Issue link: https://te.mouser.com/i/1385324
36 Proven in the Harshest Environments FIGURE 6: Fire-resistant joint before, during, and after a fire- resistant test. (TE connectivity) Fire-Resistant Heat-Shrink Cable Accessories Despite flame-retardant requirements, specific industry requirements require fire resistance properties, where cable and accessories need to maintain system integrity up to 180 minutes. This request is usually combined with low-smoke zero-halogen (LSZH) materials. However, low smoke zero-halogen properties on their own will not give the properties needed for heat-shrink cable accessories to achieve the system integrity requirements. As a solution, the heat-shrink cable accessories are combined with additional protective layers acting as a barrier against the fire application and preventing the flame from penetrating the inner insulation. A typical standard where test procedures for fire-resistant cable and cable accessories (Figure 6) are defined as IEC-60331. Heat-Shrink Cable Accessories for Nuclear Power-Plant Environments One of the most severe environments for cable accessories is applications in the containment area of nuclear power plants, which would include function under accident conditions. One of the most severe accident conditions is a loss of coolant accident (LOCA). For more than 40 years, Raychem class 1E safety- related cable accessories are in use, which in case of an accident can support, such as the emergency shutdown of the reactor, containment isolation, and prevent the release of radioactive material. A full LOCA qualification simulates the severe accident conditions and therefore has to cover the following elements: • Simulation of aging (thermal and gamma- radiation) • Radiation exposure during the lifetime • LOCA—accident simulation with high radiation, temperature and pressure profile during saturated steam conditions, and chemical spray testing The newest generation of nuclear power plants, such as AP1000 or the European Pressurized Water Reactor (EPR), is built for a 60-year service life. Therefore, the qualification process's thermal aging was already chosen to simulate a 60-year lifetime at a constant temperature of 90°C, which typically represents the maximum conductor temperature in power cables. Although the products installed in the containment area are subjected to nuclear radiation, a 40/60 years gamma radiation needs to be simulated. Also, high gamma radiation can occur during the accident, which needs to be taken into account and tested during the qualification process. Typical values can exceed 200Mrad of Gamma radiation. During the accident simulation, the heat-shrink cable accessories installed on cables will be taken into a vessel, where the temperature and pressure occurring during an accident will be simulated. A typical profile for a 30 days test on cable accessories is shown below, with maximum temperatures beyond 200°C and a maximum pressure beyond 0.8Mpa over normal environmental pressure.