Maurizio Cumo[9]

University of Rome ”La Sapienza, ”

Department of Nuclear Engineering and Energy Conversion, Rome, Italy

Lectures given at the
Workshop on Nuclear Reaction Data and
Nuclear Reactors: Physics, Design and Safety
Trieste, 25 February — 28 March 2002

LNS0520006

1. Introduction

Decommissioning of a nuclear power plant or other nuclear installations can be defined as the cessation of operations and the withdrawal of the facility from service, followed by its transformation into an out-of-service state and eventually, its complete removal, the so-called "green field" status, which, in principle, restores the site to the conditions existing before the construction of the plant. Alternative end conditions may include a situation in which the buildings, free of any radioactive contamination, are left for future conventional demolition, or situations in which these buildings, or the site itself, are used for other industrial purposes.

We will discuss the decommissioning activities starting from a situation in which spent fuel is not present any more on-site, or at least, in a completely independent storage facility. This removes from the plant more than 99,99% of the radioactivity present in the plant at the time of operation.

The main goal for the decommissioning activities is to place the facility in a condition that eliminate any risk for the health and safety of the general public and the environment, removing, in particular, from systems and structures any radioactivity that may have been accumulated during plant operations. Of course, all the decommissioning activities shall be carried out with great attention to assure the minimization of the risks to both the public and the workers involved in the process.

Decommissioning is a complex, long lasting and highly technological activity that presents smaller challenges, but similar to the plant construction activities. In some countries, in fact, it is called de-construction. Activities include use of technological tools, control of industrial safety, environmental impact minimization, licensing, safety analysis, structural analysis, etc. Other aspects very relevant are the activity planning, the calculation of related cash flow and anticipation of the funds needed to perform the activities. Aspects related to waste disposal and spent fuel strategy shall be covered as well.