The High Flux Reactor is an important component in radioisotope production for the medical sector and plays a prominent role in international energy research. A routine in-service inspection in August 2008 detected jets of gas bubbles (bubblejets) in one of the reducers, part of the primary cooling water system. Consequently, NRG decided not to start the reactor before conducting an inspection into the extent, cause and consequences of the deformations in the reducers and the prospects for carrying out repairs. It was eventually decided to use the ‘concrete route’ method to carry out comprehensive repairwork on the reducers. Using this method, after draining the basin, the concrete enclosing the reducers is removed and they are repaired.

Meticulous preparations for the repairs have been underway over the past few months. Repair techniques and radiation shielding have been extensively tried and tested. The people, materials and repair methods have been qualified by external bodies in consultation with the competent authorities. At the request of NRG and the authorities, various independent experts from the Netherlands and other countries are evaluating every aspect of the repairwork, including the supervision of the work's execution. During the repairwork the safety and health of all the employees involved will be the first consideration.

Repairwork starts on 19 February 2010 and is expected to take 25 weeks to complete.