Trip Events Research Articles

Development of a Temporal Extension to Query Travel Behavior Time Paths Using an Object-Oriented GIS

An essential requirement to better understand activity-based travel behavior (ABTB) at the disaggregate level is the development of a spatio-temporal model able to support queries related to activities of individuals or groups of individuals. This paper describes the development and implementation of a temporal extension to a geographic information system (GIS) object-oriented model for the modeling of the time path and the retrieval of its event chaining. In this approach, time path is formulated as a totally time ordered set composed by activity events and trip events, themselves organized into time ordered sets. As sets, the time path and its components can be searched using their respective indexes. A series of methods were built that implement temporal predicates as an interface to temporally query the database. A set of positional operator methods were also designed that transform temporal topological queries into retrieval functions based on set ordering indices. Taken together, the temporal predicates and the positional operator methods define a temporal query extension that meets the retrieval needs of an ABTB database.

Analysis of human error and organizational deficiency in events considering risk significance

In this study, we analyzed human and organizational deficiencies in the trip events of Korean nuclear power plants. K-HPES items were used in human error analysis, and the organizational factors by Jacobs and Haber were used for organizational deficiency analysis. We proposed the use of CCDP as a risk measure to consider risk information in prioritizing K-HPES items and organizational factors. Until now, the risk significance of events has not been considered in human error and organizational deficiency analysis. Considering the risk significance of events in the process of analysis is necessary for effective enhancement of nuclear power plant safety by focusing on causes of human error and organizational deficiencies that are associated with significant risk.

Uncertainty and sensitivity analysis of MCPs’ trip events at Ignalina NPP

Eight main circulation pumps (MCPs) are employed for the cooling water forced circulation through the RBMK-1500 reactor at the Ignalina nuclear power plant (NPP). There have been a few events when one or more MCPs were inadvertently tripped. This paper presents investigation of a one MCP trip event and all MCPs’ trip events at Ignalina NPP. Thermal-hydraulic analysis was conducted using the best estimate system code RELAP5/MOD3.3. Uncertainty and sensitivity analysis of flow energy loss in different parts of the main circulation circuit (MCC), initial conditions and code-selected models was performed. Such analysis allows to estimate the influence of separate parameters on the calculation results and find those modelling parameters that have the largest impact on the investigated events. Uncertainty analysis indicates that natural circulation provides adequate cooling in the case of all MCPs tripped, and that the reactor is reliably cooled by forced circulation in the case of a single tripped MCP. On the basis of this analysis, recommendations for the further improvement of model are developed.

Benchmark analysis of main circulation pump trip events at the Ignalina NPP using RELAP5 code

The state-of-the-art code RELAP5/MOD3 was originally designed for PWRs. Because of unique RBMK designs the application of this code to RBMK-1500 encountered several problems. A successful best estimate RELAP5 model of the Ignalina NPP has been developed. This model includes the reactor main circulation circuit (MCC) and reactor control and protection system required for this kind of transient analysis. Benchmark analysis of all operating main circulation pump (MCP) trip events was performed. During the analysis the characteristics of isolation control valves and MCP throttling regulating valves were established. Comparison of calculated and measured parameters was also used to establish realistic resistances of different MCC components and realistic behaviour of the controllers of the reactor systems. Calculations performed with the RELAP5 model, which includes these modifications, compare favourably with plant data.

Full-Load-Rejection Design Analysis for the Lungmen Advanced Boiling Water Reactor Using RETRAN

The very first work on RETRAN model development and its application to plant design study for the Lungmen nuclear power station (LMNPS) is presented. Lungmen is the fourth nuclear power plant of the Taiwan Power Company (TPC). LMNPS has two advanced boiling water reactor (ABWR) units, each with a thermal power of 3926 MW. The preliminary safety analysis report (PSAR) of LMNPS is currently under review. The Lungmen RETRAN-02/MOD5 model was developed to provide support to TPC in the PSAR review and system design study. An analysis of generator load rejection with failure of all bypass valves was performed against the analysis in the PSAR to benchmark the Lungmen RETRAN model. One of the specific designs of LMNPS is that the reactor has the capability to withstand a full-load rejection or a turbine trip event without a reactor scram. An analysis of generator load rejection with all bypass valves was done to evaluate this design. The results show that this design is appropriate.

Analyses of Startup Test, Reload Limiting Transient, and Plant Event for the Kuosheng BWR-6 Related to MSIV Closure

Three analyses are presented for the Kuosheng plant, the second nuclear power station of the Taiwan Power Company. The first is a startup test benchmark analysis of full closure of the main steam isolation valves (MSIVs). This analysis is one of a series of startup test analyses to develop the Kuosheng RETRAN model. The second is a parallel reload safety analysis of a system pressure-limiting transient for Kuosheng Unit 2, Cycle 12, which is a part of work to develop an in-house reload safety analysis methodology. The third is an operating support analysis of a reactor trip event due to a single MSIV closure in October 1997; this analysis demonstrates the application of the Kuosheng RETRAN model. The work may add to the RETRAN experience base and to the plant modeling body of knowledge. A similar approach can be adopted to support the plant, with concerns.

