Repair successfulReactor floor repaired |
 Restoring reinforcement bars.  Reducer with concrete collar, jacket pipe and dry air pipe. |
Repair successfulThe concrete of the reactor floor was repaired on Tuesday 13 July. This successfully concluded the repair work on the High Flux Reactor cooling water pipes. There have been no safety incidents during the repair period and the radiation dose levels for internal and external employees have remained well below the planned limits. In the next few weeks the sub-pile room (the space below the reactor vessel), will be prepared for normal operation, the reactor basin will be refilled with water and the extra radiation shielding will be removed. After extensive safety tests, a five-day containment test will be carried out to verify that the HFR dome is leak-tight. The inspection team will also take a “Zero Time Point” measurement of the repaired pipe sections. The results of this measurement will be used as the reference point for future in-service inspections. The repair of the High Flux Reactor is going well; safety and quality remain paramount. The return-to-service plan has recently been approved by the authorities. The first start-up preparation activities will take place at the end of August. NRG strives to achieve the first HFR Full Power Day (45 MW) on 9 September. Update |
 Reinforcement bars in place.  Monitoring the pumping of the concrete. |
Reactor floor repairedAfter the welding repairs were successfully concluded, the reducers were then wrapped with PE tape and the jacket pipes were repaired. A concrete collar was then made to seal the jacket pipe. Edwin Bach, Civil Sub Project Manager: “We chose to install a concrete collar rather than a steel collar in order to guarantee a corrosion-free connection between the reducer and the jacket pipe. The collar also prevents any concrete from getting between the reducer and the jacket pipe when concrete floor is being poured.” Before the concrete could be pumped into the two excavated sections, the reinforcement bars were replaced to their original condition. Further, ventilation pipes were installed in the four corners of both sections. Bach: “We installed a camera in one of these ventilation pipes in each section to repair”. The pumping of the concrete was watched and monitored by the civil engineers as well as the authorities by means of this remote-controlled camera. “We put a flexible tube with a camera through a vent so that we were able to watch the filling process from above. This way we could be sure that the concrete spread equally without separating.” The reactor floor has now been repaired. Bach: “Concrete of exactly the same composition was poured in an actual size model during a previous test. Heat sensors were set in the concrete to measure the temperature curve during hardening. The time point at which the concrete was hard enough to remove the shuttering was calculated on the basis of this data using a computer model. In addition, two concrete cubes were poured at the concrete plant and their compressive strength was measured after hardening. By means of the computer calculations and the results of the compression test on these cubes, we were able to ascertain that the concrete has hardened and the shuttering could be safely removed.” |