THE USE OF THREE DEDICATED NUCLEAR MEASUREMENT TOOLS FOR D & D OPERATIONS IN NUCLEAR FACILITIES

ABSTRACT

The operations of dismantling of nuclear installation are often difficult due to the lack of knowledge about the position, the identification and the radiological characteristics of the contamination. 

In this sense the gamma contamination is particularly difficult to define in a significant global background when the activities are relatively high. Identification and estimation of the activity can become more complex in hot cells, for example, where space is limited and human intervention costly in cumulated dose. 

The preparation of these human interventions leads, in addition to the standard procedures, to the need for mapping the dose-rate distribution in space from the knowledge of the contamination characteristics (position, identification, activities). 

The introduction of three recent tools has improved the results obtained in terms of characterization for D & D operations : gamma camera, spectroscopy with efficiency calculated by computer and modeling of scene doserates.

For two years, three tools : the CARTOGAM gamma camera and the MERCURAD dose-rate modeling software developed in cooperation between the CEA, COGEMA and Canberra, and the ISOCS transportable gamma spectroscopy system developed by Canberra, have been in operation in industrial conditions in Europe, America and Asia.

This communication describes the present status of these three tools : main features, combined use of these tools, last improvements and first return of experience on site, in D&D operations or preparation of operations. 

INTRODUCTION

Canberra, the Nuclear Measurement Business Unit of the AREVA Group, performs the design, manufacturing and selling of a complete range of instruments and systems for radioactivity measurement. A set of three main instruments is aimed at D&D (Decommissioning & Dismantling) activities : CARTOGAM, ISOCS and MERCURAD. Each of these tools can be used separately, but when combined, the effect is synergistic for the preparation of a dismantling project, for its carrying out and, after its completion, to prove that decontamination is complete.

At first, these three tools are briefly described and then examples of their use in dismantling operations are given, in order to give some concrete insight into their interest and the productivity gains they can offer in D&D activities.