This study describes the predicted response of Unit 1 at the Browns Ferry Nuclear Plant to Station Blackout, defined as a loss of offsite power combined with failure of all onsite emergency diesel-generators to start and load. Every effort has been made to employ the most realistic assumptions during the process of defining the sequence of events for this hypothetical accident. DC power is assumed to remain available from the unit batteries during the initial phase and the operator actions and corresponding events during this period are described using results provided by an analysis code developed specifically for this purpose. The Station Blackout is assumed to persist beyond the point of battery exhaustion and the events during this second phase of the accident in which dc power would be unavailable were determined through use of the MARCH code. Without dc power, cooling water could no longer be injected into the reactor vessel and the events of the second phase include core meltdown and subsequent containment failure. An estimate of the magnitude and timing of the concomitant release of the noble gas, cesium, and iodine-based fission products to the environment is provided in Volume 2 of this report. 58 refs., 75more » figs., 8 tabs.« less

Station Blackout at Browns Ferry Unit One - accident sequence analysis. Volume 1

Mission failure evolution is a unique aspect of complex human-machine system (CHMS), which contains failure regularity and directs emergent reconfiguration measures. Oriented to all varieties of system components, an analysis of how the parts are connected and contribute to CHMS failure is necessary. Prior work paid more attention to system design with the law of system normal operation, where a single function failure was identified positively and its consequence was analyzed to guarantee reliability and safety. In this paper, a normally operational CHMS process is divided into three layers which contains task, element and capacity as well as the conceptions of Basic Task Space (BTS) and Repair Task Space (RTS). The measurement method of these three aspects was defined. Furthermore, CHMS failure measurement will be presented with the parameters of capacity deviation. Taking multiple elements coordination and self-organization into consideration, a multi-agent based simulation approach of system failure evolution path is proposed. This method is demonstrated with the nuclear power system intending to interpret how the system fails to deal with all possible disturbance. Obvious results show that the multiple failure paths can be obtained, from which the writer provides some constructive comments for system design.

Failure evolution analysis for complex human-machine system: A case for nuclear power system

The system definition in a convergent platform needs to cover all the dimensions in which the system exists. Please check the box with links to key terms in the references at the end of this chapter to facilitate the read.

System Definition in a Convergent Platform

The Fukushima nuclear accident has generated doubts and questions which need to be properly understood and addressed. This scientific attitude became necessary to allow the use of the nuclear technology for electricity generation around the world. The nuclear stakeholders are working to obtain these technical answers for the Fukushima questions. We believe that, such challenges will be, certainly, implemented in the next reactor generation, following the technological evolution. The purpose of this work is to perform a critical analysis of the Fukushima nuclear accident, focusing at the common cause failures produced by tsunami, as well as an analysis of the main redundant systems. This work also assesses the mitigative procedures and the subsequent consequences of such actions, which gave results below expectations to avoid the progression of the accident, discussing the concept of sharing of structures, systems and components at multi-unit nuclear power plants, and its eventual inappropriate use in safety-related devices which can compromise the nuclear safety, as well as its consequent impact on the Fukushima accident scenario. The lessons from Fukushima must be better learned, aiming the development of new procedures and new safety systems. Thus, the nuclear technology could reach a higher evolution level in its safety requirements. This knowledge will establish a conceptual milestone in the safety system design, becoming necessary the review of the current acceptance criteria of safety-related systems.

/pdf/the-fukushima-nuclear-accident-insights-on-the-safety-3rnuh3idee.pdf

Sergio de Oliveira Vellozo

Papers

The Fukushima Nuclear Accident: Insights on the Safety Aspects