Throughout the nuclear industry, operators are having to examine options for the optimisation of nuclear power plants. There are many strategies available to operators; maximising the lifetime of a plant, maximising the output of a plant, minimising the operating costs of a plant, maximising the load factor, or some other criteria.

In the USA, 60 out of the 103 operating units have upgraded or are upgrading their digital control systems. In addition, US regulatory laws require nuclear plants to have simulator systems for training. These add up to a very active market for simulators.

From many points of view, state-of-the-art simulators offer operators the ability to minimise safety, environmental and operational risks, and to optimise financial performance.

Simulator Training Systems (STS), part of Powergen UK, estimates that significant business benefits can be gained from procuring a plant specific simulator for use not only as an operator training and plant engineering tool, but also as a safety & environmental incident management training tool.

The benefits from using a simulator for operator training and safety & environmental incident management training are:

• New entrant training.

• Refresher training.

• Safety & environmental incident management training.

• Increased plant availability.

• Reduction in losses due to reduced loads.

• Reduced equipment damage.

STS are able to provide a full emulation of the plant’s control and operator interface software using STS’ emulation tools, which enable the operators to learn how best to operate the plant.

Operator competence

The assessment of operator competency is an important aspect for any industrial plant and needs to be an inherent part of any training program. A simulator is the ideal training tool to use in assessing the competency of operators, not only in dealing with contingencies and abnormal conditions, but also in the training and assessment of routine operations.

More than ever, competency-based training is becoming a cornerstone of best practice in plant operation. How can we assess competency? To make a fair assessment of competency each trainee must be provided with the same set of conditions to start with. An emulation of the HMI layer can provide this standard base to work from. As the alarm list and the trend data is reloaded with a scenario this forms the ideal base for competency assessment, as each trainee will start from the same point.

A key advantage of an emulated solution for training is that it is possible to have portable or even desktop simulators. This is not possible with the manufacturers HMI as it usually contains large amounts of hardware. It is possible to have desktop operator terminals connected to one of many plant simulators. This makes it possible for engineers to look at the current status of a training simulator from the office environment. This concept can be developed further for training centres where it is possible to have one main simulator and several smaller classroom simulators with an emulated HMI. This leads to having several low cost, high fidelity simulators available for training purposes.

A Plant engineering tool

High fidelity simulator’s can also be used to study plant behaviour and test out modifications to the plant or operating procedures – either as ideas, or prior to implementation. Typical engineering uses may include:

• Investigation of automation system behaviour, such as equipment trip.

• Investigation of recurring fault conditions.

• Operator alarm handling review and optimisation.

• Optimisation of operational procedures.

• Verify control system modifications before plant implementation.

• Try out ‘what if’ scenarios.

• Investigate the dynamic & operational effects of potential modifications.

• Review and development of operating procedures before modifications.

How does it help plant life extension?

By building the tools and having a good model of the plant, it becomes possible to look at the stresses on the plant, to monitor those stresses and to look at the resulting plant damage.

This means that it is possible to look at different start-up scenarios, and determine efficient ways of start-up and shutdown of the plant in question, as well as to use the plant at its optimum level.

The simulator can be used to identify unusual work practices used in the plant, and to evaluate scenarios that can improve plant operation.

The nuclear industry tends to view simulators as a regulatory and prescriptive requirement. Interestingly, Powergen has noted that fossil plant operators see simulators in a very different light. The budget attitude is different, with fossil plant operators regarding a simulator system as an additional extra that is nice to have, but that must demonstrate a profitable return on investment. As a result, simulators for fossil plants cost, on average, approximately $400,000. Cost-effectiveness is the name of the game. By contrast, nuclear plant operators regard regulatory compliance as the key element, and compliance and quality are more important than price. It is vitally important that the simulator equates accurately to the plant. The nuclear industry uses DCS mainly for monitoring purposes rather than control. Nonetheless, there are a number of lessons that can be learnt from other industries.

For example, reduction of outage times is of vital importance in the process industries. This is achieved by developing outage procedures that can be tested and practised prior to the outage. It is possible to test control system coding prior to installation, and prove that it is acceptable for use and to give the operators confidence in the system.