Chemical control room

Control of the core is affected by movable control rods which contain neutron absorbers soluble neutron absorbers ia the coolant, called chemical shim fixed burnable neutron absorbers and the intrinsic feature of negative reactivity coefficients. Gross changes ia fission reaction rates, as well as start-up and shutdown of the fission reactions, are effected by the control rods. In a typical PWR, ca 90 control rods are used. These, iaserted from the top of the core, contain strong neutron absorbers such as boron, cadmium, or hafnium, and are made up of a cadmium—iadium—silver alloy, clad ia stainless steel. The movement of the control rods is governed remotely by an operator ia the control room. Safety circuitry automatically iaserts the rods ia the event of an abnormal power or reactivity transient. 

Plant Fireproofing. There is a growing practice in the chemical industry of locating principal equipment out of doors and to enclose only a control room where all instmments and control equipment are centered. The control room should be resistant to potential explosion, fire, and toxicity ha2ards of processes in the vicinity. Prompt and ordedy shutdown of processes following a serious incident is essential in order to minimise personnel-injury and property-loss ha2ards (65,66). 

EMEC 1974. Chemical Process Control and Control Rooms. Eoss Prevention Data Sheet No.7-45. Eactory Mutual Engineering Corporation, Norwood, MA. 

An example of what can happen in a production situation is provided in Fig. 1. This photo shows the devastation resulting from a phenol-formaldehyde reactor explosion that occurred at the Borden Chemical plant in Demopolis, Alabama on June 28, 1974. In this explosion, the stainless steel reactor was blown to bits. The reactor operators control room was obliterated. Two people were killed and several others were injured. All nearby property was demolished and windows were broken in homes for a distance of five miles from the plant. 

To combat attacks with fast-acting agents in the terminals, continuous visual surveillance of densely populated areas and observation of behavior patterns may be as useful as any detector. The TSA should study the feasibility of the widespread deployment of surveillance cameras in populated areas, coupled with behavioral-pattern-recognition software, as an alternative to chemical agent detectors. Such cameras could also provide a dual-use value in improving the overall security environment. In addition, many critical nodes in the air transportation system (control rooms, emergency-response centers, and so on) are supplied with air that is recirculated from publicly accessible areas this makes them vulnerable to being disabled by the release of... 

Note, the design and location of control rooms, particularly as regards protection against an unconfined vapour explosion, is covered in a publication of the Chemical Industries Association, CIA (1979a). 

A light in the control room of a chemical plant indicated whether a valve was closed or not. In reality it indicated only the status of the signal being sent to the valve. The valve did not close when it should have, and the plant exploded. Why How would you prevent this problem ... 

Dry chemical extinguishers should be located on elevated main platforms with stairway access and on air cooler platforms. When determining the proper location for extinguishers, consideration should be given to hydrocarbon pump and compressor areas, hot-oil areas, or similar potential hazards, as well as access to the extinguisher from control rooms or battery limits. Extinguishers should be located so that one can be reached without traveling more than 50 ft (15 m) to any hazard. 

An appropriate number, type, and size of hand-held fire extinguishers should be provided throughout the building to handle ordinary combustibles and electrical fires in the control room and related areas. Typically, clean agent or carbon dioxide fire extinguishers should be provided for electrical and electronic equipment. Dry chemical extinguishers should be avoided because of equipment contamination with powder. For use on ordinary combustible fires in the associated areas water or multipurpose dry chemical fire extinguishers should be provided. 

Another way of looking at physiological systems is not just as chemical reactors but as a complete chemical plant, which contains a control room (with its own supercomputer), a lunchroom, recreational facilities, and of course facilities for constructing a new chemical plant when the present one corrodes away or become obsolete. 

Fig. 51. Nitroglycerine manufacture — the remote control room of a Biazzi continuous plant (Ardeer Factory, Nobel Division, Imperial Chemical Industries Ltd., Great Britain, photograph...

In order to protect the thermocouple against chemical or mechanical damage, it is normally enclosed in a sheath of mineral packing or within a thermowell (Fig. 6.24). Any material which contains the junction should be a good conductor of heat on the one hand, but an electrical insulator on the other. A potentiometric converter is frequently employed to convert the thermocouple signal to the standard 4-20 mA current range prior to further processing and control room presentation. The extension wires which connect the thermocouple element to the control room should have similar thermoelectric properties to those of the thermocouple junction wires. 

The layout suggested for the chemical plant complex includes a central control room to operate all three plants. Administration, laboratory, and workshop areas are also common. The nitric acid plant is small, occupying less than 1 hectare. There is space on the 1 hectare plot for inclusion of a second parallel process train for possible future expansion. 

It features the three chemical processes flowing approximately one to the other. The joint administration and workshop facilities are located in the south-western corner of the plant. There is a central control room for all operations, and the rail link is extended into the despatch area. 

NRC (2001), Assumptions for Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release, Regulatory Guide 1.78, December. 

It is assumed that chemical plant process workers will operate the production facilities as they will replace plants traditionally operated by them. Assuming that operators will not be expected to walk more than 200 yards from the control room, the control rooms will have to be spaced 400yards apart that is, one per 33 acres. Over 750 control rooms will be required for a million pounds per year operation. Building costs will therefore be much higher that on a conventional plant, and may well make the new process uneconomic, especially now that control rooms are being made stronger than in the past. 

Sharing the Experience booklets 2003-2004 are now available to refinery and chemical process employees for a wide range of topics of interest. BP is currently reinvigorating the series, but as of this time it is not distributed via the normal book sales route (I do not think it ever was). These superb booklets cover fundamentals and are backed up by numerous case histories of hard-learned lessons. They are chock-full of easily understood illustrations and up-to-date color photos. The Sharing the Experience booklet series is a practical, timeless process safety masterpiece that should be available in every control room. The booklet on the hazards of water was first published about 50 years ago and improved to perfection. 

As technology progresses the safety of man-machine systems depends more and more on the quality of the human component (operator). This fact is very obvious in transportation, where the operator (driver) is formally and actually in control of his or her vehicle. In aviation, however, a strong trend towards software control of the aeroplane is already becoming dominant, forcing the operator (pilot) primarily into the role of supervisor or monitor of the automatic control system and into that of trouble-shooter in case of (technical) failure. In this respect a cockpit crew is facing the same situation as for instance a shift of operators in the central control room of a completely computerised chemical process plant. 

If the apparatus with intrinsically safe circuits is installed outside a hazardous area, e.g. in a control room in a chemical plant, the marking inserts Ex or EEx and the type of protection in brackets ... 

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