14 Matching Results

Search Results

Advanced search parameters have been applied.

Review of pipe-break probability assessment methods and data for applicability to the advanced neutron source project for Oak Ridge National Laboratory

Description: The Advanced Neutron Source (ANS) (Difilippo, 1986; Gamble, 1986; West, 1986; Selby, 1987) will be the world's best facility for low energy neutron research. This performance requires the highest flux density of all non-pulsed reactors with concomitant low thermal inertial and fast response to upset conditions. One of the primary concerns is that a flow cessation of the order of a second may result in fuel damage. Such a flow stoppage could be the result of break in the primary piping. This report is a review of methods for assessing pipe break probabilities based on historical operating experience in power reactors, scaling methods, fracture mechanics and fracture growth models. The goal of this work is to develop parametric guidance for the ANS design to make the event highly unlikely. It is also to review and select methods that may be used in an interactive IBM-PC model providing fast and reasonably accurate models to aid the ANS designers in achieving the safety requirements. 80 refs., 7 figs.
Date: April 1, 1989
Creator: Fullwood, R.R.
Partner: UNT Libraries Government Documents Department

Actinide partitioning-transmutation program final report. VI. Short-term risk analysis of reprocessing, refabrication, and transportation: appendix

Description: The Chemical Technology Division of the Oak Ridge National Laboratory has prepared a set of documents that evaluate a Partitioning-Transmutation (PT) fuel cycle relative to a Reference cycle employing conventional fuel-material recovery methods. The PT cycle uses enhanced recovery methods so that most of the long-lived actinides are recycled to nuclear power plants and transmuted to shorter-lived materials, thereby reducing the waste toxicity. This report compares the two fuel cycles on the basis of the short-term radiological and nonradiological risks they present to the public and to workers. The accidental radiological risk to the public is analyzed by estimating the probabilities of sets of accidents; the consequences are calculated using the CRAC code appropriately modified for the material composition. Routine radiological risks to the public are estimated from the calculated release amounts; the effects are calculated using the CRAC code. Radiological occupational risks are determined from prior experience, projected standards, and estimates of accident risk. Nonradiological risks are calculated from the number of personnel involved, historical experience, and epidemiological studies. The result of this analysis is that the short-term risk of PT is 2.9 times greater than that of the Reference cycle, primarily due to the larger amount of industry. This conclusion is strongly dominated by the nonradiological risk, which is about 150 times greater than the radiological risk. The absolute risk as estimated for the fuel cycle portions considered in this report is 0.91 fatalities/GWe-year for the PT cycle and 0.34 fatalities/GWe-year for the Reference cycle. This should be compared with Inhaber's estimate of 1.5 for nuclear and 150 for coal. All of the risks assumed here are associated with the production of one billion watts of electricity (GWe) per year.
Date: January 1, 1980
Creator: Fullwood, R.R. & Jackson, R.
Partner: UNT Libraries Government Documents Department

PRAAGE-1988: An interactive IBM-PC code for aging analysis of NUREG-1150 systems

Description: Probabilistic Risk Assessments (PRA) contain a great deal of information for estimating the risk of a nuclear power plant but do not consider aging. PRAAGE (PRA+AGE) is an interactive, IBM-PC code for processing PRA-developed system models using non-aged failure rate data in conjunction with user-supplied time-dependent nuclear plant experience component failure rate data to determine the effects of component aging on a system's reliability as well as providing the age-dependent importances of various generic components. This paper describes the structure, use and application of PRAAGE to the aging analysis of the Peach Bottom 2 RHR system in the LPCI and SDC modes of operation. 4 refs., 15 figs., 5 tabs.
Date: January 1, 1988
Creator: Fullwood, R.R. & Shier, W.G.
Partner: UNT Libraries Government Documents Department

PRAAGE: An interactive IBM-PC code for unreliability/aging analysis

Description: The more redundant a system is, the faster its unavailability increases with aging. Normally a highly redundant system has a small unavailability contribution, but aging may make it significant. This is due to the fact that, as assumed in this study, aging degradation drives up the failure rate of all redundant trains and causes a rapid loss in the effectiveness of the redundancy in reducing the unavailability. Thus aging, if allowed to cross trains, can be a significant contributor to unavailability. This conclusion demonstrates the usefulness of PRAAGE for interactive systems analysis. 3 refs., 1 fig., 1 tab.
Date: January 1, 1987
Creator: Fullwood, R.R.; Hall, R.E. & Taylor, J.H.
Partner: UNT Libraries Government Documents Department

