Ig. Kim et Hj. Kim, A REVIEW ON OPERATING EXPERIENCES OF CONTAINMENT ISOLATION SYSTEMS INKOREA, Nuclear Engineering and Design, 145(3), 1993, pp. 431-438
Wide experience, on the order of 50 reactor-years, in operating contai
nment isolation systems has been accumulated in Korea since 1978, nece
ssitating a review of the operating data to confirm the integrity of c
ontainments and to establish the future direction to the containment t
est program. The objectives of the present work are to collect, consol
idate and assess the operational data relevant to containment isolatio
n systems, and then to identify types of isolation valve failures, dom
inant leakage paths and factors affecting integrated leakage rate test
. Leakage is observed to be the most frequent type of isolation valve
failure. The causes of the valve leakage are packing leakage, seat dam
age due to foreign material, and misadjustment of torque switches. Mal
function and deterioration are also observed to be frequent failure mo
des. General leakage trends show that more careful surveillance during
preoperational test can reduce the containment leakage. Significant l
eakage paths are found to be through air locks and large valves of six
-inch or greater nominal diameter, so that weighted surveillance and i
nspection on these dominant leakage paths can considerably reduce the
containment leakage. Atmospheric stabilization is found to be the most
important factor to obtain the reliable integrated leakage rate. In o
rder to achieve a well stabilized atmosphere, temperature and flow rat
e of compressed air should be kept constant and it is preferable not t
o operate fan coolers during pressurizing the containment for test. Th
ese results are expected to be a guidance for improving the operation
of containment system.