Current practice and developmental efforts for leak detection in US reactor primary systems Page: 4 of 9
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0 12 3 4 5
UNIDENTIFIED LEAKAGE (gal/min)
10 20 30
TOTAL LEAKAGE (gal/mini
Figure 1. Amounts of Unidentified and Total Coolant Leakage Allowed at
BWRs and PWRs. Conversion factor: 1 gal/min = 3800 cm^/min.
Generally speaking, reactor operators rely on sump pump monitoring to
establish the presence of leaks. Other methods appear to be less reliable or
less convenient. In most reactors, the surveillance periods are too long to
detect a 1-gal/min leak in 1 h, as suggested by Regulatory Guide 1.45, but it
appears that this sensitivity could be achieved if monitoring procedures were
modified. Simply tightening the current leakage limits to improve sensitivity
is not adequate,however, since this might produce an unacceptably high number
of spurious shutdowns owing to the inability of current leak detection systems
to identify leak sources. None of the systems provides any information on leak
location, and leaks must be located by visual examination after shutdown.
Since cracks may close when the reactor is shut down, reducing flow rates
considerably, it would be desirable to be able to locate cracks during plant
The estimated sensitivity of leakage monitoring is occasionally addressed
in the technical specifications for reactors. For example, one specification
indicates that air particulate monitoring can, in principle, detect a
0'013-gal/min leak in 20 min, that the sensitivity of gas radioactivity moni-
toring is 2-10 gal/min, and that the sensitivity of condensate flow monitoring
is 0.5-10 gal/min. Continuous sump pump monitoring appears capable of de-
tecting a 1-gal/min leak in 10-60 min.
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Kupperman, D.S. & Claytor, T.N. Current practice and developmental efforts for leak detection in US reactor primary systems, article, July 1, 1985; Illinois. (digital.library.unt.edu/ark:/67531/metadc1074301/m1/4/: accessed January 17, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.