Relative consequences of transporting hazardous materials

Description: The objective of this paper is to discuss methods under study at Transportation Technology Center to develop a perspective on how technical measures of hazard and risk relate to perception of hazards, harm, and risks associated with transporting hazardous materials. This paper is concerned with two major aspects of the relative hazards problem. The first aspect is the analyses of the possible effects associated with exposure to hazardous materials as contained in the following two parts: outlines of possible problems and controversies that could be encountered in the evaluation and comparisons of hazards and risks; and description of the various measures of harm (hazards or dangers) and subsequent comparisons thereof. The second aspect of this paper leads into a presentation of the results of a study which had the following purposes: to develop analytical techniques for a consistent treatment of the phenomenology of the consequences of a release of hazardous materials; to reduce the number of variables in the consequence analyses by development of transportation accident scenarios which have the same meteorological conditions, demography, traffic and population densities, geographical features and other appropriate conditions and to develop consistent methods for presenting the results of studies and analyses that describe the phenomenology and compare hazards. The results of the study are intended to provide a bridge between analytical certainty and perception of the hazards involved. Understanding the differences in perception of hazards resulting from transport of various hazardous materials is fraught with difficulties in isolating the qualitative and quantitative features of the problem. By relating the quantitative impacts of material hazards under identical conditions, it is hoped that the perceived differences in material hazards can be delineated and evaluated.
Date: January 1, 1980
Creator: Fullwood, R.R.; Rhyne, W.R.; Simmons, J.A. & Reese, R.T.
Partner: UNT Libraries Government Documents Department

Probabilistic risk assessment in the design of the Advanced Neutron Source

Description: Probabilistic risk assessment (PRA) has been used extensively in the design of the Advanced Neutron Source (ANS) reactor to safety risk and enhance availability. Design feautures incorporated to minimize risk include submerged primary coolant piping, circulation cooling capability, and dual independent and diverse shutdown systems. The recently completed Level I, Phase 1 PRA shows that the risk dominating event sequence initiator is now blockage; a program to minimize this identified risk is described.
Date: September 1, 1994
Creator: Harrington, R. M.; Ramsey, C. T. & Fullwood, R. R.
Partner: UNT Libraries Government Documents Department

Relating aviation service difficulty reports to accident data for safety trend prediction

Description: A synthetic model of scheduled-commercial U.S. aviation fatalities was constructed from linear combinations of the time-spectra of critical systems reporting using 5.5 years of Service Difficulty Reports (SDR){sup 2} and Accident Incident Data System (AIDS) records{sup 3}. This model, used to predict near-future trends in aviation accidents, was tested by using the first 36 months of data to construct the synthetic model which was used to predict fatalities during the following eight months. These predictions were tested by comparison with the fatality data. A reliability block diagram (RBD) and third-order extrapolations also were used as predictive models and compared with actuality. The synthetic model was the best predictor because of its use of systems data. Other results of the study are a database of service difficulties for major aviation systems, and a rank ordering of systems according to their contribution to the synthesis. 4 refs., 8 figs., 3 tabs.
Date: October 1, 1996
Creator: Fullwood, R.R.; Hall, R.E.; Martinez-Guridi, G.; Uryasev, S. & Sampath, S.G.
Partner: UNT Libraries Government Documents Department

On the safety of aircraft systems: A case study

Description: An airplane is a highly engineered system incorporating control- and feedback-loops which often, and realistically, are non-linear because the equations describing such feedback contain products of state variables, trigonometric or square-root functions, or other types of non-linear terms. The feedback provided by the pilot (crew) of the airplane also is typically non-linear because it has the same mathematical characteristics. An airplane is designed with systems to prevent and mitigate undesired events. If an undesired triggering event occurs, an accident may process in different ways depending on the effectiveness of such systems. In addition, the progression of some accidents requires that the operating crew take corrective action(s), which may modify the configuration of some systems. The safety assessment of an aircraft system typically is carried out using ARP (Aerospace Recommended Practice) 4761 (SAE, 1995) methods, such as Fault Tree Analysis (FTA) and Failure Mode and Effects Analysis (FMEA). Such methods may be called static because they model an aircraft system on its nominal configuration during a mission time, but they do not incorporate the action(s) taken by the operating crew, nor the dynamic behavior (non-linearities) of the system (airplane) as a function of time. Probabilistic Safety Assessment (PSA), also known as Probabilistic Risk Assessment (PRA), has been applied to highly engineered systems, such as aircraft and nuclear power plants. PSA encompasses a wide variety of methods, including event tree analysis (ETA), FTA, and common-cause analysis, among others. PSA should not be confused with ARP 4761`s proposed PSSA (Preliminary System Safety Assessment); as its name implies, PSSA is a preliminary assessment at the system level consisting of FTA and FMEA.
Date: May 14, 1997
Creator: Martinez-Guridi, G.; Hall, R.E. & Fullwood, R.R.
Partner: UNT Libraries Government Documents Department

An application of probabilistic safety assessment methods to model aircraft systems and accidents

Description: A case study modeling the thrust reverser system (TRS) in the context of the fatal accident of a Boeing 767 is presented to illustrate the application of Probabilistic Safety Assessment methods. A simplified risk model consisting of an event tree with supporting fault trees was developed to represent the progression of the accident, taking into account the interaction between the TRS and the operating crew during the accident, and the findings of the accident investigation. A feasible sequence of events leading to the fatal accident was identified. Several insights about the TRS and the accident were obtained by applying PSA methods. Changes proposed for the TRS also are discussed.
Date: August 1, 1998
Creator: Martinez-Guridi, G.; Hall, R.E. & Fullwood, R.R.
Partner: UNT Libraries Government Documents Department