Forced vibration tests and analyses of nuclear power plants

Methods for conservatively predicting the response of a constructed nuclear power plant to earthquake excitations are presented. This approach is based on experimental testing of the reactor plant and using test results to develop a mathematical model of the system. First, steady state forced vibration tests are conducted using structural vibrators attached to the reactor structure to determine dynamic response characteristics. Second, modal analysis applied on a digital computer is used to create a linear multiple-degree-of-freedom model that has dynamic response characteristics nearly the same as the physical system for the experimental inputs. Finally, the input force levels are extrapolated from the levels of the inertial vibrators to earthquake levels and the response of the model is calculated for strong-motion earthquakes.Tests have been conducted on three nuclear power plants: the experimental gas-cooled reactor (EGCR) at Oak Ridge, Tennessee; the Carolinas-Virginia tube reactor (CVTR) at Parr, South Carolina; and the San Onofre Nuclear Generating Station (SONGS), San Onofre, California. Analyses in varying detail have been performed; the most extensive work has been done at San Onofre. This article summarizes test results, dynamic models, and the results of seismic response calculations for each plant.     

TMSR-SF2全厂断电事故分析

钍基熔盐堆-固态燃料二号堆(Thorium Molten Salt Reactor-Solid Fuel 2,TMSR-SF2)是基于球床熔盐堆SF1(Solid Fuel 1)的小型模块化升级堆型,这种新概念堆结合了两者的诸多优点,目前已经完成了预概念设计,对其进行典型事故的分析与安全特性的评估成为当前重要研究内容。本文基于Relap5/MOD4.0程序,建立了反应堆事故模型,进行了全厂断电事故的模拟,分析了反应性、反应堆功率、冷却剂温度和燃料温度等关键参数的变化规律。结果表明,SF2在全厂断电事故中具备高度安全性,其中固有安全性发挥了重要作用。此外还进行了全厂断电事故伴生不同事件的后果比对以及不同温度反应性系数的敏感性分析,证明了直接反应堆辅助冷却系统(Direct Reactor Auxiliary Cooling System,DRACS)在事故前期余热排出能力的局限性,而依靠主泵可以最大限度利用熔盐堆的热惰性从而显著缓解熔盐堆堆芯过热。     

Development of CFD fire models for deterministic analyses of the cable issues in the nuclear power plant

Additional fire barriers of electrical cables are required for the nuclear power plants (NPPs) in Taiwan due to the separation requirements of Appendix R to 10 CFR Part 50. The risk-informed fire analysis (RIFA) may provide a viable method to resolve these fire barrier issues. However, it is necessary to perform the fire scenario analyses so that RIFA can quantitatively determine the risk related to the fire barrier wrap. The CFD fire models are then proposed in this paper to help the RIFA in resolving these issues. Three typical fire scenarios are selected to assess the present CFD models. Compared with the experimental data and other model’s simulations, the present calculated results show reasonable agreements, rendering that present CFD fire models can provide the quantitative information for RIFA analyses to release the cable wrap requirements for NPPs.     

Seismic fragility analyses of nuclear power plant structures based on the recorded earthquake data in Korea

By nature, the seismic fragility analysis results will be considerably affected by the statistical data of design information and site-dependent ground motions. The engineering characteristics of small magnitude earthquake spectra recorded in the Korean peninsula during the last several years are analyzed in this paper. An improved method of seismic fragility analysis is evaluated by comparative analyses to verify its efficiency for practical application to nuclear power plant structures. The effects of the recorded earthquake on the seismic fragilities of Korean nuclear power plant structures are also evaluated from the comparative studies. Observing the obtained results, the proposed method is more efficient for the multi-modes structures. The case study results show that seismic fragility analysis based on the Newmark's spectra in Korea might over-estimate the seismic capacities of Korean facilities.     

Work on nuclear power plants for space

Conclusions It should be noted that the space problems gave an unprecedented impetus to improving computational methods and design of reactors and shielding and the development of the latest technology. This is not surprising, since the designs required that the mass of the nuclear power plant be determined to within several kilograms. The placement of every kilogram of a satellite in orbit costs several thousands of dollars. The development of nuclear rocket motors and the first thermionic systems "Topaz" in the world was a very important achievement in space nuclear technology. Unfortunately, as sometimes happens in practice, this achievement was far ahead of its time and remains unused. Translated from Atomnaya énergiya, Vol. 80, No. 5, pp. 357–361, May, 1996.     

