Safety analyses of the ARIES-II and ARIES-IV tokamak reactor designs

The ARIES-II and ARIES-IV designs are the final two designs of the ARIES study. The ARIES-II design uses liquid lithium and vanadium for low activation, multiple barriers between the lithium and air and an inert cover gas to prevent lithium-air reactions. The ARIES-II reactor is passively safe (level of safety assurance=2) with a total l-km early dose of about 0.88 Sv. The ARIES-IV tokamak reactor has been designed to avoid the use of materials subject to neutron activation and materials that are energy sources for the release of those activation products which do occur. The coolant is helium, the breeder is lithium oxide, and the structure of the first wall, blanket and shield is silicon carbide. For the ARIES-IV design, beryllium metal is used for neutron multiplication. Since beryllium metal is combustible, releasing about 60 MJ/kg, the multiplier is the chief source of chemical energy for the release of activation products in the structure. We can argue that less than 1O% of the ²⁴Na inventory is likely to diffuse out of the SiC during a fire in which the Be neutron multiplier is consumed. Therefore, the offsite dose would the less that 2 Sv, and the reactor satisfies the condition for LSA=1