The repair of the High Flux Reactor (HFR) in Petten, the Netherlands, is progressing well and the restart of the reactor is planned for the second half of August, according to the Nuclear Research and Consultancy Group (NRG) of the Netherlands.
Phase 1 of the repair process involving the dismantling of the reactor and positioning the radiation shield is progressing successfully and inspection of the reactor vessel has been completed ahead of schedule with satisfactory results, according to NRG.
“As part of this process, the reactor core has been unloaded and the nuclear fuel and the experiments are now in storage. In addition, the control rods and their drive mechanisms have been removed and the subpile room emptied. A trial bore hole has been made in the concrete floor containing the reducers and this has demonstrated that the radiation level is at an acceptably low level,” the group said.
Last week, the regular inspection of the HFR reactor vessel was completed successfully and the inspection results showed that the welds were in good condition, NRG reported.
The next step in the repair process is to install the radiation shield on the base of the reactor tank, the group said. The team had installed the Densimet radiation shield in the base of the half drained reactor tank. To shield the reactor core itself, a kind of folding ‘butterfly’ has been designed and manufactured from coated Densimet which will be positioned using a manipulator. Once the full base radiation shield has been fully installed, a 40 cm-thick concrete plate will be positioned over the top of the reactor tank so that the repairs can be carried out safely, said NRG.
“The Densimet shield is manufactured from a tungsten alloy and was made especially for this purpose. It has a density of nineteen kilos per litre, that is one and a half times denser than lead. It was decided to use this material, because on the one hand it’s dense enough to block the radiation and on the other hand it’s easy to cut to the required size,” explained shield project manager Chris van Wijk.