Page 192 - Neutrons for Sciences and Society

CHAPTER 8
The Dark Years
8.1 The reconstruction of the reactor
During routine inspection of the reactor vessel in April 1991 a crack was observed which would require its replacement. This operation needed a very long shutdown of the reactor which would only restart on 6 January 1995. Here is a description of the events of 1991 written by Jean Charvolin in the Annual Report for 1991.
“On 30th March, during a reactor shutdown after a normal operating cycle, a routine inspection revealed unusual marks on an anti-turbulence grid in the heavy water in the reactor vessel; on 5th April, after a detailed analysis, it was found that these marks were transverse cracks in the grid, which must therefore be replaced. Such an operation implies major intervention
work in the reactor vessel, preceded by long preparation. At that time the ILL hoped to be able to strengthen the grid to permit temporary operation during the preparation period but, as the continued investigations gave a better understanding of the origin of the damage, this idea was given up in view of the amount of strengthening work required. It was decided on 10th July to keep the reactor shut down and to initiate immediately studies for the major intervention work. The possible technical
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