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Probabilistic analysis of fires in nuclear plants

Description: The aim of this paper is to describe a multilevel (i.e., staged) probabilistic analysis of fire risks in nuclear plants (as part of a general PRA) which maximizes the benefits of the FRA (fire risk assessment) in a cost effective way. The approach uses several stages of screening, physical modeling of clearly dominant risk contributors, searches for direct (e.g., equipment dependences) and secondary (e.g., fire induced internal flooding) interactions, and relies on lessons learned and available data from and surrogate FRAs. The general methodology is outlined. 6 figs., 10 tabs.
Date: January 1, 1985
Creator: Unione, A. & Teichmann, T.
Partner: UNT Libraries Government Documents Department

Analysis of the results of the Midland PRA

Description: This paper presents the results of a limited review of the Midland PRA (MPRA), aimed at facilitating regulatory analyses and at providing insights into safety related plant failures. In particular, stress was laid on the root causes of accident sequences, particularly their failure modes, viz., hardware, human, maintenance, test, and repair. Because this information was difficult to extract in this detailed and sophisticated PRA (and in certain others) a special algorithm was developed to display the leading sequences contributing to core damage and/or to public risk in terms of the above generic failure modes. This was done in a hierarchical fashion to allow tracing the important accident sequences to the systems failures. The weighted core damage frequency (CDF) values of the sequences considered then provided a (quantitative) ranked importance listing of these failure modes, led by hardware failures (in 78%) and human factors (in 37%), etc. Multiple maintenance situations (reflecting on test and maintenance specifications) were also evaluated, but played only a small role (less than or equal to3%). Similar tabulations were also made of the (weighted) importance of the support systems (such as the electric power system, the component cooling water systems, etc.) and of the role of the major systems/functions (e.g., high pressure injection, etc.) contributions to these accident sequences. Finally, the role of certain particular operational and plant features (e.g., loss of offsite power initiators, RCP seal failure, bunkering, etc.) were briefly examined. The methods displayed seem applicable to an important class of extant and projected PRAs.
Date: January 1, 1986
Creator: Bozoki, G. & Teichmann, T.
Partner: UNT Libraries Government Documents Department

Statistical relation between single- and multiple-component failures

Description: This paper describes the results of some investigations of the statistical (and to some degree the qualitative) relation between single and multiple component failure events at US operating nuclear plants. The objectives of the investigations were to establish whether: multiple component failures could be attributed to random coincidences of single independent failures; there was any clear cut qualitative connection between the two type of failures; and there were any quantitative statistical parameters that related the two types of failure.
Date: January 1, 1982
Creator: Teichmann, T. & Papazoglou, I.A.
Partner: UNT Libraries Government Documents Department

Deadtime effects in coincidence counting: A new model. Revised

Description: This paper described a model for correcting deadtime effects in coincidence counting. The correction is based on waiting time distribution for the detection of particles. The waiting time distribution is expressed as integrals of correlation functions, using Sratonivich`s theory of random set of points. The correlation functions are solved from the basic equation governing the probability.
Date: April 1, 1997
Creator: Lu, Ming-Shih & Teichmann, T.
Partner: UNT Libraries Government Documents Department

Neutron coincidence measurements when nuclear parameters vary during the multiplication process

Description: In a recent paper, a physical/mathematical model was developed for neutron coincidence counting, taking explicit account of neutron absorption and leakage, and using dual probability generating function to derive explicit formulae for the single and multiple count-rates in terms of the physical parameters of the system. The results of this modeling proved very successful in a number of cases in which the system parameters (neutron reaction cross-sections, detection probabilities, etc.) remained the same at the various stages of the process (i.e. from collision to collision). However, there are practical circumstances in which such system parameters change from collision to collision, and it is necessary to accommodate these, too, in a general theory, applicable to such situations. For instance, in the case of the neutron coincidence collar (NCC), the parameters for the initial, spontaneous fission neutrons, are not the same as those for the succeeding induced fission neutrons, and similar situations can be envisaged for certain other experimental configurations. This present document shows how the previous considerations can be elaborated to embrace these more general requirements.
Date: July 1, 1995
Creator: Lu, Ming-Shih & Teichmann, T.
Partner: UNT Libraries Government Documents Department

