Safety-Support Systems

Various safety related systems and safety support systems are designed to appropriate safety class specifications depending on the functional importance. In addition, systems are seismically designed for two different intensities of earthquake. The operating basis earthquake (ODE) represents the intensity of earthquake for which the systems are designed to remain functional during and after the event. The safe shutdown earthquake (SSE) considers the maximum earthquake potential of the site and only those systems which are required to ... 

The site at Tarapur, Maharashtra State, for locating the first two units of 500 MWe PHWR has been cleared by the State and Federal Authorities from the point of view of environment and pollution control. The regulatory body has also approved location of the two units at the proposed site. Based on the review of the current level of progress in design, and details of all safety systems and safety support systems, regulatory body has accorded license for construction commencement. 

The general scope of safety analysis for HWRs, covering the accident categories considered, safety barriers challenged, and the technical disciplines involved are summarized in Table 4.2. Failures in safety support systems (such as instrument air) are addressed in the PSA. 

Safety support systems create the conditions required for normal functioning of the safety systems they include power supply systems and a heat removal system that transmits heat to the consumers. 

A further example in WWERs is the seismic qualification of systems important to safety, especially ventilation systems which should be safety-graded but are not, and safety support systems like the service water pumps, fire water supply pumps and indication and recording instrumentation. Since fliese are not qualified with respect to seismic loads, their functional capability on demand in the case of an earthquake would be questionable. 

The measures to maintain the function related to safety support system... 

The non-Class 1 safety support systems (ac power, component cooling water, service water, and instrument air) have a limited role in the plant risk profile because the passive safety significant systems do not require cooling water or ac power. 

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. 

Requirements for safety system redundancy and unavailability Segregation for independence or diversity and Requirements for safety support systems ... 

It is incumbent upon the toller to develop and follow internal management systems as appropriate to support business needs, production needs, process safety, environmental responsibility, and worker health. The selection process should have considered whether or not satisfactory systems are in place. Nevertheless, the contract or auxiliary documents may be the vehicle used to help ensure that the system reviewed is the system actually used for completing the toll in question. Within the process safety management system, the management of change and training elements are essential subsystems. 

Function event trees include primarily the engineered safety features of the plant, but other systems provide necessary support functions. For example, electric power system failure amid reduce the effectiveness of the RCS heat-removal function after a transient or small UJ( A. Therefore, EP should be included among the systems that perform this safety function. Siipfiort systems such as component-cooling water and electric power do not perform safety functions directly. However, they significantly contribute to the unavailability of a system or group of systems that perform safety functions. It is necessary, therefore, to identify support systems for each frontline ssstcm and include them in the system analysis. 

Nuclear power plant systems may be classified as "Frontline" and "Support. . iccurding to their. service in an accident. Frontline systems are the engineered safety systems that deal directly with an accident. Support systems support the frontline systems. Accident initiators are broadly grouped as loss of cooling accidents (LOCAs) or transients. In a LOCA, water cooling the reactor is lost by failure of the cooling envelope. These are typically classified as small-small (SSLOCA), smalt (SLOCA), medium (MLOCA) and large (LLOCA). 

The ESDs were then translated into associated event trees. A generic event tree was developed for all initiators not involving LOCA. The generic transient event tree for each category of the transient initiators and loss of offsite power were specialized by the impact of the initiators on the safety and support systems, from the success criteria of the mitigating systems, and the initiator-specific human actions which were modeled in the fault trees. 

The Task Force s mission is to design a state-of-the-art process safety management system that will support all of Company X s varied business operations, and to install it at a pilot site to be determined. The team will maintain ongoing communication with Division C s Facility Managers Council, which has accepted responsibility for focusing on the division s process safety management systems. 

Each PSM system can then be examined to determine what system modifications (if any) are needed to address the new issues. For example, the process hazard assessment system might be modified to include participation by industrial hygienists to identify potential sources of exposure. Some process safety management systems (e.g., process documentation) may require no modification to support a wider scope. 

Read Chapter 2 of the CCPS publication Guidelines for Implementing Process Safety Management Systems, 1993, for guidance on obtaining buy-in. The principles described for obtaining support and commitment for PSM are equally applicable to integration of PSM and ESH. 

The most logical suming point in tlie safety design approach is to select a site where tlie number of undesirable weather and topograpltic conditions is limited. Adequate utilities and support systems plus fire protection service arc also required for a safe eiiviromnent. Chapter 5 presented a detailed account of phuit site selection and layout. These features will now be considered from a safety point of view. The following guidelines should be observed in dctcrniining a site tliat is favorable for tlie efficient tuid economical operation of the process. 

Safety instrumented system (SIS) Any combination of separate and independent devices (sensors, logic solvers, final elements, and support systems) designed and managed to achieve a specified safety integrity level. An SIS may implement one or more safety instrumented functions. 

Normally where it is necessary, fireproofing is preferred over water spray for several reasons. The fireproofing is a passive inherent safety feature, while the water spray is a vulnerable active system that requires auxiliary control to be activated. Additionally the water spray relies on supplemental support systems that may be vulnerable to failures, i.e., pumps, distribution network, etc. The integrity of fireproofing systems is generally considered superior to explosion incidents compared to water spray piping systems. The typical application of water sprays in place of fireproofing is for vessel protection. 

Because of the increasing complexity and necessity for safety of industrial processes, efficient monitoring and decision support systems are becoming more and more important. Indeed, even in normal operational conditions, several types of disturbances may occur with serious consequences in the performance of the process. Hence, there is a clear need for advanced control in order to keep the system performance as close as possible to optimal. 

Physical data can provide a source of valuable information for investigators. Investigators should not only consider the process system itself, but also control, safety, support, auxiliary, and adjacent systems as part of the analysis. When examining physical data, typical items of interest include ... 

Mazariegos, G.. Kramer, D.. Lopez, R., Shjakil, A., Rosenbloom, A., DeVera, M., Giraldo, M., Grogan, T, Zhu. Y. Fulmer, M., Amiot, B., Patzer, J. Safety observations in phase I clini cal evaluation of Excorp medical bioartificial liver support system after the first four patients. ASAIO J. 47, 471, 2001. 

Human expertise in complex systems is constantly changing and a New Paradigm for software safety assurance is considered. As the development of Safety Critical Systems is guided by standards, the standards are to be updated3. In what follows we present a general view of how the development of safe software systems is currently practiced and show two specific solutions aimed at efficient support of the efforts. Responsibility of organizations, processes and culture, not just efforts of specific members of the organizations, is emphasized. 

This definition is widely accepted within the safety critical systems community. Safety case can be considered as a special case of the trust case where focus is on a specific trust objective, i.e., safety, and highly demanding requirements are needed to be met by the base supporting the case. 

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