Extended Station Blackout Coping Capabilities of APR1400

Abstract

The Fukushima Dai-ichi nuclear power plant accident shows that an extreme natural disaster can prevent the proper restoration of electric power for several days, so-called extended SBO. In Korea, the government and industry performed comprehensive special safety inspections on all domestic nuclear power plants against beyond design bases external events. One of the safety improvement action items related to the extended SBO is installation of external water injection provision and equipment to RCS and SG. In this paper, the extended SBO coping capability of APR1400 is examined using MAAP4 to assess the effectiveness of the external water injection strategy. Results show that an external injection into SG is applicable to mitigate an extended SBO scenario. However, an external injection into RCS is only effective when RCS depressurization capacity is sufficiently provided in case of high pressure scenarios. Based on the above results, the technical basis of external injection strategy will be reflected on development of revised severe accident management guideline.

Extended Battery to Cope with ELAP for APR1400

“…Extended station blackout coping capabilities of APR1400 which is a research done on the APR1400 by other researchers by applying an ELAP analyses using the MAAP severe accident computer code concludes that in case of failure of both EDG and AAC-DG, the extension of I&C loads associated with the TD-AFW may be necessary to assure the coping integrity for safe shutdown and more efficient core cooling capability [3].…”

“…In case that EDG fails to start, each two NPP units in the plant were equipped with AAC Diesel Generator designed in accordance with the regulatory guide RG 1.155 in early preparation for the case of simultaneously unserviceable off-site power and on-site power (main generator, emergency generator) [3].…”

Advantages of the AFWS for APR1400 in Response to SBO using MARS Code

“…It is recommended to extend the life time of the batteries to be able to continue AFWS operation for coping with SBO. Station blackout without operator action (cooldown procedure) leads to core damage at 2.0 hours and reactor pressure vessel failure at 3.7 hours in APR1400 [4].…”