Sources, types and classification of waste

As specified in the Law of the People’s Republic of China on Prevention and Control of Radioactive Pollution [9], RAW is defined as material, which contains or is contaminated with radionuclides at concentrations or radio­activity levels greater than the clearance level as established by the regula­tory body without foreseen further use. In China, RAW arises principally from NPP, research reactors, the nuclear fuel cycle, nuclear technology applications, the exploitation and utilization of uranium and thorium resources, as well as clean-up activities of contaminated sites and/or facili­ties such as that shown in Fig. 22.2: some nuclear facilities in the Gobi Desert in the west part of China (Qinghai Province), which were used during the 1950s and 1960s, need to be cleaned up.

To meet the needs for its nuclear power expansion, China has developed uranium enrichment and fuel element manufacture capability. At present, two uranium enrichment plants are in operation, with annual total centrifu­gal enrichment capacity of 1,100 tons of separation work. The first nuclear fuel assembly production line was established in 1988 in Sichuan province, supplying most of the nuclear fuel elements to the Qinshan NPP (Fig. 22.3). Subsequently, the technologies for designing and manufacturing nuclear fuel elements have been imported on a step-by-step basis, to which a techni­cal adaptation was later made. This means that China’s PWR fuel element manufacture can meet the requirements of the international generic stand­ards, so as to ensure that the supply of nuclear fuel elements meets the demands of the current PWR plants in China. Through introducing technol­ogy from Canada, a high pressure reactor fuel element production line, with

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22.2 Nuclear facilities in the Gobi Desert in Qinghai Province in the west part of China, which were used in the 1950s and 1960s, need to be cleaned up.

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22.3 Qinshan nuclear power plant with five reactor units.

a capacity of 200 tonnes per year, was built in Inner Mongolia, Northern China, where it provides HWR fuel elements for Qinshan NPP III.

China ’s RAW categorization system is based on pre-disposal manage­ment and disposal of RAW. In pre-disposal management, the RAW catego­rization system accounts for the nuclear facility operational experience in waste treatment and conditioning requirements, which includes a quantitative categorization system for radioactive gaseous, liquid and solid wastes. The disposal-based RAW categorization system focuses on the final disposal of RAW, in conjunction with the origin of the waste and the planned disposal approach.

The pre-disposal management-based waste categorization system is used to manage gaseous, liquid and solid RAW generated at nuclear facilities, with a detailed categorization for different forms of wastes according to their radioactive characteristics as shown in Table 22.3 . This is consistent with the basic requirements of waste treatment but puts more emphasis on

Table 22.3 Pre-disposal-based waste categorization system

Physical

condition

Waste

categorization

Waste characteristics/index

Gaseous

Low level waste

Concentrations not exceeding

(LLW)

4 x 107 Bq/m3

Intermediate level waste (ILW)

Concentrations greater than 4 x 107 Bq/m3

Liquid

Low level waste (LLW)

Concentrations not exceeding 4 x 106 Bq/L

Intermediate level

Concentrations greater than 4 x 106 Bq/L,

waste (ILW)

but not exceeding 4 x 1010 Bq/L

High level waste (HLW)

Concentrations greater than 4 x 1010 Bq/L

Solid

Low level waste

Specific activity not exceeding

(LLW)

4 x 106 Bq/kg.

Intermediate level

1. Half-life longer than 60 days but

waste (ILW)

shorter than or equal to 5 years, specific activity not exceeding 4 x 106 Bq/kg

2. Half-life longer than 5 years, but shorter than or equal to 30.2 years, with specific activity more than

4 x 106 Bq/kg, but not exceeding 4 x 1011 Bq/kg

3. Half-life longer than 30.2 years, specific activity greater than 4 x 106 Bq/kg.

High level waste

1. Half-life longer than 5 years, but

(HLW)

shorter than or equal to 30.2 years, with heat release rate larger than 2 kW/m3 or specific activity more than 4 x 1011 Bq/kg,

2. Half-life longer than 30.2 years, specific activity larger than 4 x 1010 Bq/kg.

Alpha radioactive

Alpha nuclides with half-life longer than

waste

30.2 years, specific activity in a single container larger than 4 x 106 Bq/kg

the cleaning index, shielding design, and other field protection require­ments. These requirements are implemented in the waste treatment and conditioning processes for various systems. It is noticeable that most Chinese standards on nuclear or radioactive waste management are coherent with the current IAEA classification scheme. For example, both the IAEA and Chinese standards specify that management of decay heat should be con­sidered if the thermal power of waste packages reaches several watts per cubic metre [10,11].

The disposal-based radioactive waste categorization system divides solid radioactive waste into solid LLW, solid ILW, solid HLW, solid alpha waste and the waste arising from mining and milling of uranium and thorium, and naturally occurring radioactive materials (NORM) waste. Disposal options considered include centralized deep geological disposal, regional near­surface disposal, and centralized landfill, and others, as shown in Table 22.4. Solid LLW containing only short-lived radionuclides can be released from regulatory control when the radioactivity contained is below the regulatory clearance levels. However, management of cleared waste should be in com­pliance with other relevant environmental requirements.

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