Source term calculations for accident management strategies for VVER-1000 reactors: part 1: text

This report describes the effect of different accident management strategies on the source term for a TMLB'-type sequence in a Pressurized Water Reactor of the type VVER-1000 up to the time when no more fission products are released from the core-concrete-interaction because the temperature of the debris is so low that it solidifies. Using the Source Term Code Package (STCP) the following scenarios were calculated: (1) Reference case without spray and LP ECC systems. (2) All spray and LP ECC systems including the coolers are available after 7 hours. (3) All spray and LP ECC systems including the coolers are available after 10 hours. (4) One spray and one LP ECC system but no coolers are available after 10 hours. (5) All spray and LP ECC systems but no coolers are available after 10 hours; the pressure increase is limited by filtered containment venting. The results show that in any case water should be supplied to the containment as soon as possible. Furthermore the effectiveness of the other accident management strategies are rated. The proposed measures reduce the source term by a factor of 2 up to several orders of magnitude. (author)