Through keeping track of the radiation level at various points in the
reactor system, any abnormalities in operation can be quickly detected
and corrected.
A leak in the heat exchangers, for example, would show up on a radiation
monitor located in the blowdown line from each of the heat exchangers.
The intermediate cooling system, which includes cooling water from the
primary pumps, shield water cooler, containment air cooler, and other
components not directly in the primary loop, is monitored at five
locations. Leakage of primary loop water into the secondary water is
possible only from the pumps and letdown coolers, because of differences
in pressure. Consequently, radiation monitors are located downstream
from the letdown coolers and in each of the return lines from the pump
cooling coils.
The demineralizers are also monitored. When the resin bed is
functioning, the flow downstream (effluent) will have negligible
radioactivity. Consequently, a monitor signal at this point will
indicate when to switch to a new demineralizer. The monitor in the
influent (water entering the demineralizer) measures the activity level
in the primary loop.
The fission product monitor keeps track of fission product activity in
the primary (reactor) system. The monitor consists of a cation and anion
column, an amplifier, and an indicating system. This monitor is located
in the primary coolant flow system.