Abstract
Scope of the paper is to summarise the experience about management of materials arising from decommissioning of Italian NPPs, and to illustrate criteria, procedures and systems, which Sogin is defining to manage the problem of the clearance of sites and materials, considering the international experience and boundary conditions existing in the Country.
Since 1962 Enel (the largest Italian utility for electric power) has operated the four Italian nuclear power plants: Garigliano (160 MWe BWR), Latina (210 MWe GCR), Trino (270 MWe PWR) and Caorso (882 MWe BWR).
These NPPs were shutdown in the 80’s: Garigliano NPP was shutdown in 1982 following a decision made by Enel, based on technical and economical reasons, Latina, Trino and Caorso NPPs following decisions made by the Italian Government after the Chernobyl accident.
The “deferred decommissioning (SAFSTOR)” was the decommissioning strategy selected by Enel and approved by the competent Authorities, due to the lack of a repository for the disposal of radioactive materials and of release limits for clearance of materials. Activities have been started aimed at reaching the “Safe Enclosure” condition, which would have lasted for some decades, before final dismantling of plants.
In 1999 the liberalisation of the Italian electricity market led Enel to separate its nuclear activities, forming a new Company, named Sogin, to which decommissioning Italian NPPs was committed.
At the same time, considering pressures, both at national and local level, to adopt the “prompt decommissioning (DECON)” strategy, in December 1999 the Italian Minister of Industry, with the intent to accelerate the dismantling of Italian NPPs, presented the plans to create a national repository for nuclear waste, and asked Sogin to revise the decommissioning plans, according to the new global strategy, taking into account all the relevant technical, organisational, financial and legislative aspects of the problem.
As the DECON strategy enhances the importance of “clean-up” both of sites and materials, the related aspects are held in due consideration in developing the decommissioning plans, which deal with the following:
• characterisation of plant systems, components and structures;
• decontamination and dismantling techniques;
• monitoring of dismantled materials for clearance;
• treatment of dismantled, radioactive materials (which cannot be cleared), prior to disposal;
• treatment and conditioning of radioactive waste, prior to disposal;
• final clearance of sites.
Authorisation requirement related to the release, recycle and reuse of materials produced during plant decommissioning, together with the acceptance criteria for disposal of radioactive materials, are of key importance, considering that the change in decommissioning strategy increases the quantity of radioactive waste to be disposed of, the costs for waste treatment, transportation and disposal, and the capacity of the national repository. In this connection, Sogin is discussing with competent Authorities and Bodies in order to define clearance criteria and disposal acceptance criteria, which neither impair nor complicate the future dismantling operations.
In (1) details are given about Italian decommissioning Regulation, decommissioning strategy and Organisation, in order to show the boundary conditions, which exist in Italy for planning and development of NPPs Decommissioning Projects.
In the following paragraphs the decommissioning strategy is summarised first together with some critical items of decommissioning; then the Italian regulation about the management of radioactive waste is reported. The management of waste and materials, which will arise from the decommissioning of Italian nuclear power plants, is driven by the requirements imposed by the competent Authorities basing on this regulation.
Overview of NRC NUREG-1482, Revision 2, Guidelines for Inservice Testing at Nuclear Power Plants: Inservice Testing of Pumps and Valves, and Inservice Examination and Testing of Dynamic Restrains (Snubbers) at Nuclear Power Plants