Nuclear Accident Analysis Methods

Radioiodine plays an important role in the diagnosis and treatment of various thyroid disorders. Production methods for various iodine isotopes, namely, and are briefly described in this paper. The chemistry of iodine and radiation effects in aqueous solutions and isotopic exchange reactions are also reviewed. An understanding of the chemistry of iodine is essential in isotope production, and for developing the procedure to prepare the radioactive iodine labeled pharmaceuticals. In radiochemical analysis of iodine, most environmental and biological samples can be accurately analyzed by neutron activation at trace levels. The use of potassium iodide (KI) has become an important remedy to prevent the harmful effects of radioiodine exposure under nuclear accident conditions. The inhibitory effect of KI administration on thyroid radioactive iodine uptake is discussed. 

These topics are the subject of DOE Standard DOE-STD-1027-92, "Hazard Categorization and Accident Analysis Techniques for Compliance with DOE Order 5480.23 Nuclear Safety Analysis Reports," which provides guidance for facility managers and Cognizant Secretarial Offices (CSOs). They are also discussed in the DOE Standard DOE-STD-3009-94, "Preparation Guide for U.S. Department of Energy Nonreactor Nuclear Facility Safety Analysis Reports," which describes a SAR preparation method that is acceptable to DOE. 

CREAM Cognitive reliability and error analysis method. In CREAM, the operator model is more significant and less simplistic than that of first generation approaches. It can be used both for performance prediction as well as accident analysis. CREAM is used for evaluation of the probability of a human error for completion of a specific task. There is good application of fuzzy logic in this method. It was again started for nuclear application but has wider applications, too. 

Further studies concerning the stability limit of water at higher pressure and temperature (where this method is expected to be less accurate) with more realistic pressure-profile are in progress. Those data would be particularly important in the safety analysis of power plants (including nuclear ones) where during a so-called LOCA (Loss of Coolant Accident) part of the cooling liquid can reach some degree of metastability due to sudden pressure loss (see e.g. [ ]). 

NUCLEAR HAZARD CATEGORY 2 FACILITIES. This category requires use of one of several analytical methods for developing qualitative accident scenarios. The choices are generally compatible with the requirements of the PSM Rule. If the PSM Rule requirements for PrHAs are met, the resulting analysis should significantly contribute to the analysis required under the DOE-STD-1027-92 for release mechanisms. However, analyses beyond PSM Rule requirements may be needed to comply with other SAR requirements for Nuclear Hazard Category 2 Facilities. 

In reactor safety studies of this nature, an attenqit is made to construct a table or- plot of accident consequences (isotope amounts released) vs likelihoods. The basis for this work began with Farmer, was continued in studies such as that by Otway and Erdmann, and has recently been utilized by the Atomic Energy Commission, with substantial methods development. A similar approach was used for a reprocessing plant safety analysis for a mixed-oxide fuel fabrication plant, in the transportation of nuclear materials, and in considerations of waste storage. ... 

The predominant method of evaluation in these studies has been fault tree analysis. The Reactor Safety Study also utilized event tree analysis to conveniently document accident sequences and to link the subsystem fault trees into a plant analysis. Failure Mode and Effects Analysis, used extensively in fast reactor safety, is the recommended method for preliminary analysis. All of these methods have application to the analysis of the fuel cycle Including the problems of safe arding special nuclear material. ... 

The advantage of this method is that the answers are prelected. directly without detailed analysis of individual component and subsystem failure probabilities. The weakness, in the case of nuclear systems, is the lack of serious accidents to provide a projection base. 

ATHENA A technique for human error analysis. ATHENA is one HRA method which has been developed to improve the state-of-the-art in HRA, especially with respect to how realistically HRA can represent the kinds of human behaviors seen in accidents and near-miss events. It requires a good amount of resources. ATHENA approach incorporates the current understanding of why errors occur, based on the work of earlier pioneers, and substantiated by reviews of a number of significant accidents. It has been developed for mainly for nuclear application, but now it is used in generic manner. 

PSA is a method of estimating mathematically the likelihood and consequences of potential accidents at Nuclear Power Plants (NPPs). The major advantage of PSA is the possibility of in-depth qualitative and quantitative analysis of NPP actual configuration with definition of factors characterizing of contribution to the general risk of reactor core damage. 

ABSTRACT Technological advancements in area of sensor-based online maintenance systems have made the possibility of repairing some failed safety support systems of Nuclear Power Plants (NPP) such as electrical supply, I C systems, ventilation systems. However, the possibility of repair during accident situation is yet to be included into PSA level-1. Therefore, this paper presents a scheme of PSA level-1 by implementing an integrated method of Repairable Event Tree (RET) and Repairable Fault Tree (RET) analysis. The Core Damage Frequency (CDF) is calculated from consequence probabilities of the RET. An initiating event of Decay Heat Removal (DHR) systems of ASTRID reactor is analyzed. The proportionate CDFs estimated with repair and without repair have been compared and found that the recoveries can reduce CDF. In sum, this paper attempts to deal with the possibility of repair of some safety systems in PSA and its impacts on CDF of the NPP. 

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