While the demand on electric power is consistently increasing, public concerns and
regulations for the construction of new nuclear power plants are getting restrict, and also operating
nuclear power plants are gradually ageing. For this reason, the interest on lifetime extension for
operating nuclear power plants by applying lifetime management system is increasing. The 40-year
design life concept was originally introduced on the basis of economic and safety considerations. In
other words, it was not determined by technological evaluations. Also, the transient design data
which were applied for fatigue damage evaluation were overly conservative in comparison with
actual transient data. Therefore, the accumulation of fatigue damage may result in a big difference
between the actual data and the design data. The lifetime of nuclear power plants is mostly dependent
on the fatigue life of a reactor pressure vessel, and thus, the exact evaluation of fatigue life on a
reactor pressure vessel is a crucial factor in determining the extension of operating life. The purpose
of this paper is to introduce a real-time fatigue monitoring system for an operating reactor pressure
vessel which can be used for the lifetime extension. In order to satisfy the objectives, a web-based
transient acquisition system was developed, thereby, real-time thermal-hydraulic data were reserved
for 18 operating reactor pressure vessels. A series of finite element analyses was carried out to obtain
the stress data due to actual transient. The fatigue life evaluation has been performed based on the
stress analysis results and, finally, a web-based fatigue life evaluation system was introduced by
combining analysis results and on-line monitoring system. Comparison of the stress analysis results
between operating transients and design transients showed a considerable amount of benefits in terms
of fatigue life. Therefore, it is anticipated that the developed web-based system can be utilized as an
efficient tool for fatigue life estimation of reactor pressure vessel.
Remaining Service Life Evaluation of Nuclear Power Plants Construction Steel Elements
