SLOWPOKE Design
The SLOWPOKE-2 reactor fuel is a sintered uranium dioxide (UO2) pellet, where the uranium is considered low enriched (~20% enriched with the fissile material, U-235). The pellets are arranged end-to-end into a long pin about 20 cm long and 1 cm in diameter. The core (shown in image) is composed of a zirconium alloy and contains 195 fuel pins. The entire core is covered with beryllium to reflect neutrons back into the core to increase the probability of causing a fission reaction.
The SLOWPOKE-2 has a maximum output in normal operating conditions of 20 kW. However, the power is controllable according to the needs of the operator. The reactor can hold 20 samples, with five sample introduction sites in the core receiving 1012 neutrons∙cm-2∙s-1, five sites in the beryllium annulus (around the core) with a flux of 5x1011 neutrons∙cm-2∙s-1 and 10 site in the pool just outside the reactor. In addition to the power control, the site choice provides options for neutron flux and neutron-to-gamma radios.
As shown in the image, the fuel core is contained in a pool of water 6 m deep. The water molecules moderate, or slow down, and contain the neutrons. The operator depicted in the image is receiving background radiation doses due to the effective containment of the radiation coming from the fuel.
Schematic of the cross-section of the SLOWPOKE-2 reactor
Inherent Safety
Many aspects of the SLOWPOKE-2 reactor design has inherent safety, meaning there are passive, natural means to ensure safe operation. The water cools the reactor core by natural convection. The reactor is fail-safe, as the fission chain reaction is designed to naturally stop in the unlikely situation of a failure in any active or passive heat control. A Cd shutdown rod is controlled by the software and mechanically in an emergency. Redundant Cd capsules in sample sites shutdown the reactor independently. The high degree of active and passive safety systems results in the reactor being able to run unattended overnight.
There are currently 5 SLOWPOKE-2 operators and at least one is always available on-call. The staff and scientists are highly trained in the nuclear sector and radiation safety. The reactor undergoes weekly maintenance, where emergency shutdown procedures are tested and confirmed. In addition, all trainees and students working with the reactor or its laboratory take a radiation safety awareness, plus additional training from our highly trained professionals before they work independently.