The ultimate emergency measures to secure a NPP under an accidental condition with no designed power or water supply

• Published in: Nuclear engineering and design Vol. 253; pp. 259 - 268
• Main Authors: Liang, K.S., Chiang, S.C., Hsu, Y.F., Young, H.J., Pei, B.S., Wang, L.C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.2012; Elsevier
• Subjects: Applied sciences; Boiling water reactors; Controled nuclear fusion plants; Damage; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Nuclear engineering; Nuclear fuels; Nuclear power generation; Nuclear reactor components; Nuclear reactors; Water injection; Water supplies; Boiling water reactor; Cooling; Accident; Hydrogen; Earthquakes; Explosions; Depressurization; Reactor core; Seawater; Damaging; Pressurized water reactor; Nuclear reactor
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2012.08.022

► An ultimate measure to secure core was developed, if power or water supply cannot be restored in time. ► This ultimate measure was simulated by RELAP5-3D to verify the concept of this emergency plan. ► Quantification of the required raw water injection rate was performed for NPPS in Taiwan ► Reactor controlled depressurization within the 1st hour is essential to reduce the required raw water injection rate. ► For PWR, even heat sink can be developed, RCP seal leak might eventually cause core uncover 10h after seal leak occurs. In the recent nuclear catastrophe which occurred in Japan on March 11, 2011, several units of Fukushima conventional BWR experienced a total loss of power and water supply triggered by a heavy earthquake and a following Tsunami beyond design basis. In Fukushima accident it was observed that sea water was injected into reactors only after hydrogen explosion took place and it was considered a little too late to prevent core from damage. With regard to this fact, the Taiwan power company develops an ultimate measure to prevent reactor from encountering core damage, if either designed AC power or reactor water supply cannot be restored in time. This ultimate measure was named as DIVing plan, abbreviated from system depressurization, water injection and containment venting. Once any designed AC power or reactor water supply is made available, this DIVing plan will be activated to (1) depressurize reactor first, (2) inject any available water into reactor by any available power supply if this critical status cannot be restored in time, and (3) vent the containment if necessary to maintain containment integrity. In this paper the DIVing plan was simulated by RELAP5-3D to verify the concept of it and also to quantify the required raw water injection rate to prevent core from damage for both PWR and BWR plants in Taiwan, after the loss of passive cooling mechanism. Provided the passive cooling mechanism is lost within the first hour, for Chinshan BWR/4 and Kuosheng BWR/6 plants 1400l/m (370GPM) and 2441l/m (645GPM) raw water injection rate are, respectively, required and for Maanshan 3-loop PWR plant 2271l/m (600GPM) water injection rate is required, to prevent the PCT higher than 1088.6K (1500°F).