysis of typical coupled nuclear power plant (NPP) systems with non-classical damping. In this program, four benchmark models of coupled building-piping/equipment systems with different damping characteristics were developed and analyzed by BNL for a suite of earthquakes. The BNL analysis was carried out by the Wilson-θ time domain integration method with the system-damping matrix computed using a synthesis formulation as presented in a companion paper [Nucl. Eng. Des. (2002)]. These benchmark problems were subsequently distributed to and analyzed by program participants applying their uniquely developed methods and computer programs. This paper is intended to offer a glimpse at the program, and provide a summary of major findings and principle conclusions with some representative results.The participant’s analysis results established using complex modal time history methods showed good comparison with the BNL solutions, while the analyses produced with either complex-mode response spectrum methods or classical normal-mode response spectrum method, in general, produced more conservative results, when averaged over a suite of earthquakes. However, when coupling due to damping is significant, complex-mode response spectrum methods performed better than the classical normal-mode response spectrum method. Furthermore, as part of the program objectives, a parametric assessment is also presented in this paper, aimed at evaluation of the applicability of various analysis methods to problems with different dynamic characteristics unique to coupled NPP systems. It is believed that the findings and insights learned from this program will be useful in developing new acceptance criteria and providing guidance for future regulatory activities involving license applications of these alternate methods to coupled systems.     

热工水力系统分析程序Courant条件计算方法研究

为分析采取不同Courant条件计算方法对反应堆热工水力系统分析程序计算速度和计算准确性的影响,研究了2种Courant条件计算方法:综合法与分组法,分析了2者的计算原理,并分别采取这2种方法对压水堆满功率稳态工况和大破口事故工况进行计算。结果表明,稳态工况下2种方法的程序计算结果无明显差异;在速度场变化剧烈的大破口事故工况下,综合法可以取得更加准确的计算结果但耗时较多,分组法可以取得更快的计算速度但计算准确性较低。      

惰性气体流出物离线监测仪的三种效率校准方法研究

介绍了3种替代的效率校准方法,并分别用它们计算1台HPGe谱仪测量1枚等效气体源时的探测效率曲线。蒙特卡罗（MC）法建立的探测器模型中所用尺寸参数为厂商提供的值,其计算结果不可靠,与实验值的最大相对偏差达130%。数值积分法和代表点法皆用了1枚多γ核素标准点源,同时还借助了MC模拟计算。当γ射线能量在60～1 836 keV范围时,代表点法计算结果的相对偏差≤±6%,数值积分法计算结果的相对偏差≤±4%,这两种方法均能满足现场工作对不确定度的要求,其中代表点法更易实施。     

Experiences and Status in Safety Assessment Methods within the Scope of Licensing Procedures for Multi-Purpose Flasks in Germany

Abstract

The Federal Institute for Materials Research and Testing in Germany (BAM) is the German competent authority for safety assessment and design testing of flasks for transport and storage of radioactive waste. Referring to the IAEA regulations (Safety Standards Series No ST-1) four different methods for demonstration of compliance with the performance standards are possible: (1) tests with prototype flasks, (2) tests with scaled models, (3) reference to previous safety demonstrations, and (4) calculation. The advantages and disadvantages of these methods. are described with reference to the nearly 20 years experience of BAM in design testing under mechanical accident conditions. Drop testing with prototype flasks and scaled model flasks was the basic method at the beginning of flask development. With better knowledge of flask behaviour under such impact conditions methods (3) and (4) were increasingly used for various flask designs. The present trend is to use numerical calculation methods also for new flask designs because of the high potential of modem computer technology. Some actual examples are given and the necessary requirements for the acceptance of this method are discussed. During recent years numerous flask designs were granted transport licences as well as licences for interim storage at the Gorleben and Ahaus sites. Because of different actions of opponents the licenses for the interim storage sites were the object of legal proceedings with special reference to the flask design testing methods. Finally, the experience obtained from these legal disputes and their relevance to acceptable safety assessment methods are discussed.     

Treatment of complementary events in constructing the linked Level 1 and Level 2 fault trees

Complementary events in the event trees for a PRA model should be treated properly in order to evaluate plant risk correctly. In this paper, the characteristics of the following three different cutset generation methods were investigated first in order to find the best practical way for treating complementary events: (1) exact method which treats complementary events logically, (2) no-delete term method which does not treat complementary events at all, and (3) delete term method which treats complementary events by deleting nonsense cutsets which are generated as a result of ignoring complementary events. Then, practical methods for treating complementary events in constructing linked fault trees for Level 1 and Level 2 PRA were suggested and demonstrated. The suggested methods deal with the following selected four typical cases: (1) Case 1—an event tree event (E) is represented by a fault tree gate whose inputs consist of only fault tree gates, (2) Case 2—E is represented by a single basic event, (3) Case 3—E is represented by an OR fault tree gate which has a single basic event and a fault tree gate as inputs, and (4) Case 4—E is represented by an AND fault tree gate which has a single basic event and a fault tree gate as inputs. In the suggested methods, first the high level logic structures of event tree events are examined and restructured, if needed. Then, the delete term method, the exact method, and the combination of the two methods are applied to through Case 1 to Case 4, respectively. As a result, it is recommended to treat complementary events, using the suggested methods, before Level 1 and Level 2 PRA fault trees are coupled.     

Approximate fracture methods for pipes — Part II: Applications

In the part I paper entitled “Approximate fracture methods for pipes — Part I, Theory” [4], five different J-estimation schemes for through-wall cracked pipes were presented. The (i) GE.EPRI method utilizes a compilation of finite-element solutions. The (ii) Paris/Tada and (iii) LBB.NRC methods utilize an interpolation between the linear elastic and rigid plastic solutions, (iv) the LBB.GE method also uses numerical solutions, and (v) the LBB.ENG uses an equivalent area method to estimate J. All five methods are very simple to use and all five give reasonable predictions of crack growth and failure in pipes. The present paper provides a comparison of some of the methods to full-scale finite-element analyses. In addition, predictions for actual pipe experiments compared to experimental data are also provided.     

Comparative assessment of theoretical and experimental measurement of photo neutron flux level in GHARR-1 after shutdown

Direct photo-neutron source strength was evaluated for the Miniature Neutron Source Reactor (MNSR) in subcritical condition in the GHARR-1 facility. Two different static methods were applied for comparison. A theoretical method based on the use of MCNP code and an experimental method based on foil activation technique. The latter has been found to be most convenient method for neutron flux measurement. The method depends only on the activity of a bare and cadmium covered foil if the irradiation positions are known. Photo-neutron flux level was determined theoretically using MNCP after measuring neutron flux at shutdown; and experimentally using Neutron Activation Analysis (NAA) technique also at shutdown with great care. The values obtained from the theoretical and experimental measurements are tabulated in Table 2. The results recorded were validated using biological peach leave and a geological rock sample. The results after validation for Mn concentration in the samples were 87 ± 1 μg/g and 432 ± 23 μg/g, respectively. Results for the two methods were in good agreement. Realization of photo-neutron source existence due to beryllium reflector was also experienced.