Application of Information Theories to Safety of Nuclear Power Plants

It is widely recognized that safety of nuclear power plants is a problem of great relevance for society. If it is not properly managed, the increase in power and complexity of the plants can lead to a catastrophic release of energy and dangerous materials and pollute the environment. To prevent this to happen, the nuclear community always put significant efforts into finding new ways to improve safety. In fact, the nuclear accidents in Chernobyl and in Three Mile Island lead to initiation of extensive research activities within the nuclear society. A consensus quickly emerged that the breakdowns could not be explained exclusively from the perspective of technological failures but indeed required new, holistic views on safety. A solution seemed to be a strong focus on human attitudes and behaviors. The concept of safety culture, first introduced by the International Atomic Energy Agency (IAEA), rapidly became increasingly popular [IAEA, 2002]. These efforts notwithstanding, incidents continued to occur indicating that important aspects of plants' safety remain unsolved. In fact,  in 2000, at the Davis Besse nuclear power plant, an extensive material degradation was detected in an area around a nozzle of the reactor pressure vessel. Commentators have suggested that a minor additional propagation of the crack would have lead to the rupture of the pressure vessel. Obviously, the plant owners did not possess accurate and updated information of current condition of the reactor pressure vessel [NUREG/BR‐0353, 2008];  in 2006, at the Forsmark nuclear power plant, a sudden disruption from an external power supply lead to the failure of the house turbine operation, the internal battery secured power supply, and of 2 of the 4 emergency diesel generators. Luckily, the 2 diesel generators that started were able to supply sufficient power to the cooling system of the reactor core, and, thus, were able to maintain the whole system in functioning conditions. This dangerous incident has resulted from errors in modifications of old components, caused by insufficient understanding of the consequences of introduced changes [Wikdahl, 2006]. These examples indicated that the established safety frameworks were in need of further improvement if the occurrence of severe accidents is to be prevented. Recognizing this need of further improvement, the IAEA has recently declared a strong focus on knowledge management and built a new knowledge management group for assisting member states in associated questions [IAEA, 2004; 2007].