A generalized model for coincidence counting

Description: The aim of this paper is to provide a description of the multiplicative processes associated with coincidence counting techniques, for example in the NDA of plutonium bearing materials. The model elucidates both the physical processes and the underlying mathematical formalism in a relatively simple but comprehensive way. In particular, it includes the effect of absorption by impurities or poisons, as well as that of neutron leakage on a parallel basis to the treatment of induced fission itself. The work thus parallels and generalizes the methods of Boehnel of Hage and Cifarelli, and more recently of Yanjushkin. This paper introduces the concept of a dual probability generating function to account for both the basic physical multiplication phenomena, as well as the detection phenomena. The underlying approach extends the idea of a simple probability generating function, due to De Moivre. The basic mathematical background may be found, for example, in Feller 1966.
Date: January 1, 1992
Creator: Lu, Ming-Shih & Teichmann, T.
Partner: UNT Libraries Government Documents Department

Insights from an overview of four PRAs

Description: This paper summarizes the findings of an investigation of four probabilistic risk assessments (PRAs), those for Millstone 3, Seabrook, Shoreham, and Oconee 3, performed by Brookhaven National Laboratory (BNL) for the Reliability and Risk Assessment Branch of the US Nuclear Regulatory Commission (NRC). This group of four PRAs was subjected to an overview process with the basic goal of ascertaining what insights might be gained (beyond those already documented within the individual PRAs) by an independent evaluation of the group with respect to nuclear plant safety and vulnerability. Specifically, the objectives of the study were (1) to identify and rank initiators, systems, components, and failure modes from dominant accident sequences according to their contribution to core melt probability and public risk; and (2) to derive from this process plant-specific and generic insights. The effort was not intended to verify the specific details and results of each PRA but rather - having accepted the results - to see what they might mean in a more global context. The NRC had previously sponsored full detailed reviews of each of these PRAs, but only two, those for Millstone 3 and Shoreham, were completed and documented in time to allow their consideration within the study. This paper also presents some comments and insights into the amenability of certain features of these PRAs to this type of overview process.
Date: January 1, 1986
Creator: Fitzpatrick, R.; Arrieta, L.; Teichmann, T. & Davis, P.
Partner: UNT Libraries Government Documents Department

A generalized model for coincidence counting

Description: The aim of this paper is to provide a description of the multiplicative processes associated with coincidence counting techniques, for example in the NDA of plutonium bearing materials. The model elucidates both the physical processes and the underlying mathematical formalism in a relatively simple but comprehensive way. In particular, it includes the effect of absorption by impurities or poisons, as well as that of neutron leakage on a parallel basis to the treatment of induced fission itself. The work thus parallels and generalizes the methods of Boehnel of Hage and Cifarelli, and more recently of Yanjushkin. This paper introduces the concept of a dual probability generating function to account for both the basic physical multiplication phenomena, as well as the detection phenomena. The underlying approach extends the idea of a simple probability generating function, due to De Moivre. The basic mathematical background may be found, for example, in Feller 1966.
Date: June 1, 1992
Creator: Lu, Ming-Shih & Teichmann, T.
Partner: UNT Libraries Government Documents Department

Simulation of high level neutron coincidence counter

Description: An algorithm for the simulation of HLNC measurement data on a personal computer (PC) has been developed and is presented in this paper. This algorithm is based on a leakage multiplication factor --- fissile mass correlation (with three parameters) derived from about 100 sets of published experimental data. Using this algorithm, the simulated totals and reals (coincidence pair) count rates agreed with all measurement data to within 10%. Uncertainties in isotopics as well as the effects of possible contaminants --- fluorine or moisture --- have also been modelled, but are not discussed in detail in this condensed account. The algorithm has been tested successfully against additional data obtained in field measurements. PC software based on the simulation algorithm has been developed for training inspectors and familiarizing them with HLNC measurement data and with errors affecting HLNC measurements.
Date: September 1, 1992
Creator: Lu, Ming-Shih & Teichmann, T.
Partner: UNT Libraries Government Documents Department

