PD IEC TR 62096:2002 pdf download
PD IEC TR 62096:2002 pdf download.Nuclear power plants——Instrumentation andcontrol — Guidance forthe decision on
modernization.
— administration costs can be reduced through improvements in the way in which information is collected, processed, stored, and presented.
Cost reductions should be considered using a life-cycle costing approach focused on minimizing the total cost of the system over its intended life cycle. Note that a modernization with an expensive type of component with high reliability may increase the procurement cost but reduce the support cost, and may give the lowest overall life cycle cost.
5.2.2 Revenue
Revenue can be increased in the following ways:
— Higher generation level
Improvements in monitoring and protection systems can give greater confidence in plant status, allowing reduction of safety margins at the same plant safety level and more power output.
— Increased availability
Shorter shutdowns for repairs, routine maintenance and fuelling, and a lower probability of spurious trips will result in better plant utilization. This can be achieved through improvements in reliability and stability, and through the use of ‘smart’ systems with capabilities for self-checking, diagnostics and auto-calibration, and improved operator support by HMI and I&C functions. The upgrading of obsolete equipment reduces the probability of a prolonged shutdown due to the unavailability of replacement parts.
— Increased plant lifetime
If the operation of the plant can be extended beyond its planned economic lifetime there is a considerable benefit in accounting terms, because the revenue is no longer offset by capital charges. It is necessary to modernize any equipment or systems whose predicted residual life will be insufficient for the planned plant life extension.
5.2.3 Economically motivated modernization
Economically motivated modernization may be initiated by one or more of the following factors:
— Obsolescence
Equipment obsolescence occurs towards the end of a product’s life cycle. When an item of equipment is no longer in production, the level of service available from the manufacturer will decrease, and spare parts and consumables become unavailable or unacceptably expensive. Obsolescence also occurs at the electronic component level, where life cycles can be as short as a few years.
The initial effect of obsolescence is to increase time scales and costs for maintenance and repair work. Ultimately, the equipment will be rendered unserviceable by the non-availability of spare parts.
— Competence of personnel
A related problem is the decreasing availability of suitably skilled maintenance personnel.
Recently trained personnel do not have the required skills for analog electronics.
Technical education and training courses tend to concentrate on digital technology.
— Ageing
The ageing effects suffered by electronic components and assemblies can lead to problems with noise, drift, response time, EMI susceptibility, and general reduced reliability.
Examples of degradation due to ageing include:
• chemical effects such as oxidation or corrosion, which lead to high resistance contacts in connectors, switches and solder joints;
• drying out of electrolytic capacitors;
• loss of insulation due to the build-up of surface contamination (particularly in high- voltage equipment);
• cables and other components made from organic material are subject to ageing effects (e.g. embrittlement) when exposed to temperature, radiation, oxygen, etc.;
• mechanical effects such as wear, seizure, and loss of spring tension, all of which eventually lead to the failure of mechanisms in switches, connectors, relays, etc.
— Compatibility issues
It is sometimes necessary to upgrade equipment which would otherwise be considered satisfactory because of the effects of changes elsewhere. The following are examples of compatibility issues:
• changes to reactor or process equipment resulting in differing l&C requirements;
• changes to other l&C equipment using newer interfacing connections or protocols.
5.3 Safety motivating factors
A safety improvement upgrade may become necessary to comply with regulatory requirements. Such an upgrade may have a significant cost and no apparent economic benefits. Nevertheless, the decision is ultimately an economic one where the plant owner should compare the costs of performing the upgrade versus the costs associated with operating restrictions on the plant.
Safety improvement upgrades may be initiated by one or more of the following:
— recommendations of a safety review;
— changes in licensing requirements;
— deficiencies revealed by an incident or reportable occurrence;
— deficiencies revealed by testing.
5.4 Summary of motivations for modernization
A report should be written summarizing the various aspects of modernization for use in the decision on future actions. It is recommended where possible that the report include a cost benefit analysis where each argument can be quantified.
