Nuclear power plant cable refers to the raw materials used in the insulation and sheath of nuclear power plant cables, including plastic, rubber and other varieties. The type of cable is determined by the type of cable.
Nuclear power plant cables have two classification methods: one by function, including measurement cables, communication cables, instrumentation cables, fire cables (silicone-insulated cables), etc.; the other is by safety level, nuclear power plant cables with the safety level belongs to the IE level, at the same time, it should have a service life of more than 4O years, IE level nuclear power plant cables and is divided into K1, K2 and K3, the three safety levels. The development process of nuclear power plant cable products is essentially the renewal of the material, the type of cable and its choice of raw materials.
Characteristics
Performance low smoke
The insulation and sheath materials of cables for nuclear power plants must be low-smoke, non-toxic, non-corrosive halogen-free flame-retardant cables, such as thermoplastic flame-retardant halogen-free or cross-linking flame-retardant halogen-free materials, in order to meet the special nuclear safety requirements. Halogen-free cables in the event of a fire, the amount of smoke released by combustion is very low, without toxicity and corrosiveness, and its flame retardant components can effectively play the role of flame retardant, will not make the cable become a channel for the spread of flame. The main technical characteristics of halogen-free flame retardant cables are: (1) the total cumulative amount of smoke from nuclear power plant cables Dm <150; (2) non-toxic and corrosive, i.e., the cable combustion does not precipitate HCI and CO; (3) has a flame retardant, polymer flame retardant is usually evaluated by the oxygen index (0I) method, the general OI ≥ 28.
Nuclear power plant cable materials must have environmental resistance, namely heat resistance, irradiation resistance and LOCA resistance.
(1) heat resistance due to nuclear power plant cables often work in high temperature environments, high temperature cables. Therefore they need to have a long-term heat-resistant use of performance, to choose the heat resistance to meet the requirements of the polymer, and can make the cable has a service life of more than 40 years.
(2) irradiation resistance (moderate environment, harsh environment) nuclear power plant cables are subjected to a large number of rays will make the insulation and sheath materials become brittle, poor mechanical properties. Therefore, as a nuclear power plant cable insulation and sheath materials, must have excellent irradiation resistance. Different polymers have different irradiation resistance properties. People usually add anti-irradiation agent in the polymer to improve its irradiation resistance.
(3) LOCA resistance in nuclear power plants, usually the loss of coolant accident (Lossofcoolingaccident, LOCA) and high-energy tube rupture accident (Highenergylinebreak, HELB) collectively referred to as LOCA. in the event of LOCA/HELB, the cable will be subjected to high-temperature and high-pressure steam impact and corrosive chemicals Role, and to be subjected to a higher dose of radiation than under normal operating conditions. Therefore, nuclear power plant cables should be LOCA resistant.r power plant cable materials must have environmental resistance, namely heat resistance, irradiation resistance and LOCA resistance.
Performance Requirements
Nuclear power plants have very strict requirements for the use of cable conditions. Cables should be able to be buried directly through cable ducts and underground pipes, or installed overhead through cable trays, cable ducts and wiring ducts, etc., and at the same time, they should be able to work in dry and warm environments:
(1) Service life. The design life of heavy water reactor nuclear power plants is generally 40 years, and the service life of cables is at least 40 years.
(2) Thermal stability. In the case of being at the maximum ambient temperature and its own heat generation, the cable shall be able to maintain the insulation performance required by the operating conditions. The minimum continuous insulation operating temperature for power and control cables is 90°C.
(3) Moisture resistance. In the event of fire sprinkler splashing under accident conditions, the cable shall be able to operate normally in a 100% relative humidity environment.
(4) Fire resistance. In order to reduce the potential impact and damage caused by the cable catching fire, the cable shall be flame retardant.
(5) Chemical stability. Cables installed in chemical environments (e.g., oil, ozone, acids and alkalis, and other corrosive agents) shall maintain the required insulation properties.
(6) Radiation resistance. During the operation of the power station, the cable should be able to receive a continuous radiation dose of 10 rad / h, the cumulative dose over 40 years is about 0.4 × 107 rad, in the accident state radiation dose can be up to 5 × 107 rad. after withstanding the total cumulative radiation dose, the cable should still maintain the electrical properties unchanged.