[2C17-23] Fukushima Nuclear Accident

[2C18] Analysis of Plant Data Measured at Fukushima-Daiichi NPP Unit 3

Estimated Mechanism of PCV Pressure Variation during the expected MCCI phase

*IKKEN SATO¹ (1. Japan Atomic Energy Agency)

Keywords:Unit 3, pressure transducer, water level sensor, data correction, MCCI

In the Unit 3 of Fukushima-Daiichi NPP, PCV pressure increase and decrease took place cyclicly. Although earlier part of this pressure change can be explained with venting, later part does not seems to be caused by venting nor increase of leak through the PCV boundary. In this study, tentative correction for pressure measurement data is applied based on assumed consistency among different pressure measurement data. With this correction, slight pressure difference among RPV, D/W and S/C becomes visible and it provides information on possible accident progression behavior. A new interpretation on possible automatic PCV pressure decrease mechanism will be presented.