An integrated approach for multi-level sample size determination

Description: Inspection procedures involving the sampling of items in a population often require steps of increasingly sensitive measurements, with correspondingly smaller sample sizes; these are referred to as multilevel sampling schemes. In the case of nuclear safeguards inspections verifying that there has been no diversion of Special Nuclear Material (SNM), these procedures have been examined often and increasingly complex algorithms have been developed to implement them. The aim in this paper is to provide an integrated approach, and, in so doing, to describe a systematic, consistent method that proceeds logically from level to level with increasing accuracy. The authors emphasize that the methods discussed are generally consistent with those presented in the references mentioned, and yield comparable results when the error models are the same. However, because of its systematic, integrated approach the proposed method elucidates the conceptual understanding of what goes on, and, in many cases, simplifies the calculations. In nuclear safeguards inspections, an important aspect of verifying nuclear items to detect any possible diversion of nuclear fissile materials is the sampling of such items at various levels of sensitivity. The first step usually is sampling by ``attributes`` involving measurements of relatively low accuracy, followed by further levels of sampling involving greater accuracy. This process is discussed in some detail in the references given; also, the nomenclature is described. Here, the authors outline a coordinated step-by-step procedure for achieving such multilevel sampling, and they develop the relationships between the accuracy of measurement and the sample size required at each stage, i.e., at the various levels. The logic of the underlying procedures is carefully elucidated; the calculations involved and their implications, are clearly described, and the process is put in a form that allows systematic generalization.
Date: December 31, 1997
Creator: Lu, M.S.; Teichmann, T. & Sanborn, J.B.
Partner: UNT Libraries Government Documents Department

An integrated approach for multi-level sample size determination

Description: this paper gives an integrated approach to sampling problems involving a series of increasingly sensitive measurements on correspondingly smaller sample sizes which proceeds logically from level to level with increasing accuracy. The methods and results are consistent with those presently used by the International Atomic Energy Agency (IAEA), serve to elucidate the underlying concepts, and often simplify the calculations.
Date: February 1, 1997
Creator: Lu, M.S.; Sanborn, J.B. & Teichmann, T.
Partner: UNT Libraries Government Documents Department

A flexible method for multi-level sample size determination

Description: This paper gives a flexible method to determine sample sizes for both systematic and random error models (this pertains to sampling problems in nuclear safeguard questions). In addition, the method allows different attribute rejection limits. The new method could assist achieving a higher detection probability and enhance inspection effectiveness.
Date: April 1, 1997
Creator: Lu, Ming-Shih; Sanborn, J.B. & Teichmann, T.
Partner: UNT Libraries Government Documents Department

PAIR (Planning and Analysis of Inspection Resources)

Description: The safeguards inspection effort of the International Atomic Energy Agency consists of the efforts for the Physical Inventory Verifications to close the annual material balance, Interim Inventory Verifications, conducted mainly to satisfy the Timeliness Criteria, Flow Verifications to verify the transfer of material, and Containment and Surveillance activities, which help preserve continuity of knowledge concerning the material. Estimating the requiring overall future inspection effort under a variety of conditions is an important part of Agency planning. As exemplified by the sample results provides a straightforward means to analyze `What if` situations in safeguards implementation. It thereby permits managers and analysts to study future scenarios and their effect on human resources. It is planned to introduce into PAIR a direct capability for studying costs associated with these hypothetical changes in safeguards implementation. In this way PAIR could more easily assist the Safeguards Department in its current program of investigating new safeguards approaches.
Date: March 1994
Creator: Teichmann, T.; Santaniello, A. & Fishbone, L. G.
Partner: UNT Libraries Government Documents Department

Statistical cluster analysis and diagnosis of nuclear system level performance

Description: The complexity of individual nuclear power plants and the importance of maintaining reliable and safe operations makes it desirable to complement the deterministic analyses of these plants by corresponding statistical surveys and diagnoses. Based on such investigations, one can then explore, statistically, the anticipation, prevention, and when necessary, the control of such failures and malfunctions. This paper, and the accompanying one by Samanta et al., describe some of the initial steps in exploring the feasibility of setting up such a program on an integrated and global (industry-wide) basis. The conceptual statistical and data framework was originally outlined in BNL/NUREG-51609, NUREG/CR-3026, and the present work aims at showing how some important elements might be implemented in a practical way (albeit using hypothetical or simulated data).
Date: January 1, 1985
Creator: Teichmann, T.; Levine, M.M.; Samanta, P.K. & Kato, W.Y.
Partner: UNT Libraries Government Documents Department

