Plant modifications generally

In-Plant Waste Control. Pollution can be reduced or eliminated by process modification, chemical and raw materials substitution, or recovery of by-products. In addition, process modification generally increases product yield by incorporating control devices. 

Rather than dealing with the consequences of a runaway reaction it is usually better to prevent the runaway in the first place, so the designer should generally prefer preventive to protective safety measures. Whatever safety measures are chosen, it is important that they make the plant safe under the full range of operating conditions and credible maloperations and remain effective after plant modifications. 

CONTROL OF PROCESS AND PLANT MODIFICATIONS Uncontrolled modifications to a process or plant can result in a situation that was not considered in the original hazard assessment and the existing safety measures may no longer be effective. It is not possible to produce a generally applicable check-list of significant" modifications — serious incidents have been caused by relatively small changes in process conditions or plant construction — but some examples are ... 

The general experience from the implementation of risk criteria is positive, and various benefits have been recorded. In a number of cases, design weaknesses or procedural weaknesses in NPPs have been identified using PSA and PSA criteria, resulting in the introduction of safety improvements. In many cases, the implementation of risk criteria and safety goals has lead to plant modifications in order to meet the probabilistic risk criteria. The implementation of safety goals often emphasizes the need for more detailed and realistic PSA models, and it appears that the use of safety goals has increased the focus on the correctness and quality of PSA models. 

Chapter 4, General Topics, deals with safety topics not directly related to specific operations. Principal subjects include the inspection and maintenance of equipment, spare parts handling, storage and warehousing, plant modifications, hazardous work, and worker protection. 

This chapter covers general plant safety topics not directly related to specific activities or equipment. Principal subjects are the inspection, maintenance, and calibration of equipment (4.1) spare parts handling (4.2) storage and warehousing (4.3) plant modifications (4.4) hazardous operations (4.5) the use of outside contractors (4.6) and the protection of workers by safety gear and the control of the working environment (4.7,4.8). 

Some operating companies have adopted a formal approach to APC safety, treating it in much the same way as any other plant modification. The weU-documented Hazard and Operability (HAZOP) approach is generally too rigorous for APC, since it is difficult to... 

Damage done to the pipe by IMCO General Construction Inc during the 1999 water treatment plant modification project. 

There have been significant sodium leaks and fires from the BN-600 primary (1993) and secondary (1994) circuits. In both cases the protective systems were effective, the damage was not extensive and repairs were effected quickly. Nevertheless the protective systems have been improved. A secondary sodium leak and fire at the MONJU plant in late 1995 has caused a longer operational delay, and plant modifications will be made. The finding of cracks and defects in stainless steel components of older reactors such as PFR and Phenix has contributed to the general concern to provide adequate sodium fire protection measures. 

While process and equipment modification are generally the preferred alternatives for reducing emissions from a plant, some form of control is necessary before emissions are discharged into the environment. Technologies discussed in this section are applicable in preventing emissions from point sources such as process or tank vents. These technologies fall into two main categories ... 

Compared with whole plants, there has been limited development of foreign protein expression systems specifically for use in tissue culture. Some modifications of expression constructs have resulted in improved protein accumulation or have allowed simplified protein recovery. However, in general, modified expression systems have been tested only in a restricted number of cases and have not resulted in the large increases in product yield required for plant cultures to compete with other foreign protein production vehicles. Transient expression techniques, for example using viral vectors, that have been developed for use in whole plants have not yet been applied in plant tissue culture. 

In an attempt to understand the factors which lead to a successful and acceptable implementation of a robotic system, Molet et al. [2] have described the history of the implementation of a robotic installation in the steel industry in France. TTiey analysed the reactions of the various participants. Most of the difficulties encountered were related to the technological modifications required in the plant to install the robot and its peripheral equipment, and the labour and organizational changes which affected those most directly involved. TTiis experience provides some general lessons about the dos and do nots of rohotization (see also Besson [3] and Guest [4]). 

Intact plants are also suitable for cost-effective production of recombinant pharmaceutical proteins providing products free of contaminations with endotoxins or human pathogens. Plants generally promote the proper fold of foreign proteins and post-translational modifications that are somehow similar to those of mammalian systems. Also, production of vaccine candidates in cereal seeds allows antigen protection from proteolysis which ensures their stability for a long period of time. 

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