Unforeseen events are inevitable in a nuclear power plant. And when they do happen, the operators’ practical skills are of immense significance, according to Margaretha Engström. During her 42 years at Vattenfall, she has worked with almost all areas relevant to the company. She has now completed a PhD on the relationship between practical skills and nuclear power safety.
“The human factor is often viewed negatively,” she says. “But I want to stress the positive aspects of human judgement and behaviour. Not everything can be solved by technology.”
The plant “in the blood”
It takes a long time to become a skilled plant technician, and even longer to become a shift supervisor – some ten years of experience in the various tasks of a shift team are needed. Many of those who know their job inside out have the whole plant “in their blood”.
“Interviewees tell me that they use all their senses when they inspect the plant; how it smells, how they sense that the temperature in a certain place is normal, how they respond if a door no longer slams like it used to, or how the knowledge of opening a valve is in their hands,” Engström explains. “They possess an intuition based on an in-depth understanding of the relevant systems and processes.”
Operating personnel are regularly trained to handle various situations in simulators, but real operating disturbances also provide important experience. Engström feels that a nuclear power plant that suffers from many minor disturbances is safer than one in which nothing unplanned ever happens.
“It’s rather like driving a car. You can’t just read about driving on a wintry road, you have to practise in real conditions,” she says. “And the more you get used to slippery roads, the better prepared you will be for the day you have to control an actual skid.”
Deep-seated practical skills are a safety issue according to Engström. Many unexpected operating disturbances in the Swedish nuclear plants Forsmark and Ringhals have been successfully controlled thanks to practical skills, fast responses and good judgement.
An event of this kind occurred in Forsmark in 2006 when a rewiring mistake outside the facility led to a short circuit in a switchgear unit. The power went off, the standby power supply failed to work as planned and the instruments in the control room no longer showed the correct values. However, the operating personnel focussed on the most important thing – ensuring that the core was covered with water – and soon had the situation under control.
“This incident led to enquiries and a series of measures to deal with faults and failures. That’s important, but it’s also interesting to see what was done right,” Engström notes. “We have many drawings, process diagrams and instructions for all conceivable incidents. But we also need to be prepared for what no one has even imagined,” she adds.
Engström describes these processes as Black Swans – things no one believed could ever happen, but which happen nevertheless. And skilled operators with extensive experience and good judgement are crucial in such cases.
PRACTICE BEFORE THEORY
“It’s not always easy for a theoretician to understand the importance of practical action in a nuclear power plant. So it’s very good that Vattenfall's Business Unit Nuclear has introduced a possibility for office staff to work at a nuclear plant for a period. This way they get a better understanding of how it is operated. If nothing else, it can give them insights into what they do not understand,” she says. “When Forsmark was built in the 1970s, the relationship between head office and the power plant was much closer and the knowledge of what the plant was like in reality was greater. For a time, there were even daily buses on the 130 kilometre route between the Råcksta office and Forsmark.”