Reporting and classification of loss of balance accidents

The main objective of the study was to assess how a classification system designed to code slip, trip and fall accidents (STF) could extract data provided in accident reports and the use of the system by the coder. Its specific aims were to evaluate the importance of loss of balance (LOB), other than that related to a slip–trip–fall event (STF), and the impact on statistics of overlapping LOB events, as well as to characterize the nature of the descriptive material, in particular as concerns the implicit nature of events or circumstances reported. Two databases were constituted from an initial group of 1540 accident reports acquired from a large telecommunications company. The classification system provided three codes to cover S, T, and F accidents, as well as 25 subcodes (S: 7; T: 6; F: 12) for classifying STF context. The first database grouped together 378 accident descriptions coded S, T, or F, while the second grouped together 104 accident descriptions reporting an LOB but not coded ST or F. For the three main STF codes and 25 subcodes, all vocabulary or locutions referring explicitly or implicitly to these codes were identified. In 81% of the descriptions for the first database, an S, T, or F corresponding to its resultant coding was identifiable (S: 98%, T: 73%; F: 72%). The study shows that the coder was very reliable and consistent. However, the system as designed led to significant distortions. In particular, the subcodes led to misclassifications. Correspondence between the descriptive data and the subcodes was low for trip events (51%), average for slipping (75%), and almost perfect for fall events (96%). An LOB other than an STF was identified in 23% of the descriptions. Two different LOB events were reported in 32% of the cases. A review of the second database revealed that only 32% of the descriptions could have suited the proposed classification system. The study showed that implicit data were used by the coder. Overall, the combined analysis of both databases showed that slipping events as well as other LOBs were underestimated and that a good number falling events were falsely identified. The statistics appeared to be seriously flawed. A possible strategy for structuring LOB events is proposed.

Empirical Steam Generator Water-Level Modeling Using Neural Networks

Neural networks such as the radial basis function network, adaptive neuro-fuzzy inference systems, and the multilayer feedforward neural network were adopted to model the steam generator water level, which was intended to be the analytic redundancy in the signal validation system. The training data were the simulation results of the small-demand turbine power variations around the steady state. The test data were from two small-load maneuvers: the load reduction from 100 to 50% of the rated power, and one feedwater pump trip event. The network training required only a short time, and the simulation results show that the neural networks are suitable for the modeling of steam generator water level.

RETRAN-02 MOD5 and RETRAN-03 code benchmarks for Beaver Valley plant transients and FSAR analyses

A RETRAN-02 MOD5 model and a RETRAN-03 model for the Beaver Valley Unit 1 plant were developed from an existing, but untested RETRAN deck. This study uses FSAR transient analyses, actual plant event data, and similar plant analyses performed with RETRAN and TRAC-BF1 MOD1 to benchmark the RETRAN-02 MOD5 and RETRAN-3 plant model. Eight transients were chosen to qualify the RETRAN models: (1) a standard reactor trip, (2) a loss of one reactor coolant pump, (3) a loss of all reactor coolant pumps, (4) an inadvertent opening of a pressurizer relief valve, (5) a loss of normal feedwater with auxiliary feedwater available, (6) a turbine trip, (7) a main steam line isolation valve closure, and (8) a main steam line break. These design basis transients were each chosen to isolate specific phenomena or plant design aspects of the RETRAN models that are exhibited in depressurization events, over-pressurization and over-temperature transients, and over-cooling accidents. Both the RETRAN-02 MOD5 and RETRAN-03 Beaver Valley models were successfully benchmarked. The RETRAN results compared well with the FSAR LOFTRAN analyses, an actual Beaver Valley single pump trip event, and Ringhals 2 and 4 analyses. The RETRAN-03 model performed well and provided a better best-estimate of plant phenomena than the RETRAN-02 MOD5 results; moreover, both the RETRAN models predicted more realistic transient behavior than the FSAR LOFTRAN results.

Man-Machine Design and Analysis System (MIDAS) Applied to a Computer-Based Procedure-Aiding System

Difficult issues in design criteria confront the designers of human—computer interaction (HCI) implementations for future power plant control rooms. Such HCI-intensive control—room elements include “soft” controls and displays, computerized procedures, alarm presentations, and support for cooperative information—sharing among crewmembers. This shift in technology, from dedicated controls and displays in fixed locations to multifunction computer—driven operator workstations and wall displays, must focus not only on the required functionality of these interfaces, but also on their crafting and integration in such a way as to minimize the likelihood of operator error. With the objective of providing early insight into the cognitively error—prone consequences of selected interface dynamics, we are adapting a computer—based cognitive modeling tool, the Man—machine Integrated Design and Analysis System (MIDAS), to quantitatively model certain user requirements for operating different types of interfaces while dealing with high—consequence events in a control room setting. MIDAS was conceived and is being developed as a joint Army/NASA program at the NASA Ames Research Center to test different design approaches to computerizing the cockpits of advanced commercial and military aircraft. This report presents preliminary results from a project to adapt the MIDAS tool to the nuclear control room domain. These results have enabled comparative observation of cognitive loading depending on whether a supervisor uses computerized procedures or paper procedures to direct crew response to a plant trip event. The results suggest that each technology for procedural support, in its current respective implementation, has its own strengths and weaknesses at different points in the control task dialog.

Deaths and injuries caused by slipping, tripping and falling.

‘Underfoot accidents’ is suggested as a description of slipping, tripping, falling and other events causing injuries on floors, stairs, roofs and scaffolding, etc. Some statistics are available for falls but there is no information about the numbers of other underfoot accidents. In 1979 there were 5886 fatal falls in England, Wales and Scotland. Statistics published by the Health and Safety Executive and the Home Accident Surveillance System indicate that there are at least half a million injuries from falls requiring hospital treatment or causing absence from work of at least 3 days. The United States Health Service recorded 13·6 million falls in 1972. National statistics on underfoot accidents would be valuable for accident prevention and could be obtained by investigating the causes of all accidental injuries attending hospital accident and emergency departments.