GB/T 40408-2021Nuclear grade isostatic graphite for high temperature gas-cooled reactor internals (English PDF)

3.1 Nuclear grade isostatic graphite

Graphite for nuclear industry that is manufactured from raw materials such as carbon aggregate and asphalt through grinding, kneading, isostatic pressing, roasting, impregnation, graphitization, purification and other process steps.

NOTE: In the case of fast neutron (En>=0.1MeV) irradiation, this kind of graphite needs to consider the influence of size and material property changes on the design. It is mainly used for high temperature gas-cooled reactor reflector components. These components also perform the function of the core support structure.

3.2 Isotropy; alpha

The ratio of the thermal expansion coefficient in the molding gravity direction to the thermal expansion coefficient in the vertical molding gravity direction.

5.1 Unirradiated basic indicators

See Table 1 for the basic technical indicator requirements of nuclear grade isostatic graphite that are not irradiated.

6.1 Bulk density

According to the provisions of GB/T 24528.

6.2 Thermal conductivity

According to the provisions of GB/T 8722.

6.3 Thermal expansion coefficient

According to the provisions of GB/T 3074.4.

6.4 Isotropy

6.5 Tensile strength

According to the provisions of GB/T 8721.

6.6 Compressive strength

According to the provisions of GB/T 1431.

6.7 Flexural strength

According to the provisions of GB/T 3074.1.

6.8 Fracture toughness

According to the provisions of GB/T 38338.

6.9 Elastic modulus

According to the provisions of GB/T 3074.2.

6.10 Ash

According to the provisions of YB/T 5146.

6.11 Boron equivalent

According to the provisions of JY/T 0567, the impurity content of at least six elements Gd, B, Sm, Eu, Cd and Li shall be tested. The boron equivalent is calculated according to formula (1):

Where, A - The boron equivalent;

CGd - The content of Gd gadolinium element in the sample;

CB - The content of B boron element in the sample;

CSm - The content of Sm samarium element in the sample;

CEu - The content of Eu europium element in the sample;

CCd - The content of Cd cadmium element in the sample;

CLi - The content of Li lithium element in the sample.

NOTE: The coefficient before each content in the formula is the boron equivalent factor of the corresponding impurity element.

6.12 Test method for graphite irradiation

Refer to Annex A for the test method for graphite irradiation.

NOTE: Annex A is for reference only.

7.1 Batching

Each graphite block shall have a unique traceability number. The same designation of graphite in the same graphitization furnace is a batch.

7.2 Sampling

When sampling for testing of tensile strength and compressive strength of graphite, the sampling quantity A specified in Table 2 shall be carried out. When sampling for testing of graphite thermal conductivity, thermal expansion coefficient, isotropy, graphite flexural strength, fracture toughness, graphite composition, it shall be carried out according to the sampling quantity B specified in Table 2. When sampling for testing of other characteristics, it shall be carried out according to the sampling quantity C specified in Table 2.

When the testing sample is extracted, different positions of the graphite block shall be […]