Research in high-energy particle physics performed on the synchrocyclotron of the laboratory for nuclear problems of the joint institute for nuclear research

Summary In brief summation of the physics research performed on the six-meter synchrocyclotron in the Laboratory for Nuclear Problems, one may say that it has contributed valuable information to high-energy physics. It has broadened our knowledge in this field of modern physics and it has aided in exposing a series of new important problems and indicating effective methods for their study.To a large extent it is due to this research that the young science of high-energy physics has come to occupy a lasting place among the other sciences of our nation.Work on the six-meter synchrocyclotron has proved a good school in developing a large group of Soviet scientists with a mastery of modern physics, as well as engineers and designers with various specialties who have become familiar with totally new techniques.During 1956–1957, as a result of the organization of the Joint Institute for Nuclear Research, the laboratories of the Institute have been enriched by scientists from foreign countries. The Institute has become an international center for nuclear research, and one of its goals is the instruction of groups of physicists from the twelve nations participating in the Institute.On the glorious fortieth anniversary of the Great October, The High-Energy Laboratory of the Joint Institute for Nuclear Research has turned on the gigantic 10 Bev proton synchrotron, opening for modern nuclear physics additional new perspectives for further development.     

Probabilistic safety analyses developments resurgence in Bulgaria—Kozloduy nuclear power plant example

This paper presents some of the main technical features and insights of the Kozloduy nuclear power plant (NPP) units 5 and 6 probabilistic safety analysis (PSA) level 1. Probabilistic analyses and their applications in Bulgaria were given further impetus in recent years. More than 17 years after the first PSA study in Bulgaria in 1992 today probabilistic analyses receive increasing attention and application than ever before. The Bulgarian regulatory body (BNRA) is also interested in expanding their capability of reviewing and using PSA in plant safety assessments. In November 2008 within the framework of the program financed by European Union (PHARE), a project for assisting the BNRA in establishing the regulatory requirements on the base of PSA was completed. One of the objectives of this project was performance of the independent review of Kozloduy NPP units 5 and 6 PSA. This review was a new impulse for the authors to present in more details of Kozloduy NPP probabilistic assessment studies in the present paper.     

Welding consumables for nuclear power plants

In nuclear power plants, submerged arc welding and covered arc welding have long been employed especially for main weld seams, including the core region of RPV.This paper investigates the mechanical properties of several welding consumables we have developed for industrial plants — that is, welding consumables which lower the phosphorus and copper content of the welded metal, those for plates possessing particularly high tensile strength and those for the narrow gap welding method.Recent data derived from irradiation embrittlement tests show that these welded metals using a non-copper coating are highly effective in minimizing shifts in the transition curve.Welding consumables for A533B C1.2, A543 C1.1 or A508 C1.4 steels have a higher tensile strength than those for A533B C1.1 or A508 C1.3.We have developed submerged arc and covered arc welding consumables to be used with these kinds of steels, and it was confirmed that these consumables possess excellent tensile strength and notch toughness.Our tests also confirmed that the narrow gap SAW and MIG welds are more efficient than the conventional ones. Moreover, the mechanical properties of the welded metals are also excellent.     

Flood hazards for nuclear power plants

Flooding hazards for nuclear power plants may be caused by various external geophysical events. In this paper the hydrologic hazards from flash floods, river floods and heavy rain at the plant site are considered. Depending on the mode of analysis, two types of hazard evaluation are identified: (a) design hazard which is the probability of flooding over an expected service period, and (b) operational hazard which deals with real-time forecasting of the probability of flooding of an incoming event. Hazard evaluation techniques using flood frequency analysis can only be used for type (a) design hazard. Evaluation techniques using rainfall-runoff simulation or multi-station correlation can be used for both types of hazard prediction.     

激光喷丸技术在核电设备上的应用

应力腐蚀或疲劳破坏严重威胁核电设备安全稳定运行,缓解或消除应力腐蚀或疲劳,是确保设备安全稳定运行的有效手段。采用激光喷丸技术,不存在影响设备正常运行的残留物,可以遥控至核岛内辐照区复杂狭小部位作业,而且效果显著,是一项前景广阔值得深入研究的应用技术。