Ageing Management of the Kinshasa Trico II Research Reactor Components and Structures. A Case Study of the 5 Tonne Overhead Travelling Crane and the Ventilation System Inlet and Outlet

The cable isolation sheath of the overhead traveling crane became fragile and brittle on a length of more than two meters. This degradation of the sheath has been caused by the ageing of the cable and the effects of heat, with changeable ambient temperatures in the reactor hall combined with the Joule effect, in relation to the cyclic use of the crane. This ageing effect was discovered when a failure occurred at the end of a nearly completed routine operation of displacing slightly radioactive spent ion exchange resins into waste storage. During the return of the hoist to its rest position, a severe short circuit happened between the cable and the mass of the hoist motor support, followed by a strong detonation that produced sparks and immobilized the overall system. A visual examination of the cable showed a change of its physical properties as mentioned above. A further investigation showed that two master contacts of the hoist were also burned. The bridge crane was inspected and certified in January 2010 by a competent authority eleven months before the event. On the other hand, the reactor ventilation system started presenting its limits in the late 1990s after more than 17 years of operation. Many failures occurred in the extraction motors and the air conditioning system, causing both a temperature increase and a lack of negative pressure in the reactor hall. The crane problem was solved after replacing the damaged cable and the two burned contacts. A review of the overall status of the bridge crane by the licensing authority is scheduled before the end of 2011. The paper also describes steps related to the renewal of the air inlet system and the restoration of negative pressure in the reactor hall. (author)