Station Decommissioning

Nuclear waste is classified as high, intermediate or low-level radioactive waste based on the amount of radioactivity it contains. All nuclear waste must be treated with great care, subject to very strict procedures to prevent any possible radiation impact on people and the environment. At Daya Bay Nuclear Power Station, all processes are regulated by the National Nuclear Safety Administration in China based on guidelines and practices formulated by the International Atomic Energy Agency (IAEA).

High-level Radioactive Waste

Photo: Daya Bay Nuclear Power Operations
  and Management Co., Ltd.

Photo: Daya Bay Nuclear Power Operations
  and Management Co., Ltd.

Photo: Nuclear Regulatory Commission

Photo: Sellafield Ltd.

High-level waste refers to spent fuel after use for power generation or the waste remaining from the reprocessing of spent fuel. It occupies 3% of the total volume but contains 95% of radioactivity in the nuclear waste. Some countries such as the United States plan to store spent fuel deep underground after proper packaging. Others such as France and Japan choose to reprocess spent fuel for recycling.

Commonly Seen Interim Storage: Spent fuel is hot and radioactive. Handling and storing it safely can be done as long as it is cooled. Water can conveniently provide both cooling and shielding, so a typical reactor will have its fuel removed underwater and transferred to a spent fuel pool, a robust construction made of thick reinforced concrete with steel liners.

After around 8-10 years it can be transferred to a ventilated storage module made of concrete and steel, known as the Dry Cask Storage, but otherwise it can safely remain in the pool. Some nuclear plants will transfer the spent fuel to the reprocessing plant.

Reprocessing: About 96% of the spent fuel (containing uranium and plutonium) can be extracted and re-used for further energy generation. In France, such reprocessed fuel accounts for about 17% of all nuclear power output. The remaining 4% of the spent fuel will undergo further treatment such as vitrification before being sent to underground storage.

Underground Storage: High-level waste will be vitrified, packed in capsules and stored in underground repositories. The amount of high level radioactive waste is small and the waste can be technically isolated for a very long time until its radioactivity has reduced to the original natural ore level.

Each year, Daya Bay Nuclear Power Station generates about 50 tonnes of spent fuel. The spent fuel assemblies are kept in the fuel storage pool for about eight years before being delivered to a spent fuel facility in Northwest China. China plans to commission a spent fuel reprocessing plant to recycle spent nuclear fuel when the amount of spent fuel generated nationally reaches a commercial scale.

Like nuclear power stations, reprocessing plants and nuclear waste repositories are subject to safety regulations specific to each country and are designed, built, operated and decommissioned to comply with the relevant regulations and requirements.

Intermediate-level and Low-level Radioactive Waste

Photo Source: Daya Bay Nuclear Power
  Operations and Management Co., Ltd.

Photo Source: Kirstie Hansen / IAEA

Intermediate-level and low-level waste refer to spare parts / components from the reactor and other contaminated materials used in the power plant (e.g. staff clothing). They occupy 97% of the total volume but contains 5% of radioactivity in the nuclear waste. Low-level and Intermediate-level waste are packed in sealed drums and usually stored by means of shallow burial.

At Daya Bay Nuclear Power Station, typically less than about 150 cubic metres of intermediate-level and low-level wastes including package are produced each year. The waste may fit into three 40-foot shipping containers, which is about a thousand times less than the coal ash produced by a conventional coal fired power station supplying the same amount of electricity.