Engineered safety features

This section should present relevant information on the engineered safety features and associated systems as described in paras 3.65-3.70. Where necessary, additional system specific information should be added as indicated below. 

This subsection should present relevant information on the emergency core cooling system and associated fluid systems. The actuation logic should be described subsequently in the section on protection systems and need not be described here. 

This subsection should present relevant information on the containment (or confinement) systems incorporated to localize the effects of accidents, and should include, among other things the heat removal systems of the containment, the functional design of the secondary containment, the containment isolation system, the protection of the containment against overpressure and underpressure, where provided, the control of combustible gas in the containment, the containment spray system and the containment leakage testing system. Further discussion on matters to be covered in this subsection of the SAR is provided in Ref. [28]. 

This subsection should provide relevant information on the systems for the removal and control of fission products. In addition, the following specific information should be presented to demonstrate the performance capability of these systems considerations of the coolant pH and chemical conditioning in aU necessary conditions of system operation effects on filters of postulated design basis loads due to fission products and the effects on filter operability of design basis release mechanisms for fission products. 

This chapter of the SAR shall identify and provide a summary of the types, locations and functions of the engineered safety features (ESFs) provided in the facility. Examples of ESFs are the emergency core cooling system and the confine-ment/containment system. The requirements of these systems and supplementary features are discussed in paras 635-645 of Safety Series No. 35-Sl. 

The design basis and various modes of operation of the ESFs should be discussed in detail. The accidents with which these systems must cope should be presented and analyses should be provided which demonstrate that the systems fulfil the requirements. The subsystems which are essential for the proper operation of the ESFs shall be described (e.g. unintemiptable power supply for the emergency core cooling system). The extent to which the ESFs are automated and the conditions for which manual override is warranted should be clearly indicated. 

Reference shall be made to the relevant chapters in the SAR or to other 

This chapter of the SAR shall provide information regarding the instrumentation and control (I C) systems of all safety systems and of safety related items and systems. The information provided shall emphasize those instruments and associated equipment which affect reactor safety. The requirements for I C are discussed in paras 646-651 of Safety Series No. 35-Sl. 

All I C and supporting systems (with emphasis on safety systems and safety related systems), including alarm, communication and display instrumentation, shall be listed, and considerations of instrumentation errors shall be included. Adequate schematic diagrams shall also be provided. 

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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. 

The preceding overviewed the operation and engineered safety features of current and advanced LWRs. Before preceding to describe how PSA is performed on nuclear power plants, two accidents are described that have profoundly affected the industiy... 

Ceitain engineered safety features (containment sprays, suppression pools, ice condenscr.s i will effectively remove fission products regardless of form. Other ESF such as filters are less effective. 

Postma, A.K. Pasedag, W.F. (1986) Overview of fission product release and the effectiveness of engineered safety features. In Source Term Evaluation for Accident Conditions, IAEA, Vienna, pp. 621-32. 

In order to reduce radionuclide transportation from the primary to the secondary cooling system, containment isolation valves should be installed. These valves will be automatically closed by the signal detecting the heat transfer tube rupture of IHX. Meanwhile, the current engineered safety features actuating system is not designed to detect the rupture since the scenario did not impact on the reactor safety of the original HTTR. Therefore, a detection method of heat transfer tube rupture of IHX should be established. 

The strategy of detection method establishment is to apply the simple and reliable method since it would comprise the engineered safety featured actuation system. 

Reactor protection (reactor trip and associated engineered safety features, diesel load sequence),... 

Actuator network The IE actuator netwoik is based on a master/slave protocol and uses many of the NERVIA network components. It is dedicated to safety actuator control needed for example for the Engineered Safety Features,... 

There are five safety systems in Lungmen DCIS. They are Reactor Protection System (RPS), Neutron Monitor System (NMS), Process Radiation Monitoring System (PRMS), Containment Monitoring System (CMS), and Engineered Safety Features (ESF). The software development for all these safety systems follows the BTP-14 requirements. Along with the development, the IV V activities are performed. Of the safety systems, RPS, NMS, PRMS and CMS are designed by GE NUMAC, and ESF is sub-contracted by GE to Eaton Corporation. 

ESF Engineered Safety Feature Actuation System ESFAS... 

