About hot cells

Hot cells JHR

The fuel and the samples to be irradiated and to be inserted into the reactor in the so-called “irradiation probes” are being prepared in the hot cells. Between the cells and the reactor the baskets with irradiated fuel cells and irradiation probes are being transported by an underwater conveyor (a thick layer of water is used to shield off the radiation). Once irradiated, the probes are being disassembled in the cells, the samples taken out, sorted, evaluated, and stored into the shielded containers being connected in which they are moved for additional processing, measurements or other utilization. Waste materials are also caught up in the cells. These materials include, for example, irreparable parts of the irradiation probes or of the reactor’s and hot cells’ inner equipment. Repairs of damaged parts of the reactor equipment, irradiation probes equipment, and of the equipment of the cells themselves are also being carried out in the hot cells. Such repairs mainly consist in disassembly of a damaged part and/or a unit of coupled parts and in putting the new unit together. The parts must be specially adapted to be suitable for such a repair action at the phase already when being devised by the design engineers. The joints to be dismounted in the future, for example, must be realized by means of adequately sized and easily accessible screws. The adaptation is to utmost simplify all the operations scheduled to be carried out in the cells. To protect the cell operators against exposure to radiation and radioactive contamination the operations must be carried out remotely from outside of the cells.

Protected against irradiation by a thick wall the operator will follow the happenings inside the cell through a lead glass eyehole (or with a camcorder), handling the objects and tools by means of the mechanical arms, called “remote manipulators”. Necessity of the operator’s entries inside the cells should be confined to a minimum as almost all the materials placed permanently inside the cells will become radioactive over time and this activity cannot be eliminated by any decontamination efforts.

To enable proper testing of the equipment parts and foreseen principles of manipulation before the production itself a unique test stand came to being in Řež. The stand is actually a model of one big and one small cell, scaled 1 : 1. The wooden sliding walls allow simulation of the geometry and dimensions of either of the cells under design.

The set of the JHR hot cells consists of four big and three adjoining small cells. To allow for manipulation with the whole irradiation probes in them the cells have clear height of 10 meters. Small cells are mainly intended for maintenance operations. Basic non-destructive measurements are being taken in them on the irradiated samples. Their internal equipment is foreseen to be much less contaminated and activated than in the case of the big cells, and the operator entries, whenever necessary, may therefore be more frequent. This is why these cells are also equipped with doors and transfer spaces. External walls of all the cells are 1.2 m thick and all the doors are, because of the shielding, so massive that they withstand comparison even with the A-bomb shelter doors.