Standard Approach to Transient Operations in Nuclear Control Rooms

Standard Approach to Transient Operation.

Operation of Nuclear Power Plants is a serious business; it needs very competent people at the controls. Governments around the world demand it, and so does the general population; how do we as an industry fulfill that commitment? In fact we do that very well. We teach all the theory, all the mechanics, present all the relevant documentation, and we examine our people continually, but we need to ensure that we prepare our operating personnel for that time in their career when they will need to do what is required in an off-normal, or 'Transient' situation, the time that they must perform to the highest level.

Billions of dollars are invested to build and put into operation a nuclear power plant. If you are somehow responsible for the results of the plant operation, ask yourself this question: What will the Operators of the plant look at when an alarm, any alarm occurs, what will they do? The answer is that we don’t know exactly what they will look at. We need a 'Standard Approach' to transients.

Background to the Standard Approach:

When a nuclear power plant is in a transient situation, specific verifications have to be taken in a timely manner, competently, and initially without reference to procedures in order of their importance. The Operators have to deal with real time transient development, adrenaline flow, nervousness and uncertainty as to how they as individuals, will deal with it.

The Standard Approach to Transient Operation is an effective, simple concept that addresses the above concerns. It is prioritizing the things that are required to be performed, in a timely manner, ensuring that 'Control, Cool and Contain' of the nuclear fuel is maintained, and performing the required actions in a manner that is compliant with the basics of Operator performance standards, such as, STAR, 3-Way Communication, and Peer Checks.

The 3 C’s (Control, Cool and Contain), are not just words, they are the priority and always a requirement of Operating Personnel to fulfill. The 3 S’s, Safety of the People in the plant, Safety of the Public, and Safety of the Environment, are just as important, but if we look after the 3C’s and ensure the 3S’s are addressed, the best response is possible to any event. In fact most of the procedures in the Nuclear Business do just that, but are often inadequate when the conditions don’t exactly match the entry conditions for the procedure. That is where the Standard Approach to Transient Operation functions to ensure that the foregoing concerns are all addressed and every off-normal situation is correctly handled and the effects of the transient are mitigated.

Transient Operation can occur from a Unit that is in stable state, or is in an evolution of some sort, i.e. approach to critical, primary system warm up, raising power, change over of equipment etc.

No matter what the starting point of the transient, the response is the same.

The First Response

Consider an alarm annunciates in the main control room.

It doesn’t matter what the alarm is, something is out of the ordinary. It is human nature to, as a first response try to diagnose the cause of the alarm. This however is not the right thing to do in a Nuclear Control Room. Alarm conditions can be caused by many conditions, process failures, electrical failures, intended change in the unit configuration. One thing is for sure, when equipment fails, their will be immediate effects and annunciations, but there will also be delayed effects that often go unnoticed in the wash of alarms that often occur during transient conditions. In every case the Operator must as a first response, consider what reactor power is doing, is it stable, rising or falling and how big is the event, major event or isolated system failure, and then proceed to respond to the specific conditions dictated by the alarm.

This means that regardless of the alarm condition, the Operator must look at Reactor Power long enough for the effects of the off-normal condition(s) to show. Experience and observations reveal that this is not a natural response for the Operators of the Plant. Computer or panel display update times etc. and the natural response of the Operator to 'chase the brightest light' often cause him to be unaware of reactor power changes immediately after a transient. If reactor power is going up without being requested, the reactor should be scrammed, if power is going down, it should be monitored, along with the plant response to the automatic power reduction. This is the first step. This is not the time to try to diagnose why reactor power is going up and to try to take corrective action to stabilize the unit at power. How much is this one concern stressed to plant staff in your organization? The Nuclear power industry and it’s plant designs, control systems and fail safe operation of equipment, have improved over the years, such that unexpected increase in reactor power are few theses days. However, they do occur and it is imperative that they be recognized on the onset of the excursion as the potential for large power increases in a short time cannot be ignored or their importance minimized.

The fear of not doing the right thing during major transients keeps many senior and experienced personnel away from the training programs that would eventually authorize them. Once this fear is removed, the pool of available candidates is increased and allows the plant to better select the people it wants to operate the plant. The Confidence gained from a Standard Approach technique removes this fear, and results in Operators joining the programs, and performing in a Calm, Controlled Manner during any upset condition, clearly aware at all times of the important parameters, and priorities.

There are a number of Standard Steps that follow this initial response step, and each would take a chapter to explain in detail. Even with the reactor power check, I have only brushed the surface of the rationale.

It is important to add that the Standard Approach to Transient management (of which I have only given a brief outline,), was developed over the course of many years and is currently in use at nuclear power plants in North America and Europe.

The approach has been very successful in improving control room performance, reducing human errors, and resolving the problem of high regulatory examination failure rates.

In addition, WANO as well as other Regulatory Organizations in Canada and Europe have recognized the superior performance of operating personnel employing this response strategy.

Please feel free to contact me if you are interested in investigating this unique approach for your plant.

Please post any requests or comments for further information if interested.

Sincerely

Robert MacDonald.