Common requirements for the reactor protection system, engineered safety features actuation system and emergency load sequencer on one side, and for the reactor limitation system on the other side have been set forth in the following areas ... 

In the Indonesian Atomic Energy Act there is no specific difference in the present licensing steps for large-, medium-, small- and very small-sized nuclear power plants. The adoption of passive safety concept, non-active components, and other improvement of engineered safety features will be taken into consideration in making possible simplification of the licensing process. 

Prevention of Criticality in Fuel Storage and Handling. Criticality in the fuel storage and handling system shall be prevented by physical systems or processes to maintain adequate subcriticality at all times. The preferred order to maintain subcriticality is favorable geometry, other passive engineered safety features then active engineered safety features. 

NRC Regulatory Guide 1.52, "Design Testing and Maintenance Criteria for Post Accident Engineered-Safety-Feature Atmosphere Cleanup System Air Filtration and Adsorption Units of Light-Water-Cooled Nuclear Power PI ants."... 

Controls means, when used with respect to nuclear reactors, apparatus and mechanisms that, when manipulated, directly affect the reactivity or power level of a reactor or the status of an engineered safety feature. When used with respect to any other nuclear facility, "controls" means apparatus and mechanisms that, when manipulated cou I d affect the chem i caI, phys i caI, meta11urg i caI, or nucI ear process of the nuclear facility In such a manner as to affect the protection of health and safety. 

Engineered Safety Features means systems, components, or structures that prevent and/or mitigate the consequences of potential accidents described in the FSAR including the bounding design basis accidents. 

The design of hydraulic engineered safety features for LWRs has traditionally been performed according to high reliability and leak proof standards. These systems are usually called into operation to protect the fuel barrier in the case of a loss of the primary system barrier. In addition, being strictly connected to the primary circuit pressure boundary, they have to be equipped with leak proof isolation devices, normally closed during plant operation. 

The engineered safety features, for example, have been optimized for the removal of elemental and organic iodine, while the closure time of the isolation valves has been established on the basis of the immediate release from the core. The Technical Information Document 14844 (TID) releases, as they were then named, have been used for the verification of the resistance to radiations of equipment inside the containment, as well as for the evaluation of control room habitability after an accident and for the design of liquid and gas sampling systems. 

The following design principles are followed in order to ensure a high reliability level of the engineered safety features (Level 3) ... 

B Radiological Consequences of a Design Basis Loss-of-Coolant Accident Leakage From Engineered Safety Feature Components Outside Containment... 

The containment sump should be designed to permit mixing of emergency core cooling system (ECCS) and spray solutions. Drains to the engineered safety features sump should be provided for all regions of the containment which would collect a significant quantity of the spray solution. Alternatively, allowance should be made for dead volumes in the determination of the pH of the sump solution and the quantities of additives injected. 

It is conservative to assume that organic iodides are not removed by either spray or wall deposition. Radiolytic destruction of iodomethane may be modeled, but such a model must also consider radiolytic production (Reference...). Engineered safety features designed to remove organic iodides are reviewed on a case-by-case basis. 

DOE Order 5480.23, Chg. I, Nuclear Safety Analysis Reports, Paragraph 8.b.(3)(d), as amplified in paragraph 4.f.(3)(d)4 of Attachment 1 to the Order, requires a description of the facility and operations conducted in the facility, including design of principal structures, components, systems, engineered safety features, and processes. (DOE 1994a). 

The next point which makes the digital solution more vulnerable from common causes is eventual aggregation of different safety systems automation into one actuation system - e.g. Reactor Trip System (RTS) and Engineered Safety Features Actuation System (ESFAS), RTS + Reactor Limitation System C S). 

The Main Steam Line Isolation System (see Section 10.3.2 for more details) is composed of portions of the Main Steam System and the Engineered Safety Features Actuation System. Discussed here are those portions of these systems that respond to a Main Steam Isolation Signal, as defined in Section 7.3. A discussion of radiological considerations is provided in Section 12.3. 

Each of the four main steam lines is provided with a power-actuated Main Steam Isolation Valve designed to stop flow from either direction when it is tripped closed. Each valve is located outside containment and is provided with means of actuation from the Engineered Safety Features Actuation System, meeting the requirements of IEEE Standard 279. 

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