Automatic shutdown procedures

Control regimes (restrictions of waste feeds failsafe, interactive control systems automatic shutdown procedures, etc.). 

Maximum demand alarms are available for individual organizational use and these can be made to shut down non-essential plant in order to maintain a lower actual maximum demand. Where automatic shutdown is not in use alarms can be used to trigger a manual shutdown procedure. 

Instrumentation and automatic control is desirable in plants of this size to allow for automatic shutdown and alarm in case events should occur during unattended periods which might be deleterious to the plant or the product water. Automatic startup, however, is not a requirement if there is adequate product water storage, if the startup procedure for the plant can be carried out in a short time, and if an operator is available on call. 

It is now recognised as a design weakness by the Russians that positive provision was not made, for example, to shut the reactor down automatically under these conditions. In the UK it is normal procedure to have an automatic shutdown if important safety limits are violated. 

Load rejection without reactor trip (Y/N) - Yes Full Cathode Ray Tubes (CRT) display (Y/N) - Yes Automated start-up procedures (Y/N) Interactive Automated normal shutdown procedures(Y/N) Procedures, but Automated off normal shutdown procedures automatic plant... 

Answer First Back-up of coolant supply piping and pumps. Second but no less important Operational procedure and automatic shutdown Instrumentation. For Instemce the reactor start-up Is a sensitive part of reactor operation since the cheuice for excessive rates of rise Is greatest at this time. Rigid standards and procedures mxist be used to make the ensuing rise to power within the limitations of the operator s reaction time this time In which he has to react can be Increased by more sensitive and faster responding Instrumentation. In case of human failure the operational procedures are backed up with automatic shutdown Ins trumentatlon. 

If reactor operation is well covered by operating procedures, why are automatic shutdown systems necessary ... 

Identified hazards can either be reduced at the root (e.g., reduction of inventory) or by introduction of protective systems (e.g., automatic emergency shutdown). The increased understanding of the chemistry and the process that is obtained from hazard evaluation procedures provides guidance for many other elements of process safety management as well (e.g., procedural instructions, emergency strategies, personnel training, and preventive maintenance). 

Shatdowm. For,a normal intentional shutdown the operator has the choice of a variety of procedures. For-example, he could set all shim rod switches (S-21 through 28) On "jpg and leave them there. This would run all the shim rods completely in. If the manual-automatic switch is on automatic, the operative servo will be left with its regulating rod completely withdrawn and its rheostat completely lowered. Since this procedure leaves all the shim rods at the bottom of their travel, it is suitable for a relatively permanent (e.g., maintenance) shutdown but would not be advisable if the plan was to raise the level back up in a short time. In such a case, lowering of the control point, followed by careful insertion of preferred rods, would be a better plan. 

If computer-integrated resin handling systems are considered, one must compare their operating procedures with one s process requirements. These process requirements describe the flow of resin and product through the system, which determines the system s electronic architecture. Pertinent considerations include batch vs. continuous operations, the type and number of conveying lines, resin storage and distribution, quality control means and procedures, inventory control, the type and quantity of process parameter sensors, the type and quantity of controlled devices, modes (automatic, semiautomatic, manual, and/or shutdown modes), process information, process management controls, and centralized vs. local operation (Fig. 9-1). 

There are sequential shutdown and start-up procedures for complex continuous plants that must be carefully followed for safety of plant and personnel. Typically a start-up or shutdown will take several hours. After starting, a complex continuous process plant may need automatic controllers to control the flow rates, concentrations, pressures, temperatures, levels in circulation and overhead tanks, etc. 

The computer system of the station control and data acquisition is a distributed micro processer based systems. A digital multiplexed control system takes the place of hard wired analogue control. This accounts for a significant reduction in cable usage. Built-in diagnostics and board level maintenance makes restoration of operability of any fault in the system a matter of replacement of printed circuit cards. Automatic control systems and procedures are deployed to simplify these procedures and power level manoeuvers. In case of unsafe conditions the reactor protection system (PMS) takes over and automatically scrams the reactor and actuates the relevant safety systems. Diverse methods are used to assure the shutdown of the reactor in hypothetical situations. The systems also provide for post-accident monitoring. 

Both EdF reference sets of EOPs cover aU plant modes from normal power operation down to hot and cold shutdown, cold shutdown with RCS open, and refueUing. The diagnosis procedure is valid for all shutdown plant modes where automatic protection signals no longer exist or are actuated with long delay. 

LOCAs (and other events) during low power, hot standby or hot shutdown modes are usually not well covered by procedures which are focused on power operation, mainly due to the fact that many automatic actions are disabled because of a low reactor power. At least one plant performed a systematic review of the operational procedures for LOCA in modes 3 and 4, and adjusted those to specific low power conditions. Other plant developed a specific EOF for small LOCA in shutdown. Another plant developed specific operating instructions focused on mitigating a small LOCA before the RCS level drops below the mid-loop level. 

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