Methods of conducting an exercise

Time mode, stimulation versus free play and the use of simulators, are important factors that must be determined when preparing an exercise.

2.4.1. Time mode

An exercise is carried out in a real time mode when each activity is conducted on the same time scale as it would during an actual emergency. The time scale is compressed when otherwise necessary steps or time lapses are simulated or foreshortened during the exercise.

An expanded time scale may result from the provision either of additional time to that normally required to complete a particular event or of a prolonged time period within a sequence of events to enable the convenient management of the exercise.

Compression or expansion of the time scale for certain sequences in the scenario may be advisable in order to make efficient use of the time personnel invest in the exercise. This is often appropriate for tabletop exercises and for drills, but not usually for larger exercises, where coordination between various groups makes it harder to synchronise the exercise unless real-time is used. There are exceptions. For example, in the early stages of an emergency exercise, off-site government officials may be relatively slow in arriving at the site, and time compression may be advised. For the purpose of the exercise, the time scale for this stage may be compressed in order that their particular assessment and decision-making activities be put into practice without prolonged delays. Another case where time compression may be appropriate is a reactor event sequence leading to a major failure, which in reality could take many hours.

There are cases where time compression is definitely disadvantageous. A prime example is the compression of the time required for off-site monitoring teams to check equipment, travel to a monitoring point, take samples, perform measurements and record and communicate results. These time delays are crucial to the understanding by the off-site dose assessment staff of the time delays that would be incurred in data collection and monitoring procedures under real emergency conditions.

Where possible, however, this procedure (and, in particular, time expansion) should be avoided during the early stages of an integrated exercise as it is essential that players obtain a genuine appreciation of the actual time available for the completion of particular tasks, especially when these involve coordination with other groups. As a guiding rule, the time sequence of the associated series of events in an exercise may be compressed or expanded, provided that this does not compromise exercise objectives.

2.4.2. Free play versus stimulation

Two factors, which are at odds in the design and conduct of exercises, are free play and stimulation.

Free play means that players are free to react to a simulated problem according to their perception of the most appropriate solution. A scenario that allows free play is the preferred method of training technical staff members to carry out their assigned functions under emergency conditions. Free play also allows the evaluators to determine more accurately the adequacy of emergency preparedness. However, a scenario incorporating the facility for free play requires much more effort to produce and implement due to the complication of accommodating multiple actions by, and options available to, the players.

Stimulation refers to actions that controllers may take to correct errors or to interrupt actions made by the players, which might otherwise lead them to depart from the scenario and possibly jeopardise the overall objectives of the exercise. In general, the controllers should avoid correcting players’ errors whilst the exercise is in progress unless it is absolutely necessary so that the exercise can stay on track.

This guidance regarding free play and stimulation does not apply to drills, where, if anything, the opposite approach should be taken. Free play is generally less important because drills are relatively short in duration and rigidly structured. As drills are largely instructional by nature, there is a need for the immediate correction of errors and for the repetition of difficult parts of the drill. Such requirements are part of the objectives of most drills.

2.4.3. Using a simulator during an exercise

For facilities such as power reactors, a simulator may be available to develop the scenario and/or run the exercise. This can add realism and reduce the requirement for including extensive simulation data (e.g. all control and safety parameters) in the exercise manual.

If the data stream from a full-scope simulator is delivered to the actual or simulated data acquisition systems that would be used by operators and plant systems engineers during an emergency, the training of these staff will not be limited by the resources required to prepare detailed event descriptions or the lack of realism inherent in bypassing actual information systems.

The scenario should be tested on the simulator for the full length of the exercise. Simulators have been known to crash under certain conditions and you want to guard against that. You should also ask the training staff about any operator interventions that could fix the problem and stop the emergency, thereby also stopping the exercise. To deal with those, additional failures may have to be entered into the simulator.

The advantages of using a simulator are:

• The shift crew will have to react realistically and perform many of the actions that they would perform during a real emergency.

• Simulators allow a test of compatibility between emergency operating procedures (EOP) and the emergency response plan. The shift crew will execute both sets of procedures. If the requirements are incompatible, this will be detected. Also, the shift crew and training staff will have positive changes to suggest at the end of the exercise.

• Simulators allow a test of notification delays. Delays resulting from operators executing the EOPs and emergency procedures simultaneously can be assessed more accurately.

• Simulators generally give realistic timing for the simulated events.

• The use of simulators involves important stakeholders. The shift crew and training staff get a chance to be involved with emergency response issues from their perspective and will undoubtedly give valuable feedback.

The disadvantages are:

• The location is different from the one normally used by operators. Interactions between the on-site emergency response organization and the operators, which would be simple in the real control room, may become difficult because the simulator room is in a different building. When the operators leave the simulator room to perform interventions in the plant, they spend more time reaching their workplace.

• The scenario preparation involves more people. The simulator staff will be involved in the preparation and their availability may become an issue.

• The simulator may not be able to execute the scenario. There are scenarios that are not regularly used for operator qualifications and which can make the simulator crash because of snags or limitations of the simulator.

To complete the instruction manual for the exercise, ask the training staff for a copy of the procedures that will be executed. Collect the work permit forms and maintenance tags that will be required during the exercise. Once the complete scenario (on-site and off-site) has been defined, check the timing and the sequence of events to ensure the causality of the required actions.

Each simulator has its limitation. For example, not all data are simulated and some of those data may be critical for the exercise. They would have to be developed and provided to the control room personnel through exercise inputs and messages. The most serious limitation is probably the inability of some simulators to go into the “severe emergency” domain. Many simulators crash when you try to simulate conditions that could lead to extensive fuel failures.

It is wise to run through the emergency and possible responses well before the exercise!

One of the risks of using the simulator is that a clever operating crew may be able to fix the problem before real trouble starts, which would jeopardise the rest of the exercise. This requires a back up plan.