Recent events

Considerable discussion and analysis has taken place during conferences, seminars, workshops and reviews on the main causes of recent events in the nuclear industry: the Davis Besse nuclear power plant reactor head event in

TOPICAL ISSUE 2

125 USA, the Brunsbüttel nuclear power plant hydrogen explosion event in Germany, the TEPCO falsification event in Japan and the Paks nuclear power plant fuel event in Hungary. In several cases, these discussions identified the lack of an adequate and effective operating experience philosophy compounded by deficient management of safety issues as one of the contrib-uting factors in the events.

This is not necessarily a unique situation confined to the nuclear industry.

For example, the analysis conducted by the Accident Investigation Board of NASA into the root causes of the Columbia shuttle accident highlights similar concerns.

At Davis Besse nuclear power plant, deposit indications of boric acid leaks had been noticed in 1998 but further extensive inspections were not performed and proper measures against defects were not taken. Subsequently, a cavity was discovered with only the layer of the stainless steel liner remaining to contain the primary circuit. While the equipment deficiency was rectified relatively quickly with a replacement head, the financial penalties caused by delayed return to service due to the need to correct organizational and managerial deficiencies were considerable.

At Brunsbüttel nuclear power plant, indications of water leakage within the reactor containment were detected. Plant management made a decision to continue operation because they considered the leakage had been isolated and was insignificant. A subsequent inspection showed that a piping section of a reactor head spray line had been completely destroyed by a hydrogen explosion.

At Paks nuclear power plant, the cooling to a fuel cleaning device containing 30 nuclear fuel elements was lost due to incorrect operation and inadequate design of the cooling facility. This led to the complete destruction of the fuel elements in the cleaning device. Cleaning operations of five previous batches of fuel had been completed, yet the event showed a number of uniden-tified significant deficiencies in the whole process.

At TEPCO, various records of maintenance inspections and work were inadequately recorded, analysed and reported. Some records were even found to have been falsified. These included records on important equipment, such as the core shroud of the reactor. Others involved the falsification of containment test procedure in order to present acceptable results.

If these events associated with important equipment (reactor internals, fuel, containment) are analysed, some common causes and contributory factors can be identified, such as:

— The decision making process in a situation that conflicted with the planned production process;

WERDINE et al.

126

— Reliance on recent successful operating performance history;

— Lack of full consideration and analysis of all available information, with potential consequences;

— Insufficient review to ensure that all pertinent information was considered and analysed;

— Insufficient challenge of assumptions or a desire to look for alternate acceptable explanations that supported continued operation.

In all of these four events, an apparent lack of respect for the reactor internals and components could be deduced.

Recently, an event involving a leak of high temperature steam from a secondary circuit pipe due to erosion/corrosion killed five contract workers and injured several others. Erosion/corrosion in secondary steam and water systems is a well identified phenomenon and significant operating experience is available.

All these factors and contributors demonstrate insufficient consideration of the operating experience feedback programmes, either to proactively identify situations of potential safety concern learned from experience by others or to identify and rectify early in-house indications of issues through apparently minor deficiencies. Also, some of these important problems had initially been treated as minor deficiencies within the close boundaries of normal engineering or maintenance and were not analysed more broadly to identify possible human and organizational operating experience factors.

The inadequate and ineffective use of operating experience, together with the desire of senior management to minimize the number of operational events reported, may send a message of complacency to all the organization — a message that is often supported by a decreasing graph of reportable events in a monthly performance report. This is often a perfect combination to contaminate the entire organization with ambiguous expectations and perceptions.

It has often been stated that the managers set the tone for how the operating floor will play the game, and that it is not what it is said in slogans that will affect plant personnel attitudes, but the actions performed by the managers towards their objectives. The final practical result of the perceived message may again lead to inadequate analysis of issues or insufficient challenge of the subsequent explanations. There may be a tendency to only report good news and even hide the results that demonstrate poor performance, thus preventing the identification and implementation of effective corrective actions.

TOPICAL ISSUE 2

127 3. PRIORITIES FOR FUTURE WORK

Priorities for future work include to:

— Continue to encourage and promote the use of operating experience feedback in nuclear installations, especially in support and regulatory organizations, vendors and contractors, fuel fabrication facilities and research reactors, etc., through workshops, seminars, information exchange and assistance;

— Provide an effective assessment service to assist the nuclear industry to identify and correct deficiencies in their programmes and also to promote good practices;

— Promote new initiatives and developments in analysing operational experience and good practice;

— Develop technical documentation to promulgate the lessons learned to the nuclear industry. Topics include the following:

• Knowledge management: ensuring that lessons learned from previous events remain embedded in safety programmes and that the new generation of nuclear personnel receive the benefit of the experience of the past;

• Effect of change: analysis of the effects of change, both technological and organizational;

• Lowering the threshold of reporting and analysis: investigating error precursors and error likely situations;

• Assessing success: identifying and analysing success to ensure that lessons are learned not only from failures but also from good performance;

• Utilization of lessons learned from major events that have occurred outside the nuclear industry;

• How the lessons learned from in-house collective analysis of low level events and near misses should be shared.

4. NEED FOR STRENGHTHENING INTERNATIONAL