Practitioner versus analyst methods: a nuclear decommissioning case study.

A requirement arose during decommissioning work at a UK Magnox Nuclear Power Station to identify the hazards involved in removing High Dose Rate Items from a Cartridge Cooling Pond. Removing objects from the cooling pond under normal situations is a routine event with well understood risks but the situation described in this paper is not a routine event. The power station has shifted from an operational phase in its life-cycle to a decommissioning phase, and as such the risks, and procedures to deal with them, have become more novel and uncertain. This raises an important question. Are the hazard identification methods that have proven useful in one phase of the system lifecycle just as useful in another, and if not, what methods should be used? An opportunity arose at this site to put the issue to a direct test. Two methods were used, one practitioner focussed and in widespread use during the plant's operational phase (the Structured What-If method), the other was an analyst method (Cognitive Work Analysis). The former is proven on this site but might not be best suited to the novelty and uncertainty brought about by a shift in context from operations to decommissioning. The latter is not proven on this site but it is designed for novelty and uncertainty. The paper presents the outcomes of applying both methods to a real-world hazard identification task.