Design safety limits in prototype fast breeder reactor

Full text: PFBR is designed to operate at 450 W/cm peak linear heat rating to a peak burn up of 100,000 MWd/t which corresponds to a damage dose of 85 dpa. The targetted reliability is to restrict pin failure to 1 in 10,000. All the design basis events are classified into four categories. Design safety limits imposed for DBE are in terms of temperatures, radiation doses and structural design parameters. Radiation limits are imposed in relation to RCB from the plant personnel and public point of view. Fuel pin integrity is assured with a detailed damage analysis by adopting cumulative damage concept for fixing clad temperature limits. Fuel temperatures are limited to melting point to preclude fuel slumping for events up to category 3. Partial melting is allowed for events in category 4 and the results obtained from transients experiments show that partial melting up to 50% of pellet area does not result in clad failure. Coolant temperatures are limited to boiling point to avoid burnout and reactivity effects