HKNIC - Radioactivity Released during Normal Operation
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Radioactivity Released during Normal Operation
Two types of radioactivity are released from a nuclear power station into the environment. Both are small in quantity and closely regulated. Gaseous radioactivity is released through the ventilation system of the nuclear island. Liquid radioactivity is discharged through the outfall of sea water which is used as coolant for the power station. Such releases arise from the residuals when the plant operates its purification system for the primary circuit to remove and sequestrate its excessive radioactivity that originates from the fission process in the nuclear reactor.

Gaseous Release
Radioactive gases are passed through treatment systems installed with filters and iodine absorbers to reduce radioactivity. They are then kept in storage tanks at the station for typically several weeks, allowing the radioactivity to reduce naturally over time.

This gaseous waste contains mostly noble gases, halogens and aerosols. Regulations cover both the concentration of the radioactivity in any release and the annual quantity of release, and stringent checks are carried out to ensure these statutory requirements are met. The waste is released together with the power station's exhaust ventilating air through the ventilation stack, where radioactivity is monitored and the release stopped if necessary. [ Radioactive Release ]

Image Credit : DNMC

Liquid Release
Radioactive liquids are filtered and then processed in an ion-exchanger or an evaporator. The treated liquids are held in tanks for several weeks, allowing the radioactivity to reduce naturally over time. If necessary, the liquids are given further treatment. Only when their contents meet statutory requirements, will they be discharged into the sea following dilution with the sea water taken into the power station for cooling.

The radioactivity of the discharge is monitored and as with gases, regulations cover the concentration of radioactivity in any release and the annual quantity of release. [ Radioactive Release ]

Thermal Pollution
Of the heat produced in the nuclear reactor, about one-third is used to produce electricity and the remaining two-thirds is absorbed by the sea water taken into the power station through the condenser for cooling.

Measurements taken on the impact of thermal discharge on the sea around the Daya Bay site which in this case includes the Guangdong Daya Bay Nuclear Power Station and the nearby Ling Ao Nuclear Power Station have found them not to be significant, showing an increase in sea water temperature of or above 1ºC over a sea surface area of several tens of square kilometres.