Wastewater Discharge Standards for Nuclear Power Plants

Nuclear power plants generate various types of wastewater during normal operation, which can be broadly categorized into radioactive liquid effluents and non-radioactive wastewater. 

To prevent cross-contamination between these two categories, plants implement a strict policy of separate collection, storage, and treatment. Consequently, the discharge management of nuclear power plant wastewater follows two parallel yet equally rigorous standard systems: radioactive effluents are governed by national mandatory radiation protection standards, while non-radioactive wastewater is subject to general industrial discharge regulations supplemented by specialized group standards.

Radioactive Liquid Effluent Standards

The management of radioactive liquid effluent discharge lies at the core of environmental radiation protection for nuclear power plants. China has established extremely stringent limits on the radioactive concentration of effluents from nuclear facilities. The current regulatory framework is anchored by the Regulations for Environmental Radiation Protection of Nuclear Power Plants (GB 6249). This standard explicitly stipulates that the effective dose to any member of the public from radioactive releases from nuclear power reactors at any site shall not exceed the dose constraint of 0.25 mSv per year.

In terms of total annual discharge control, nuclear power plants must implement annual limits on radioactive effluent releases on a per-reactor basis. For a 3000 MW thermal power light-water reactor, the annual discharge control values for liquid effluents are: tritium at 7.5×10¹³ Bq/a, carbon-14 at 1.5×10¹¹ Bq/a, and other nuclides combined at 5.0×10¹⁰ Bq/a. For multi-reactor sites, cumulative control requirements apply to the total annual effluent releases from all reactors.

Regarding concentration control, the standard sets differentiated limits based on the type of receiving water body. For coastal sites, the concentration limit for radioactive nuclides other than tritium at the system discharge point is 1000 Bq/L; for inland river, lake, or reservoir sites, this limit is reduced to 100 Bq/L. Even more stringent is the requirement that for inland sites, the total beta radioactivity concentration in the receiving water body at 1 km downstream of the discharge point shall not exceed 1 Bq/L. The standard also specifies activity concentration control values for individual radionuclides, such as cobalt-60 at 0.03 Bq/L and cesium-137 at 0.7 Bq/L.

Nuclear power plants must incorporate appropriate design features to ensure that the quantity of radioactive effluents remains below the permitted discharge limits and is maintained at levels as low as reasonably achievable.

Non-Radioactive Wastewater Standards

Non-radioactive wastewater from nuclear power plants mainly includes domestic sewage, oily wastewater, and general industrial wastewater from floor washing and similar sources. The discharge management of such wastewater follows conventional environmental protection standards. 

Domestic sewage, after treatment to meet the required quality, is discharged in accordance with the Class I-A standard of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002). Other non-radioactive production wastewater is discharged in accordance with the Class I standard of the Integrated Wastewater Discharge Standard (GB 8978-1996). Oily wastewater must be treated to meet the relevant local standards before discharge.