SOLID BREEDER THERMAL TRANSIENT UNDER PURGE-LINE-BREAK ACCIDENTS

The breeder thermal performances under a purge line break have been an alyzed for two blanket design options: a blanket design using a packed breeder bed and a blanket design using a sintered breeder product. Un der a purge line break open to a vacuum environment, the packed bed br eeder temperature exceeds its operating temperature limit at a faster rate than that of the sintered breeder blanket design for the same bre eder temperature gradient. Depending on the breeder material and nomin al operating conditions, the breeder reaches its maximum operating tem perature in time ranging from 32 seconds to 125 seconds for a break ar ea of 10 cm2 in packed bed designs. However for the sintered product d esign, the consequence of this transient might not result in the breed er exceeding its maximum operating temperature if a reasonable contact pressure could be established at the interface. To reduce the safety hazards, the tritium concentration build up in the vacuum vessel in co njunction with the purge gas pressure inside the blanket module should be used as a measure for initiating the reactor shutdown for this typ e of accident. The consequence of the purge line break outside the vac uum vessel on the breeder transient thermal performance is less signif icant because of a longer transient time involved.