Jl. Rempe et Tj. Walker, OVERVIEW OF NRC SPONSORED LWR LOWER HEAD FAILURE RESEARCH-PROGRAM, Nuclear Engineering and Design, 148(2-3), 1994, pp. 327-341
The US Nuclear Regulatory Commission (US NRC) has sponsored a research
program to investigate the mode and timing of vessel lower head failu
re. Major objectives of the program were to identify plausible failure
mechanisms and to develop a method for determining which failure mode
would occur first for different light water reactor designs and accid
ent conditions. Failure mechanisms, such as tube ejection, tube ruptur
e, global vessel failure, and localized vessel creep rupture, were stu
died. Newly developed models and existing models were applied to predi
ct which failure mechanism would occur first in various severe acciden
t scenarios. So that a broader range of conditions could be considered
simultaneously, the calculations relied heavily on models with closed
-form or simplified numerical solution techniques. Finite element tech
niques were employed for analytical model verification and examination
of more detailed phenomena. High-temperature creep and tensile data w
ere obtained for predicting the vessel and penetration structural resp
onse. This paper summarizes major accomplishments and conclusions from
research performed in the NRC sponsored lower head failure project.