HLNC calibration and application to waste measurement

Description: Using the established equations governing the counts and the underlying nuclear parameters involved in neutron coincidence measurements, the calibration procedure used in calculating the effective Pu{sup 240} mass in plutonium bearing samples is carefully reexamined and restructured in a physically and mathematically consistent form. The characteristics of this approach are described and its application to existing data illustrated. The implications for waste measurements are discussed.
Date: June 1, 1992
Creator: Lu, Ming-Shih; Teichmann, T.; De Ridder, P. M. & Delegard, C.
Partner: UNT Libraries Government Documents Department

HLNC calibration and application to waste measurement

Description: This paper addresses problems of calibration and estimation of a parameter, p{sub o}, in high level neutron coincidence counting (HLNC) measurement. The presentation begins with a deductive approach, based on the generally accepted physical equations which are satisfied by the total and coincidence count rates. A new approach for the estimation of p{sub o} via measurement and a new calibration procedure consistent with the physical theory of coincidence counting measurement are presented. The approach is compared with the existing conventional approach in which possible inconsistency with the theoretical model is shown. In addition, the original model for neutron coincidence counting in a multiplying medium was extended to simultaneously account for the possible presence of poison, as well as for the neutron detection. The equations suitable for the data analysis of measurement of waste and their criteria are given.
Date: March 4, 1992
Creator: Lu, Ming Shih; Teichmann, T. & De Ridder, P. M.
Partner: UNT Libraries Government Documents Department

Simulation of HLNC and NCC measurements

Description: This report discusses an automatic method of simulating the results of High Level Neutron Coincidence Counting (HLNC) and Neutron Collar Coincidence Counting (NCC) measurements to facilitate the safeguards` inspectors understanding and use of these instruments under realistic conditions. This would otherwise be expensive, and time-consuming, except at sites designed to handle radioactive materials, and having the necessary variety of fuel elements and other samples. This simulation must thus include the behavior of the instruments for variably constituted and composed fuel elements (including poison rods and Gd loading), and must display the changes in the count rates as a function of these characteristics, as well as of various instrumental parameters. Such a simulation is an efficient way of accomplishing the required familiarization and training of the inspectors by providing a realistic reproduction of the results of such measurements.
Date: March 1, 1994
Creator: Lu, Ming-Shih; Teichmann, T. & De Ridder, P.
Partner: UNT Libraries Government Documents Department

Well coincidence counting and analysis

Description: In several recent papers a physical/mathematical model was developed to describe the nuclear multiplicative processes in samples containing fissile material from a general statistical viewpoint, starting with the basic underlying physical phenomena. The results of this model agreed with the established picture used in ``standard`` HLNCC (High Level Neutron Coincidence Counter) measurements, but considerably extended them, and allowed a more detailed interpretation of the underlying physical mechanisms and of the higher moments of the neutron counts. The present paper examines some recent measurements made at Y-12 (Oak Ridge) using the AWCC, in the light of this model. The results show internal consistency under a variety of conditions, and give good agreement between experiment and theory.
Date: March 1, 1994
Creator: Lu, Ming-Shih; Teichmann, T.; Ceo, R. N. & Collins, L. L.
Partner: UNT Libraries Government Documents Department

Fissile mass-multiplication factor correlation for Pu measurement

Description: An empirical correlation between the fissile mass and the leakage multiplication factor, as determined by High Level Neutron Coincidence (HLNC) counting, was developed based on available measurement data. This correlation has been used successfully for the simulation of HLNC counting. With the singles count rate (totals), the correlation can be used to obtain a quick estimate of the plutonium mass of the sample in less time than required to measure the real coincidence count rate. The correlation can also be used to evaluate samples contaminated with ({alpha},n) sources such as fluorine.
Date: June 1, 1993
Creator: Lu, Ming-Shih; Teichmann, T.; De Ridder, P.; Verrecchia, G. P. D.; Chare, P. & Vocino, V.
Partner: UNT Libraries Government Documents Department

HLNC calibration and application to waste measurement

Description: Using the established equations governing the counts and the underlying nuclear parameters involved in neutron coincidence measurements, the calibration procedure used in calculating the effective Pu{sup 240} mass in plutonium bearing samples is carefully reexamined and restructured in a physically and mathematically consistent form. The characteristics of this approach are described and its application to existing data illustrated. The implications for waste measurements are discussed.
Date: January 1, 1992
Creator: Lu, Ming-Shih; Teichmann, T. (Brookhaven National Lab., Upton, NY (United States)); De Ridder, P.M. & Delegard, C. (International Atomic Energy Agency, Vienna (Austria))
Partner: UNT Libraries Government Documents Department